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

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7. SunPower: the Most Efficient Solar Panels on the Market Today


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Now what matters for a high-end mobile home like the TerraLiner is not cost, but rather efficiency, at least for the solar panels fixed to the roof. SunPower advertises that it has the most efficient solar cells in the industry, in the sense that they get the maximum possible amount of power per square cm – see http://us.sunpower.com , http://us.sunpower.com/home-solar/solar-cell-technology-solutions/ , http://us.sunpower.com/why-sunpower/high-efficiency-solar-technology/ ,
http://us.sunpower.com/home-solar/ , http://www.sunpowercorp.co.uk/products/solar-panels/ , http://us.sunpower.com/solar-panels-technology/e-series-solar-panels/ , http://us.sunpower.com/sites/sunpow...s-e20-series-327-residential-solar-panels.pdf , http://us.sunpower.com/solar-panels-technology/x-series-solar-panels/ , http://us.sunpower.com/sites/sunpow...35-345-residential-solar-panels-datasheet.pdf , http://www.sunpowercorp.co.uk/products/rooftop-solar-solutions/ , http://www.sunpowercorp.co.uk/cs/Sa...goBlobs&blobwhere=1300288362686&ssbinary=true , and http://www.sunpowercorp.co.uk/cs/Sa...goBlobs&blobwhere=1300288362661&ssbinary=true :


2 images from PDF of Sunpower X-series




Here are some SunPower panels installed on homes:


8 images




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And here are some SunPower videos:

https://www.youtube.com/watch?v=0LLzstESwTw
https://www.youtube.com/watch?v=Rh2JVQJgsns


https://www.youtube.com/watch?v=AHGZ92Estno
https://www.youtube.com/watch?v=kdi-qmhCLgI

https://www.youtube.com/watch?v=ECgQHlDkIos
https://www.youtube.com/watch?v=sznZHSuZXrc

https://www.youtube.com/watch?v=OXUF8tyddJ0
https://www.youtube.com/watch?v=VX3QV_pnm0k

https://www.youtube.com/watch?v=2lTotfOgLWs
https://www.youtube.com/watch?v=VqqS1Exq2Hk



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https://www.youtube.com/watch?v=GnKT6kRO55E
https://www.youtube.com/watch?v=RbzKvyjgy2I

https://www.youtube.com/watch?v=OEtzyS_OnDA
https://www.youtube.com/watch?v=sznZHSuZXrc


https://www.youtube.com/watch?v=L-K919cEueg
https://www.youtube.com/watch?v=kdi-qmhCLgI

https://www.youtube.com/watch?v=p78dOmzIkxk
https://www.youtube.com/watch?v=Ca2jkDehGGY
https://www.youtube.com/watch?v=6v1N21xB1BU


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Extra in case

,,..987



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https://www.youtube.com/watch?v=xn78SHbhQvQ
https://www.youtube.com/watch?v=Vx_i7dwjxrQ

https://www.youtube.com/watch?v=oGcFqpY8it0
https://www.youtube.com/watch?v=5Jny4t4U4gI


https://www.youtube.com/watch?v=C4_WlfsOxhM
https://www.youtube.com/watch?v=T76MGQpo--o
https://www.youtube.com/watch?v=cOYLYIpNcoQ
https://www.youtube.com/watch?v=oZqf-X3MlZ4



For the SunPower YouTube channel, see https://www.youtube.com/channel/UCOvb0zfbBxC9P_sgxMojCvg .


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I could only find one specific example of SunPower panels installed on an an RV, and again, the coverage is only partial – see


5 images


See http://jdfinley.com/tag/environment/ and http://jdfinley.com/tag/environment/ .

If anyone reading this knows of other SunPower installations on motorhomes, please post! SunPower panels are a premium product, after all, so cost-conscious motorhome owners will probably avoid them. As the following recent comparison tables make clear, SunPower continues to lead the pack in terms of efficiency:


1 image


See http://www.theecoexperts.co.uk/which-solar-panels-are-most-efficient , http://www.theecoexperts.co.uk/which-solar-panels-are-best-how-much-should-i-expect-pay , http://www.pv-tech.org/news/sunpower_lifts_lid_on_new_record_21.5_efficient_x_series_solar_modules , and http://www.prnewswire.com/news-rele...rd-efficiencies-of-215-percent-201220521.html

In some “Top 10” rankings the panels from other suppliers will rank higher than SunPower, even though they are less efficient, because they seem better value for the money. SunPower panels will be on the comparatively expensive side. But again, our concern for the TerraLiner is not the price/performance ratio, but rather, the performance-per-square-cm ratio.

However, if anyone knows of a leading-manufacturer of solar panels that can beat the SunPower in terms of performance, please post!!! For instance, Panasonic recently set a world record for crystalline solar cells, with 25.6 % efficiency – see http://solarlove.org/panasonic-hit-solar-cell-sets-world-efficiency-record/ . But that means nothing if Panasonic has not brought a product to market that can beat SunPower's efficiency.

Haf-E, above you wrote:

The highest efficiency commonly available PV modules are producing 300 watts from 1.6 square meters of space. This includes all of the losses and the frame, interconnects etc. These panels are about 1 meter wide by 1.6 meters long - so two can fit side by side on most large expedition vehicles (2 meters wide solar array with allowance for clearance between and on the edges for mounting. So if the vehicle's roof was, say, 10 meters long, the roof could hold 12 of these modules for a total rated output of 3600 watts. These are glass type modules with up to 30 year warranties. Depending on the supplier/brand etc these are available for as little as $1 USD a watt or even lower. With an air gap under them for cooling, they will also reduce the heat gain of the vehicle during the afternoon just like the land rover's "safari" roof they used to offer.

I've seen large RVs with a second slide out PV array mounted under the normal PV array which could be deployed when parked for more capacity. The complexity of doing this is considerable though and might be difficult to make it rugged enough for true expedition travel.

What solar panels are you thinking of? The SunPower X-series panels, which are considered industry leaders, have almost exactly the dimensions you describe – they are 1.046 m x 1.559 m, or 1.63 m[SUP]2[/SUP] , and produce 345 KW. So your statement is certainly correct, although just a tad low….. Do you know of any commercial panels that could beat this figure?

Of course even more efficient than mono-crystalline silicon, are gallium arsenide multi-junction solar cells of the kind used in spacecraft. But they cost a bundle, which is why their use has been confined mostly to satellites – see https://en.wikipedia.org/wiki/Solar_panels_on_spacecraft , https://en.wikipedia.org/wiki/Multijunction_photovoltaic_cell , https://en.wikipedia.org/wiki/Gallium_arsenide , and https://en.wikipedia.org/wiki/Gallium_arsenide#Solar_cells_and_detectors . And no, I am not about to propose that the roof the TerraLiner be covered with gallium arsenide multi-junction solar cells….. emoticon




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8. Alta Devices Thin-Film Gallium Arsenide Technology


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So safas, your links to solar cells produced by Boeing for use in space are definitely interesting – again, see http://www.spectrolab.com/cic.htm , http://www.spectrolab.com/DataSheets/cells/PV XTJ Cell 5-20-10.pdf ,http://www.spectrolab.com/DataSheets/cells/PV UTJ Cell 5-20-10.pdf . These also indicate perhaps the kinds of efficiencies that might be possible in commercial, terrestrial solar cells 5 years from now, i.e. somewhere in the neighborhood of 25 or 26 %, instead of 21.5 %, which is what SunPower is currently selling. But when making the calculations that follow below, I will be using SunPower solar cells as my benchmark, for reasons that should become clear.

The links to the pdfs from Alta Devices about solar cells used in cars and a UAV are also interesting – see http://www.altadevices.com/pdfs/uavs.pdf and http://www.altadevices.com/pdfs/automotive.pdf . 250 W m[SUP]2[/SUP] would certainly be impressive; SunPower achieves a power density of 212 W m[SUP]2[/SUP]. But most of the PDFs on the Alta Devices website strike me as “Vaporware”, rather vague on details. Most of the PDFs describe possible applications, not the solar cells and their technology. I looked up the company, at http://www.altadevices.com and http://www.altadevices.com/technology-overview.php , and found the following PDF that describes their technology in better detail:


Image of PDF


See http://www.altadevices.com/pdfs/single_cell.pdf .

But what I've noticed amongst those selling Thin-Film flexible solar, is that they tend to be evasive as regards providing clear power numbers in terms of wattage per square meter for actual products. Alta will state that its cells are 25 % efficient, but what I ultimately want to know is how many Watts a given finished product, of a certain size, actually produces.

Alta and other producers of thin-film flexible solar cells are certainly correct when they argue that peak efficiency as measured under ideal conditions with the sun directly overhead at the equator, is just one metric. And they are correct that real-world performance, which takes into account shading, dust, non-optimal alignment in relation to the sun, etc., is actually more important:


Quote

Achieving Both High-Efficiency and Flexibility
Among all available PV technologies today, GaAs is the recognized leader for performance and reliability. This technology, originally developed for use in satellite power systems in the 1980s, is well known as the technology with the highest potential for performance in single-junction PV cells. GaAs cells and modules, with their high-energy efficiency, small size, light weight, and extended operating temperatures, are also ideal for use in extreme conditions. A cost-effective, flexible mobile power technology based on GaAs would be a game-changing technology. Unfortunately, traditional GaAs cells are extremely expensive (10x to 100x more than other PV technologies). They are also heavy and brittle, making them completely inappropriate for use in mobile power systems. Recent advances in the development of new, thin and flexible single-crystal GaAs thin-film PV technology have changed this situation. These systems can be made into lightweight, robust, and flexible form factors, with extreme environmental endurance and reliability. They can also be manufactured at a fraction of the cost associated with traditional GaAs PV technology. This advance in technology represents a revolutionary breakthrough for mobile power systems.
As an example of the advances described above, Alta Devices has developed a thin, mobile power technology on a flexible substrate that has been independently certified by NREL as world-records for both single (28.8%) and dual (30.8%) junction solar cells. The performance in both cases is under AM1.5G solar illumination at 1 sun intensity. What is most intriguing, however, is that these world record performances were achieved in lightweight, flexible thin-film cells with a cost-structure that is compatible with mass-deployment. Modules from this technology have already been certified by NREL at 24.1% efficiency (another world record).
More than Just Highest Peak-Efficiency . . . 
Best Real World Performance
While peak efficiency is the most common metric used to compare PV cells and modules, it is not the only critical metric. Portable systems must perform and generate electricity under a broad range of environmental conditions of temperature and cloud cover (or dust cover), and they need to produce electricity at all times of the day (from dawn to dusk). As such, critical parameters by which systems must be evaluated also include temperature sensitivity, and low-light/diffuse-light performance. Here again, Alta Device's mobile power technology excels compared to all other solutions. Under real-world operating conditions, mc-Si PV power output degrades 5x more than Alta's mobile power technology under typical field operating temperatures, and degrades 2.5x more under early/late/cloudy sun conditions.
This additional improvement under real-world conditions results in even greater performance potential for Alta's technology in any mobile power system. Alta Devices produces between 2x and 4x more electricity per unit area and per unit weight than all competing technologies.
This breakthrough in PV technology means that users do not need to trade off performance for cost, weight or flexibility that is inherent in other technologies. For mobile power, this is a truly enabling change, allowing extremely high charging efficiency in a small, lightweight and highly-portable form-factor, and is ideal for use on anything that moves, can be carried, or worn.


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This is all very interesting, as are the various applications that Alta speculates might be possible – see http://www.altadevices.com/applications-overview.php , http://www.altadevices.com/applications-uavs.php ,
http://www.altadevices.com/pdfs/uavs.pdf , http://www.altadevices.com/applications-consumer.php ,
http://www.altadevices.com/pdfs/consumer_devices.pdf , http://www.altadevices.com/applications-wearables.php ,
http://www.altadevices.com/pdfs/wearables.pdf , http://www.altadevices.com/applications-automotive.php , http://www.altadevices.com/pdfs/automotive.pdf , http://www.altadevices.com/applications-internet.php , and http://www.altadevices.com/pdfs/sensors.pdf :


4 pdfs, Automotive, Wearables, Tablet, and UAV


But most interesting for me is the PDF about an actual product, a solar charging mat, with clear wattage figures and measurements – see http://www.altadevices.com/applications-remote-power.php , http://www.altadevices.com/pdfs/charging_mat.pdf :


1 pdf about charging matt


The 60 W charging mat measures 69.85 cm (27.5 in) x 66.04 cm (26 in), or .4612 m[SUP]2[/SUP], and this gives it a power density of 130 W per m[SUP]2[/SUP]. That's certainly good in a flexible thin-film solar panel; but it's not even close to the power density of 212 W m[SUP]2[/SUP] that SunPower currently sells.

The web is literally packed to the brim with videos explaining the supposed “real world” performance superiority of thin-film solar over mono-crystalline panels. For instance, see the following video that compares the performance of a PowerFilm 120 KW panel, versus a Goal Zero 120 KW mono-crystalline set-up, in a specifically mobile application:


https://www.youtube.com/watch?v=AExFl6LUqxk


And very much agreed, if I were a soldier and needed to carry a 120 KW panel to power something that I was carrying, I would much prefer the PowerFilm product.




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But the roof of a mobile home is more like the roof of a house (albeit mobile), than it is like a wearable bracelet, a cell-phone or Tablet PC case, or a portable charging set-up.

Furthermore, there's flexible and then there's flexible. A bit further along I will be discussing solar cells as applied to the TerraLiner's awnings, i.e. the truly flexible solar cells made by PowerFilm. Now it would be great if the solar cells made by Alta Decices could be similarly incorporated into flexible arrays that can be rolled around a cylinder just 2 inches in diameter. But based on the videos below, it does not seem that Alta Devices gallium-arsenide technology is flexible to quite the same extent as PowerFilm's technology:


https://www.youtube.com/watch?v=eNWkemmxGqw
https://www.youtube.com/watch?v=6ozplczrPbw
https://www.youtube.com/watch?v=OAYsN0uaBCI
https://www.youtube.com/watch?v=HWBVi0FcrdM
https://www.youtube.com/watch?v=P3Sr5bbMivc#t=20
https://www.youtube.com/watch?v=3cO5ZEVM41k
https://www.youtube.com/embed/P3Sr5bbMivc
https://www.youtube.com/embed/HWBVi0FcrdM


I could be wrong about this, and so when doing power calculations for the TerraLiner's awnings, I will also run calculations on “theoretical” awnings using solar cells by Alta Devices, alongside power calculations for an actual awning that already exists (actually, a solar field shelter), produced by PowerFilm.


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PART Ib: SOLAR ENERGY – Calculating the potential power of the TerraLiner's Solar Array


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1. The amount of surface area available for Solar on the TerraLiner's Roof


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So far, my friends and I have only done very rough calculations of the amount of solar power the TerraLiner will have available. We've been concentrating on other things, namely, the design of the tubular space-frame, and I've been concentrating on the design of the interior….. Remember just how “undetailed” about mechanical matters Hamid Bekradi's concept study was for his futuristic OEX-B overlanding vehicle – see posts #972 to #985, at http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page98 and http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page99. So from a design school perspective, the level of technical detail that I am exploring in this thread is actually not necessary…..emoticon

The following is then my first stab at calculating just how much solar power the TerraLiner might have available.

The roof of the TerraLiner is a single piece, because it's a fully integrated motorhome. No gap between the cab and the cabin, as per a typical expedition motorhome. So imagine that almost all of the roof is covered by solar cells, just like egn's Blue Thunder: 10.5 m x 2.55 m wide = 27.775 m[SUP]2[/SUP]. However the front windshield will be canted back, so use a length of 10 m instead, to arrive at a figure of 25.5 m[SUP]2[/SUP].


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2. The Roof Gangway: Walkable Solar Panels


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Although there will be a gangway down the center of the roof to for access, that too will be composed of the new kinds of solar panels emerging that can be walked upon – see http://www.gizmag.com/solar-powered-sidewalk/29351/ ,http://www.designboom.com/technolog...st-walkable-solar-paneled-pathway-10-10-2013/ , http://www.thevoltreport.com/sidewalk-solar-panels-you-can-walk-on/ , http://inhabitat.com/students-install-the-worlds-first-solar-pavement-panels-in-virginia/ , http://www.onyxsolar.com , http://www.onyxsolar.com/walkable-photovoltaic-roof.html , http://www.onyxsolardownloads.com/d...ecifications-Example-III-Walkable-floor-f.pdf , http://www.krdglobalgroup.com/uploa...yxsolar-corporate-brochure-bipv-bureau-en.pdf , http://assets.selector.com/assets/d.../onyx-solar-project-references-brochure-1.pdf ,http://selector.com/au/products/onyx-solar-bipv-walkable-roofs-and-floors#img2 , and http://www.archello.com/en/product/walkable-pv-floor :


9 images


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These walkable solar panels are now available for sale, and can be installed “backlit” in a variety of bright colors:


3 images



And see the YouTube video at:


https://www.youtube.com/watch?v=SK9NffR7OmQ


Their specification runs as follows:


QUOTE
PV Module Electrical Characteristics at STC
Module Quantity: XXXXXXXXX
Product reference: 636BN-06000600-00-1 as ONYX PHOTOVOLTAIC GLASS Manufacturer: Onyx Solar Energy
Length: 23 5/8”
Width: 23 5/8”
Thickness: 5/8”
Surface area: 0,36 m or 3,8 sqf
Weight density: 40 kg/m or 8,1 pounds/sqf
Type of PV Cell: a-Si Thin Film Solar Cells
Transparence degree: XL DARK Clear 0%
Nominal peak power: 23,00 Wp
Open-circuit voltage: 45,35 Voc(V)
Short-circuit current: 0,72 Isc (A)
Voltage at nominal power: 34,02 Vmpp(V)
Current at nominal power: 0,65 Impp(A)
Power tolerance not to exceed: ± 5%
Maximum system voltage: 600 Vsys (V)

UNQUOTE
See http://www.onyxsolardownloads.com/d...ecifications-Example-III-Walkable-floor-f.pdf .
I am not sure how to translate this electrical information into a simple statement like “10 W power output per panel”. So if anyone reading this might know the answer, please post! So far, as near as I can tell Onyx has not released any clear information to this effect.

On the web one can only find articles stating that the grid of 27 panels installed at George Washington University have a maximum peak output of 400 Watts, and that they form an area of 100 square feet – see http://www.treehugger.com/solar-technology/GWU-solar-walk-worlds-first-solar-paneled-sidewalk.html , and http://inhabitat.com/students-insta...virginia/solar-walk-up-jmc-2013-9954-460x260/ . So that works out to just 4 W per square foot:


3 images


The panels installed at George Washington University seem much more rectangular than the square panels that Onyx is now officially bringing to market, so perhaps the commercial panels will also prove more efficient?

But if they are not, then given that they are 3.8 square feet each, they would have a maximum power output of 15.2 W, which is fairly negligible. But it’s still better than nothing. If a line of them ran down the center of the TerraLiner’s roof, serving as a load-bearing walkway, 16 of them in a row (60 cm x 16 = 9.6 m) could potentially produce 243 W of electricity. And if they were back-lit and brightly colored, located between the solid black one version of the the SunPower X-series solar panels, that would be one very beautiful central gangway indeed!


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