Inflatable Solar: Coolearth Concentrated Photovoltaics
by Sami Grover, Carrboro, NC, USA 
on 12. 6.07
Inflatable solar? It’s not the first time we’ve come across the idea. But according to Coolearth Solar, they’ve patented a design for inflatable solar collectors that are supposedly a cheaper way to concentrate sunlight onto photovoltaic cells. The makers claim their design is up to 400 times cheaper than polished aluminum mirrors which, if true, would certainly improve the economics of concentrated photovoltaics. Maybe they can team up with the makers of the inflatable car. ::Coolearth Solar::via YouTube::
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there goes my design.. darn.. :). but congrat to coolearth solar.
Most inflatables are vinyl. Boy, talk about a conflicted trade-off. This could cause exploding heads over at Greenpeace central.
This idea should be modified .. as these will pop with the hot air that will build inside. they should have a couple small inflater fans running constantly and a smaller exit hole to constatly circulate the heat out and increase the efficency of the PV (they don't work as well with heat), this may cut into the efficiency a touch but I think it would equal out with the PV being cooler. This would also reduce maininence as another small hole would not deflate the bubble.
Also to reduce the heat on the PV it should be connected to the outside, the reflecor side could bubble out more and the PV side could be more "flat" and the PV integrated into that side. Possibly being thin film flexable PV unless the high efficency PV is more economic per watt.
In regard to VOCs:
VOCs should only matter when they occur indoors in enclosed spaces. Because they are volitile they will react with almost anything and won't stay around outdoors with UV cooking them too peices. Its only indoors where the concentrate unreacted that they harm our lungs and can eventually cause cancer.
And as an asside I wanted to state an argument that has been building in me; sometimes we don't want what we build to degrade, but to last. We should only want what is disposable to degrade, as its a horrible waste of energy otherwise.
I am not even sure I want plastics in general to degrade, after all future generations can mine the landfills for useful materials. If they were degraded the usefulness and energy they represent would be devalued. right now plastic recycling has to be proped up with a false economy of our tax dollars in order to be profitable and only aluminum and paper are inherintly profitable to recycle. (and paper only because there is a demand for the "recycled" label)
If plastics don't degrade however they can be saved for future generations when it would be profitable to recycle/mine from our now filled landfills.
(An exception to this is plastic objects that are a hazard to wildlife like the plastic ring can holders, they should degrade.)
I think our top priority should be our climate/air polution, followed quickly by our water quality issues, land polution in the form of landfills are minor in compaired to those two, its just an esthetic blight if managed well.
400x cheaper is a specious claim.
Lifecycle cost - including paying the guy with the roll of tape - is much more important than unit cost.
If the units last as long as polished aluminum mirrors and cost the same to maintain, then 400x cheaper would be meaningful.
We talk as if solar panels getting to $0.30/watt would change the world. But not if they only had a 1 year lifespan.
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Author's comment:
True enough John, but don't aluminum reflectors need a lot of maintenance in terms of polishing etc? Would be interesting to know more about the lifetime costs of either - I'll see if I can grab time to fish around for more info.
I'm pretty sure the balloons will need to be replaced once a year or more. Have you ever seen a plastic film that maintained its integrity in the sum for extended exposure? A plastic bag becomes brittle in weeks. Surely these will be better made than that, but they will be under fairly high stress as the shape of the balloon is essential, and exposed to every kind of weather, plus the daily thermal cycle. Replacing them will probably cost $50-$100 per balloon. If the balloons produce 750 W each (pretty optimistic), that's an additional 7 to 14 cents per watt each year, which is problematic and yields a lot of waste.
I couldn't find anything on the Cooltech site about durability of the balloons, which I believe confirms that this is a real problem. Otherwise, they would address it.
I don't mean to be a naysayer, but it's important to acknowledge the real liabilities of a design.
Some vinyl is very sun resistant, and long lasting. Think of football stadium domes, inflatable kayaks etc. That said, maybe glass would be a better way to go. Possibly some existing tube designs could be used. Silver paint could be rolled down the tube, and thain rolled back and forth to cover one side, if that would be helpful. The heat from the glass might be tapped for use by attaching them to a water bath. A water bath might work for the plastic also.