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

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3. Combining SunPower and Onyx Panels


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SunPower solar panels come in two versions, the usual white-on-black grid, and their new “signature black” series:


9 images

https://vimeo.com/67203789


See http://www.aurora-energy.com/sunpower-monocrystalline-solar-panels/ , http://www.thesolarco.com/what-are-black-solar-panels/ , http://www.archiexpo.com/prod/sunpower/product-54500-1297477.html , http://hipowersolar.com/products/sunpower-solar-products/ , and http://www.sunpower.de/haus/solarmodule/x-series/ .


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So imagine a series of back-lit, walkable Onyx solar panels in a variety of colors:


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Flanked on either side by SunPower's Signature series black panels:


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In other words, the central gangway will not be just aluminum plating……emoticon

All of the solar panels above are to scale, as is the roof: 10 m longs, x 2.55 m wide. Notice that the “SunPower” panels would in fact overlap the Onyx colored walkable panels.

As already stated above, I'd like to get some feedback on whether being able to “tilt” solar panels to catch the sun is really worth it, given the additional mechanical complexity involved. But if so, then this overlap depicted would certainly not be a problem. The walkable panels would sit underneath the SunPower panels, and the SunPower panels would raise and lower to achieve the best angle towards the sun.

Of course, the above is merely an “idealization”. There are still those hatches, ventilators, sunroofs, and AC units to think about….. So once one gets into the details, one would also want to subtract some surface area for these. The hatches, however, might be covered with the walkable panels just described, although the panels would have to be smaller than 60 cm on each side, so that they could fit in the space available between the SunPower “Signature Black” panels. A/C units mounted on the back of the TerraLiner might also have their tops covered with solar cells, albeit not with the large 1.559 x 1.045 SunPower panels.

In a design exercise like this, it's best not to get too “hung up” on the details and dimensions of just one manufacturer, and the particular product it offers at one stage in its development. So given the efficiency improvements that are likely to occur in the next five years, it's probably best to just use the SunPower numbers for the entire roof, all 25.5 square meters.



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4. One Possible Design Precedent: the World's First 3 KW Solar-Powered Trailer?


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To provide a rough-ballpark estimate of what now seems possible, here is an image and some videos of a recent project (2013) to create a trailer that is completely solar-powered:


1 image


https://www.youtube.com/watch?v=k5Fb0kQMwQg
https://www.youtube.com/watch?v=wlLume1XeDY
https://www.youtube.com/watch?v=I2s63JU3zqQ

See http://roadtreking.com/total-grid-solar-powered-rv/ , and his YouTube channel is at https://www.youtube.com/channel/UChiIAdjrhDEVelNvjRn_0ng .

The roof of this trailer is completely covered by a solar array, producing 3,130 W, or about 3 KW. At the end of the first video he suggests that this may be the world's first 3 KW-solar RV, and based on what we've seen above, this seems quite possible.

The array is comprised of 6 “Helios” 420 W panels from the 9TC series, which measure 1.976 mm x 1.310 mm, for a surface area of 2.59 m[SUP]2[/SUP]– see http://www.sundeavor.com/helios_9t6_series.pdf , http://heliossolar.us/index.asp , http://heliossolar.us/about.asp , https://www.facebook.com/heliossolarworks , http://powerupco.com/site/?page_id=1342 , and http://www.solardesigntool.com/comp...ar/1646/9T6-420/specification-data-sheet.html . These 6 panels combined have a surface area of 15.54 m[SUP]2[/SUP] . In addition, up front there are two slightly smaller Helios 305 W panels, which are a bit less wide, 1.984 m x 0.984 m, for a surface area of 1.95 m[SUP]2 [/SUP]each – see http://pvpower.com/uploads/products/Helios_Solar_7T2_Spec-Sheet.pdf . So the total surface area of this solar array is 19.44 m[SUP]2[/SUP].

Put in proportional terms, his Helios panels have a power density of 161 W per square meter.

Note that at 1.310 m wide, the 420 W Helios panels placed side-by-side are 2.62 m wide, which would exceed the standard European width limit for trucks, motorhomes, etc., i.e. 2.55 m. In the video he states that his trailer is 24 feet long, or 7.32 m. And in the videos the trailer does seem narrower than the solar panels on top, so assuming that it's only 2.55 m wide, he should have managed just 18.67 square meters of solar paneling. But he crammed in 19.44 m[SUP]2[/SUP] instead, so let's just say that his solar array has considerable “overhang”…..emoticon.

Scaling up on the basis of this project, the TerraLiner's roof alone, with its 25.5 m[SUP]2[/SUP], should be able to produce 4106 W of power, or 4 KW, under ideal conditions. The TerraLiner should be able to produce 4 KW simply because it's a bigger vehicle, it's roof 33 feet long (10 m), instead of 24 feet long. Yes, the TerraLiner will have hatches/skylights, and a central gangway with a different kind of “walkable” solar panel, so these may reduce the amount of wattage available. But in 5 years time all solar panels will be more efficient, so 4 KW seems a good, rough-ballpark basic “minimum” guestimate.


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5. The Solar Potential of the TerraLiner's Roof: About 5 KW


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Now for the sake of simplicity, let's imagine the TerraLiner's solar array as similar to the one discussed in the previous post, with total coverage by the same kind of solar panel everywhere.

The SunPower X-series is their top-of-the-line model, and produces 345 W – see http://us.sunpower.com/solar-panels-technology/x-series-solar-panels/ and http://us.sunpower.com/sites/sunpow...35-345-residential-solar-panels-datasheet.pdf ; compare this to their perhaps older product, the E-series, at http://us.sunpower.com/solar-panels-technology/e-series-solar-panels/ and http://us.sunpower.com/sites/sunpow...s-e20-series-327-residential-solar-panels.pdf , which instead produces 327 W. Again, an X-series panel measures 1.046 m x 1.559 m, or 1.63 m[SUP]2[/SUP] , so right off the bat, the SunPower panel is better sized for mounting on the roof of a motorhome. As we saw above, two X-series panels side-by-side will still leave space between them for a 46 cm wide “gangway”, composed of solar panels of the “walkable” kind. But for the sake of simplicity, imagine just one kind of panel covering the entire roof of the TerraLiner. We then arrive at a power figure of 5,397 W.

Clearly, the current SunPower X-series panels are considerably more efficient than the Helios panels that were installed on the trailer above. The latest SunPower panels have a power density of 211.65 W per square meter.

There is some possibility, however, that back in 2013 (just 2 years ago!!) this guy was using an older series of Helios panels. On the Helios website these models seem to be no longer produced, and it's difficult to determine what the “successor” product might be – see http://heliossolar.us/product.asp?page=1& and http://heliossolar.us/product.asp?page=2& .

In short, given the general trend in solar technology, it's probably safe to say that 4 year or 5 years from now the TerraLiner's roof should have no problem generating 5 KW of energy with high-efficiency solar panels.

Of course this would be the power production only under in ideal conditions. Someone like egn, who has plenty of experience using a mono-crystalline solar array on top of his own motorhome, might be able to indicate what the “typical” power production is likelier to be. egn might be able to suggest just how much of a percentage one has to knock off because of clouds, or a sun that's low in the sky in winter, etc.


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PART Ic: SOLAR ENERGY – TerraLiner Solar Power Output considered Geographically, in terms of DNI


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1. What will be the likely power output of the TerraLiner's solar array, in different parts of the world?


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To state the obvious: the performance of the solar panels on the roof of the TerraLiner, no matter how efficient or how well-tilted towards the sun, will vary greatly as the TerraLiner travels around, because different parts of the world have different “solar potentials”.

It is a singular tribute to German eco-idealism, or dogged bloody-mindedness, or both, that Germany now has one of the largest solar industries in the world. Even though climatologically speaking, Germany is one of the very worst places on the planet for solar power:


6 images


Only central China, northern Scotland, Iceland, and southern Chile seem like they might be worse places for solar. And yet as one of the maps states, roughly 60 % of the world production of solar modules is consumed by Germany.

Here is a great video about the solar revolution to come, and why despite it's non-optimal location, Germany has developed an unusually strong commitment to solar:


https://www.youtube.com/watch?v=nr-grdspEWQ


When one looks at Europe as a whole, the real “solar potential” is all in the south:


4 maps



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But that too is relative. In another map comparing southern Europe to northern Africa, there is simply no contest. When driving through north Africa the TerraLiner's solar panels will most probably function very differently than when driving in Italy, even in regions as arid and sun-drenched as Puglia, Basilicata, and Calabria:


2 maps


In the United States, all the “solar potential” is in the western states:



8 maps


Even southern Florida, although it's warmer and further south than any other state (apart from Hawaii), does not have nearly the same solar potential as California or Arizona, probably because it's so comparatively wet.

I am particularly interested in the second-to-last metric: what exactly is “Weighted Mean Instantaneous Solar Irradiance on the Ground”, and why does it create map that looks different than the other metrics?


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2. Different Solar Metrics


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At a more global level, I find it interesting that the Tibetan plateau, the Altiplano, and the Australian desert seem to be “solar hotspots”, with levels of solar radiation that surpass even the central Sahara, at least if one uses the metrics of “Mean Solar Irradiance”, “Direct Normal Solar Radiation”, “Direct Normal Irradiation”, and “Horizontal Irradiation”:


3 images

3 images

2 images



Does this mean that solar panels will work especially well in Tibet, Bolivia, and Western Australia?

In the following map, the dry sections of the Andes seem to have a solar potential that far outstrips the solar potential of the American Southwest:


1 map




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3. Precipitation and the DNI: the Case of India


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Precipitation also seems a strong factor influencing the “DNI”, or “Direct Normal Irradiation”. As near as I can tell, the DNI is the most indicative metric for measuring the solar energy potential of a region – see http://www.3tier.com/en/support/sol...t-direct-normal-irradiance-solar-prospecting/ .

Here are two maps of the “Solar Resources” for India, and if one knows something about India's climate, the pattern becomes immediately apparent. The solar “hotspots” are comparatively dry regions in the north like the Thar desert and Leh/Ladakh, as well as the comparatively dry area in the south in central Karnataka:


2 maps



Whereas the wetter areas of the Himalayas that receive lots of rainfall, like Kashmir, Sikkim, and Arunchal Pradesh have much lower solar potential. Similarly, even though Kerala is in the very south, it's also very wet, and so it's solar potential is poor. But not as poor as the “poor solar potential” corridor along the Ganges river plain.

In short the above map of Indian solar potential does not so much track temperature or latitude, but rather, it tracks rainfall:



3 maps


And it would appear to correlate only partly with a map of India's “Annual Average Global Insolation”, and the “Annual Average Global Horizontal Irradiance” (GHI):


3 maps



The Gangetic plain has high insolation, but apparently comparatively poor solar potential, measured in terms of the DNI.




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4. Precipitation and the DNI: Africa


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A similar pattern obtains in Africa. Although most of the continent is quite hot, the DNI pretty much tracks African rainfall patterns:


1 map DNI

3 maps precipitaton


In Africa's case, unlike India's, the DNI and “Global Horizontal Irradiation” seem to be strongly correlated:


1 map




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5. Seasonal Precipitation and hence a Seasonal DNI? Back to India


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But further research turned up these gems. The first explains why DNI varies, while the second is usually labeled as a map of “Global Solar Potential”. It more or less correlates with the DNI, but for some reason suggests that the Tibetan Plateau's solar potential is not that high:


2 maps


Here again are the two best maps of the DNI that I've been able to find so far:


2 maps


Notice how, in comparative global terms, the solar potential of India is only moderate, with the exception of the Thar desert. Most of India seems to have less solar potential than Spain.

However, there is also this to consider. As we saw in the posts about itinerizing India for water autonomy, India's precipitation is very seasonal -- see posts xxx to xxx at . From June until October/November, most of India is drenched by the monsoon, one day after another of solid rain:


3 maps of the monsoon.


By far the coolest way tools I've been able to find on the web to describe India's ultra-seasonal rainfall, are some animated GIFs. The first two are maps of changes in precipitation globally. So make a point of focusing just on India, and watch how the sub-continent gets literally flooded with blue from June through October:


2 maps


The third is an animated GIF of the monsoon understood as a low-pressure system, with animated isobars:


1 map


So for a vehicle with solar cells on the roof, travelling in India out of the monsoon season, the DNI might prove quite high, and more comparable to Spain in the summer. It would be interesting to see separate maps of “annually adjusted” Indian DNI for December, January, February, March, and April. As we already saw above, these are by far the best months to see the country in any case, if water were not such a big issue as well.

So to say that India has comparatively low “solar potential” is not exactly correct. Sure, from the point of view of a stationary edifice, those months of June, July, August, and September when sunshine is rare will be important. One's stationary house will need to obtain electricity some way other than solar. But for a moving, mobile motorhome, a motorhome that can schedule a visit to India for the 6 months of the “sunny season”, India's solar potential might be very high. For the TerraLiner, December and January in Kerala might be a very nice place to be, both from a DNI perspective, as well as the perspective of relative humidity, and hence, AWG operability.


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5. It’s hot and wet, the DNI is low, so we must be in Ecuador…..


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Here we should also add that most equatorial countries have poor DNIs, because they are lush and wet. Note that the Andes in Ecuador and Colombia also have 5000 m peaks – the highest in Colombia is 5,700 m, and in Ecuador, 6.228 m – see https://en.wikipedia.org/wiki/Pico_Cristóbal_Colón , https://en.wikipedia.org/wiki/Chimborazo , and http://www.gnosis.us.com/642/top-ten-south-american-mountains/ . But these are peaks surrounded by sylvan, green alpine landscapes and forests, not bone-dry desert, as per many of the mountains on the Altiplano in Peru and Bolivia:


10 images



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