TerraLiner:12 m Globally Mobile Beach House/Class-A Crossover w 6x6 Hybrid Drivetrain

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21. Making Sense of the Data Points


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Now there is no question that the KW per hour requirement is accelerating, meaning that the rate of increase is itself increasing. This is already patently evident in the chart that the first web-calculator produces, where doubling the speed from 40 kph to 80 kph more than triples the per-hour power requirement, from approximately 42.7 KW to 131.5 KW:







But once we calculate for a given distance, the increased speed of travel almost "cancels out" this non-linearity. The following is a spreadsheet that demonstrates how when we calculated the Total Power required for 128.6 km, driving this distance at 90 kph, 100 kph, 110 kph, and 120 kph (without headwind), a linear increase in speed by 10 kph increments, produces only a comparatively moderate non-linear increase in the power requirement -- in increments separated by 32.3 KW to 38.46 KW:







Notice that I didn't bother doing the Total Power calculations for the first web calculator, at http://ecomodder.com/forum/tool-aero-rolling-resistance.php , because its results vary systematically in any case with the results produced by Iain's equations and the second web calculator. The results produced by the second web calculator -- when there is no headwind -- are so close to those produced by Iain's equations, that they do seem more reliable, and hence worth developing further.

Yes, there is still a non-linear increase in the Total Power requirement. But nothing like the non-linearity of the increase in the Per-Hour power requirement. Here is a more complete set of values of the Total Power requirement for 128.6 km generated using the second web-calculator, running from 50 kph to 120 kph -- again see http://buggies.builtforfun.co.uk/Calculator/analyse-metric.php :


Change in total power required for 50 kph versus 60 kph: 339.61 KW versus 358.09 KW, a change of 18.48 KW, and an increase of 5.44 % (travel time at 60 kph: 2.143 hours)

Change in total power required for 60 kph versus 70 kph: 358.09 KW versus 379.87 KW, a change of 21.78 KW, and an increase of 6.08 % (travel time at 70 kph: 1.837 hours)

Change in total power required for 70 kph versus 80 kph: 379.87 KW versus 405.22 KW, a change of 25.35 KW, and an increase of 6.67 % (travel time at 80 kph: 1.608 hours)

Change in total power required for 80 kph versus 90 kph: 405.22 KW versus 433.67 KW, a change of 28.45 KW, and an increase of 7.02 % (travel time at 90 kph: 1.429 hours)

Change in total power required for 90 kph versus 100 kph: 433.67 KW versus 465.5 KW, a change of 31.83 KW, and an increase of 7.33 % (travel time at 100 kph: 1.286 hours)

Change in total power required for 100 kph versus 110 kph: 465.5 KW versus 500.76 KW, a change of 35.26 KW, and an increase of 7.57 % (travel time at 110 kph: 1.169 hours)

Change in total power required for 110 kph versus 120 kph: 500.76 KW versus 539.44 KW, a change of 38.68 KW, and an increase of 7.77 % (travel time at 120 kph: 1.0717 hours)


Remember, to obtain the total power required, one takes the KW figure per hour, and then multiplies that by the travel time, a travel time that becomes progressively shorter. This progressively shorter travel time then in effect "cancels out" the strong non-linear effect that one would expect to see v[SUP]3 [/SUP]produce. One does see that strong non-linearity at the level of the per-hour KW consumption, but not at the level of the KW figure required for a fixed distance.

There is still a non-linear increase in the Total Power requirement, and driving faster does consume more energy per unit distance travelled. I calculated the percentage of increase, because a mere increase in the absolute value of the increment would not by itself necessarily suggest a non-linear increase. Rather, only an increase in the percentage reliably suggests as much. But the increase in the percentage is not quite as dramatic as one might think, and driving 100 kph does not consume double the amount of energy for a given unit of distance travelled as driving 50 kph. Instead, it only consumes about 37.5 % more energy.

Now strange as this may seem, the percentage changes in efficiency as one increases speed in 10 kph increments listed above, do seem to roughly correspond to empirical test data produced by a study of 74 vehicles. Although the TerraLiner is pure conjecture, and Iain's equations are at best just "approximations" or "abstractions" of reality, the results they produce for the extra power required to overcome air-resistance at higher speeds for a given unit of distance, do seem to correlate with real-world test data. The following two charts summarize the drop in efficiency as the test vehicles increased their speeds in 10 mph increments, from 50 to 60 mph, 60 to 70 mph, and 70 to 80 mph -- see http://www.greencarcongress.com/2013/01/thomas-20130117.html :







Instead of total Kwh for a fixed distance as per my table above, the measure of efficiency here is mpg, or "miles per gallon". As a measure of efficiency this pretty much amounts to the same thing, even though in an mpg metric the quantity of energy becomes fixed, and distance becomes the variable: mpg means the amount distance achieved (miles) using a fixed quantity of of energy (gallons). The increments are 10 mph instead of 10 kph. But when we divide both the percentage decrease in efficiency and the percentage speed increase in order to get something equivalent for kph, we get similar figures. A decrease in efficiency of 12.4 % for an increase of 10 mph between 50 and 60 mph, for instance, becomes a decrease of of 7.7 % for an increase of 10 kph. 50 mph is roughly 80 kph, and the drop-off in efficiency that Iain's equations suggest would take place between 80 kph and 90 kph is 7.02 %. Or a decrease in efficiency of 15.4 % for an increase of of 10 mph between 70 and 80 mph, becomes a decrease of 9.56 % for an increase of 10 kph.

80 mph is roughly 130 kph, and sure, a loss of efficiency of 9.56 % is more than a loss of 7.7 %. But what concerns me here is the overall pattern, and the character of the curve that gets produced. In this empirical study, between 50 mph and 80 mph fuel efficiency drops on average 13.9 % per increment, or roughly 42 % in total. (Yes, I know it's not quite as simple as that, but here I am only concerned with rough outlines.....). And between 80 kph and 130 kph (prorating for 120 kph), Iain's equations would suggest a loss of efficiency of roughly 38 % in total. In short, we are very much in the same ballpark.

Here again, if the loss in energy efficiency measured by this empirical test -- due to speeding up and air-resistance -- is somehow "exponential", then that exponential increase is still very subtle, and not dramatic at all. That's the general point that the overall reveals.


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22. The extra power required to overcome Air-Resistance at higher speeds for a given unit of distance:v[SUP]3[/SUP] or v[SUP]2[/SUP]??


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Put another way, if we are in fact on some kind of v[SUP]3 [/SUP]curve here, we are not yet on the part of v[SUP]3 [/SUP]curve where the slope of the curve has become so steep (closer to vertical), that doubling the speed would require at least doubling the power, for a given unit of distance......

Iain briefly mentioned that air-resistance is a cubic function, v[SUP]3[/SUP], a function that quickly becomes asymptotic. Put graphically, a cubic function looks like this:







So if, as speed increases, the curve for the Total Power required for a given unit of distance in order to overcome Air-Resistance were a cubic curve, then at 50 to 120 kph we are still very much at the beginning of any such v[SUP]3 [/SUP]curve. Perhaps at speeds above 500 kph or above 1000 kph the curve gets asymptotic; I haven't don't the calculations....:ylsmoke: . But between 50 and 120 kph, the curve for the Total Power required to overcome Air-Resistance for a given unit of distance is still fairly flat and closer to horizontal than vertical.

However, following the insight quoted above in post #2111, I think that when it comes to the energy required per unit of distance, we are actually finding ourselves on a squared, v[SUP]2[/SUP] curve, and not a cubic curve -- see http://www.truck-drivers-money-saving-tips.com/air-resistance.html :

"The power to overcome air resistance increases roughly with the cube of the speed, and thus the energy required per unit distance is roughly proportional to the square of speed."

And here too, we would only be at the beginning of a v[SUP]2 [/SUP]curve; either that, or we are on a v[SUP]2 [/SUP]curve that has been appropriately "broadened" by a coefficient:







I could be wrong about this. Unfortunately I have not taken a course in aerodynamics, which in hindsight would have been very useful!! This is getting fairly technical, and answers are not easily available on the web. So if anyone reading this truly, honestly has the necessary engineering background to explain what's going on here mathematically, in a clear, easy-to-understand way, please post!!

By "engineering background" I mean just that: at least a B.A. or an M.A. in transportation engineering specifically, with the necessary course or courses in aerodynamics under one's belt. The mere opinions of laypersons who've tried teaching themselves this stuff are interesting only up to a certain point. Even a structural or civil engineer might not have the requisite knowledge vis-a-vis this, specific area of expertise. Whereas a bona-fide professional transportation engineer could clarify the mathematical side of the question, for instance: v[SUP]2 [/SUP]or v[SUP]3[/SUP], for the curve describing the energy required per unit distance as one speeds up.... And no doubt such an engineer could offer many more insights, and genuine corrections.....:ylsmoke:

This may seem strange, but a course in aerodynamics is not necessarily included in the traditional education of a transportation designer. As a number of students at Art Center explain in the following video, before they took a course in which they were asked to constantly refine their car designs keeping aerodynamic flow model data in mind, they had not studied aerodynamics:






thjakits suggested that I need to work with an automotive engineer who understands such things well, and this is correct. But in addition I like to understand things for myself, which is why I did all the calculations on these pages. What I also need is a course in automotive aerodynamics, and specifically, a course that would include coverage of the comparative fuel-consumption characteristics for ICE vehicles versus hybrids, as Fair and Fslope increase. This will become even more clear in the next post. The "energy efficiency profile" of an electric vehicle is actually quite a bit different than an ICE vehicle, which kind of stands to reason, if you think about it.....


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23. The fuel economy curves of ICE vehicles, electric cars, and the TerraLiner


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For those who don't have the math to understand the kinds of questions that I am raising here, the following might provide some additional explanation.

It is commonly known that for many cars, the optimum speed is around 55 mph. Above 60 mph fuel economy begins to drop at an increasing, non-linear rate, because (it is said) the degree of air-resistance from drag increases in a non-linear, "exponential" manner -- see http://www.mpgforspeed.com , http://www.bridgestonetrucktires.co.../ra_special-edit_4/ra_special4_fuel-speed.asp , https://uk.answers.yahoo.com/question/index?qid=20111101082503AAgy9rE , http://message.snopes.com/showthread.php?t=73160 , http://www.greencarcongress.com/2013/01/thomas-20130117.html , and https://en.wikipedia.org/wiki/Fuel_economy_in_automobiles :

According to CNN, "Pushing air around actually takes up about 40% of a car's energy at highway speeds. Traveling faster makes the job even harder..." The increase is actually exponential, meaning wind resistance rises much more steeply between 70 and 80 mph than it does between 50 and 60.....

If the national speed limit were reset to 55, it would save 1 billion barrels of oil per year. The old national speed limit of 55 mph was created to address the energy crisis in the early 1970's - not safety purposes (although it did help safety).

Every vehicle is slightly different, but for most vehicles, fuel economy first increases with speed, until it plateaus somewhere between 40 - 55 mph, or 65 - 90 kph. And above that, it begins to decrease, because of increasing air-resistance, or so it is commonly said:








But surely fuel economy begins to decrease above 60 mph not just because of increasing air-resistance. ICE piston-driven motors tend to be optimized for 40 - 60 mph, which is also why that tends to be the "sweet spot" in terms of fuel economy. So irregardless of air-resistance, fuel economy is bound to drop off on either side of that sweet spot, simply because the engine is no longer operating in its optimal, preferred zone:

Engines are designed for specific speed, temperature, and rpm ranges. Driving out of these ranges goes against the fundamental design of the engine.

Again, see http://www.mpgforspeed.com .

In the case of a true serial hybrid like the TerraLiner, however, such "engine effects" on fuel economy won't be an issue, because the generators will always be running at their optimal speed, and the batteries will happily dole out whatever energy is required to the electric motors. There will still be an optimum "sweet spot" where the electric hub motors + their gearboxes operate at maximum efficiency relative to speed, and aerodynamic drag has not yet kicked in as a major issue. But who knows where that sweet-spot might be?

Based on the Tesla, we can guess that in all likelihood the TerraLiner's optimum fuel-efficient sweet spot might be something more like 15 - 20 mph, and not 55 mph. The relationship between fuel efficiency and the speed of the TerraLiner might be a curve that looks like this chart of the "Watt-hours-per-mile efficiency versus Speed" of a Tesla -- see http://physics.stackexchange.com/qu...ph-optimal-for-gas-mileage-of-a-passenger-car and https://www.teslamotors.com/blog/roadster-efficiency-and-range :







Here is the explanation

• aerodynamic losses increase with increasing speed to possibly the 3rd power
• tire losses are from rolling drag; tire air pressure has a lot to do with this
• drivetrain losses include the motor and gearbox type stuff
• ancillary losses include electrical loads like the AC and radio. If they are constant power demands, then the power per mile demanded will decrease inversely with speed.

Relative to total power consumption, at the very beginning of the curve drivetrain and ancillary losses are proportionately significant. But they decrease dramatically as a proportion of total power consumption once an electric vehicle is traveling around 20 mph.

This alone is an interesting datum, because it suggests that the TerraLiner should prove more energy-efficient at lower speeds than a comparable motorhome driven by a diesel piston-engine, simply because vehicles driven by electric motors are more efficient at lower speeds. Granted, contemporary diesel engines, even very high-powered ones in the 600 - 750 HP range, have been designed to still function well at power levels that are much lower than their maximum output, and also lower than their "optimal" sweet-spot in the 40 - 60 mph range. But it would be interesting to see how their "fuel economy curve" compares to a serial hybrid or "full" hybrid (i.e. not a parallel hybrid, and not a mild hybrid -- see https://en.wikipedia.org/wiki/Hybrid_vehicle_drivetrain#Full_hybrids , https://en.wikipedia.org/wiki/Hybrid_vehicle_drivetrain#Parallel_hybrid , https://en.wikipedia.org/wiki/Mild_hybrid ). I suspect that the "sweet spot" of maximal fuel economy for a full hybrid will still be much lower than any vehicle driven by a piston engine.

At the very least, the calculations for the total power requirements for various speeds that I undertook over the last 8 posts or so, most probably do increase in a fairly representative way. In actual practice the numbers as a set may be off, because the coefficient of rolling resistance or the coefficient of drag may be quite different; or because drivetrain inefficiency is different. But the overall "pattern", and the curve that would be created if we graphed the numbers, is probably quite close to what the TerraLiner's actual "Watt-hours-per-mile efficiency versus Speed" curve would look like. The TerraLiner's electric motors won't have an optimally efficient power output, so we don't have to take that into account as a variable when calculating the Total Power output required for a given speed. Whereas in ICE vehicles the zone where the engine achieves optimally efficient power output is a big factor in determining the fuel economy at a given speed, in addition to air-resistance (Fair), rolling resistance (Froll), and Fslope.

Now looking at the Tesla curve above, notice that while the watts required per mile do increase with speed, the increase seems much more like a v[SUP]2[/SUP] curve as opposed to a v[SUP]3 [/SUP]curve. Or consider the following graph of the drop in fuel economy of various cars as they drive faster than 50 mph -- see http://www.mpgforspeed.com :





In a number of cases, for instance the BMW 535d Touring, and the Mercedes C 180 K, the rate of drop in fuel economy actually decreases with increasing speed. Their fuel-economy curves actually "flatten out" at higher speeds!! If this were a v[SUP]3 [/SUP]function, we should not see anything like this.

Returning to the standard observation that fuel economy begins to plummet "dramatically" above 55 mph, I then suspect that the initial plummet from 55 mph to 70 or 80 mph might also be significantly compounded by the reduced operating efficiency of an ICE. Again, if an ICE were optimized for 55 or 60 mph, then its performance will be worse on either side of that, irregardless of increasing air-resistance. So factor in the performance drop-off of an ICE as it leaves its optimal zone + air-resistance, and the drop-off above 55 or 60 mph would prove initially dramatic.

But actually, if we look at typical fuel economy curves again, what I notice most is that the drop-off in gas mileage for many vehicles is much steeper as one lowers one's speed, as opposed to increasing one's speed. For a Subaru Outback, for instance, fuel economy drops off much more dramatically as one slows down from 50 mph to 30 mph, as opposed to speeding up from 50 mph to 70 mph -- see http://blog.automatic.com/cost-speeding-save-little-time-spend-lot-money/ :







Put simply, "engine effects" on fuel economy seem to matter much more in ICE vehicles than air-resistance.

In short, agreed, the increase in air-resistance due to speed will raise the TerraLiner's power requirement, for a given unit of distance. But not as dramatically as seems to be sometimes suggested or implied, especially on websites that advocate driving more slowly.....:ylsmoke: ...In the second graph immediately above where the green line represents the Toyota Prius, even though fuel efficiency seems to begin to plummet after 85 mph, the slope of the Prius' curve is still nothing near vertical, and at best approaches about 45 degrees. And the slopes of the curves of the other vehicles above 70 mph are much less dramatic than that.


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24. The best power figures for Velocity + Headwind


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As for the calculations we arrived at using that incorporate headwind, as already stated in post #2115 above, the figures we arrived at using the second web-calculator are more or less worthless. For instance, if the speed was 100 kph, and the headwind was 18 kph, I simply entered 118 kph into the second web-calculator. This produces what is no doubt an accurate figure for 118 kph without headwind. But it does not produce an accurate figure for 100 kph with 18 kph headwind, which is a different thing. And it's a different thing, because technically speaking our final multiplication of Ftotal by velocity should be a multiplication by ground-speed velocity, and not ground-speed velocity + wind-speed velocity. We should only multiply Ftotal by 100 kph, and not 118 kph. Otherwise, we are multiplying Froll and Fslope by the added extra 18 kph of wind velocity, and that does not seem mathematically nor mechanically correct.

This basic insight may seem confirmed by the fact that the first web calculator, which includes Froll and Fair, but not Fslope, produces results once Flsope is added in that are much closer to Iain's equations than the second web-calculator. The first web calculator produces results that are only about 15 - 17 KW more than Iain's equations, as opposed to the second web-calculator, which produces results that are 50 - 80 kW more. But this is not really confirmation at all, because the first web-calculator also has no way to distinguish between velocity without headwind, and velocity with headwind, as per Iain's equations. If anything it's a bit suspicious that the first web-calculator produces results that are systematically lower than Iain's equations when there is no headwind, which suggests that either Iain's equations are producing results that are too high, or the first web-calculator is producing results that are too low. The fact that the second web-calculator produces results which incorporate all three Force requirements, Froll and Fair, and Fslope, and that these results that are nearly identical to Iain's equations, inclines me to think that it's the more accurate or "sophisticated" web-calculator. So I'd be inclined to trust Iain's equations and the figures they produce more, when it comes to calculating a given velocity + a headwind.

Now let's return for a moment to the question of the ideal size for the first generator so that it functions well as a "fail safe" even in the most extreme circumstances, namely, a 3 % slope for 128.6 km, at 50 kph with an 18 kph headwind. Using Iain's equations, we determined that the power requirement would be 576.82 KW; using the first web-calculator, 618 KW; and the second web-calculator, 782.57 KW. See posts #2108 and #2109 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1973665#post1973665 and http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1973667#post1973667 . Again, the third figure is probably worthless as a value, and the figure produced by Iain's equation is most probably right. But let's just assume the second figure, to err on the side of caution.

The ideal "fail-safe", size for the first generator will depend, in part, on the size of the battery pack we deem necessary. And the size of the battery pack, in turn, will depend much more on camper-box considerations, not TerraLiner driving power requirements. Here the critical factor will be our estimate of the maximum electrical load the camper-box will draw, in the most environmentally demanding conditions, and for how long, without additional input from solar or wind power. And this, in turn, comes down to just how much Air-conditioining we think the TerraLiner will need, in order to cope with a certain specified maximum degree of environmental stress.

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A Brief Tangent on Air-Conditioning, & the Size of the TerraLiner's Battery Pack

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25. Some more thoughts regarding a 200 KW battery pack: all about Air-Conditioning, and Why it is Necessary


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As discussed in posts #2108 and #2109, there would probably be independent value in having a battery pack that's 200 KW instead of 100 KW, even though this would add about 1000 kg of weight to the TerraLiner, because this would allow generator-free glamping for at least 10 days even in circumstances where solar irradiation was poor, and wind was virtually nonexistent; that is to say, if the camper-box power consumption were 20 KW per day.

Based on my earlier discussions of the character of most equatorial climates (with the exception of Kenya/Tanzania), one place where this is very likely to occur is near the equator, in a band between 10 degrees north and 10 degrees south -- again see posts , at xxx . Here the TerraLiner's owners would also probably want to keep the air-conditioning running 24/7 at maximum power, so we can assume a "peak" camper-box power demand of at least 20 KW per day, and probably more than that. If the TerraLiner carried a 200 KW battery pack, then even in this climatologically demanding scenario the TerraLiner would not have to recharge the batteries using a generator for at least 10 days. In other words, the TerraLiner would enjoy at least 10 days of silent, generator-free glamping. Given that even the TerraLiner's smaller, primary generator would be comparatively large, at least 120 KW, and more like 200 KW; and given that it will not be merely the 20 KW model that Class-A motorhomes typically carry; then the TerraLiner's smaller, primary generator should be able to recharge the battery pack in just a few hours, or at most a day, even if these were Proterra's extended range batteries that charge more slowly.

But there are lots of basic assumptions here that need examining, not least of which is, "How many KW would the TerraLiner need to consume per day, in a hot equatorial climate, with the Air-Conditioners running full blast, 24/7?" And when not running the Air-Conditioiners, what should be a reasonable rough-ball-park guesstimate of the TerraLiner's stationary power consumption needs?

Note that earlier in the thread egn suggested that the average German household uses only about 4 KW per day per person, so 10 - 12 KW per day, he reasoned, should be sufficient for a TerraLiner occupied by 2 or 3 people -- see post #1299 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1756034#post1756034 . However, although I respect egn tremendously, and his contributions to this thread have proven invaluable, here in particular I think his suggestion is off. Not a little bit off, but rather, way, way off. No doubt the problem here is that egn is German, and so he will bring to bear German intuitions about what "normal" levels of power usage should be; intuitions that are radically different from North American, Scandinavian, or Australian intuitions.

Speaking from experience, Germans tend to be much more "energy conscious" and energy-frugal than Americans, Canadians, or Scandinavians -- see https://en.wikipedia.org/wiki/List_of_countries_by_energy_consumption_per_capita and http://shrinkthatfootprint.com/average-household-electricity-consumption :








As the above maps and charts make clear, Germans are not only much more frugal in terms of electricity consumption, but in terms of all forms of energy consumption. Germans also tend to think that Air-Conditioning is unnecessary, because they don't have much personal, direct, first-hand experience with really hot climates. Most of them haven't experienced the American South during the summertime, for instance.

The figure for the average daily consumption of an American household is very different from egn's figure. The figure commonly cites by the U.S. energy Information Administration is typically between 900 to 950 KW per residential household per month (depending on the year cited), which on average works out to about 30 - 32 KW per day, and not egn's 10 - 12 KW per day, and not even 20 KW per day -- see https://www.eia.gov/tools/faqs/faq.cfm?id=97&t=3 and http://understandsolar.com/calculating-kilowatt-hours-solar-panels-produce/. So here I would suggest that egn's German "intuitions" about energy usage should be considered completely unreliable, and not worth following. I am stating this very strongly in order to be crystal clear. But once again, it should also be emphasized that this is one of the few places in the thread where I am inclined to seriously question egn's reasoning......:sombrero:

Furthermore, in the United States energy usage was the highest in Louisiana, at 15,497 KW per household per annum, which works out to 42 KW per day!! Again, see https://www.eia.gov/tools/faqs/faq.cfm?id=97&t=3 , and also see https://www.pointclickswitch.com/household-energy-consumption/ , http://insideenergy.org/2014/05/22/using-energy-how-much-electricity-do-you-use-each-month/ , http://apps1.eere.energy.gov/states/residential.cfm/state=LA , http://instituteforenergyresearch.org/media/state-regs/pdf/Louisiana.pdf , https://wallethub.com/edu/most-least-energy-expensive-states/4833/ , and http://www.latimes.com/la-spendsave-story6-story.html . Louisiana is not alone. Electricity consumption specifically per household per annum is highest in the south-eastern United States, even though the overall energy bill per household (which includes heating oil or gas during the winter) is usually not the highest:







See http://www.huffingtonpost.com/2014/08/19/electricity-cost-by-state-map_n_5688500.html .

I could not find an on-line article that explains exactly why Louisiana uses so much electricity. But it's probably not because electricity is especially cheap in Louisiana. Electricity is actually a bit more expensive than the national average in Louisiana. Electricity is the most expensive in Hawaii, and least expensive in New Mexico. The average monthly energy bill also tends to be lower in southern, south-western, and Pacific-coast states because they have more moderate climates than northeastern states, and they do not have big winter heating bills for gas or oil -- see https://wallethub.com/edu/most-least-energy-expensive-states/4833/ . Lousiana ranks as number 10 from the bottom, in terms of lowest monthly energy bill.

(But granted, when it comes to the monthly energy bill expressed in dollars, as opposed to energy consumption expressed in KW or BTU, the biggest factor that explains the wide variations between Americans states is undoubtedly the price of natural gas, heating oil, and electricity, and not consumption levels per se -- see http://247wallst.com/special-report/2012/09/17/the-10-states-that-use-the-most-energy/ ).

In short, one can only presume that the reason why southern states like Lousiana use so much electricity, even though their overall energy bills per household tend to be at the lower end, is because they are not heating much with oil or gas in the winter; and they are using lots of electricity to run air-conditioners during the summer. This alone should then give one pause for thought, because Louisiana's 42 KW per day is averaged over an entire year. Louisiana's average KW per day figure for the summer months specifically is bound to be much more than that, when Louisiana's air-conditioners are running full blast.


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26. Temperature, the Heat Index, the Humidex, the Apparent Temperature, the DewPoint Temperature, and the WBGT


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Consider: because of humidity, New Orleans and Baton Rouge will sometimes experience "feels like" temperatures in August as high as 124 degrees F, or 51 degrees Celsius -- see http://www.nola.com/news/index.ssf/2015/08/louisiana_energy_use_heat_wave.html .

Remember that a humid heat feels fundamentally different than a dry, Sahara heat, and most people find a humid heat to be far more uncomfortable -- see http://www.alabamawise.org/hot-and-humid-can-feel-worse-than-death-valley-heat-record/ . This basic idea is captured by a cluster of related concepts: the "Heat Index", the "Humidex", the notion of "Apparent Temperature", and the less commonly known but much more empirical "Dew Point Temperature", "Wet Bulb Temperature" , and "Wet Bulb Globe Temperature" -- see https://en.wikipedia.org/wiki/Heat_index , http://thevane.gawker.com/this-is-why-the-heat-index-is-so-important-1609195413 , http://www.weather.com/news/weather/video/why-does-heat-index-matter , http://www.weather.com/tv/shows/wake-up-with-al/video/bodys-response-to-working-out-in-heat , https://en.wikipedia.org/wiki/Humidex , https://en.wikipedia.org/wiki/Apparent_temperature , https://en.wikipedia.org/wiki/Dew_point , http://www.weatherquestions.com/What_is_dewpoint_temperature.htm , http://www.weatherworksinc.com/humidity-vs-dewpoint , https://en.wikipedia.org/wiki/Wet-bulb_temperature , https://en.wikipedia.org/wiki/Wet-bulb_globe_temperature , http://web.science.unsw.edu.au/~stevensherwood/wetbulb.html , http://www.ccohs.ca/oshanswers/phys_agents/hot_cold.html , and http://www.bom.gov.au/info/thermal_stress/ .






Most people are by now familiar with charts which suggest that if the "official" temperature is 30 degrees Celsius, but the relative humidity is 85 %, then the temperature will actually "feel" more like 45 degrees Celsius. This combination is then usually reported as the "Heat Index" temperature, arrived at via various formulas whose results are available in chart form. Most charts combine temperature with relative humidity:








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During a heat wave, the "apparent" or "felt" temperature is typically much worse than the temperature as measured by a thermometer, because of humidity. So in the American South in particular, weather maps will often report the "Heat Index" temperature, as opposed to the "dry bulb" temperature, i.e. what we normally think of as air temperature -- see http://www.engineeringtoolbox.com/dry-wet-bulb-dew-point-air-d_682.html :







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27. Dew-Point Temperature


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Now some Heat Index charts combine temperature and dew-point, instead of relative humidity:







The dew-point temperature is always lower than the dry-bulb air temperature, because the dew-point temperature is the temperature at which air can no longer "hold" all of the water vapor that it contains. It's a common misconception that cold air can hold more water-vapor than hot air, because Europeans especially tend to associate cold with damp, and they associate heat with dry -- especially in Mediterranean countries where winters are cold and damp, and summers are hot and dry. But actually hot air has a much better capacity to hold water vapor than cold air. Put another way, the dew-point temperature is the temperature that a given body of air would have to drop down to, in order to reach 100 % relative humidity, becoming cold enough that it needs to "shed" its vapor as rain, dew, etc.

So if the dew-point temperature is very high, this means that the relative humidity is extremely high as well; and if it's not raining, that's only because the "dry bulb" air-temperature is yet higher still -- see http://www.weatherquestions.com/What_is_dewpoint_temperature.htm :







The moist, swampy conditions along the Mississippi valley, the lowland areas immediately adjacent the Gulf of Mexico, and northern Florida, generate lots of humidity that -- combined with very hot summer temperatures -- give rise to high dew-point temperatures. In effect the air retains moisture as vapor at a much higher temperature before releasing it as rain or dew, than elsewhere.

A high dew-point temperature, combined with a simultaneously high "dry bulb" air temperature, then yields a very high Heat Index temperature:







See http://us-climate.blogspot.it/2015/09/feels-like-temperature-range-2014-2015.html , http://www.wunderground.com/blog/weatherhistorian/record-dew-point-temperatures , http://weather2020.com/extreme-humidity-over-the-missouri-river-valley/ , and http://upandhumming.com/2014/06/humidity-dew-points-temperature-and-when-you-shouldnt-run/ .

Or at least I think that's how it works.....:sombrero:... I am not a meteorologist, and although I've studied chemistry, my grip on this stuff is very weak. But what I do know at an experiential level, is that the combination of high relative humidity and high temperatures that one experiences on mainland Florida during the summers, is completely unlike anything that most continental Europeans are familiar with.

Here are some videos that try to explain the difference between relative humidity and dew point, arranged by increasing order of technicality, which might provide further clarification:






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28. Wet-Bulb Temperature and Wet-Bulb Globe Temperature (WBGT)


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To complicate things even further, according to the following Australian website, the only really useful and truly "objective" metric here is something known as the Wet Bulb Temperature -- see http://web.science.unsw.edu.au/~stevensherwood/wetbulb.html :

....[condisider] a meteorological quantity called the wet-bulb temperature. You measure this quantity with a normal thermometer that has a damp cloth covering the bulb. It is always lower than the usual or "dry-bulb" temperature; how much lower depends on the humidity. At 100% humidity (in a cloud or fog) they match. In Sydney and Melbourne, even during the hottest weather, the wet-bulb usually peaks in the low 20's C. The highest values in the world are about 30-31C, during the worst heat/humidity events in India, the Amazon, and a few other very humid places. This map shows peak annual afternoon wet-bulb temperature attained in the present climate (this is a better-quality version of the figure in our PNAS paper):







Aside: It is surprising how often I hear people say "...it was 38C and 80% humidity," or something like that. So far these claims have invariably been incorrect---usually, the high temperature was in the afternoon while the high relative humidity was in the morning or evening. If they had coincided, the wet-bulb temperature would have been well over 30C, but I do not find any evidence of this and there are good reasons (explained in the paper) why the atmosphere would not let it happen....in today's climate at least. The warmer the tropical oceans become, however, the higher this "thermostat" will be reset.....

Heat stress is more conventionally measured by other quantities such as the "wet-bulb globe temperature" (WBGT), "Apparent temperature," "humidex," and so on. These are essentially empirical approximations of how a person would feel, that take the humidity and the temperature into account and "translate" them into a single, "feels like" temperature. None of these numbers has any theoretical basis or direct relation to heat-transfer laws, and they are only good approximations within a certain range of temperatures and humidities (often excluding the most extreme conditions).

The wet-bulb temperature is probably not a very good predictor of the "feels-like" temperature for most common conditions, which is why it is not used for this. However, it can be used to establish an absolute limit on metabolic heat transfer that is based on physical laws rather than the extrapolation of empirical approximations. That is why we focused on it instead of the usual measures.

As suggested by this quote, the Wet Bulb Temperature is different again from the Wet Bulb Globe Temperature, or WBGT, which is the metric most commonly used by militaries around the world to assess the potential heat stress and overall environmental risk of working in different places around the world. The WBGT is a more composite index, which combines temperature, humidity, wind speed (and/or wind chill), visible, and infrared radiation -- see https://en.wikipedia.org/wiki/Wet-bulb_globe_temperature and http://www.srh.noaa.gov/tsa/?n=wbgt :






But even still, the map immediately above does a very nice job demonstrating visually and graphically the idea that Germany and western Europe in general hardly ever experience the same combination of humidity + heat as the southern United States, Central and South America, equatorial Africa, and South and Southeast Asia. Those who grow up in the continental Europe, the Pacific northwest, or New Zealand certainly know what a cool humid climate feels like. But they have no idea what a truly hot-humid climate feels like. Or how dangerous it can become.


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29. TerraLiner Air-Conditioning is a Health & Safety Issue


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The following is the very best article available on the web that explains in simple, clear, lay-person's terms why high humidity + intense heat can become very dangerous, much more dangerous than mere heat -- see http://www.nytimes.com/2015/06/07/opinion/sunday/the-deadly-combination-of-heat-and-humidity.html and http://beforeitsnews.com/environmen...combination-of-heat-and-humidity-2530890.html :

SundayReview | OPINION

The Deadly Combination of Heat and Humidity

By ROBERT KOPP, JONATHAN BUZAN and MATTHEW HUBERJUNE 6, 2015



image


The most deadly weather-related disasters aren't necessarily caused by floods, droughts or hurricanes. They can be caused by heat waves, like the sweltering blanket that's taken over 2,500 lives in India in recent weeks. Temperatures broke 118 degrees in parts of the country. The death toll is still being tallied, and many heat-related deaths will be recognized only after the fact. Yet it's already the deadliest heat wave to hit India since at least 1998 and, by some accounts, the fourth- or fifth-deadliest worldwide since 1900.

These heat waves will only become more common as the planet continues to warm. They don't just affect tropical, developing countries; they're a threat throughout the world. The July 1995 heat wave in the Midwest caused over 700 deaths in Chicago. The August 2003 heat wave in western Europe led to about 45,000 deaths. The July-August 2010 heat wave in western Russia killed about 54,000 people.

But as anyone who's spent a summer in the eastern United States knows, it's not just the heat; it's also the humidity. Together, they can be lethal, even if the heat doesn't seem quite so extreme.

Scientists measure the combination using a metric known as wet-bulb temperature. It's called that because it can be measured with a thermometer wrapped in a wet cloth, distinguishing it from the commonly reported dry-bulb temperature, measured in open air. Wet-bulb temperature can also be calculated from relative humidity, surface pressure and air temperature.

It's essentially a measure of how well you can cool your skin by sweating, which is how humans stay alive in the worst heat. But high humidity can defeat that cooling system; it makes the heat that much more dangerous.

The wet-bulb temperature is not typically reported. While dangerous levels depend on a person's activity level and clothing, wet-bulb temperature offers a stark measure of risk in a warming world that will experience more extreme combinations of both heat and humidity.

Temperature and wet-bulb temperature are not in a one-to-one relationship; both higher temperatures and higher humidities increase wet-bulb temperature. For instance, during the Chicago heat wave, on July 13, 1995, the maximum wet-bulb temperature of 85 degrees occurred at noon when the temperature was 99 degrees. But when it hit 106 degrees at 5 p.m., the wet-bulb temperature was 83 degrees. The former was more dangerous.

A human's core temperature is about 98.6 degrees, but the skin temperature of the trunk is about 4 to 9 degrees colder, depending on how warm it is and how active a person is. But sweating, which helps keep the core body temperature constant, becomes increasingly ineffective in increasingly humid air, and it can never cool the skin to below the wet-bulb temperature. A person who is physically active at a wet-bulb temperature of 80 degrees will have trouble maintaining a constant core temperature and risks overheating. A sedentary person who is naked and in the shade will run into the same problem at a wet-bulb temperature of 92 degrees. A wet-bulb temperature of 95 degrees is lethal after about six hours. In the Indian state of Andhra Pradesh, the highest wet-bulb temperatures of the latest heat wave have peaked around 86 degrees — levels approaching the worst of the 1995 Midwest heat wave, which set records in the United States for humid heat.

Heat waves are the natural disasters easiest to tie to climate change. Statistical analyses and climate modeling indicate that the 2010 Russian heat wave was about five times more likely to have occurred in 2010 than it would have been in the cooler 1960s. An analysis conducted after the 2003 European heat wave concluded that it was twice as likely as it would have been before the Industrial Revolution. A recent study in the journal Nature Climate Change found that the 1.5 degrees of global warming since the start of the Industrial Revolution had quadrupled the probability of moderate heat extremes.

In work one of us (Robert Kopp) led for the Risky Business Project, we found that over the period from 1981 to 2010, the average American experienced about four dangerously humid days, with wet-bulb temperatures exceeding 80 degrees. By 2030, that level is expected to more than double, to about 10 days per summer. Manhattanites are expected to experience nearly seven uncomfortably muggy weeks in a typical summer, with wet-bulb temperatures exceeding 74 degrees, about as many as residents of Washington have experienced recently.

That increase over the next couple of decades is locked in by the greenhouse gases we've already emitted and by our current energy system. Since we can't avoid it now, we must make our communities more resilient to heat and humidity extremes. One step is to expand access to air-conditioning for those who can't afford it. We must also improve cooling in stiflingly hot factories and warehouses, strengthen public health systems, improve public warnings when heat and humidity are dangerously high, and be willing to shift outdoor work schedules.

Of course, air-conditioning poses its own problems. Air-conditioners use a lot of electricity, and generating it with our current power system along with the leakage of coolants from these machines will add to the heat-trapping gases in the atmosphere.

Still, as a society, we can influence the weather of the future by the decisions we make today. If we choose not to reduce emissions of heat-trapping gases and instead continue to rely upon fossil fuels, the average American could expect to see about 17 dangerously humid days in a typical summer in 2050 and about 35 in 2090. Some summers would have days so stiflingly muggy that a healthy individual would suffer heat stroke in less than an hour of moderate, shaded activity outside. And carrying on this way through the 22nd century locks in a trajectory where summer outdoor conditions could become physiologically intolerable for humans and livestock in the eastern United States — and in regions currently home to more than half the planet's population.

But this fate is not yet locked in. Moderate reductions in emissions of heat-trapping gases — sufficient to stop global emissions growth by 2040 and bring emissions down to half their current levels by the 2070s — can avoid those paralyzing extremes and limit the expected late-century experience of the average American to about 18 dangerously humid days a year. And strong reductions — bringing global emissions to zero by the 2080s — can cap the growth of humidity extremes by the midcentury.

Climate change is increasing the risks to our health, our economy and our environment. Communities need to prepare. But as world leaders get ready for the United Nations climate change conference in Paris this December, it's also important to recognize that shifting to carbon-free energy will reduce the risks we will face from extreme heat and humidity. As India's tragic heat wave shows, these risks cannot be ignored.



Robert Kopp is associate director of the Rutgers Energy Institute. Matthew Huber is a professor of earth science at the University of New Hampshire, where Jonathan Buzan is a Ph.D. candidate.

For more about the 2015 Indian Heat-Wave, see https://www.washingtonpost.com/news.../06/10/indias-hellish-heat-wave-in-hindsight/ , http://uk.reuters.com/article/uk-india-heatwave-idUKKBN0OD0AJ20150528 , http://www.slate.com/blogs/future_t...extreme_temperatures_in_new_delhi_mumbai.html , http://www.pbs.org/newshour/rundown/photos-indias-heat-wave/ , http://www.theguardian.com/world/2015/may/25/india-heatwave-deaths-heatstroke-temperatures , http://edition.cnn.com/2015/05/25/asia/india-heatwave-deaths/ , http://www.weather.com/safety/heat/news/pakistan-heat-wave-latest-news , and https://en.wikipedia.org/wiki/2015_Indian_heat_wave . And here are some videos:



[video=youtube;QC-GAGUIEOQ]https://www.youtube.com/watch?v=QC-GAGUIEOQ [/video] [video=youtube;dTl24-iwhmI]https://www.youtube.com/watch?v=dTl24-iwhmI [/video]



Note that one of the main reasons why so many elderly Europeans died in the summer 2003 heat wave, is precisely because like egn, many Europeans tend to think of Air-Conditioning as a luxury that they can do without, and that is not really "necessary".

In Paris, most of the dead were elderly women who were living alone in the top floor walk-up apartments (i.e. the the cheapest ones), apartments that had no A/C, were located directly under a scorching roof, and were poorly ventilated -- see http://www.livescience.com/22050-heat-waves-high-death-tolls.html , https://www.newscientist.com/article/dn4259-european-heatwave-caused-35000-deaths/ , http://www.earth-policy.org/plan_b_updates/2006/update56 , http://www.metoffice.gov.uk/learning/learn-about-the-weather/weather-phenomena/case-studies/heatwave , and https://en.wikipedia.org/wiki/2003_European_heat_wave . Heat-waves are the "silent killers", far more devastating in terms of loss of life than tornadoes and hurricanes. But the damage caused by heat-waves is largely unnoticeable, and the human toll tends to become clear only months later, after statisticians crunch their numbers. 2003 was unusual, because in France the bodies of elderly people were piling up so fast that mortuaries ran out of room, and special warehouses and refrigeration vans had to be commandeered.

So there is in fact a "health and safety" dimension to Air-Conditioning the TerraLiner, especially given its target-demographic: Active Elderly People. Even if they are in good shape, older people in general are more susceptible to heat stroke than younger people, because after 65 their nervous systems begin to deteriorate -- see http://www.mayoclinic.org/diseases-conditions/heat-stroke/basics/risk-factors/con-20032814 and http://emergency.cdc.gov/disasters/extremeheat/faq.asp .


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30. The Wet Bulb Globe Temperature, and Heat Stress Risk


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The only other web-resource that I could find which illustrates the WBGT graphically, is a brief paper that shows how merely a 3 degree increase in average temperature over and above the benchmark year 2000, will be enough to turn highly populated areas like India's Ganges valley into "extreme risk" zones for occupational heat stress -- see http://www.globalhealthaction.net/index.php/gha/rt/printerFriendly/5715/6500 :







It's interesting that in 2000, northern India during the summer is a much "riskier" sort of place, in terms of the WBGT, than southern Africa during its summer, which takes place Dec/Jan/Feb:







And it's interesting to learn that the wettest parts of northern Australia, as well most of the southern United States from Florida through to Texas, and also southern New Mexico/Arizona/Nevada, are much "riskier" in terms of the WBGT during the summer, than southern Africa:







Southern Africa becomes a bit yellowish during the summer humid rainy season, but there is no broad swathe of light orange as per the southern United States, nor patches of dark orange "high risk" as per southern Texas, the Arizona desert, or the Yucatan peninsula in Mexico. It's interesting that according to these maps, in the summer months the Sonoran desert in Arizona and northern Mexico is much more dangerous than the Namib desert in southern Africa, because the Sonoran combines summer temperature and humidity in a way that yields a much higher WBGT.


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31. Some thoughts on Germans and Air-Conditioning


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But again, perhaps the most important point to be made here is that those who grow up in more temperate climates like western Europe, south-eastern Australia, Tasmania, or the Pacific northwest, really have no idea what superhot+humid actually feels like, unless they have travelled a bit, and have actually experienced it for themselves. And again, on my own view most Germans fall into this boat, because most have not spent summers in the American South, let alone have they visited very hot and wet countries located in the band that lies between 10 degrees north and south of the equator -- countries like Ecuador, Colombia, Venezuela, Guyana, Suriname, French Guiana, Cameroon, Gabon, Indonesia, Malaysia, Brunei, or the Philippines.

Yes, I know that many Germans think they know what a very humid and hot climate feels like, because they tend to think that German summers are hot and humid, in contrast to the dry-hot summers of Mediterranean countries like Italy. They may feel even more convinced after this last summer, which saw record-breaking temperatures throughout Europe, in Germany in particular -- see http://www.foxnews.com/world/2015/0...-service-measures-record-temperature-403.html , http://www.slate.com/blogs/the_slat...nd_london_england_approach_all_time_high.html , http://www.usatoday.com/story/news/world/2015/07/06/germany-record-temparature/29757041/ , http://www.weather.com/news/climate/news/europe-heat-wave-poland-germany-czech-august-2015 , https://www.washingtonpost.com/news...st-temperature-record-during-europe-heatwave/ , http://www.cbc.ca/news/technology/july-2015-was-the-hottest-month-on-modern-record-1.3197748 , and http://www.usatoday.com/story/weather/2015/08/20/july-record-warm/32045131/ .

But even a dry-bulb air-temperature of 105 degrees Fahrenheit really says nothing, unless we know what the Heat Index was. And unfortunately I could not find any articles on the web suggesting that the the Heat Index in Germany this summer topped 110 degrees Fahrenheit, let alone 120. Instead, German newspapers only reported record dry-bulb temperatures -- for instance, see http://www.spiegel.de/panorama/kitzingen-hitzerekord-in-deutschland-mit-40-3-grad-a-1042198.html , http://www.faz.net/aktuell/gesellschaft/40-3-grad-hitzerekord-in-deutschland-gebrochen-13686987.html , http://www.badische-zeitung.de/deut...hmal-hitzerekord-in-kitzingen--109371734.html , http://www.sueddeutsche.de/panorama/hitzerekord-in-deutschland-kitzingen-schwitzt-bei-grad-1.2552656 , http://www.tirschenreuth-wetter.de/index.php/wetterrekorde/deutschland-weltweit , http://www.abendzeitung-muenchen.de...and.29349bef-e4c4-4119-916a-4714fe75d424.html , and https://de.wikipedia.org/wiki/Hitzewellen_in_Europa_2015 . My general sense is that Germans are relatively unfamiliar with the whole concept of the Heat Index ("HitzeIndex"), and one can find only a few webpages dedicated to the topic -- see http://wetterkanal.kachelmannwetter.com/was-ist-der-hitze-index/ , http://v1.wetter.tv/de/wetterblog/2015/08/28/temperatur-vs-gefuehlte-temperatur-4649 , and http://www.wetter24.de/news/detail/2014-07-29-gefuehlt-wie-in-den-tropen/ .

Many Germans then reason that if they can handle their "hot and humid" German summers without Air-Conditioining, they should be able to handle just about anything. So quite honestly, the very last person on earth I would take advice from about Air-Conditioning, is a German.....!!!:sombrero: ...

egn, if you are reading this, and if you have never experienced summer heat + summer humidity of the kind that occurs on mainland Florida, in Louisiana or Alabama, or in equatorial countries like Ecuador, Colombia, Venezuela, Malaysia, etc., then you really have no idea what such heat is like, and how uncomfortable it is. If you have never personally experienced a super-humid climate with a Heat-Index temperature of 105 -110 degrees Fahrenheit, let alone 115 or 120, then you really will not be able to understand why the advent of Air-Conditioining in the United States in the 1950's completely revolutionized living conditions in Dixie, and made possible the post-war "Sun-Belt" economy, and the shift in the U.S. population southwards and westwards.
Once you do experience such an intense combination of heat and humidity for the first time, you may find yourself reconsidering Air-Conditioning for Blue Thunder after all, if you ever intend to travel through such countries in the summer....:coffeedrink: ...

On the other hand, if you have already experienced such intense hot+humid summer heat, and if you still decided that Blue Thunder should not need Air-Conditioning when traveling through such countries in the summer, then my hat goes off to you! :bowdown: ...You are a better man than me, gunga din. I only enjoyed the summers that I spent in the Florida Keys, for instance, precisely because as I wrote in post #1985, summers on Duck Key were relatively dry and humidity-free, in marked contrast to the hot, muggy, super-humid weather up in Miami -- see http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1964734#post1964734 .

Incidentally, this is yet another reason why I would suggest that argument, evidence, images, maps, and weblinks are so important in a thread like this one. Perhaps one needs some degree of training as a scientist, a philosopher, or world traveller -- or all three -- in order to realize just how particular, provincial, and parochial one's individual "life experiences" tend to be. When designing a globally capable motorhome -- a motorhome suitable for all climates and circumstances -- it is absolutely imperative that one not fall into the trap of naively extrapolating from one's own limited, non-universal, rather quaint and narrow "personal experience." The only way to do that is to get empirical, quantitative, graphical, and evidentially objective. It just stands to reason that Germany would not have a climate that is even remotely "representative" or "normal" relative to the rest of the world. Indeed, given that Germany is not a very big country, and that Germany has only a rather narrow range of climate types, a continent-sized country like the United States (which includes Alaska, Hawaii, Puerto Rico, the U.S. Virgin Islands, etc.) is bound to provide a more "representative" sample of climates, one that might better approximate the range of climactic possibilities around the world.

But even the United States will not be and cannot be completely representative of the rest of the world. The continental United States does not have high-altitude plateaus comparable to Tibet or the Altiplano; nor does the United States have year-round high humidity + high heat comparable to equatorial countries; nor does it have winter cold comparable to the Canadian prairie provinces, the Yukon, the Northwest Territories, and Siberia; nor does it have desert heat and dryness comparable to the central Sahara; nor does the United States have a monsoon climate comparable to South and Southeast Asia.

Only the world is the world. Hence, only a rather sophisticated understanding of the full range of climate possibilities, as captured by the Köppen climate classification, will prove sufficient as a basis for TerraLiner design.


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32. Why the Heat Index matters most for Air-Conditioners


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So in a nutshell, the TerraLiner will have Air-Conditioning, and plenty of it!! And it will have the kind of Air-Conditioining that allows it to cope well with "Heat Index" temperatures as high as 125 degrees Fahrenheit, or 51.6 degrees Celsius.

Here I am citing a Heat Index temperature, and not a dry-bulb temperature, because both relative humidity as well as temperature will affect Air-conditioner performance. Air-conditioners remove both heat and moisture from the air, and so when the air is packed with both -- as the air tends to be in the American South during the summer -- many Air-Conditioners that theoretically "should" be able to work at a given temperature in the abstract (i.e. a given dry-bulb temperature), simply cannot cope. This is why Air-Conditioners are often combined with de-humidifiers in the American South, with the latter doing the work of reducing humidity specifically. It may even be possible to combine the TerraLiner's Air-Conditioiners with its AWGs, so that the latter function as dehumidifiers....?

Again, all of this is beyond my level of competence. Yes, I know that mechanically speaking Air-Conditioners and De-Humidifiers are the same thing, and yet different; and that some of the better Air-Conditioiners can operate in "only-dehumidify" mode. But I also know that humidity is such a big problem in the southern United States, that many homes have AC systems installed with dehumidifiers providing additional "backup" during the summer months. Only a combination of the two seems to work -- see http://airconditioningdfw.com/blogs/does-air-conditioning-dehumidify/ , http://byrdheatingandair.com/articles/how-does-humidity-affect-air-conditioning-and-heating , http://www.differencebetween.net/object/difference-between-air-conditioner-and-dehumidifier/ , http://www.greenbuildingadvisor.com...ce-between-air-conditioners-and-dehumidifiers , http://www.breathingspace.co.uk/blog/2014/06/03/do-i-need-a-dehumidifier-or-air-conditioner/ , http://airconco.com/news/air-conditioner-and-dehumidifier-41.html , http://www.comfort-pro.com/2015/03/do-air-conditioners-dehumidify/ , http://www.comfort-pro.com/2015/03/do-air-conditioners-dehumidify/ , http://diy.stackexchange.com/questions/66669/does-running-a-dehumidifier-with-an-ac-unit-save-money , and https://en.wikipedia.org/wiki/Dehumidifier .

So the central point here is simply that whatever system gets finally installed in the TerraLiner, it has to be good enough to handle a Heat Index of 125 degrees Fahrenheit, or 51.6 degrees Celsius.

This may seem alarmist, but consider: just recently a city located in Iran near the Persian Gulf had a record 165 degree Heat Index temperature -- see https://www.washingtonpost.com/news...-heat-index-of-154-degrees-near-world-record/ , http://www.msnbc.com/msnbc/heat-index-just-hit-165-degrees-iran , http://www.telegraph.co.uk/travel/d...eriences-second-hottest-temperature-ever.html , http://www.weather.com/news/news/iraq-iran-heat-middle-east-125-degrees , http://www.israelnationalnews.com/News/News.aspx/198954#.VnckOnmuD6k , http://www.dailymail.co.uk/news/art...perature-hits-165F-heat-dome-Middle-East.html , http://www.currentresults.com/Weather-Extremes/hottest-cities-in-the-world.php , and http://www.usatoday.com/story/weather/2015/07/31/heat-index-iran-163-degrees/30933451/ :



[video=youtube;W53KFoK6MMg]https://www.youtube.com/watch?v=W53KFoK6MMg [/video]



The water temperature in the Gulf was in the 90's, pouring humidity into the air, raising the dew-point temperature to 90 degrees Fahrenheit. That, combined with air-temperatures around 113 - 114 degrees Fahrenheit, yielded a Heat Index temperature of 165 degrees Fahrenheit.

The whole surrounding Gulf region seems to be like this, with the Heat Index in Dubai, Abu Dhabi, Doha, etc. regularly topping 120 during the summer months, because of extreme desert heat combined with proximity to ocean humidity generated by the shallow, easily heated waters of the Gulf -- see http://www.wunderground.com/blog/weatherhistorian/record-dew-point-temperatures , http://www.nytimes.com/2015/10/27/s...ddle-east-by-the-end-of-the-century.html?_r=0 , https://www.washingtonpost.com/news...temperatures-to-lethal-extremes-report-warns/ , http://www.smithsonianmag.com/ist/?...-expected-persian-gulf-end-century-180957039/ , http://www.usatoday.com/story/weath...-gulf-climate-change-global-warming/74625754/ , http://edition.cnn.com/2015/10/27/world/persian-gulf-heat-climate-change/ , and http://news.mit.edu/2015/study-persian-gulf-deadly-heat-1026 :



[video=youtube;ZMvtS63au9g]https://www.youtube.com/watch?v=ZMvtS63au9g [/video]



My sense is that in the United States the Heat Index only occasionally rises above 120 Fahrenheit, or 49 degrees Celsius. Even very hot American cities like Phoenix and Yuman, Arizona, have average Heat Indexes during the summer months in the upper 90's, or 35 to 38 degrees Celsius -- see http://www.bestplaces.net/blog/?p=1340 , http://www.bertsperling.com/2013/07/02/sizzling-cities-ranked-our-new-heat-index/ , and http://www.currentresults.com/Weather/US/hot-humid-days-cities.php . On the other hand, the Heat Index in Louisiana, Arkansas, and Oklahoma can hover between 110 to 120 degrees Fahrenheit for many weeks during the summer, and highs up to 124 degrees Fahrenheit are possible -- see http://www.weather.com/forecast/regional/news/heat-wave-dallas-texas-louisiana-south , http://www.nola.com/weather/index.ssf/2015/08/cooler_temps_prompt_only_heat.html , http://whnt.com/2015/08/08/heat-ind...es-in-parts-of-the-deep-south-through-monday/ , and http://www.nola.com/weather/index.ssf/2015/08/heat_index_could_reach_124_as.html . So too in Darwin Australia, located in the Northern Territories, because of the humidity the Heat Index often rises above 113 degrees Fahrenheit, or 45 degrees Celsius -- see https://en.wikipedia.org/wiki/Darwin,_Northern_Territory .

Outside the developed world, during India's heatwave this past summer some regions had "felt-like" Heat Index temperatures that exceeded 140 degrees Fahrenheit -- see http://www.pbs.org/newshour/rundown/photos-indias-heat-wave/ , https://www.washingtonpost.com/news.../06/10/indias-hellish-heat-wave-in-hindsight/ , and http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=3000 . And this April, weather stations in and around Bangkok recorded dry-bulb temperatures in the 38 - 41 degree Celsius range, or 100 to 106 Fahreheit -- see http://www.bangkokpost.com/learning/easy/535791/ . Although humidity was highest in the morning at 90 %, presumably later in the day when it was hottest the humidity was not that much better. So if the Heat Index Conversion tables posted above are anything to go by, the Heat Index in Bangkok this past April could well have peaked somewhere in the 130 to 150 range.

So I figure that citing a Heat-Index "maximum" target of 125 degrees Fahrenheit or 51.6 degrees Celsius for the TerraLiner's Air-Conditioining system, seems about right.



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33. Another useful indicator of possible TerraLiner camper power needs in a hot+humid climate: Singapore


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I have focused on America's southern states, because they suggest most strongly what the preferred air-conditioning usage and energy consumption habits of wealthy citizens of the First-World will be, when faced with really high levels of combined heat and humidity. But an even more relevant benchmark might be Singapore, an economically rich First-World society located just 1° 21' N north of the equator, with a humid tropical climate that almost never has less than 70 percent relative humidity, and on average in all months has relative humidity above 80 % -- see https://en.wikipedia.org/wiki/Singapore .

Singapore's technocratic government produces a wealth of statistics, and provides a superb chart of average electricity consumption per month broken down by dwelling type at http://www.singaporepower.com.sg/ir...0d-2f10-81a5-beb38060addd?spstab=Our Services :







Also see https://www.ema.gov.sg/cmsmedia/Publications_and_Statistics/Statistics/MSA23.pdf , https://www.ema.gov.sg/cmsmedia/Publications_and_Statistics/Statistics/MSA22.pdf , https://www.ema.gov.sg/cmsmedia/Publications_and_Statistics/Statistics/MSA21.pdf , https://www.ema.gov.sg/cmsmedia/Publications_and_Statistics/Statistics/MSA5.pdf , https://www.ema.gov.sg/Statistics.aspx , https://www.ema.gov.sg/cmsmedia/Pub...cs/Publications/SES2015_Final_website_2mb.pdf , http://www.singstat.gov.sg/statistics/browse-by-theme/utilities , and http://www.lowcarbonsg.com/tag/electricity-consumption/ .

"HDB" is Singapore's government-subsidized public housing (80 % of Singaporeans live in such housing), whereas the last four categories are private housing -- see https://www.singstat.gov.sg/docs/de...ndards/standards_and_classifications/sctd.pdf and https://www.99.co/blog/singapore/a-general-guide-to-types-of-housing-in-singapore/ . The TerraLiner will be a particularly large sort of motorhome, in terms of square-meterage, somewhere between an HBD 2-bedroom and 3-bedroom apartment, or 45 - 60 square meters, once we take into account the expanded floor area and volume provided by the TerraLiner's slide-outs and the pop-up. But I wonder how many of these government-provided public-housing apartments are actually air-conditioned, and to what extent their average energy-use bill per month reflects this? From various websites I get the impression that the older and smaller HBD flats are very basic, and are not air-conditioned -- see http://www.expatsingapore.com/content/view/1178 and http://www.hdb.gov.sg/cs/infoweb/re...ssional-help-and-contractors/air-conditioners. So it's quite possible that the more indicative figures in this table are the monthly energy consumption figures for "apartments", "terrace", and/or "semi-detached" houses. And here it's worth remembering that 20 KW per day is 600 KW per month, or the typical energy consumption figure for a Singaporean apartment.

In short, for a motorhome the size of the TerraLiner, 20 KW per day when the air-conditioners are running full blast in a tropical-equatorial climate, is at best a "moderate" estimate. It should not be considered "excessive", or "over the top", and may in fact be much too low for the high-energy consumption context of an equatorial country, especially one whose heat-index might be peaking as per Thailand this last April. If 20 KW proves too low, and something more like 30 KW per day were required (again, equivalent to 900 KW per month), then a 200 KW battery pack would still last almost 7 days, before it needed recharging. Whereas a 100 KW battery pack would last just just bit more than 3 days.

On my own view, a central operational "ideal" for the TerraLiner should be not needing to run the generators to recharge the batteries more than 1 day for every 7 days, or one day for every week of completely silent battery-fed glamping, with all camper-box systems fully functional (including water-making), even given the complete absence of any available solar or wind power. A 200 KW battery pack seems like it might be able to guarantee this operational objective, whereas a 100 KW battery pack most definitely could not. But only might. As we think things through, we'll see that even 30 KW per day may be too low.

Note that in general, equatorial climates like Singapore's that are hot-and-humid all year round do not seem to achieve Heat Indexes as high as the American South, the Persian Gulf, or the monsoon climate of India. For instance, according to one website Singapore's record Heat Index temperature is 41.3 degrees Celsisus, or about 106 degrees Fahrenheit -- see http://www.singaporeweather.info/record.htm . In 2013 Rio de Janeiro briefly experienced a record Heat Index temperature of 122 degrees Fahrenheit, but that seems like a bit of an anomaly -- see http://www.weather.com/science/environment/news/2013-6th-hottest-year-record-wmo-20140207 . So I suspect that most genuinely "tropical", equatorial, non-monsoon climates located within 10 degrees of the equator will have Heat Indexes hovering between 100 to 110 degrees Fahrenheit during their hottest periods.

A Heat Index of 106 degrees will still be very uncomfortable; I merely wanted to signal that I realize that a Heat Index maximum "target" figure of 125 degrees Fahrenheit should be imagined as an outlier, "maximum" case.


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34. One Possible Vehicular Precededent


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The above are all very rough-and-ready, extremely "ball-park" sorts of estimates. Clearly, only a detailed analysis of the TerraLiner's internal volume, the thermal properties of its insulating envelope, the types of Air-Conditioners and De-Humidifiers available, their power needs when run full blast, and so on, would provide a final, reliable KW consumption figure.

However, there is one possible precedent in the world of expedition motorhomes: the 8x8 UniCat created specifically for challenging desert conditions on the Arabian peninsula -- see http://www.unicat.net/en/info/MXXL24AH-MAN8x8-sh.php , http://www.unicat.net/en/pics/MXXL24AH-MAN8x8-sh-2.php , http://www.unicat.net/pdf/UNICAT-MXXL24AH-MAN8x8-en-es.pdf , and http://www.unicat.net/pdf/MXXL24AH-MAN8x8-sh-en.pdf . It too is about 12 m long, although the internal volume of the TerraLiner will be much larger, because the TerraLiner will have more slide-outs and a pop-up. The UniCat's solar capacity is a mere 440 Watts, and its generator is a Fischer-Panda that produces 18.4 KW.

So it's interesting to learn that it has no less than 9 (yes, nine!) Air-Conditioners, that have a combined power rating of 29 KW, or 100,000 BTU. This motorhome seems deliberately designed for the extreme climatological conditions of the Persian Gulf, where as we've seen the Heat Index is guaranteed to top 100 during the summer months, sometimes venturing into 130 territory.










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Parenthetical Note. Just for the record, and just in case anyone gets the wrong idea: no, I am absolutely not holding up this 8x8 UniCat as a paragon of good expedition motorhome design. The design is completely unintegrated; the camper box is pure rectilinear FRP composite sandwich panel construction, which would seem to dictate a "Haute IKEA", ultra-rectlinear, rather utilitarian-looking interior design; and the interior is a far cry from a Concorde, a Hymer, or the curvilinear elegance of ARC (American Retro Caravan), or a Christopher C. Deam Airstream. It's simply not my personal taste in interior design at all. But even still this vehicle is interesting because it carries 1000 liters of water, and because its nine Air-Conditioners combined have an output of 100,000 BTU, or 29 KW.

Given that its Fischer-Panda generator produces 10.6 KW less than the output of the Air-conditioners, the assumption seems to be that when the Air-Conditioners operate at full-tilt, this UniCAt will be hooked up to shore power. But this is not an assumption that we would want to make with the TerraLiner. Remember, the figure of 29 KW for the generators is 29 KW per hour, not per day!! At that rate of consumption, even the energy available in a 200 KW battery bank would deplete in a little less than 7 hours.

In short, this UniCat vehicle provides another interesting "benchmark" reference point, another real-world "reality check", one that suggests that estimating a daily power consumption below 20 KW for hot climates in the Third World, or even the southern United States, is most probably very unrealistic. This UniCat suggests that a truly globally-capable, 12 m, Class-A sized TerraLiner equipped with enough Air-Conditioning to handle the high Heat Indexes (100 to 120) found in genuinely hot-humid climates, will have a daily power consumption of at least 30 KW and above. And more likely 70 KW - 100 KW per day.


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35. Guesstimating the per-day KW requirement of the TerraLiner's camper box in a challenging, hot-humid climate


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Here it must be emphasized that not just this UniCat faces the problem of power-hungry Air-Conditioners. Even more "regular" Class-A American motorhomes like the Foretravel mentioned in post #2078 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1972813#post1972813 , will mount four 15,000 BTU Air-Conditioners, or 60,000 BTU in total. Newell seems to mount roughly the same amount of Air-Conditioning -- see http://www.fmcmagazine.com/back-issues/2002/december-15565/1896-newell-coachs-mansion-on-wheels.html and https://www.fmca.com/home-mainmenu-...torhome-review-newells-redesigned-p2000i.html . 60,000 BTU is roughly 17.6 KW, so it then becomes understandable why American Class A motorhomes so equipped often seem to run their 20 KW generators round-the-clock during July and August, in order to generate the electricity needed to keep their interiors cool.

Remember, just because a Newell comes equipped with a 20 KW generator, does not mean that it is designed to consume just 20 KW of electrical power per day! A 20 KW generator running round the clock can produce 480 KW per day. Now whether a Newell actually needs that kind of power 24/7 to stay nicely air-conditioned when the Heat Index is 100 degrees Fahrenheit, well, that's another question entirely. Once a motorhome has been cooled down, clearly the full power of the Air-Conditioners is no longer required. Here everything will depend on the quality of the roofing and side-wall insulation, as well as the Heat Index temperature outside, whether the motorhome is parked under the shade provided by some trees, (or whether it even wants to be parked there, because trees would also block the solar arrays.....), whether it's mid-day, late afternoon, or night, and so on.

At this stage there is simply no point in doing complicated calculations of the kind that would require a finished TerraLiner design, + the specified make and model of the air-conditioners used. Yes, I know that's what the more "engineering-oriented types" participating in the thread are hankering for. But that level of design-and-engineering detail would be premature. Personally speaking, I still see myself as defining the architectural "program", once again so that the TerraLiner does not land itself in "Kirivan" territory, where premature detailed drawing, premature detailed CAD, and premature detailed engineering consumes lots of wasted time and effort. Every stage in the design process has an appropriate level of focus and precision. And the appropriate level at this stage, as far as I am concerned, is still fairly general guesstimating.

For what it's worth, there is a diesel generator sizing-calculator at http://www.hardydiesel.com/calculators/generator-sizing-new.html . But that web-calculator won't give us a reasonably good estimate of the daily energy consumption of the TerraLiner in terms of KW, in the middle of August when the Heat Index is 100.

Much better would be daily KW-consumption figures found via online discussion forums posted by Newell and/or other luxury-premium Class-A motorhome owners; statements something to the effect, "In August in Louisiana when the Heat Index was 100 outside, we ran all interior systems including A/C and kept the interior of our Newell (Millennium, Liberty, etc.) coach at 75 degrees Fahrenheit, consuming on average x number of KW per day...." So far I have not been able to find a statement to this effect anywhere. Neither on the http://www.luxurycoachlifestyle.com web-forum that caters to Newell owners specifically, nor on more generalized web-forums. The only threads that came even remotely close to discussing this topic can be found at http://www.luxurycoachlifestyle.com/forums/showthread.php?t=242 and http://www.luxurycoachlifestyle.com/forums/showthread.php?t=1809 . If anyone reading this comes across some good leads, please post!

However, outside the orbit of luxury-premium coaches, I did come across this gem -- see http://www.irv2.com/forums/f59/typical-rv-water-and-electrical-cost-57756.html :

40-50 KWH per day is probably the ball park usage when heating or air conditioning much of the day. That's about what I use in my stick house at our home base during the a/c season, or for electric heating in the winter. More like 12 KWH per day otherwise. I know my rig pulls about 34 amps all day along when both a/c's run continuous, as they do on a hot (90+) day, so that's roughly 10 hours x 34 amps x 120v = 40.8kwh plus another 10A x 120v x 14 hours = 16.8 kwh for the rest of the day/night. That's almost 58 KWH.

In short: 58 KW per day!!

Next, there's a terrific webpage on the always-useful technomadia website, at http://www.technomadia.com/2015/02/the-almost-fantasy-of-solar-powered-rv-air-conditioning/ . Amongst other things, this webpage makes the interesting point that the roof is quite possibly the very worst place on a motorhome to mount air-conditioners! The Class-A motorhome that they "tested" (their own motorhome) consumes 77 KW per 24-hour day for A/C alone on a 100 % cooling cycle, 43 KW per day on a 50 % cooling cycle, and 26 KW per day on a 25 % cooling cycle:







Finally, there are the typical per-day KW consumption figures reported by ordinary homeowners during the peak summer months of June, July, and August, especially homeowners living in hot states with high Heat Indexes like Florida, Louisiana, Alabama, Texas, etc. Year-average per-month KW consumption figures are easy to find on the web, but for some reason much more specific, monthly figures for June, July, and August are hard to come by. However on one blog in particular, some Florida participants with homes in the 1000 - 2000 square foot range (about double the size of the TerraLiner) reported that their electricity consumption drops down to 900 KW per month during the winter (which is the American national average), and goes up to 2000 KW per month during the summer, which works out to 66.6 KW per day -- see http://www.city-data.com/forum/fort-worth/1297741-average-summer-electric-bill-costs-c-3.html .
The TerraLiner will be smaller than such residential Florida homes. But so too, the TerraLiner may have electrical requirements that such homes do not, for instance, water-making and the AWGs. So combining these various sources of information, and erring on the side of caution, it seems very possible that the TerraLiner's electrical systems -- including full Air-Conditioning down to 75 degrees Fahrenheit -- will require roughly 70 - 100 KW per day when glamping in particularly hot climates, climates with Heat Indexes in the 100 - 120 range. Notice how this is a very far cry from egn's 12 KW per day guesstiimate!!! :sombrero:

Here I quoted 75 degrees Fahrenheit, splitting the difference between the A/C temperature preferred by women (77 degrees) versus the A/C temperature preferred by men (72 degrees) -- see http://www.dailymail.co.uk/sciencet...ffice-based-preferences-middle-aged-male.html . So too, according to the American Society of Heating, Refrigerating, and Air-Conditioning:

The preferred [air-conditioned] temperature range for occupants dressed in summer clothes is 73° to 79°F (22.5° to 26°C).

See http://www.bounceenergy.com/blog/2013/07/home-temperature-air-conditioner-summer/ and http://courses.washington.edu/me333afe/Comfort_Health.pdf .

So if no additional power were provided by a solar array or wind-generator, then a 200 KW battery bank would last only about 2 - 3 days, before it would need recharging by the primary generator. On the other hand if a 10 KW solar array were working on average 5 hours a day (i.e. when there's sun), it might produce 50 KW DC per day. Multiplying that by the .80 de-rate factor for DC-to-AC conversion, this would yield 40 KW available AC power for Air-conditioning per day -- see http://understandsolar.com/calculating-kilowatt-hours-solar-panels-produce/ . But this assumes the solar panels would be working at maximum efficiency. If instead we assume they are working at considerably less than that, and were producing only 20 or 30 KW per day, then they might allow a 200 KW battery bank to last up 3 day days without recharging, if the camper load were 100 KW per day; and up to 5 days without recharging, if the camper load were 70 KW per day.

Note that according technomadia, DC Air-Conditioning makes absolutely no sense, and it's much better to install a residential "mini-split" Air-Conditoning system, which will be AC in any case. Apparently most motorhome Air-Conditioning systems are very energy-inefficient, and those built for the residential market are much better -- again see http://www.technomadia.com/2015/02/the-almost-fantasy-of-solar-powered-rv-air-conditioning/ . If anyone reading this begs to differ, and has some good web-inks proving otherwise, please post!!

In short, thinking things through further, it seems unlikely that in a very demanding climate a 200 KW battery pack alone would prove sufficient to allow silent, generator-free glamping for 7 days at a stretch, without any need for additional input from the solar array or wind generator. Furthermore, in equatorial climates like Singapore days will often be cloudy and overcast, the solar array will operate inefficiently, and wind-speed will be minimal-to-non-existent. In such contexts it probably just will prove necessary to recharge the battery pack once every 3, 4, or 5 days, and not once every 7 days. Even if the battery pack were as large as 200 KW. But that's still better than recharging the batteries once a day, or once every two days. And so too it's better than keeping a 20 KW generator running almost continuously, non-stop, as American Class-A motorhomes tend to do during the summer months.

Remember, one of the singular advantages of having the TerraLiner go "serial hybrid" in a big way, is precisely that it will have a two very big generators on board. Even the smallest, "primary" diesel generator will produce somewhere between 150 - 200 KW per hour (still to be determined), and Proterra does make "slow charging", extended-range battery packs, where by "slow-charging" Proterra means that they can by topped up in just 90 minutes (!!). The trick here is having a diesel generator big enough to provide the massive surge of KW necessary for the fast-charging of such a big battery pack.

Note that the technomadia webpage simply takes for granted a standard Class-A motorhome as background assumption, a motorhome equipped with a fairly ordinary-sized RV diesel generator. The technomadia webpage does not imagine a super-innovative hybrid TerraLiner that comes equipped with a mega-sized diesel generator that can pump out more than 100 KW, combined with a 200 KW battery pack. So the technomadia webpage very rightly points out the folly of imagining that one might power motorhome Air-Conditioning by either batteries alone, or solar alone, or even by some combination of the two alone:

I hate to be a destroyer of dreams, but… Running an RV air conditioner exclusively off of solar power is a fantasy that is extremely difficult and expensive to turn into a reality. Cooling a conventional RV using a solar-powered AC is akin to pushing a boulder up a mountain… while wearing roller skates. Leaving all other electrical loads out of the picture, it is easy to see that you could regularly need to generate over 10kWh a day of energy dedicated to running a single RV roof air conditioning unit – even if you only leave the AC on during the hottest part of the day. You could pay for a seeming infinite amount of generator run time, or years of camping with full hookups, for what building a solar system so powerful would cost!

This technomadia webpage comes to the same conclusion that I've come to: that if one wants Air-Conditioning, then it's simply impossible to be a "solar + battery" purist.

However, what a serial hybrid TerraLiner does make possible is full 100 % Air-conditioning even in the hottest climates, combined with "mostly silent" glamping. Even in the very worst-case scenario, the primary generator would need to run for only a few hours to top up the battery pack at most once every 2 - 3 days. And this does seem like a serious improvement over running a much smaller 20 KW generator constantly, 24/7. Furthermore, although technomadia is most certainly right that the size of a solar array to keep Air-Conditioining units fully powered in hot climates would have to be ridiculously huge, a 10 KW array of the kind I have been imagining for the TerraLiner could still provide a substantial "supplement". Think of the TerraLiner's solar array as a "battery extender". Things don't have to be all-or-nothing, and indeed they can't be all-or-nothing in this age of transition from a fossil fuel economy to an all-electric economy. All-electric purists may not like it, but for at least another two or three decades -- if not longer -- we will be living in a transitional age, when mixed "hybrid" solutions make the most sense.

In closing, please remember that all of this is very tentative rough-sketching. Furthermore, it's rough-sketching of the TerraLiner's possible Air-Conditiioning power requirement and battery-pack size within the context of a posting series whose main focus is the TerraLiner's power requirement for driving. But of course the two kinds of power requirement can't be completely separated in a hybrid vehicle, because the larger the battery pack, the more "noise-free" days of glamping the TerraLiner will be able to enjoy. There might also be additional advantages to a larger battery pack on the driving side, for instance, a bigger capacity to absorb energy when the large electric motors function as retarder-generators, as the TerraLiner descends extended slopes. So when balancing all considerations via cost-benefit analysis, it may even turn out that a 300 KW battery pack that weighs a whopping 3 tons makes sense after all. Indeed, who knows? Only a truly competent automotive engineering specialist, with plenty of heavily-hybrid truck experience under their belts (e.g. Wrightspeed), could even begin to make a reasonably educated guess here.

So for now I'll just stick with the 200 KW figure, knowing that it's somewhat arbitrary, in order to then guesstimate the ideal size of the primary generator.

Finally, note that a 100,000 BTU or 29 KW Air-Conditioning system might function as a supplementary "energy dissipation system" as well, a system for getting rid of excess energy when descending extended slopes in hot climates. If the air-conditioners were set up in such a way that they could blast cold air outside, and not just inside. Just as roof-top heating panels (to melt snow) might be a way of dissipating excess energy when descending slopes in cold climates like Siberia. It's just a thought, a somewhat "wild idea" that I wanted to throw into the mix. If anyone wants to run with it, or add something to it, by all means please post!!

The problematic of dissipating excess braking energy when descending extended slopes was first brought up by Iain in post #1994 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1965033#post1965033 . My initial response, right off the top of my head, immediately followed in post #1995.

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Now Back to Drive-Train Power Calculations......

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36. Revisiting the ideal "fail-safe" size for the TerraLiner's primary, smaller generator:

.....Sea level to Monarch Pass, assuming a 3 % ascent, from zero to 3,858 m at 100 kph, without a headwind


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In post #1208 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1973665#post1973665 we took a look at what is probably by far the most demanding extended climb the TerraLiner is ever likely to encounter in the real world, a continuous 3 % ascent from sea level to 3,858 m, over the course of roughly 2 1/2 hours and 128.6 km, driving at 50 kph with a 18 kph headwind. And recall that we used a horizontal distance of 128.6 km, because that's the distance from Canon City to Monarch Pass (see post #2104 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1973661#post1973661 :






But now let's imagine a slightly more "aggressive" possibility, ascending the same 3 % incline at 100 kph without a headwind, of if you prefer, 90 kph + 10 kph headwind. I say 100 kph without a headwind, because this allows us to merely plug numbers into our second web-calculator, and obtain what we know will be an accurate result -- see http://buggies.builtforfun.co.uk/Calculator/index.html :







Here I am thinking of a rather more extended and more challenging version of the I-70 in Colorado that leads up to the Eisenhower pass. Recall that the I-70 ascended at a 2.2 % average grade, over the course of 74 km. So here instead we're imagining something a good deal steeper and longer: ascending 3 % for 128.6 km. But I-70 in Colorado, we're imagining a 4-lane highway where it actually would be possible to sustain such high speeds in a large truck while ascending. Do I know whether such a road exists, perhaps in the Alps, or in Japan? No, I don't. But nonetheless it's a useful exercise.

Deducting for the 10 % efficiency loss of the hybrid drive train, we arrive at a per-hour figure of 518 KW, which as we know from previous calculations is almost the same as the result we would have obtained with Iain's equations. Then multiplying this by 1.286 hours (because we are now driving at 100 kph), we obtain a final Total power figure for the duration of the climb of 666.148 KW.

The 200 KW battery bank will be able to contribute 200 KW of that, but this does leave us with the rather startling conclusion that the primary generator would have to be able to produce 362.4 KW per hour to make up the shortfall. Whether it should or not is an open question. Remember, there's also a second generator available, so if the TerraLiner's owners wanted to tackle such a steep and extended incline at high speed, the second generator could in fact provide the added juice. Here the ultimate issue is what one wants to define as "fail safe" capability: what a single, primary generator should be able to accomplish on its own, without extra power provided by the secondary generator.

Based on the calculations done in post #2108 of the same degree of slope travelled at 50 kph instead of 100 kph, using Iain's equations to reliably include 18 kph headwind, the total power figure for the duration of the climb came to 576.82 KW , instead of 666.148 KW. Which may not seem like that much less, except that it's spaced out over 2.57 hours, instead of 1.286 hours, thereby giving a generator a longer period of time to contribute juice. With a 200 KW battery pack, this would leave 376.82 KW for the generator to cover for 2.57 hours, or 146.62 KW per hour. More than a Jenoptik, which produces only 120 KW, but nothing like 362.4 KW.

So erring on the side of caution, my first, very tentative-guesstimate is that if the TerraLiner were to carry a 200 KW battery pack, then in order to function as a reliable "fail-safe", the primary generator should be rated to produce somewhere between 150 - 200 KWh. Probably best if the primary generator produced closer to 200 KWh, because then a speed more like 60 kph might be possible, ascending such a hypothetically extreme incline.



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37. Sea level to Monarch Pass, assuming a 3 % ascent, from zero to 3,858 m, at 120 kph, with an 18 kph headwind


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Now what interests me at this stage is some even more "extreme" scenarios, in which we imagine what kind of power would enable the TerraLiner to engage in some fairly aggressive driving, climbing a steep extended 3 % slope at 120 kph, with an 18 kph headwind. In Colorado the speed limit for truck is 75 mph, or 120 kph -- see http://www.speed-limits.com/colorado.htm . What would the power requirement of the TerraLiner have to be, in order to manage such a sustained slope at this kind of speed, and with this sort of headwind? Again, I know perfectly well that this is most probably utterly hypothetical, and that a 4-lane highway with this kind of slope, for this extended distance, does not exist. Even the I-80's ascent in California from Auburn to the Donner Summit has a grade overall of 1.8 %, and is only 96.6 km long -- see post #1990 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1964740#post1964740 . But who knows what kinds of feats of highway engineering the Chinese will attempt over the next decade, so let's do the calculations anyway, merely as an academic exercise.

Here we'll use only Iain's equations, to reliably include headwind. Ascending at 120 kph, with a moderate headwind of 18 kph, our total speed relative to the air of 38.33 m/s.


In this scenario Froll is still the same: Froll = 0.010 x 32,000 kg x 9.81 m/s[SUP]2 [/SUP]= 3139.2 kg m/s[SUP]2[/SUP]

Fair will change, however = (1.29 kg/m³ x 0.85 x 10 m[SUP]2[/SUP] x (38.33 m/s)[SUP]2 [/SUP])/2 = 16,109.66 m/s[SUP]2 [/SUP]divided by 2 = 8054.83 m/s[SUP]2
[/SUP]
And Fslope will be the same as in the previous calculation for a 3% grade, as shown in post #2108: Fslope =0.03 x 32,000 kg x 9.81 m/s[SUP]2 =[/SUP] 9,417.6 kg m/s[SUP]2[/SUP]


Ftotal increases to 3139.2 kg m/s[SUP]2[/SUP] + 9,417.6 kg m/s[SUP]2 [/SUP]+ 8054.83 m/s[SUP]2[/SUP] = 20,611.63 kg m/s[SUP]2[/SUP]. Multiplying this figure by the vehicle’s velocity of 33.33 m/s (which does not include windspeed), we get 686,985.63 kg m[SUP]2[/SUP]/s[SUP]3[/SUP], or 687 KW per hour. Quite an increase. We still have to divide by 0.90 to account for a 10 % loss of efficiency from the Hub-motor gearing, so we get 763.3 KW.

But that’s only for one hour,. The travel time required to cover 128.6 km at 120 kph will be shorter, 1.0717 hours, or about 1 hour and 4 minutes. Multiplying, we get 763.3 KW x 1.0717 = 818.3 KW in total for the duration. What this means, in effect, is that if one wants to sustain a speed of 120 kph on a 3 % slope for 128.6 km, then the TerraLiner will need:


(1) A primary generator that produces 200 KW
(2) A battery bank that has 200 KW in reserve
(2) A secondary generator that produces 450 KW


In other words, if the TerraLiner had a Boeing DreamLiner all-electric APS 5000 on board as the secondary generator, an APU that produces 450 KW, it would have no problem driving up such a hypothetically steep, 3 % slope at the maximum allowable speed in Coloardo, 120 kph, with an 18 kph headwind. But it would completely drain down the battery pack in so doing.


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38. 3 % - 3.5 % slopes in Nepal and Tibet


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Do such such long extended 3 % slopes actually exist? They do, but I would wager that very few of them -- or none of them -- are superhighways like the I-70 in Colorado, or the I-80 in California. So it would not be possible to travel at 100, 110, or 120 kph simply because they will be single-lane highways, filled with curves and switchbacks. The TerraLiner would ascend most such slopes at 50 kph or 60 kph in any case, so just the first, primary 200 KW generator might suffice, combined with a fully charged 200 KW battery bank; or at most, as second 200 KW generator may also be needed.

For instance, there is a really useful bicycle log for the G219 in Tibet, complete with mile-markers and altitudes, at http://www.raize.ch/Reisen/velo-eurasien/profil-yecheng-tibet-kathmandu.htm :







Beginning in Nepal, where the highway is called the "Friendship" highway between Nepal and China, the rise between the lowest point at Dolalghat (elevation 630 m) and the highest point at the Tong La Pass (elevation 5120 m), is 4490 m, over the course of 151 km, for an average slope of .029735; in other words, roughly 3 % -- see https://en.wikipedia.org/wiki/Friendship_Highway_(China-Nepal) and https://en.wikipedia.org/wiki/Sino-Nepal_Friendship_Bridge :







Oddly enough, you'd think that the Nepalese bit between Dolalghat and Kodari would be steeper. But actually, it's the Tibetan side after Kodari that's steeper, the stretch between Kodari (elevation 1800) and Tong La Pass (elevation 5120 m). Here the vertical rise is roughly 3320 m over the course of 95 km, for an average slope of 0.034947, or 3.49 %:


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Tong-La Pass at the top is a bit of an anti-climax, really just the crest of a hill, albeit it's marked by a dramatic gate, and festooned with prayer flags:










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On the other side of the Tibetan Plateau, coming up from Kashgar, there is also a fairly steep highway called the G219, discussed before in this thread -- see post #366 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1605612#post1605612 and following. From Yecheng/Kargilik in the Taklamakan desert, up to the Chiragsaldi Pass in the KunLun mountains, is 217 km, and the elevation rises from 1290 m to 4960 m, or 3670 m in total. The average slope here is not too bad: 1.654 % . The areas circled in green in the two maps immediately below correspond to the area shown in the third, much more detailed map:








As is evident in the map immediately above, the G-219 outside of Yecheng/Kargilik only begins to ascend in a serious way after the first 50 km or so. The steepest sustained slope is further along, between Kudi (elevation 3000 m) and the Chiragsaldi Pass (elevation 4960 m), over the course of 56 km. The total rise on this stretch of highway is 1,960 m, giving a sustained slope of 3.5 %.



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39. A realistic calculation for Dolalghat to the Tong La Pass: a sustained slope of 3 %, at 60 kph with 20 kph headwind, for 151 km


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Again, these are single-lane highways with lots of twists and turns, and no doubt lots of traffic, at least on the Friendship Highway at the China/Nepal border. The "Friendship Bridge" is notorious for having traffic backed up for miles -- see http://www.mountainsoftravelphotos....ngmu Tibet, Zhangmu, Zhangmu Main Street.html :







In the last video clip, which captures the second stage of Landrover Germany's "Silk Road Tour", there is especially good footage of the traffic backup at the Nepal/China border. Just jump ahead about 34 minutes, 40 seconds into the video. The Germans use words like "chaos" and "crazy" at least 10 times, but they figure they have no choice but to stay calm and cool. The whole set-up strikes them as inexcusably inefficient, badly planned, and slightly nuts; it's definitely not Germany.....:sombrero:...For more about LandRover Germany's Silk Road Tour, see posts #350 to #362, beginning at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1605593#post1605593 .

In short, the extreme scenario in which the TerraLiner might find itself on a broad, 4-lane highway that sustains a 3% slope for a bit more than an hour -- a highway that allows trucks to drive up to 120 kph -- is most unlikely indeed, at least for now. Again, if anyone knows of such a steeply sloped, sustained 4-lane highway anywhere in the world -- in Norway, Sweden, the Alps, the Caucasus mountains, the Himalayas, or the Andes -- please post! But somehow I doubt there are any. On the other hand, given the billions that the Chinese have been investing in Tibetan infrastructure, I wouldn't be surprised if the Chinese construct a 4-lane highway stretching all the way from Lhasa to the border before 2030. And because China and Nepal have good relations, the Chinese will probably extend the 4-lane highway all the way down to Kathmandu for free, on the Nepalese side. By 2030, the "extreme scenario" calculations performed in section 37, in post #2124 just above, may cease to be purely hypothetical.

For now, let's instead calculate what an ascent from Dolalghat in Nepal to the Tong La Pass in Tibet might require, a slope that's roughly 3 % the whole way, with lots of twists and turns, and so we'll used a more realistic average speed of 60 kph, here leaving out the time wasted at the border crossing. We'll also add a 20 kph headwind, so using our second web-calculator, we'll then plug in 80 kph:









It's interesting, because here we now get 370,107 Watts per hour, or 370 KW. The distance is 151 km, and we're traveling at 60 mph, so the time it will take us is 2.517 hours (again, excluding the wait at the Nepalese border). So the Total KW required to get from Dolalghat to the Tong La Pass will be 370 KW x 2.517 = 931.17 KW. One 200 KW generator running for about 2 1/2 hours will be able to produce 503.4 KW of power, and the battery pack will contribute 200 KW. But that leaves us with 703.4 KW -- more than 200 KW short.

Now we could just add another 200 KW generator, and the problem would be solved. But should the secondary generator be merely a repeat of the first, also a 200 KW piston-driven diesel? Here I wonder whether just one Boeing DreamLiner APU producing 450 KWh might be more fuel-efficient than two separate piston-driven diesels? If it turns out that the Boeing APU is actually more efficient when 400 KWh is required from the generators, then it might be preferable to install the APU instead. A Boeing APS 5000 APU could have produced 1,132.65 KW for the duration of the ascent, more than enough to power the TerraLiner even without the battery's help.

Also note that in all of the scenarios I've been developing, the battery has been imagined as fully topped up, able to provide an additional 200 KW. But suppose it's not? Or suppose there's something wrong with the battery system? Having as much as 650 KW (about 871 HP) available from just the generators alone might also prove valuable, in certain scenarios. In effect what we're imagining here is a triple-fail-safe system: a 200 KW battery pack + a 200 KW generator + a 450 KW generator.

One might also say that it's not very good to rely on the generator + the battery pack to ascend such long slopes, arriving at the top with the battery pack completely drained. Better instead if two 200 KW generators were running simultaneously, producing 503.4 KW + 503.4 KW = 1006.8 KW of power for the duration, completely meeting the power requirement of 931.7 KW. If the batter is to act as a buffer against sudden steep inclines (in the 4 - 8 % range), then it probably should always be kept loaded above 100 KW.


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40. Even Steeper Slopes for Short Bursts: Poncha Springs to Monarch Pass, 4 % slope for 29.29 km, at 120 kph


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Now, let's see what the "instantaneous" power requirement might be for much shorter stretches that are nonetheless very steep. In a certain sense it's academic, because the battery pack will function as a "buffer" providing all the surge in power that the electric motors might need. But it's interesting to do the calculation nonetheless.

From Poncha Springs to the Monarch Pass is 18.2 m, or 29.29 km, and according to google maps, should take 23 minutes:






[video=youtube;9qJArUk9Vas]https://www.youtube.com/watch?v=9qJArUk9Vas [/video]


The elevation at Poncha Springs is 2,275 m, and Monarch Pass is 3448 m, for a vertical rise of 1,173 m over roughly 30 km, and an angle of slope of 4 %. Using our second, more reliable web-calucator, we get a figure of 806.6 KW:







But because in this hypothetical scenario we're traveling at 120 kph, much faster than the speed that google maps assumes, we'd cover the distance in 14.6 minutes. So actually, we can take the figure of 806.6 KW and divide it roughly by 4, to arrive at the power required for the duration; which is about 201.65 KW. The battery pack alone would be enough to get us up that slope at the requisite speed, for the duration of roughly 1/4 of an hour. But not just the primary generator alone, because over the course of 1/4 of an hour it would produce only 50 KW. However if the secondary generator were an aircraft APU rated for 450 KW, then it would produce 112.5 KW in the same amount of time. So combined with the first generator's output, we'd have 162.5 KW of power. We'd still need to rely on the battery, but not for much, just 39.15 KW.

So one way to think about the second generator, whether it's another 200 KW piston-driven diesel, or a 450 KW turbine-driven APU, is that it might serve well as a "battery saver". It might allow the TerraLiner to charge and drain the battery pack less often, thereby extending the battery's life.

Again, this was a rather unrealistic scenario, because the road up to Monarch Pass is a single-lange highway with lots of swichbacks and turns, so a speed of 120 kph would be impossible. But there is at least one place where a very realistic high-powered scenario exists: the Eisenhower pass.


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41. Eisenhower Pass, 7 % slope for 13 km, at 120 kph


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As already indicated in posts #2112 - #2114, driving 120 kph on the I-70 highway that goes through the Eisenhower Pass is perfectly possible, and it's a potentially realistic scenario. For an abundance of imagery, maps, and videos, see http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1973704#post1973704 and following. The I-70 highway is 4-lane and in good condition, and the speed-limit for trucks in Colorado is 120 kph. Last but not least, on the I-70 there are sections that are awfully steep right before and right after the Eisenhower tunnel, and one section in particular has a 7 % grade (1 in 14) for 13 km -- see https://www.codot.gov/travel/maximum-grades-on-colorado-mountain-passes.html and http://www.crashforensics.com/eisenhowerpass.cfm :










Using the second web-calculator the final per-hour figure we get here, after deducting 90 % for hub-gear inefficiency, is 1,170.25 KW:







At 120 kph, 13 km is the distance we'd cover in 6.5 minutes, or 10.8333 % of an hour. So the actual burst of energy required for those 6.5 minutes would be 126.77 KW, again nothing that the 200 KW battery pack couldn't handle. But the primary generator working on its own definitely could not handle it: in those 6.5 minutes, it would produce only 21.67 KW. And the supplementary 450 kW APU also could not handle it: in 6.5 minutes, it would produce only 48.7 KW.

This is quite incredible, if you think about it: there will be situations, realistic situations, where the combined 650 KW of power provided by the two generators will not suffice. This then suggests a very interesting function the battery pack would play: it would allow the TerraLiner to drive like a nimble bus on the I-70 leading up to the Eisenhower pass. Even when faced with the steepest section that has a 7 % grade, it will be able to maintain the constant permitted speed of 120 kph. As it turns out, 1170 KW is equivalent to 1569 HP, which would be the HP rating of the six electric motors in total, 250 HP each.

Now there is no way that that the TerraLiner would ever be fitted with a 1,569 HP piston-driven ICE, just so that it could accomplish this feat on the I-70 in Colorado. But the beauty of a serial hybrid is that a large battery pack can provide a wallop of extra juice for just such "peak power" moments. The battery pack combined with 1500 HP electric motors will act as a very secure "buffer" against such extreme slopes. Even though the generators themselves combined produce only 650 KW maximum, or 872 HP, the TerraLiner will be able to behave as if it were carrying an ICE rated at 1500 HP. Although the TerraLiner will be built much like a truck, it will still handle and drive as fast and gracefully as a powerful bus. With the battery bank providing this kind of "buffer power", climbing steep gradients would be one less thing that its owners need worry about.


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42. Denver to the Eisenhower Pass, 2.2 % slope for 74 km, at 120 kph with a 20 kph headwind


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Before we get too enthusiastic, let's also do a calculation for the I-70 as a whole, from where it dpearts Denver at about 1,700 m, and reaches a peak altitude of 3,401 m inside the Eisenhower tunnel, for a total vertical travel of 1,670 m, almost the same as the vertical travel necessary to reach the Monarch Pass. But the I-70 accomplishes this over a distance of just 46 miles, or 74 km, with an average grade of 2.2 % -- see post #2104 at http://www.expeditionportal.com/forum/threads/124789-TerraLiner-12-m-Globally-Mobile-Beach-House-Class-A-Crossover-w-6x6-Hybrid-Drivetrain?p=1973661#post1973661 , and #2112 to #2114 at http://www.expeditionportal.com/forum/threads/124789-TerraLiner-12-m-Globally-Mobile-Beach-House-Class-A-Crossover-w-6x6-Hybrid-Drivetrain?p=1973704#post1973704 and following. Plugging these numbers into our second web-calculator, we arrive at a figure of 795,274 kg m[SUP]2[/SUP]/s[SUP]3[/SUP], or 795 KW, which we know from experience is a bit high, because the second web-calculator will have multiplied Fslope and Froll by 140 kph, instead of by 120 kph:







Doing a more meticulous calculation, using Iain's equations to reliably include headwind, 120 kph + 20 kph = 140 kph, so our total speed relative to the air will be 38.889 m/s.

In this scenario Froll is still the same: Froll = 0.010 x 32,000 kg x 9.81 m/s[SUP]2 [/SUP]= 3139.2 kg m/s[SUP]2[/SUP]

Fair will change, however = (1.29 kg/m³ x 0.85 x 10 m[SUP]2[/SUP] x (38.889 m/s)[SUP]2 [/SUP])/2 = 16582.96 m/s[SUP]2 [/SUP]divided by 2 = 8291.48 m/s[SUP]2
[/SUP]
Fslope here will be a bit lower than in previous calculations, just 2.2%: Fslope = 0.022 x 32,000 kg x 9.81 m/s[SUP]2 =[/SUP] 6,906.24 kg m/s[SUP]2[/SUP]


Ftotal increases to 3139.2 kg m/s[SUP]2[/SUP] + 8291.48 m/s[SUP]2 [/SUP]+ 6906.24 m/s[SUP]2[/SUP] = 18,336.92 kg m/s[SUP]2[/SUP]. Multiplying this figure by the vehicle’s velocity of 33.33 m/s (which does not include windspeed), we get 611,224.55 kg m[SUP]2[/SUP]/s[SUP]3[/SUP], or 611 KW per hour. We still have to divide by 0.90 to account for a 10 % loss of efficiency from the Hub-motor gearing, so we get 679.1KW. -- about 100 KW less than the web-calculator,

However, the TerraLiner is now traveling at 120 kph, and the distance is only 74 km, so it should be able to cover that distance in 0.6167 hours, or 37 minutes to be more analog. Multiplying, we get 679.1 KW x 0.6167 = 418.80 KW in total for the 74 km duration. And incredibly enough, 126.77 KW of that will be devoted to climbing the last 13 km that have a 7 % grade (actually the figure would be even higher, because recall that we obtained 126.77 KW without headwind).

Now here's the rub. We know that the two generators -- one of them a super-powerful 450 KW APU -- will only be able to contribute about 70 KW to that last 13 km stretch where the slope is 7 %. Those last 13 km are where the battery pack's function as a buffer will be critical. Going up the hill, it's already clear that the primary 200 KW generator alone could not provide enough power: just 123.34 KW for 37 minutes. Even two generators both rated at 200 KW per hour would provide only 246.68 KW for 37 minutes. We would still be shy 172.12 KW. One might say that this is energy that could come from the battery pack, but 30 KW does seem to be cutting things awfully close. And given how critical it will be to have at least 60 KW left available in the battery pack for the final 13 km with the 7 % slope, does one really want to risk draining down the battery pack before one gets fairly near the crest of the pass? At the beginning of those final 13 km, one would ideally still want to have at least 100 KW left in the battery pack.

Now imagine instead that both the APU and the primary generator provide all of the energy for the length of the highway that has a 2 or 3 % grade -- call it 61 km, or 82 % of the distance. They would be left needing to produce 418.80 KW - 126.77 KW = 292.03 KW, over the course of .5083 hours, or roughly 30 minutes. This they could do: 650 KW divided by 2 is 325 KW in 30 minutes. And then, only when they get to the 7 % slope, will the battery pack kick in.

This is a very rough approximation, one that makes all kinds of assumptions. But from the above it's clear that for "bus-like" performance in the most demanding circumstances, it does seem like a 450 KW secondary generator would be required. A second 200 KW generator would not be enough. And even with both generators running full tilt, the TerraLiner will still need an additional boost from the battery pack. Yes, what I've painted here is a scenario involving very "aggressive" driving. But it's also a realistic scenario: a 4-lane highway of this kind does exist, and the state in which the I-70 highway locates, Colorado, does allow trucks to travel 120 kph as they approach the Eisenhower tunnel -- if they can.


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43. How much power should the battery pack hold back in "reserve"?


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Stepping back, it should be noticed that throughout I've been imagining scenarios where the battery pack makes some kind of contribution; but not always. For instance, in the initial fail-safe scenario where we had the TerraLiner climbing from Canon City to Monarch Pass, at 50 kph with a moderate headwind of 18 kph, and a slope of 1.4% for 128.6 km, the Final total power figure for the distance was 377.28 KW over the course of 2.57 hours -- see post #2108. Just a primary generator rated for 200 KW alone could produce that amount, without having to rely on the secondary APU, or the batteries. See post #2108 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1973665#post1973665 . But turns out that 1.4 % is a bit on the "light" side as extended slopes go, and we've seen a number of slopes in Nepal and Tibet that average 3 - 3.5 % for many kilometers. So it turns out that the second, hypothetical calculation in the post, this time for a 3 % slope over the course of 128.6 km, is perhaps much nearer to the "fail safe" scenario we should want to consider. There the total power requirement came to 576.82 KW for the duration, again over the course of 2.57 hours. A 200 KW generator could supply 514 KW of that for the given timeframe, but we'd still have to draw down the battery pack by about 62 KW, leaving 140 KW in reserve. This seems reasonable and manageable -- but notice how it depends on having a 200 KW primary generator.

Now consider the very realistic Dolalghat to Tong-La Pass scenario just worked out above: a sustained slope of 3 %, at 60 kph with 20 kph headwind, for 151 km. It will take 2.517 hours, and require 931.17 KW of power. Two 200 KW generators could produce 1006.8 KW of power during that time, but notice that just one generator plus the battery pack would produce only 703.4 KW, not enough to make it to the top. So just one 200 KW generator alone, even with a 200 KW battery pack, could not function as a fail-safe back-up in this situation.

So here again I am wondering: why not just run one 450 KW APU instead? It might actually prove more fuel-efficient than running two 200 KW generators simultaneously. Furthermore, I am thinking of the APU as a generator that does not necessarily see much use. The turboshaft APU should be imagined primarily as a "steep-grade-climbing" generator. It's the generator that kicks in only when long, steep grades need to be tackled, at fairly high speed, or with a strong headwind. And because it sees less use than the primary generator, it would be more truly "fail safe", and would come in very handy in scenarios like the one just described, where 913.17 KW of power is needed, in total, before the batteries begin charging again because the terrain has become more flat.

Furthermore, we've already seen that a 200 KW generator wouldn't have too much trouble tackling a 3 % slope at 50 kph with an 18 kph headwind, needing only a minor assist from the battery. So most of the time the 200 KW generator would do most of the work. But when a slope gets too steep, and the speed too fast, to save on the use of the battery pack and the primary generator, the 450 KW APU would kick in. That way the battery pack could always maintain perhaps 100 - 120 KW "in reserve". But of course, in certain truly extreme scenarios like the Eisenhower Pass, where there's a short, sharp, steep 7 % ascent in just 6.5 minutes possible at 120 kph, the ascent will consume so much power that even with both generators running, the battery bank will still have to be draw down about 60 KW. Sure, this is an extreme 120 kph + 20 kph headwind scenario, but this is the kind of capability I would like the TerraLiner to have, when necessary or desirable.

We also meed tp factor in high-KW camper systems like:

• Air-Conditioning
• the Incinerating Toilet
• the AWG
• the Watermaker
• thin-fim radiant heating panels

None of these has to be running while the vehicle is driving, with the exception of the A/C or the heating,, and the hourly draw of the camper box will most likely be below 20 KW. On the other hand, driving might be a very good time to run many of these, especially on extended down-slopes when the TerraLiner may need to get rid of excess electricity created by regenerative braking......

What I've now sketched is a vehicle that probably would be very fuel-economical when just the 200 KW greater is running; when the dips and ascents are moderate, and regenerative braking recovers significant power on every short dip; and the 450 KW APU is sitting idle. But when extreme scenarios arise, a huge surge of power from the APU + the batteries would make it possible for the TerraLiner to ascend the I-70 west of Denver as if it had 1500 HP under the hood. And so too, that APU could allow the batteries and the primary generator to have a rest on a long, steep, 3 % average ascent such as Dolalghat to Tong La Pass.



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44. Other Possible Steep 4-Lane Highways Similar to the I-70 at the Eisenhower Pass


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I could keep investigating other real-life examples, for instance the I-17 that heads north from Phoenix up to Flagstaff on the Arizona plateau, and that has a 6 % grade around Camp Verde -- see https://en.wikipedia.org/wiki/Interstate_17 and https://en.wikipedia.org/wiki/Camp_Verde,_Arizona ; or the I-24 in Tennessee as it runs down a 6 % grade at Monteagle; or the Coquihalla Pass on Highway 5 in British Columbia:



[video=youtube;1jAgbHS8yKw]https://www.youtube.com/watch?v=1jAgbHS8yKw [/video] [video=youtube;KqO6-MhL4b4]https://www.youtube.com/watch?v=KqO6-MhL4b4 [/video]



But even the Monteagle is not nearly as challenging as the Eisenhower Pass: it has a slope of 6 % for just 4 1/2 miles -- see http://www.crashforensics.com/monteaglemountain.cfm . So too, Highway 5 in British Columbia has an overall grade of just 3 % from Hope B.C (elevation 43 m) to the summit of the Coquihalla pass (elevation 1,244 m). What makes the Coquihalla pass dangerous is that the final of 5 or 6 km just before the pass has a slope of 8.5 % -- see https://en.wikipedia.org/wiki/Coquihalla_Pass , https://en.wikipedia.org/wiki/British_Columbia_Highway_5 :



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But that's still not comparable to the Eisenhower's 7 % sustained slope for 13 km. Furthermore, even in Colorado very few of the smaller, two-lane highways ever seem to get steeper than 8 %, and then only for a very short stretches -- see https://www.codot.gov/travel/maximum-grades-on-colorado-mountain-passes.html . Note that, like Colorado, British Columbia has a 120 kph speed-limit -- see http://www.cbc.ca/news/canada/briti...n-some-b-c-highways-to-hit-120-km-h-1.2694277 .



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45. Summing Up the Considerations So Far


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Summing up the thinking so far, the following seems clear:

1. A battery pack of 200 KW seems just above right from a drive-train point of view, because it would allow the TerraLiner to tackle even the steepest section of the I-70 near the Eisenhower pass, at the maximum allowable speed of 120 kph. But so too, 200 KW seems about right from the point of view of "mostly silent" glamping, here also assuming that the TerraLiner's "basement" Air-Conditioiner will be very silent, too (Air-conditioners seem to vary widely in the amount of noise they make).

2. A surge of power from the battery pack combined with power from both generators, will be able to feed TerraLiner's six electric motors a maximum potential power of 1500 HP, for short bursts. This may come in very handy. Think of it this way: the generators can deliver 650 KW over the course of an hour, or 325 KW over the course of 30 minutes. If the TerraLiner drew down the full 200 KW in the battery pack over the course of 30 minutes, then the TerraLiner would have 325 KW + 200 KW available for 30 minutes. Per hour, that works out to 1050 KW, which is just a 68 KW short of 1118 KW, which is 1500 HP. So for roughly 25 - 30 minutes, the TerraLiner could behave like a truck that has a 1500 HP engine.

3. A battery pack of 200 KW and just one 200 KW generator will not be sufficient to get the TerraLiner from Dolalghat to Tong La Pass, at 60 kph with a 20 kph headwind. A second generator, rated for at least 200 KW, would be needed to solve the problem. However, two piston-dirven 200 KW generators may not be as fuel-efficient as just one Boeing Dreamliner APU, producing 450 KW.

4. Just two 200 KW generators would not enable the TerraLiner to ascend the I-70 leading up the Eisenhower pass at "bus-like" speeds. 400 KW would not give the TerraLiner bus-like handling capabilities. After all, 400 KW is just 536 HP, and American Class-A motorhomes like Newells or Marathons come equipped with 650 HP Cummins engines. And the largest truck engines now approach 800 HP. True, the TerraLiner can draw down the battery pack in order to "boost" its HP. But the TerraLiner should probably always keep 100 KW in reserve. 500 KW corresponds to 670 HP, more like the performance of a Newell; but 800 HP corresponds more nearly to 600 KW. As we saw in the Eisenhower Pass scenario above, at 120 kph with a 20 kph headwind, even 650 KW of generator power running full tilt is not sufficient for the final 13 km where the grade is 7 %. There the battery pack will also need to contribute 60 - 70 KW.

5. Reflecting on all of the previous, needless to say the question of fuel-efficiency arises. During the moments when the TerraLiner uses the Boeing Dreamliner 450 KW APU, it would be the least fuel-efficient. But that's the price one needs to pay if one wants a large motorhome that behaves more like a bus, instead of a heavy construction truck.

On the other hand, if we remember that for 95 % of the time, the TerraLiner will be driving either on flat country, or through gently rolling hills where the battery pack will kick in with an extra amount of power on ascents, recovering that power via regenerative braking on descents, then perhaps in more "normal" driving circumstances the TerraLiner might be very fuel efficient indeed. 200 KW is just 268 HP, which is an awfully small truck engine, if you think about it. But this is actually the amount of power that most trucks need for "regular" driving. They only have the big 600 or 700 HP engines so that they can climb long ascents, and so too, so that they can get going more quickly from a standstill when pulling heavy loads. But in the case of the TerraLiner, starting from a standstill will be child's play, because it will have a 200 KW battery pack and the instant torque of 1500 HP electric motors. And for long steep ascents, the TerraLIner will have a 450 KW APU.

So who knows: overall, the TerraLiner may indeed prove more fuel-efficient than the average big truck or Class-A motorhome, because in the course of normal driving it will use such a comparatively small, 200 KW engine. Think of the TerraLiner as a fuel-efficient hybrid that can also suddenly throw fuel efficiency to the wind, and function like a 1500 HP vehicle when necessary.


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46. Optimizing the Size of the Primary Generator for "Normal" Driving


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So far I've been thinking only of increasingly extreme scenarios, with a view to (a) the ideal fail-safe size of the primary generator, and (b) the amount of power necessary to give the TerraLiner bus-like handling capabilities on steep, 4-lane highways that would allow it to drive at 120 kph. 200 KW looks good so far, but let's do one last set of calculations for completely flat terrain: for 90 kph, 100 kph, 110 kph, 120 kph, and 130 kph, with no headwind:








Note that if you open the above image in a new window, and then zoom in a bit, all of the text is perfectly clear, and reasonably sharp. The final power values range as follows:

90 kph	182.3 KW
100 kph	227.4 KW
110 kph	280.4 KW
120 kph	341.8 KW
130 kph	412.8 KW

These are the power values required in order to keep the TerraLiner running flat at a constant speed, without a headwind. So one might guesstimate that 90 kph with a 20 kph headwind would require somewhere between 227 KW and 280 KW; let's say 250 KW. This would suggest that a 200 KW generator is not nearly large enough. The battery pack doesn't really help here, because that merely gives out and absorbs energy to allow the TerraLiner to run through moderately hilly country at a constant speed. It acts as an energy "buffer", so that the engine does not have to be as big as the power rating required for a given length and grade of hill. So these are in fact the correct power figures to keep the TerraLiner running at a constant speed, through flat or moderately hilly terrain. And they seem to suggest that an optimal size for the primary generator would be something more like 300 KW, not 200 KW.



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47. Re-Evaluating Some Basic Assumptions: Cd, Frontal Area, and Atmospheric Pressure


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Again, before jumping to conclusions one needs to remember a few things. First off, I set the drag-coefficient very high. As safas suggests further along in the thread, a more common drag coefficient cited today today for trucks is 0.65. And as the following recent PDF by the Rocky Mountain Institute writes:

Thetypical tractor-trailer has a 400-hp engine (about 300 KW), an aerodynamic drag coefficient Cd of 0.6, dual tires with a rolling resistance coefficient of 0.0073, and an empty weight of 30,000 lb (13,608 kg).

See http://www.rmi.org/cms/Download.asp...fficiency+Limits+of+a+Class-8+Tractor+Trailer .

Note that it seems very difficult -- if not impossible -- to get drag-coefficient numbers from manufacturer's websites. Their websites always seem to talk in vague generalities, with sentences like, "And due to our complete redesign, we have achieved the best drag coefficient yet for one of our trucks". A sentence like this means absolutely nothing. Instead one needs to do a bit of digging into the more technical literature, where I found this gem: a truck-by-truck comparison of drag coefficients, on page 31 -- see http://publications.lib.chalmers.se/records/fulltext/133658.pdf :






Here only the Volvo and Scania trucks seem to achieve CD's as low as .62, .58, and .59. However this PDF is dated, the research conducted in 2010.



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Furthermore, is a truck the best analogy for the TerraLiner? Wouldn't a bus be more apropos? To demonstrate what is possible in drag-reduction, the first article quoted ran a test in which it incorporated all the drag-reducing features it recommends, in a Prevost articulated bus, which typically have drag coefficients ranging from 0.311 to 0.384:







Again, see http://www.rmi.org/cms/Download.asp...fficiency+Limits+of+a+Class-8+Tractor+Trailer . So in Prevost buses at least, a drag coefficient as low as 0.311 would seem possible.

Last but not least, I came across this wonderful video about the MAN SkyLiner bus (the first video), which clearly states its drag coefficient as 0.41:






In all of my previous calculations I set the drag-coefficient rather high, because I did not want to be accused of "cheating" or "making unreasonable assumptions". But as everyone knows, changing the drag coefficient significantly changes the power requirement. Now for the TerraLiner a drag coefficient of 0.3 seems wildly optimistic. But the SkyLiner's drag-coefficient of 4.1 seems within the bounds of possibility, if the TerraLiner were properly designed. Remember, one of the reasons why a COE or CBE truck will have a much worse drag coefficient than a Prevost bus, is because in s Prevost bus the engine is a "Pusher", mounted at the rear of the coach. So when designing COE and CBE trucks, aerodynamic engineers have to do battle with motor-propulsion engineers regarding radiator grill sizes and airflow. This conflict between these two engineering requirements is very nicely captured in the following video about the FreightLiner "Super-Truck", a fully working prototype designed to radically reduce fuel consumption. In the Super-Truck, the front grill opens and closes; skip ahead 2 minutes, 10 seconds into the video:









Whereas in a pusher engine placement the shape of the front of the bus can be maximized for aerodynamic performance. The same will be true in the TerraLiner, because its generators will be located in the low-slung side-lockers between the tandem axle in front, and the third axle in the rear. And the TerraLiner's generators will have air-intakes high up on the sides of the vehicle, much like a MAN HX-series trucks, to enable deep fording capability -- see posts #511 and #512 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1653001#post1653001 . So in the TerraLiner, too, the front of the vehicle can be optimized for maximal aerodynamic efficiency, and a low drag coefficient.

In addition, estimating 10 square meters for the frontal area of the TerraLiner is too high. As the truck-by-truck comparison above suggests, 9.7 m[SUP]2 [/SUP]is more nearly right, for a vehicle that is 4 m high and 2.5 m wide. The same table quotes a variety of air-density values, ranging from 1.228 to 1.294. Here again I used an air-density value that is probably much too high, especially given that I was calculating for the TerraLiner ascending slopes that end at 3500 to 5000 m elevation. There are various useful air-density calculators at http://www.denysschen.com/catalogue/density.aspx , http://www.baranidesign.com/air-density/air-density.htm , and https://wahiduddin.net/calc/density_altitude.htm , calculators that incorporate temperature, humidity, humidity, and even barometric pressure. An air-density of 1.29 kg/m[SUP]3[/SUP] only occurs at sea level only when the temperature is 0 degrees Celsius, and humidity is 0 %. Set humidity instead to a semi-arid 35 %, the altitude to 3000 m, and the temperature to 10 degrees Celsius (summertime in the Rockies, or the highlands of Nepal), and the air-density becomes 0.858 -- a huge difference from 1.29. So if anything all of my previous power calculations are too high. The only assumption in my calculations that might be too low is drivetrain efficiency, where I simply guesstimated that the gearing on an electric hub motor would reduce efficiency by about 10 %.

As for the rolling resistance of tires, here too I erred on the side of caution, setting this at 0.01, which seems typical for a car tire on a smooth tarmac road. For reasons that I don't quite understand, apparently truck tires can do better, and the two different tables quote a range of values from 0.006 to 0.01 for truck tires. But I will still stick with 0.01:







Now when calculating the power required to run flat at sea level, instead of 1.29 for the air density, let's use a more reasonable 1.26, the air density at sea-level when the temperature is 6 degrees C. Let's also use a frontal surface area of 9.7 m[SUP]2 [/SUP], and let's assume that the TerraLiner will be aerodynamically designed so that it achieves a drag coefficient of 4.1. Here are the power figures that we get instead, for different speeds:







Again, this is an image where I deliberately used "smart sharpen" and "unsharp mask" in Photoshop, so that even when compressed down to 500 K or thereabout, all of the information should still be perfectly legible. Just open the image in a new window, and then zoom in.

Quite a difference, eh? Laid out in tabular form, the power required for each speed level is:

90 kph	130.6 KW
100 kph	156.6 KW
110 kph	186.0 KW
120 kph	219.4 KW
130 kph	257.0 KW

Even at a nominal cruising speed of 100 kph, and even given a 20 kph headwind, a 200 KW primary generator should still suffice. However, as must be apparent by now I want the TerraLiner to be a bit of a potential "speed demon". I don't want it to be the hybrid motorhome equivalent of a Prius. So in American states and countries that allow trucks and motorhomes to drive at 120 kph, I do want the TerraLiner to be able to do just that: 120 kph, + 20 - 30 kph headwind. Which does suggest that the primary generator needs to be something more like 260 - 300 KW in size, and not 200 KW.


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48. A Primary Piston-Powered Generator that produces 300 KW, or thereabouts


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What's wanted, it would seem, is a "scaled up" version of the Jenoptik. If the Jenoptik weighs 350 kg and produces 120 KW, then what's wanted is a 300 KW generator that weighs about 875 kg. A quick perusal of the usual suspects like Kohler, Cummins, Volvo's "Penta" series, etc. suggests that they only offer high-power (200 - 300 KW) generators that weight upwards of 2 - 3 tons -- see for instance http://www.kraftpower.com/wp-content/uploads/2015/03/Kohler-Commerical-Marine-Brochure.pdf , http://www.kraftpower.com/wp-content/uploads/2015/03/Kohler-Industrial-Product-Line-Brochure.pdf , http://www.kohlerpower.com/industri...r=13261&categoryNumber=11961&prodnum=20939802 , http://www.kohlerpower.com/onlinecatalog/pdf/g5373.pdf , http://www.kohlerpower.com/mobile/d...ber=403561&sectionNumber=13361&prodnum=257661 , http://www.kohlerpower.com/onlinecatalog/pdf/g5569.pdf , http://www.kohlerpower.com/onlinecatalog/pdf/adv7579.pdf , http://www.kohlerpower.com/industri...r=13261&categoryNumber=12261&prodnum=20939802 , http://www.kohlerpower.com/onlinecatalog/pdf/g5373.pdf , http://www.kohlerpower.com/onlineca...Number=..&categoryNumber=11961&prodnum=355261 , http://www.kohlerpower.com/industri...ber=13261&categoryNumber=12261&prodnum=355261 , http://www.kohlerpower.com/onlinecatalog/pdf/g5352.pdf , http://power.cummins.com/content/nta855 , https://powersuite.cummins.com/PS5/...Binary_Asset/pdf/Commercial/Diesel/s-1144.pdf , http://www.volvopenta.com/SiteColle...strial brochures/English/GE-brochure 2014.pdf , and http://www.hardydiesel.com/downloads/volvo-tad-1351-ge-300.pdf . Most of these generators are intended for industrial or heavy-duty marine applications (e.g. tugboats), and so weight is not such a big engineering concern.

Looking further afield, there does exist a very sophisticated, fuel-efficient, variable-RPM, and comparatively lightweight generator made by WhisperPower called the MGV-200, which generates 200 KW, and weighs just 480 kg, including the sound-shell enclosure -- see http://www.whisperpower.com/uk/4/21/products/generators-(variable-rpm).html , http://www.whisperpower.com/uk/4/21/products/generator-systems-(high-power).html and http://www.whisperpower.com/uk/4/21...-systems-(high-power)/m-gv-200-genverter.html , http://www.whisperpower.com/uk/10/26/hybrid/big-boat-systems.html :







Recall that the Jenoptik weighs 350 kg and produces 120 KW, for an energy density of 2.92 kg per KW. Whereas the Whisper Power MGV-200 weighs 480 kg and produces 200 KW, for an energy density of just 2.4 kg per KW. This represents an energy-density improvement of roughly 20 % over the Jenoptik:







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Furthermore, although the Jenoptik does not clearly state its specific fuel consumption in the product literature, we know that it uses a 6-cylinder, 3.2 L "Type M160015-0" engine manufactured by Steyr, rated for either 135 KW, 160 KW, or 200 KW (Jenoptik doesn't specify which ) -- see http://www.steyr-motors.com/automotive/engines/diesel-engine-6-cylinder-3200-cm3-m16/ , and see post #673 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1670215#post1670215 . According to Steyr, whatever the KW output of this engine, it has a specific fuel consumption of 205 grams per kWh:







Whereas the Whisperpower MGV-200 has a specific fuel consumption of 215 grams per kWH. Note however that the Steyr figure is the KW of shaft power produced by the diesel engine; it is not the KW of electrical power produced by the Jenoptik generator, which will be worse. So I very strongly suspect that the Jenoptik generator's specific fuel consumption expressed in terms of electrical power output, will at best be the same as the WhisperPower 200 KW generator; and probably worse.

Note the size of the MGV-200: 86 cm x 86 cm x 1.4 m long. To be sure, slightly bigger than the Jenoptik's 85 cm x 60 cm (wide) x 1.375 m long. But 200 KW would be much closer to what the TerraLiner needs in a primary generator.

Whisperpower has also released a new 150 KW "HyGen" variable speed generator, but as of this writing, detailed specifications are not available yet -- see http://www.whisperpower.com/uk/2/33/company/press-kit.html , http://www.whisperpower.com/uk/2/14...power-&-propulsion-system-to-san-lorenzo.html , http://www.yachtandcoast.com/uncategorized/hybrid-system-generates-savings-quiet-and-speed/ , http://www.charterworld.com/news/tag/whisperpower , http://iims.org.uk/hybrid-technology-based-power-and-propulsion-system-launched-by-whisper-power/ , and http://www.whisperpower.com/phpimg/wp_hoofdstuk_131_0c_Engine_room_San_Lorenzo_106_AC_Powercube.jpg . Furthermore, I have reason to think that Whisperpower may soon release a 300 KW version, which given its track-record of building light-weight and low-noise generators, might be perfect for the TerraLiner -- see http://www.whisperpower.com/uk/2/13...-and-whisperpower-enter-into-partnership.html .

The only sticking point would be size. A tall, "thin" generator like the Jenoptik is actually better for the TerrrLiner's purposes than a squat one. Whisperpower's 100 KW generator, for instance, is also 86 cm x 86 cm x 126 cm long, and also weighs 480 kg -- a size- and weight-to power ratio much worse than the Jenoptik -- see http://www.whisperpower.com/uk/4/21...-systems-(high-power)/m-gv-100-genverter.html . So there would not be much value in combining WhisperPower's 100 KW generator with its 200 KW generator to achieve 300 KW, because the 100 KW generator is exactly the same weight -- 480 kg -- and only just a bit shorter, 1.26 m instead of 1.4 m -- see http://www.whisperpower.com/uk/4/21...-systems-(high-power)/m-gv-100-genverter.html :






Better to get a second Whisperpower 200 KW generator instead, for 400 KW in total.

Note that 86 cm wide is not a "deal breaker", and could still fit into the space between the external wall of the TerraLiner, and the rail of the ladder frame running down the center of the vehicle. Indeed, it would probably be a good idea to engineer generator enclosures on both sides of the vehicle that are structurally integral and completely fused with the ladder frame, so that the rigidity of the ladder frame is not compromised; and yet at the same time two volumes are created on either side of the vehicle that are large enough to allow some variation in the size and dimensions of the generators. Volumes perhaps 1 m deep, x 1 m tall, x 1.6 m long, or thereabouts. While still allowing for 60 - 65 cm of ground-clearance under the TerraLiner; after all, the below-axle ground-clearance won't be any better than that. Again the idea here is a "plug-and-play" format, with the primary generator and the APU sitting on slide-out trays so that they can be easily serviced, and also so they are easily "swappable": easily replaced when they get old, or when newer and better generators and/or turbine-driven APUs become available.

In addition, once more detailed specifications for Whisperpower's new 150 KW generator become available, it may turn out that the very best configuration would be two of these 150 KW generators producing 300 KW in total, both of them located on one side of the TerraLiner; and the Boeing APS 5000 APU on the other side. Looking at the revised table in the previous post of TerraLiner power requirements, there are at least two scenarios in which just one 150 KW generator would suffice, namely, driving at 90 kph without headwind, and 100 kph without headwind. Remember, in the course of normal driving on flat or slightly hilly terrain, the generator's output only needs to be as good as the required output on flat terrain. In hilly terrain the 200 KW battery bank provides the HP "buffer" necessary to ascend hills, and the TerraLiner then recovers most of the electricity lost on the ascent via regenerative braking on the descent, when the electric motors switch over to functioning as generators.

Here it's worth noting that WhisperPower is specialized in providing complete "hybrid electric" drivetrains for large, yacht-type sailboats. These are systems that completely eliminate the diesel engine used to dock in port when the sails are down. Instead, a Whisperpower electric engine linked to a battery bank, and Whisperpower's generators, provides non-sail propulsion:







Whisperpower is well worth looking into, because it sells a complete range of hybrid products, from premium-lithium ion batteries and solar cells, to DC-convertors, battery isolators, intelligent battery links, heavy duty battery switches, galvanic protection, shore-power connections, battery monitors and controllers, battery chargers, and inverters, all beautifully described in the WhisperPower marine catalog for 2016 -- see http://www.whisperpower.com/nl/2/13/phpimg/WhisperPowerBookMarine2016-UK.pdf . The major advantage of having the TerraLiner's electric system handled in part by Whisperpower is, of course, the fact that all components, wirings, and parts will be designed to resist salt-water corrosion. The TerraLiner will be a "surf-glamper", and so not just any old hybrid system will do. The TerraLiner will spend a cumulative total of years glamping perhaps just 100 m from the water, either directly on a beach, or on hills or cliffs directly above the ocean. So all TerraLIner systems need to be designed to be "ocean proof", as ocean-proof as the systems installed on yachts. This includes the generator.



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49. Possible TerraLiner Fuel Mileage


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There do exist other companies specialized in selling high-performance generators for rugged conditions that are lighter than Kohler or Cummins, for instance, Perkins. I want to focus on Perkins not because of the weight of their generators -- they're actually still not light enough -- but rather, because Perkins' website provides particularly detailed information about fuel consumption relative to electric output in KW.

Perkins makes a range of generators beginning at 5 KW and topping out at 600 KW -- see https://www.perkins.com/en_GB/products/new/perkins/electric-power-generation.html . The 200 KW Perkins is EPA Tier IV Final and EU Stage 4 compliant, but otherwise does not compare favorably with the WhisperPower MGV-200. The Perkins generator weighs 1087 kg, it's much larger the Whisperpower in all dimensions, and it produces only 180 KW of "prime power"; 200 KW is "standby power". The Perkins consumes 210 grams per kWh in "prime power" mode at 1800 rpm. However, the PDF provides a very useful figure for what this means in liters. At 100 % "prime power" this Perkins generator consumes 55 liters per hour to produce 180 KW of electricity. See https://www.perkins.com/en_GB/produ...generation/diesel-generators/1000001900.html# , and http://s7d2.scene7.com/is/content/Caterpillar/C10378884 ; and for the same generator that produces 135 kWe, see http://s7d2.scene7.com/is/content/Caterpillar/C10378884 . Again, although Perkins generators have nothing like the power density of a Jenoptik or Whisperpower, at least they're much lighter than generators in the same KW range made by Kohler or Cummins.

Perkins does produce a 320 kWe "prime power" generator that is EU Stage 2 and EPA Tier 2 compliant -- see https://www.perkins.com/en_GB/produ...-generation/diesel-generators/1000001931.html and http://s7d2.scene7.com/is/content/Caterpillar/C10414626 ; and for the same generator that produces 280 kWe prime power, see http://s7d2.scene7.com/is/content/Caterpillar/C10414624 . It's huge, weighs 1478 kg, and it's specific fuel consumption is pretty much the same, 206 grams per kWh. But because it produces more KW, at 100 % it consumes 85 liters per hour, and at 50 % it consumes 46 liters per hour. Needles to say, the 1 1/2 ton weight of this generator automatically rules it out. Just consider: two Whiisperpower MGV-200's would weigh 960 kg, and would produce 400 KW!!

Now even though Perkins' generators are not in the running, the abundance of information provided by the Perkins' website might give us a rough-ballpark idea of the TerraLiner's fuel consumption on flat terrain, without taking into account the benefits of regenerative braking. To drive fairly aggressively -- above 100 kph -- the table in the previous post suggests that the TerraLiner will need 186 KW for 110 kph. Let's say that it drives slightly slower than that, 108 kph, so that it draws exactly 180 KW. If the TerraLiner's generator were a Perkins, producing 180 KW in "prime power" mode, then it would consume 55 liters per hour, and in that time the TerraLiner would cover 108 km. In Imperial units, the equivalent would be 12 gallons to cover 67 miles, or 5.58 miles per gallon. Remember, we've already deducted for hub-gear drive-train inefficiency.

Believe it or not, this is not a bad figure in the world of Class-A motorhomes.

Big 45-foot diesel "Pusher" motorhomes typically get 6 - 8 mpg driving "normally", and they get closer to 5 mpg when driving 110 kph, as per our scenario -- see http://www.everything-about-rving.com/how-many-miles-per-gallon-does-your-motorhome-get.html . Smaller motorhomes in the 35 - 40 foot range, driving 55 or 60 mph, seem to get somewhere between 7 - 12 mpg. See http://community.fmca.com/topic/7900-diesel-motorhome-mpg-honest-answers-please/ , http://www.everything-about-rving.com/what-is-the-best-mpg-for-diesel-motorhomes.html , http://www.gonewiththewynns.com/bounder-gas-rv-fuel-economy-mpg , and https://rv-roadtrips.thefuntimesguide.com/2009/12/pros_cons_rv_diesel_pusher.php . But none of these motorhomes have regenerative braking. So I figure that once we throw in regenerative braking, if the TerraLiner were able to do above 8 or 9 mpg driving at 65 mph, it would compare veryfavorably to most current large Class-A motorhomes. And if the TerraLiner could pull off 10 mpg at the same speed during "normal" highway driving, then that would be magnificent. The TerraLiner would be considered a truly "eco-friendly" large motorhome.

Here I should note that I don't quite understand why Perkins describes the specific fuel consumption of its 180 KW generator at "prime power" as 210 grams per kWh, and then lists fuel consumption for the same 180 KW as 55 liters per hour -- again, see http://s7d2.scene7.com/is/content/Caterpillar/C10378884 :







Working out the first number mathematically, 210 grams x 180 kWh would be 37.8 kg. The very definition of a liter is that it weighs 1 kg, so using the first specification, the Perkins should only consume 37.8 liters to produce 180 KW of power. And yet the specification sheet instead says 55 liters per hour.

If anyone reading this understands why there is this discrepancy, please post!!



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50. Where to Research Low-Weight 300 KW Generators in Future


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Stepping back a bit, it seems clear that larger generators that produce 120 KW (the Jenoptik) or 200 KW (the Whisperpower) are possible, but these are generators that were purpose-built for transportation applications. The Jenoptik was created specifically as a "backup" generator for a trolley bus that would otherwise use an overhead electric catenary grid, and Whisperpower generators are primarily created for sailing yachts, where weight really does matter. The difference for a sailing yacht between a 200 KW generator that weighs 500 kg, versus one that weighs over 1000 kg, is huge.

So it seems that further generator research should concentrate on generators created either for sailing yachts, for trolley-buses, or for serial-hybrid transit buses. In the case of trolley-buses one should not be too optimistic, because although many are now being fitted with 4 x 80 KW electric motors, or 320 KW of potential power, the generators that give them some measure of autonomy when they are not using an overhead catenary grid, are generators that have power ratings typically in the 60 KW - 120 KW range -- see posts #1909 and #1910 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1959799#post1959799 . I would guess that the Jenoptik is probably the most powerful generator (120 KW) built specifically to be used as an APU in a trolley-bus.

For a very thorough, detailed, up-to-date, albeit sometimes confusing webpage about various contemporary electric trolley technologies, packed with lots of "insider" information, see http://citytransport.info/Buses03.htm#top. But unfortunately, it does not contain much information about the APUs these trolleys use as "back ups", when not linked to the catenary grid.

By way of contrast, more research into MAN's Lion-City hybrid bus and the generator it uses, and other similar transit hybrid vehicles that are not electric trolleys, might turn up significant and useful information. MAN's Lion City hybrid transit bus is not designed to use an overhead catenary grid, and it's smaller than most electric trolleys, with just two 75 KW electric motors driving two axles, instead of 4 x 80 KW motors. But because it can't rely on electric power coming from outside the bus, the electric generator in the MAN Lion City hybrid bus is bigger, 150 KW, powered by a 6-cylinder 250 HP motor. It also has ultra-capacitors that can store up to 200 KW -- see http://www.bus.man.eu/global/en/city-buses/man-lions-city/overview/Overview.html , http://www.bus.man.eu/global/en/city-buses/man-lions-city-hybrid/overview/Overview.html , http://www.bus.man.eu/global/en/cit...and-transmission/Engine-and-transmission.html , http://www.neoplan.se/uploads/files/hybrid_eng.pdf , http://www.bus.man.eu/man/media/en/content_medien/doc/business_website_bus_master_1/Lions_City.pdf , and http://www.mantruck.co.kr/nhc/index/BusCatalogue_City Bus.pdf . MAN does make 15 m and 18.75 m Lion City transit buses, but as near as I can tell from the product literature, none of these longer buses is available yet as an electric hybrid.

On the other hand, IVECO does make a full serial-hybrid 18.75 m bus called the "URBANWAY". But it's so new, that detailed information is not yet available -- see http://www.iveco.com/ivecobus/en-us...uments/City/BrochureUrbanwayFH_EN_Euro_VI.pdf and http://www.busandcoachbuyer.com/bus-euro-test-2014/ . Presumably once more information becomes accessible, it will provide specifications for a generator, one that might produce somewhere between 200 - 300 KW.

But it also might not. The Mercedes Citaro hybrid diesel-electric articulated bus discussed earlier in the thread is 18 m long too, but has a small diesel engine that produces only 218 HP (160 KW), driving a generator that combined with the 180 KW lithium battery pack delivers 240 KW of power to the electric motors -- see http://www.mercedes-benz.mu/content...e/buses_world/update/news_2013/stuttgart.html , and post #1915 at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1959993#post1959993 . There are four electric motors rated at 80 KW each, so combined they have a potential output of 320 KW. Again, as per all hybrid vehicles, the basic principle is that the ICE can be much smaller because it does not have to produce peak-power:

A big advantage of the serial hybrid drive in the Citaro is downsizing: instead of the large 12-litre six-in-line OM 457 hLA engine normally used in the articulated model, the hybrid bus is fitted with a compact OM 924 LA unit which develops maximum power of 160 kW (218 hp) from a displacement of 4.8 litres. This reduces the weight of the engine from approximately 1000 kg to around just 450 kg.

Since the diesel engine of the Citaro G BlueTec Hybrid does not drive the vehicle directly, it is not required to produce peak outputs and is therefore able to operate very economically and with low environmental impact over a narrow rpm range at or close to its peak efficiency. The torque curve of the hybrid-bus engine is therefore tailored predominantly to steady-state operation, for optimal emissions performance and fuel efficiency.

See http://media.daimler.com/dcmedia/0-...1-1216602-0-0-12637-854946-0-1-0-0-0-0-0.html

Here it's worth noting that much of the hybrid technology that IVECO uses comes from BAE systems -- see http://www.hybridrive.com , http://www.hybridrive.com/hybrid-transit-bus.php , http://www.hybridrive.com/how-it-works-hybrid-bus.php , http://www.hybridrive.com/hybridrive-series-e-bus.php , http://www.hybridrive.com/hybridrive-series-products.php , http://www.hybridrive.com/lithium-ion-energy-storage-system.php , http://www.hybridrive.com/any-oem-any-class.php , http://www.hybridrive.com/literature.php , http://www.baesystems.com/en-uk/product/hybridrive-series-e , http://www.hybridrive.com/pdfs/hybridrive_articulated_bus_brochure.pdf and http://www.hybridrive.com/pdfs/HybriDrive-MTS.pdf .
And for BAE's parallel hybrid solution for trucks, see http://www.hybridrive.com/hybridrive-for-trucks.php , http://www.hybridrive.com/how-it-works-trucks.php , and http://www.hybridrive.com/pdfs/HDS Parallel Promo handout US.pdf .

BAE systems does not seem interested in selling the diesel motor part of the hybrid equation, but rather, seems focused on selling just its motor/generators, which it calls the "HybriDrive-MTS" -- again, see http://www.hybridrive.com/pdfs/HybriDrive-MTS.pdf . These do not seem intended as hub-motors as per Wrightspeed, but rather, they are motor-generators driving a single live axle, and behind the motor/generator will sit the diesel engine, for instance, a Cummins ISL 330 hp engine in a large articulated bus. The largest motor/generator, the HDS 300, can produce 308 HP of traction, and in regenerative braking and/or generator mode it produces the same, i.e 230 KW. The concept is a bit difficult to understand, because in effect BAE has combined the motor with the generator, in a single reasonably large unit.

BAE's motor/generators are so large, that I doubt they could be repurposed as hub motors. The smallest 255 HP motor/generator is 55 cm long x 61 cm wide x 57 cm high, and weighs 297 kg; while the largest 308 HP motor/generator is 65 cm long x 61 cm wide x 57 cm high, and weighs 388 kg. On the other hand, Wrightspeed's 250 HP purpose-built hub motors combined with its "Geared Traction Drive" (an inverter and a gearbox), doesn't seem that small or lightweight either -- see http://www.wrightspeed.com/technology/ . I've read in one place that Wrightspeed's motor weighs 110 lbs (50 kg), and that the gearbox adds another 20 kg -- see http://www.electric-vehiclenews.com/2010/08/wrightspeed-hints-at-1000-hp-all-wheel.html . And I've read in another place that just the motor alone weighs only 70 lbs, or 30 kg, which is a bit hard to believe -- see http://breakingenergy.com/2015/03/1...-trucks-are-the-cutting-edge-of-truck-design/ :

[Wrightspeed's] proprietary motor weighs only 70 pounds and delivers 250 horsepower, among the best power to weight ratios found in any motor. Wrightspeed also uses very strong regenerative braking that can completely stop a truck on an incline and delivers 730kw of power back to the batteries. The lithium iron phosphate batteries are provided by A123 Batteries.

But even if Wrightspeed's electric motor + gearbox + inverter combination weighs 100 kg in total, that would still be much less than the weights quoted by BAE for its "HybriDrive-MTS" motor/generators.

What we've been envisioning so far is two generators (for redundancy) quite separate from electric hub motors, electric hub motors that also function as generators when braking. So it's at least interesting to run across BAE's combined "motor/generator" alternative solution. And it's worth remarking that BAE can claim that it has the largest diesel-electric hybrid bus fleet by far, with its systems installed in over 3,500 buses worldwide.

I may discuss BAE systems a bit further along, because it's such a major player in the hybrid market, and its solution is difficult to understand without pictures. Like Wrightspeed, BAE's hybrid drivetrain -- which includes lithium-ion batteries and controllers -- is vendor-independent. BAE will sell its hybrid system to just about anyone, regardless of the make of the vehicle. BAE's hybrid drive-train is not part of a "total bus package" as per the serial hybrid system developed by MAN. But in a BAE type system to get the necessary total HP needed for the TerraLiner, one would probably have to insert two or three HDS 300 generator/motors, one for each axle, with a single largish diesel motor driving all three axles directly, as in a standard AWD set-up. Which sounds much too complicated, and needless to say, BAE did not intend its motor/generators to be used this way. Instead, BAE intended its motor/generators to drive just one axle, with the other axles non-driven. So the BAE solution is probably not what we're looking for, even though it is the market leader in serial hybrid drivetrains for buses.

Just a quick side-note: in parallel hybrid systems for large trucks, the market leader is Eaton Corporation. And for what is probably the most thorough survey of quite literally every Heavy Duty Diesel Truck and Bus Hybrid Powertrain yet created -- with the odd omission of Wrightspeed -- see the Department of Defence study published in 2012, at www.dtic.mil/get-tr-doc/pdf?AD=ADA567008 . It's 198 pages long, and covers parallel hybrid trucks just as much as serial hybrid buses. Also see the useful but not quite as comprehensive PDF at http://cdn.intechopen.com/pdfs-wm/41487.pdf .

In addition, it would be worth investigating further the generators used in Oshkosh's Propulse system, albeit it seems very difficult to find detailed information about Propulse and its various parts via the web. So far, all we know is:

1) that the 4-axle ProPulse HEMMT has a 470 HP diesel engine, that directly powers a generator that produces 340 KW (or alternatively, a 450 HP engine that drives a generator that produces 335 KW; different Oshkosh literature quotes different figures); which then drives four electric motors, one for each axle;

2) second, we know that Oshkosh's 3-axle MTVR has a generator that's almost as big, 280 KW;

3) and third, we know that the hybrid 2-axle L-ATV that Oshkosh tested in the Baja 1000, had a 400hp 6.6L Duramax engine built by Gale Banks Engineering, but the size of the generator is a mystery:







Unfortunately, the dimensions and weights of Oshkosh's generators remain unknown, and so too, their specific fuel consumptions in grams relative to a KW of electricity they produce. For a fairly condensed summary of the Oshkosh ProPulse information that I've been able to find so far, see posts #1195 to #1208, at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1744053#post1744053 and following.

Finally, it's worth noting that specialized companies exist whose purpose is to create "tailor made" or "bespoke" generators, often for military applications. A good example would be Kirsch-Energie -- see http://www.kirsch-energie.de/fileadmin/user_upload/redakteur/pdf/Referenzlisten/Referenz_MIL_en.pdf , http://www.kirsch-energie.de/en/products/special-generating-sets.html , http://www.kirsch-energie.de/en/products/special-generating-sets/integrated.html , http://www.kirsch-energie.de/en/products/special-generating-sets/variable-speed.html , http://www.kirsch-energie.de/en/products/military/integrated.html , http://www.kirsch-energie.de/en/products/electrical-drive-systems/buses.html , http://www.kirsch-energie.de/en/products/electrical-drive-systems/buses/apu.html , http://www.kirsch-energie.de/en/products/electrical-drive-systems/buses/pu.html , and http://www.trolleymotion.eu/www/index.php?id=2&L=-1 .

Kirsch draws an interesting distinction between an "APU", and what it calls an "MPU", or "Main Power Unit":

APU

Our auxiliary drive does its work safely and reliably everywhere and everyday when buses have to be moved without power from the contact wire. Whether circumventing obstacles, shunting at depots, driving through the washing system or if there are just malfunctions in the primary power supply – the auxiliary drive from KIRSCH always keeps the bus “live”. Since our auxiliary drive's availability and performance is so reliable, the route network is extended more and more frequently to interesting urban areas where there is no contact wire – or may never be built. You expand your range of products with an auxiliary drive from Kirsch and our customers derive benefits from it.


MPU

The drive system is designed as a main drive if the bus drive is engineered to run down both central urban areas and fringe zones with the same bus. Normally power is supplied from the contact wire in central urban areas and from our main drive in fringe zones where there is no contact wire.

Electrical power is provided ranging between 170 to 200 kW so that the bus has sufficient energy. This aggregate also has a full-value auxiliary drive function as standard equipment.

The following PDF covers most of the APUs that Kirsch has created for trolley buses, from gen-sets as small as 20 KW to as large as 100 KW -- see http://www.kirsch-energie.de/fileadmin/user_upload/redakteur/pdf/Referenzlisten/Referenz_APU_en.pdf . But what should interest us the most is the MPUs that Kirsch has created for more independent kinds of "true hybrid" buses, MPU's rated at 175 and 195 KW:







We might then reason that if Kirsch thinks a more "independent" kind of hybrid bus needs a 200 KW MPU, then specifying a 300 KW primary generator for the TerraLiner seems to be in the right ballpark. Or possibly, two 150 KW generators made by Whisperpower, so that in certain circumstances the TerraLiner might become even more fuel-economical.....



**************************************************


51. Conclusion


**************************************************


All of the above is merely preliminary guess-work. And it certainly would be interesting to run the power calculations again for the Eisehower Pass, and the road from Dolalghat to the Tong La Pass, using the revised, more "accurate" assumptions for the drag coefficient, frontal area, and atmospheric pressure. And this time around, assuming a 300 KW primary generator, instead of 200 KW.

But a number of basic design parameters have emerged, parameters that should be taken into account in future:


************************


(1) In many places the TerraLiner will be able to drive 120 kph. So it should be designed to do so; in fact, it should be designed so that using just its primary generator, it can drive 120 kph on flat terrain with a 20 - 30 kph headwind.

(2) The TerraLiner should also be designed so that only very rarely will it need to draw down its 200 KW battery pack to below 100 KW.

(3) The TerraLiner should be designed so that using both generators + the battery pack, it can ascend a 4-lane highway like the I-70 in Colorado with a 7 % slope for 20 km, at 120 kph with 20 kph headwind. I haven't done the calculations yet, but I imagine that given a 300 KW primary generator instead of a 200 KW generator, this should be possible.

(4) The TerraLiner's mpg "target" for normal highway driving on flat or moderately hilly terrain, at 65 mph, should be at least 8 - 9 mpg, and ideally 10 mpg, via the massive use of regenerative braking.

(5) The primary, 300 KW piston-driven diesel generator should weigh no more than 900 kg, and preferably more like 700 kg. If we pro-rate the WhisperPower MGV-200 that produces 200 KW, and weighs 480 kg, then a generator that produces 300 KW and weighs 720 kg should be possible.

(6) The advantage of a jet-aircraft APU versus a second piston-driven generator should be obvious. Instead of weighing another 700 - 900 kg and producing only another 300 KW of power, an APU like the Boeing DreamLiner APS 5000 will weigh just 245 kg, or thereabouts, and produce 450 - 500 KW of power. The details here are still fuzzy, and I've written to Pratt & Whitney for the specific fuel consumption, the exact output in KW, and the probable weight and size of the whole assembly once a cooling manifold (if necessary?), insulation, and sound shielding is taken into account. We'll see whether they write back.

I fully realize that a APU whose turboshaft engine is rated at 1,100 HP will be a gas-guzzler. But the extra performance characteristics this will give the TerraLiner are undeniable, for not much added weight. Many more 4-lane highways with long, steep ascents exist than most people seem to realize. And many of these really would be highways where the TerraLiner could legally drive 120 kph, if it had the power available. I am a bit of a "speed freak", so I figure that if the TerraLiner proves very fuel-efficient in the course of "normal" driving, because of massive regenerative braking, then it has "earned" the right to behave like a super-fast bus, when the owners so desire.

Yes, the incorporation of a turboshaft APU is a bit "science fiction"; it's probably the most sci-fi element of the TerraLiner that I've proposed thus far. But I do want to investigate it further, to see if it's do-able.

(7) Iain's equations are very useful, and as it turns out, quite correct. When computing the power requirements for various speeds without headwind, the results generated by Iain's equations are virtually identical to the results produced by the second web-calculator, which again can be found at http://buggies.builtforfun.co.uk/Calculator/index.html . The only defect in the second web-calculator is that it cannot factor in wind-speed, whereas Iain's equations can. Here I want to thank Iain once again for introducing some clarity and precision to the power debate.


************************


Needless to say, I worked my way through all of these calculations because as a designer, I am always a bit wary of thread participants and/or engineers who might try to steer me in the direction of their preconceived notions of what is "realistic", by flooding me with equations, extreme calculations, and alarmist scenarios. I worked through all of the above in detail because I really do want to understand this stuff for myself. I would prefer it that way, instead of relying upon the "say so" of anyone on the ExPo forum, or even an engineer in "real life".



**************************************************


52. Coda: Honeywells' Electric Green Taxiing System (EGTS)


**************************************************


There is another major development which has implications for the KW output and efficiency of turboshaft APUs: Honeywell's "Electric Green Taxiing System." The idea is dead simple: instead of a jet aircraft using its main engines to propel it forward when taxiing at an airport, instead the aircraft's wheels will be driven by electric motors, the electricity supplied by the plane's APU:






The fuel savings are potentially significant, because an aircraft's main engines are optimized for flying at high speed, not providing a bit of thrust to taxi at an airport. See https://en.wikipedia.org/wiki/EGTS , http://www.safranmbd.com/sites/nmbd/files/egts_brochure.pdf , http://www.albawaba.com/business/pr...an-and-honeywell-412781?quicktabs_accordion=2 ,http://airsideint.com/previous-issues/airside-october-2013/powering-more-fuel-efficient-future , https://aerospace.honeywell.com/abo...ectric-green-taxiing-system-at-paris-air-show , http://www.safranmbd.com/egtstm , https://aerospace.honeywell.com/~/media/Brochures/etaxi-brochure.ashx , and https://aerospace.honeywell.com/news/egts-v4 .

In its literature Honeywell makes it clear that this new system will necessitate a bigger and/or "all electric" APU, similar to Pratt & Whitney's APS 5000 developed for the Boeing DreamLiner. But I haven't been able to find any information anywhere about a new Honeywell APU designed specifically to be used in concert with EGTS. So, at least so far, Pratt & Whitney's APS 5000 is the best (and only) turboshaft APU that seems like it might radically enhance the TerraLiner's capability, while adding very little weight.

Here are some videos that provide good further explanations of Aircraft APUs:



[video=youtube;2iYGb_d7S38]https://www.youtube.com/watch?v=2iYGb_d7S38&index=72&list=PL_RkPTMHqWNfjPp 7hS1rT6N7J48iQIcpX [/video]



Also see https://www.youtube.com/watch?v=RbH0uNFVt1Q and https://www.youtube.com/watch?v=9YE87Va25LY&index=89&list=PL_RkPTMHqWNfjPp7hS1rT6N7J48iQIcpX , and see the playlists at https://www.youtube.com/playlist?list=PL_RkPTMHqWNc2-p022xzT8x_Dt9XSf_Eq and https://www.youtube.com/playlist?list=PL_RkPTMHqWNdsGj-xGF5Y8h3ruIxCb9_u .

Most APUs include pneumatic compressors that provide "bleed air" for the aircraft, whereas the APS 5000 is "all electric", and produces only electric power, and no bleed air -- see http://www.boeing.com/commercial/aeromagazine/articles/qtr_4_07/AERO_Q407_article2.pdf . The APS 5000 also promises to be 50 % less loud than its rivals, but I couldn't find a video example of its noise-level.


All best wishes,


Biotect

 

[biotect]

Hi Iain:

You may not have enough time to read all of the above (once I have finished posting everything), but please if possible read this post in particular.

I think the above calculations are probably much more accurate than the first set that I attempted for the ascent from Sacramento up to Lake Tahoe. They seem like they should be more accurate, because I “tested” my use of the equations against the "campo" scenario, to see if I could get the same result that you did: 157 KW. See post #1981, at http://www.expeditionportal.com/for...edition-RV-w-Rigid-Torsion-Free-Frame/page199

Recall that in the "campo” scenario, you calculated the amount of power that would be necessary to keep a 30-ton truck rolling along at 90 kph on a flat plane, with no headwind. If you read the posts above, you may noticed that this time around I assumed a fairly robust rolling resistance, 0.1 %. So for Froll with respect to campo’s 30 ton truck, I might be tempted to calculate:


Froll = 0.010 x 30,000 kg x 9.81 m/s[SUP]2 [/SUP]= 2943 kg m/s[SUP]2 [/SUP]


Fslope is irrelevant in this scenario, because slope is 0 %. And the Fair equation only needs 90 kph expressed as 25 m/s, because there’s no headwind. In my calculations above I have also been assuming a slightly worse drag coefficient than you did: .85 instead of .8. And for the campo scenario, I have assumed the same front-area as the TerraLiner, i.e. 10 m[SUP]2[/SUP], or 2.5 m x 4.0 m tall:


Fair = (1.29 kg/m³ x 0.85 x 10 m[SUP]2[/SUP] x (25 m/s)[SUP] 2[/SUP])/2 = 6,853.13 m/s[SUP]2 [/SUP]divided by 2 = 3426.56 m/s[SUP]2[/SUP]


Adding the two together, I get Ftotal = 6,369.56 m/s[SUP]2 [/SUP], and multiplying that by the velocity, 25 m/s, I get 159,239 kg m[SUP]2[/SUP]/s[SUP]3[/SUP], or 159.2 KW. Deducting 30 % for efficiency lost from the transmission, I get 227 KW, which is actually quite a bit worse than the figure that you arrived at in post #1981. But least we’re now in the same general ballpark, which suggests to me that I may (finally!) be using the equations properly. Unfortunately 228 KW translates as 304 HP, which is about 50 HP more than campo specified in post #1980, at http://www.expeditionportal.com/forum/threads/124789-Fully-Integrated-MAN-or-TATRA-6x6-or-8x8-Expedition-RV-w-Rigid-Torsion-Free-Frame?p=1964283#post1964283 .

However, it’s fascinating what a big difference changing one’s assumptions regarding rolling resistance and the drag coefficient can make. If I change rolling resistance to 0.006 (plausible for a truck on smooth asphalt), and if I give the Fair equation a better drag coefficient of 0.8, as you did, then Ftotal = 4,990.9 m/s[SUP]2[/SUP], and the power demand – before accounting for 30 % lost to the transmission – is 124,770 kg m[SUP]2[/SUP]/s[SUP]3[/SUP], or 124.8 KW. I still end up with 178 KW after dividing by 70 %, to account for the transmission, but at least 178 KW is 239 HP, much closer to campo’s guesstimate of his truck's horsepower size.

Would you be willing to let me know what your exact figures were when you calculated the campo scenario, i.e the figures that you used for:


A – the projected frontal area of campo’s truck?
cr – the coefficient of rolling resistance that you used"
cd – the drag resistance coefficient that you used?


That way, if I have exactly the same figures as you used, and I come up with the same result, then I will know that I am using the equations properly. And if my result is still different, then I would still be missing something.

Also, if possible, could you very quickly check my use of the equations above, and let me know if I am still doing something wrong in terms of procedure?

All best wishes,



Biotect

 

[Iain_U1250]

Sorry, my spreadsheet is just a bunch of formulae, every time I check something, I lose the previous data. I think I used 0.08 for the Cd, given it was a modern truck, but as for the rest, I can't remember.

Last one I did was for my own truck. You can check your formulae using these figures:

Frontal Area: 7.48m2
Cd: 0.9
Air Density: 1.29kg/m3
Speed: 100kph

Roll Resistance: 0.008

Total Power: 109.4kW
Engine Power: 142.2kW ( 30% transmission loses)

Which is 190Hp, so pretty close to my actual horse power. I have not found a flat road when there is no wind to test the theory, but one day I will be able to try.

.
Hi Iain:

You may not have enough time to read all of the above (once I have finished posting everything), but please if possible read this post in particular.

I think the above calculations are probably much more accurate than the first set that I attempted for the ascent from Sacramento up to Lake Tahoe. They seem like they should be more accurate, because I “tested” my use of the equations against the "campo" scenario, to see if I could get the same result that you did: 157 KW. See post #1981, at http://www.expeditionportal.com/for...edition-RV-w-Rigid-Torsion-Free-Frame/page199

Recall that in the "campo” scenario, you calculated the amount of power that would be necessary to keep a 30-ton truck rolling along at 90 kph on a flat plane, with no headwind. If you read the posts above, you may noticed that this time around I assumed a fairly robust rolling resistance, 0.1 %. So for Froll with respect to campo’s 30 ton truck, I might be tempted to calculate:


Froll = 0.010 x 30,000 kg x 9.81 m/s[SUP]2 [/SUP]= 2943 kg m/s[SUP]2 [/SUP]


Fslope is irrelevant in this scenario, because slope is 0 %. And the Fair equationonly needs 90 kph expressed as 25 m/s, because there’s no headwind. In my calculations above I have also been assuming a slightly worse drag coefficient than you did: .85 instead of .8. And for the campo scenario, I have assumed the same front-area as the TerraLiner, i.e. 10 m[SUP]2[/SUP], or 2.5 m x 4.0 m tall:


Fair = (1.29 kg/m³ x 0.85 x 10 m[SUP]2[/SUP] x (25 m/s)[SUP] 2[/SUP])/2 = 6,853.13 m/s[SUP]2 [/SUP]divided by 2 = 3426.56 m/s[SUP]2[/SUP]


Adding the two together, I get Ftotal = 6,369.56 m/s[SUP]2 [/SUP], and multiplying that by the velocity, 25 m/s, I get 159,239 kg m[SUP]2[/SUP]/s[SUP]3[/SUP], or 159.2 KW. Deducting 30 % for efficiency lost from the transmission, I get 227 KW, which is actually quite a bit worse than the figure that you arrived at in post #1981. But least we’re now in the same general ballpark, which suggests to me that I may (finally!) be using the equations properly. Unfortunately 228 KW translates as 304 HP, which is about 50 HP more than campo specified in post #1980, at http://www.expeditionportal.com/forum/threads/124789-Fully-Integrated-MAN-or-TATRA-6x6-or-8x8-Expedition-RV-w-Rigid-Torsion-Free-Frame?p=1964283#post1964283 .

However, it’s fascinating what a big difference changing one’s assumptions regarding rolling resistance and the drag coefficient can make. If I change rolling resistance to 0.006 (plausible for a truck on smooth asphalt), and if I give the Fair equation a better drag coefficient of 0.8, as you did, then Ftotal = 4,990.9 m/s[SUP]2[/SUP], and the power demand – before accounting for 30 % lost to the transmission – is 124,770 kg m[SUP]2[/SUP]/s[SUP]3[/SUP], or 124.8 KW. I still end up with 178 KW after dividing by 70 %, to account for the transmission, but at least 178 KW is 239 HP, much closer to campo’s guesstimate of his truck's horsepower size.

Would you be willing to let me know what your exact figures were when you calculated the campo scenario, i.e the figures that you used for:


A – the projected frontal area of campo’s truck?
cr – the coefficient of rolling resistance that you used"
cd – the drag resistance coefficient that you used?


That way, if I have exactly the same figures as you used, and I come up with the same result, then I will know that I am using the equations properly. And if my result is still different, then I would still be missing something.

Also, if possible, could you very quickly check my use of the equations above, and let me know if I am still doing something wrong in terms of procedure?

All best wishes,



Biotect

 

[biotect]

Hi Iain,

Many thanks for your response. I managed to find two on-line web-calculators, one that includes Fslope, and one that doesn't -- see http://buggies.builtforfun.co.uk/Calculator/index.html and http://ecomodder.com/forum/tool-aero-rolling-resistance.php . I am currently re-writing the posting series to include their results, which sometimes seem to vary in non-explicable and non-patterned ways from the results that I am getting when using your equations. Sometimes these web-calcultors agree with my results, sometimes not, no doubt due to an error on my part!! :sombrero: ...

The posting series will require at least another 2 or 3 days to finish. Only by reading and re-reading what I've written, have I been able to figure out the usually "clerical" data-entry mistakes that I am making. Once I finish the series, however, I will conclude that precise figures do not matter so much. Rather, what really matters is the general overall "picture", and what it tells us about the size of the generators and the battery bank that the TerraLiner will need to carry, in order to climb various slopes at various speeds. The web-calcuators provide a sufficient degree of external "control", such that I might be able to claim that I am more or less on the right track. That's really all I need, in order to make the arguments that I want to make at this stage.


**************************************************


However, just to be sure, I would like to plug in the numbers for your truck. But I need to know the weight or your vehicle to calculate Froll. The sequence of steps that I'd then go through looks like this:


(1) Froll for Iain's truck = 0.008 x (??? weight of Iain's truck in kg ???) x 9.81 m/s[SUP]2 [/SUP]= ??? m/s[SUP]2[/SUP]

(2) No calculation for Fslope, because the truck is running along a flat surface.

(3) Fair for Iain's truck = (1.29 kg/m³ x 0.9 x 7,48 m[SUP]2[/SUP] x (27.7778 m/s)[SUP] 2[/SUP])/2 = 6,700.84 kg m/s[SUP]2[/SUP], divided by 2 = 3350.42 kg m/s[SUP]2 [/SUP]


Froll + Fair = Ftotal = ??? m/s[SUP]2
[/SUP]

Ftotal x 27.7778 m/s = ??? m[SUP]2[/SUP]/s[SUP]3 [/SUP] = ??? KW


Total Power: ??? KW

Engine Power: ??? KW (divide by .70, to account for 30% transmission loses)


So if you might just give me the weight of your truck, I could run the numbers!


**************************************************


Once again, many thanks for steering me in this direction. My sense of the power requirements of the TerraLiner in various scenarios has sharpened immensely, and so too my sense of exactly why -- and why not -- I would like the TerraLiner to be fully hybrid. You are absolutely right that batteries are a very bad deal from a weight-to-power point of view. True-blue zealots for all-electric vehicles notwithstanding, batteries will continue to underperform relative to our hopes and expectations for at least another decade, and possibly for another two decades. Your general point on this score was very well taken. See post #2110, which is now more or less complete, at http://www.expeditionportal.com/for...w-6x6-Hybrid-Drivetrain?p=1973669#post1973669 , titled "The Problem with Batteries".

But even still, I think there are strong arguments in favor of trying to design a fully hybrid TerraLiner, which I list in the same post. Above all, a 200 KW battery bank could supply 10 days' worth of power for noise-free glamping, even if consumption were 20 KW per day, and that would be most excellent indeed. When glamping in an equatorial climate where there is comparatively little wind and poor solar irradiation due to constant cloud cover and rainfall, it would be great if the TerraLiner could run A/C full blast for 10 days, and then run the generator for just one night to recharge the battery bank, after which glamping could continue noise-free for another 10 days....:ylsmoke:

All best wishes,


Biotect