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

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2. The Overlap of Wind-Calm and Solar Radiance; or Lack Thereof


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Here we can begin by placing two very general maps side-by-side, a global map for DNI, and another for global mean wind speed (albeit at 80 m above ground):


2 maps


One important caveat: notice that virtually all of these wind-speed maps were created using data compiled to serve the needs of the wind-power industry. So they state average or “mean” wind-speeds at 30 m, 50 m, or even 80 m above the ground. The speed of the wind at this height is much greater than wind-speed on the ground, which is why wind-turbine towers are built so high. Simply increasing the height of the tower can have a dramatic impact on turbine efficiency – see https://en.wikipedia.org/wiki/Wind_turbine_design and https://en.wikipedia.org/wiki/Wind_turbine_design#Tower_height . We might then discount all the data in these maps by a factor of 10 – 20 %; or alternatively, we could accept the data “as is”, with said margin error also providing a margin of safety in our reasoning.

Now right from the start, notice that many places that have excellent Solar Radiance, also have fairly moderate average wind speeds, for instance all the “green” and “yellow” parts of the Sahara and the Arabian peninsula, and all the green and yellow parts of Australia.

Conversely, some of the windiest places on earth, like Scotland, Norway, and Tierra Del Fuego, also have very poor Solar Radiance. So presumably, one would not want to deploy the solar awnings in any case. These are exactly the kinds of places where the TerraLiner would need to obtain more power when stationary from a diesel generator.


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3. The Equatorial Belt of Low-Wind, Low Solar Radiance


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Many places along the equator also have low average wind speeds, but more moderate Solar Radiance, like the Amazon basin, or the rainforests of central Africa and Indonesia. From the perspective of wind, these would be great places to deploy the TerraLiner's awnings, because they are unlikely to get blown away. The awnings merely need to withstand lots of rainfall. However, in terms of energy output the solar cells on the awnings will probably do only as well as solar arrays deployed in Florida, southern Spain, or Italy, because for much of the time the sky will be cloudy, and the awnings will be covered in water:


6 maps


Compare these to maps of Europe, England, and China, where “blue” more or less means the same thing, a DNI of 400 kwh/m[SUP]2[/SUP]:


3 maps


Quite startling, isn't it? Many parts of Colombia, Ecuador, and northern Vietnam have DNI's as low as England and Germany. But note that the DNI scale on the maps of Vietnam and Indonesia begin at 600 kwh/m[SUP]2[/SUP], and not at 400 kwh/m[SUP]2[/SUP]; and Thailand's scale begins at 900 kwh/m[SUP]2[/SUP]. Notice how much the DNI falls in Thailand as one heads south, towards the sopping wet equator…..



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Even the mountainous parts of Peru that are wet (think Machu Pichu) have a low DNI:


1 map Peru


But again notice: Peru's scale begins at 600 kwh/m[SUP]2[/SUP], not 400 kwh/m[SUP]2[/SUP].

Once more, the very best map that I've been able to find that expresses this idea of “low equatorial DNI”, due to high precipitation, is the following low-res image:


1 map


Bands of low DNI shown in purple occur three times on this map: a band in the northern hemisphere across Canada, Ireland, Britain, Germany, Poland, Scandinavia, and Russia; a band at the bottom that represents Antarctica; and a band at the equator that covers at the northern end of South America, the Congo, Indonesia, Borneo, and New Guinea.

The rather low DNI of these equatorial countries drenched in rain is quite remarkable, and should once again give us pause for thought before we imagine the TerraLiner as completely reliant on solar. They may be great places to deploy the awnings because of low wind, but that won't do much good if it's always cloudy and raining. In some of these countries the amount of cloud and rain will vary seasonally (e.g. India), but in others it won't. So complete reliance on solar might mean that one can't visit some parts of these countries unless one uses the Steyer 182 HP engines to generate electricity even when stationary and boondocking.

Ergo , we return to the rationale for a separate, small diesel generator.….


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4. A Cautionary Side-Note: Attention When Using Country-Maps of DNI


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It's important to be cautious when interpreting many of the more “local” country maps of DNI.

For instance, consider the following maps of the DNI in Cuba, the Congo, Japan, and India. The scales of Japan and the Congo begin at 700 kwh/m[SUP]2[/SUP], the scale of India begins at 1100 kwh/m[SUP]2[/SUP], the scale of Cuba begins at 1200 kwh/m[SUP]2[/SUP]!!


3 maps


Only a map of global DNI puts everything into proper perspective:


1 map global DNI


Vietnam really does have a poor DNI in the north, and most of Burma is worse than Florida. India and Italy are similar, except for the Gangetic plain, which is more like Romania. Cuba is more like some parts of Spain or Sicily, even though it's much wetter than either of these. Japan is similar to middle and northern France, and both are similar to the Congo.


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5. A Few Caveats


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Now with that all that said, the more detailed DNI maps suggest that the solar irradiation received in some some areas of equatorial countries is quite substantial, and better than the solar irradiation available in northern Europe, the northern United States and Canada, or most of Russia.

For instance, up in the mountains of Ecuador and Columbia, the DNI rises to 1600 kwh/m[SUP]2[/SUP], and the capital of Ecuador, Quito, is right in the center of such a high-DNI zone. So too in Indonesia the eastern half of the island of Java, and the string of islands that continues from there including Bali, also have good DNI’s levels at 1600 kwh/m[SUP]2[/SUP] and above. It’s in the super-wet highlands of Sumatra that the solar panels and awnings of the TerraLiner won’t work so well.

So what might be true in general for a country, is not necessarily true at a more specific level, especially for countries that have big extremes of altitude, and widely varying climatic conditions, as per countries like Ecuador and Colombia.

In a country as geographically complex as Ecuador, even rainfall does not necessarily correlate with DNI. Here is Ecuador’s map for DNI placed beside its map for rainfall:


3 maps


A coastal city like Portoviejo has a fairly low DNI, around 800 kwh/m[SUP]2[/SUP]

And yet Portoviejo also has comparatively low rainfall. Quito, the capital city, has about the same amount of rainfall as Portoviejo, and yet Quito’s DNI is at least double, 1600 kwh/m[SUP]2 [/SUP]. The following map even classifies coastal, low-DNI Ecuador as a “semi-arid” region:


1 map


So what’s going on here? The answer here is fog, haze, and cloud-cover:

QUOTE

On much of the coastline, the cool current inhibits the formation of clouds that can generate rains, for many months a year. However, the sunshine amount is low, because even in the dry period, the sky is often cloudy, and fogs and mists form……

Along the southern part of the coast (see Santa Elena, General Villamil Playas) there's even a desert, where less than 4 in (100 mm) per year fall; rainfall is concentrated in the period from January to April. Even though generally the rains are very scarce in this period, in the years of El Niño there can be heavy rains, and even floods.

In addition, in this period, although it's the warmest of year, the sunshine is not so frequent, because there is often a haze that covers the sun. The period from June to October is better: the heat is less intense and therefore more enjoyable, and it never rains. It must be said that the amount of sunshine is not good even in this period.

UNQUOTE


We’ll see this phenomenon again in a later series of posts, about arid and semi-arid regions known as “Coastal Fog Deserts”. See http://www.climatestotravel.com/Climate/Ecuador .

Columbia presents a more standard tropical picture, where rainfall and DNI correlate. The wettest parts of the country are also those that have the lowest DNI levels:


4 maps


By way of contrast, Medillin, Cali, and Bogota all have very solar-friendly DNI’s of 1600 kwh/m[SUP]2 [/SUP], and are located in comparatively dry areas. For an ultra-detailed, map-filled, and very clear description of the varied climate zones in Columbia and Ecuador, see http://www.climatestotravel.com/Climate/Colombia and http://www.climatestotravel.com/Climate/Ecuador .

And like other equatorial countries, in general Columbia and Ecuador have very low mean annual wind-speeds across virtually their entire territories:



1 map



In this map, purple represents a mean annual wind-speed of 3 m/s or less up to 4 m/s, or 0 mph – 6.7 mph – 8.9 mph ; and dark blue to light blue represents a mean annual wind-speed of 4 m/s – 6 m/s, or 8.9 mph – 13.4 mph. So the drier highland areas of of Ecuador and Columbia might be excellent places for the TerrrLiner to deploy its solar awnings.

Areas of intense red or orange – high wind speed – only appear in a few places in central Ecuador, and virtually nowhere in Colombia. The contrast here would be with the Altiplano across Peru / Bolivia, where wind-speeds can become significant. Orange areas on this map have mean annual wind-speeds of 8 m/s – 9 m/s , or 17.0 mph – 20.1 mph, while red areas are 9 m/s – 10 m/s and above, or 20.1 mph – 22.4 mph and above. So the orange and dark-red-spotted complexion of the Altiplano indicates many areas with unusually high mean annual wind speeds.


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6. The Problem of Wind in Greater Detail: The Case of South and Central America


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Now some places with excellent Solar Radiance like the Bolivian Altiplano, the Saharan coastal desert along Mauritania and Western Sahara, the horn of Africa (i.e. Somalia), the Tibetan Plateau, and certain mountainous regions in both the Central Sahara as well as South Africa and Namibia, do seem to get quite windy:


2 maps again, side by side: global DNI and global wind



Here are four excellent, much more detailed maps of mean annual wind-speed in North, Central and South America, including the Caribbean and Canada:


4 maps


One immediately notices the huge contrast between North America versus Central and South America. There are huge swathes of purple (very low wind-speed) covering southern Mexico, central America, and most of the northern half of South America. Whereas one sees purple only in North America's mountain states and provinces: a little bit in the Appalachian mountains, much more in the Sierra Nevada and costal ranges in California, Oregon, and Washington, so too in the Rocky Mountains in Idaho, Montana, and northern Washington state, and throughout the mountain ranges of British Columbia and the Yukon.

But anywhere that's flat in the United States and Canada is never purple, whereas the greater part of the Amazonian basin in South America is purple. Indeed, the great central “flatland” of the United States is colored orange and occasionally red, and it's very windy: prairie states like north and south Dakota, eastern Montana and eastern Wyoming, Nebraska, Iowa, Nebraska, Kansas, Oklahoma, and northern Texas, and so too parts of Saskatchewan and Manitoba. Remember, the orange areas on these maps have mean annual wind-speeds of 8 m/s – 9 m/s , or 17.0 mph – 20.1 mph, while red areas are 9 m/s – 10 m/s and above, or 20.1 mph – 22.4 mph and above.

These maps graphically reveal how Central and South America are not very windy places. The overwhelming preponderance of purple, blue, and green in South America, in contrast to all that orange in the central United States, pretty much says it all. Only down in southern Argentina and southern Chile do things get windy, and there they get very windy indeed: a large unified block of the darkest possible shade of red, unlike anything seen in North America. But this is also a low-latitude region with a poor DNI. So there's not much value in deploying solar awnings in Tierra del Fuego in any case….. emoticon.


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Further up the South American continent, the only places that need concerns us are the orange and small red bits, because those are the places where mean annual wind-speeds rise to 17 mph and above: the Altiplano in the Central Andes, and northeastern Brazil. The problem is then this: those orange and red bits further up are also some of the best places in South America from the point of view of DNI, or Direct Normal Irradiation:


6 maps


The Altiplano and northeastern Brazil would be great places to deploy large awnings covered with solar, if average wind-speed were not an issue.

They are also great places to visit. The reasons why one might want to visit the Altiplano in Bolivia/Peru are obvious enough (the Incas, lake Titicaca, etc.). In the case of northeastern Brazil, it should be stated that many beautiful beaches and Brazil's most historic cities are located in the northeast – see https://en.wikipedia.org/wiki/Northeast_Region,_Brazil and
http://www.telegraph.co.uk/travel/d...09/Brazils-10-best-beaches.html?frame=2928297 . The historic centers of Olinda in Pernambuco, and Salvador in Bahia, have been declared UNESCO world heritage sites – see http://www.touropia.com/best-places-to-visit-in-brazil/ . And Forteleza and Recife are considered attractive cities to visit.

One might also mention that the northeast is the sunniest region of Brazil, with the least rainfall:


4 images


So when travelling around Brazil, the TerraLiner would most definitely not want to avoid bits that are marked orange and red for wind speed. It will want to go to these places, and so it should be designed deploy its awnings in these places confident that they'll be able to stay open at least 70 % to 80 % of the time.

These orange and red bits are places where “mean” annual wind-speed is about 20 mph or above, which more or less means that for 50 % of the time, the wind-speed is lower than that, and for 50 % of the time the wind-speed is higher than that. So here one begins to think that an “ideal” TerraLiner awning should be able to withstand wind-speeds of at least 30 mph, without risk of any kind of breakage or tearing. That way, in such regions the awnings could be deployed more like 70 % or 80 % of the time, instead of just 50 % of the time. After all, according to the TORRO scale, the serious risks only begin when wind-speed rises above 39 mph.



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It's also worth remarking that, as per Africa and India already addressed above, there's a fairly strong correlation overall in South America, between low rainfall and high DNI, or high rainfall and low DNI, as well as global horizontal solar radiation:


2 maps rainfall


4 maps radiation


But there is not much of a correlation between DNI and latitude, or mean annual temperature. If anything, the opposite: as one goes south and the temperature becomes more temperate, the DNI improves. Argentina's DNI, for instance, is much better than northern Brazil's, even though Argentina is a colder country. This is almost exactly the opposite of what a North American or European would expect.


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7. DNI, Temperature, Rainfall, and Wind: Confounding Euro-Centric Expectations


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The general point that I am trying to develop in this section, is that in Europe we often tend to think of wet/dry, cold/warm, north/south as opposites that naturally pair up together. Where it's further south, it's also drier and warmer; and where it's further north, its also wetter and colder. So we'll have a natural tendency to think that good DNI also correlates with dry/warm/further south, while poor DNI correlates with wet/cold/further north.

But in tropical countries all of these expectations are confounded.

To once again use my favorite example of Ecuador: it's a country about as far “south” as you can get, sitting right on the equator. And yet it's the colder parts of Ecuador that have a better DNI level. The map on the left illustrates this well in terms of color: Ecuador's capital Quito in the high Andes, at 2,850 m above sea level, or 9,350 feet, is considerably cooler than places that have low elevation in the Amazon or on the coast – see https://en.wikipedia.org/wiki/Quito . And yet Quito has a much better DNI, even though it's colder:


3 images


The third map on the right is the official temperature map from Ecuador's ministry of agriculture – see http://186.46.35.10/inventario.html . Perhaps the person who made it is color-blind, and could not tell the difference between green and red. So it's nowhere nearly as clear, in color terms, about which locations are colder and which are hotter. But at least it's high-resolution.

The ministry's maps of precipitation and climate-type are a bit better, and both classify Ecuador's coast as arid or semi-arid, with low rainfall:


2 images


And once again, although the coast of Ecuador is on the equator, very warm, and very dry, for the most part it has a poor DNI level. Only the area in the very far south is sunnier, with better DNI. The city of Salinas, for instance, has a DNI somewhere between 1000 kwh/m[SUP]2 [/SUP]– 1200 kwh/m[SUP]2[/SUP] : see https://en.wikipedia.org/wiki/Salinas,_Ecuador .

In short, when thinking about DNI, temperature, rainfall, wind-speed, you name it, we have to deliberately abandon our North American or European pre-conceptions and intuitions. For instance, it was a real surprise for me to realize that South America is a much less “windy” place than North America. Or that high altitude might so strongly correlate in some Andean countries with good DNI levels.



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PART Lii: WIND – Designing for really serious wind


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1. Withstanding Coastal Winds up to 40 MPH


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The following few sections were originally located much further along, after I discussed glamping in some prime windsurfing and kite-surfing locations like Cabarete, a legendary spot for watersports in the Dominican Republic. But given the previous in-depth discussion of awnings, this seems like a better place to locate these sections.

Local websites that serve kite-boarders and windsurfers are quite clear about the seasonal wind-conditions in Cabarete:


QUOTE

January to April, Winter: Good and consistent wind, averaging 15-20 MPH (24-32 km/h, 13-17 knots).

June, July and August, Summer: Greatest winds, averaging 15-25 MPH (24-40 km/h, 13-22 knots) side shore.


UNQUOTE


QUOTE

The wind is a powerful trade wind, blowing from 20 knots to 35 knots from the beginning of April until the end of November and almost 100% consistency of more than 20 knots from June to October!
The stats indicate that the most consistent months for wind are from June to mid September and for the best waves and wind combined from February to April.
The regular trade winds blow cross shore from right to left (starboard tack) typically increasing from a light morning breeze to a windy Force 5-6 most afternoons as a result of a local thermal effect. As a result of this the wind is actually underestimated by both www.windguru.cz and www.magicseaweed.co.uk .
[Note: Force 5 – 6 refers to the Beaufort scale, in which a Force 5 wind is 17.9–24.1 mph, and a Force 6 is 24.1–31 mph– see https://en.wikipedia.org/wiki/Beaufort_scale ]

UNQUOTE

See http://www.cabaretekiteboarding.com/weather.php and http://boards.co.uk/travel/world-travel/cabarete-dominican-republic.html#quT131SwCjshVs1p.97 .

So in Cabarete, at least, even if the TerraLiner's awnings were designed to auto-retract only at 30 mph, they might still find themselves in trouble when the wind rises above 26 knots, which is the nautical equivalent. The 35 knots cited in the second quote is equivalent to 40 mph.

What the writer of the second quote is basically saying is something to the effect, “In Cabarete in the summer, you will encounter ideal kite-surfing conditions. It will be a cloudless, sunny sky, and yet the side-shore wind-speed will be terrific for advanced kite-surfing, because it might rise as high as 40 mph.”


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2. Retractable Patio Cover Systems


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Now needless to say, I really have no idea whether the kind of awning that I sketched earlier could withstand a windspeed of 40 mph:


3 images again


One thing does seem clear, however: virtually all retractable motorhome awnings are not designed for such wind-speeds. For two excellent summary articles that describe the limits of standard motorhome awnings, see https://www.fmca.com/motorhome/basics/83-wind-forces-and-your-awning.html and http://rv-roadtrips.thefuntimesguide.com/2011/03/rv_awning.php. Now that we've covered all the different types of awnings, the specialized terminology used in these articles should be perfectly clear.

It's quite possible that what the TerraLiner really needs is not a “retractable awning” system, but rather, something a bit different, something known in the trade as a “retractable patio cover system”. Here is a very useful PDF that explains the differences clearly and succinctly:



1 pdf




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