FEB 19

We wrote a bit about Cool Earth Solar a few months back. Frankly, the idea seems pretty genius to me. Some folks work to squeeze every possible watt out of sunlight with ultra-reflective (extremely expensive) mirrors. But Cool Earth Solar wants to make the mirror as cheap as possible, in order to squeeze every possible watt out of a every single dollar.

They're doing it by creating solar collecting balloons. The top of the balloon is transparent, while the back of the balloon is reflective. While some of the power will be lost because of imperfect transparency and reflectivity, the "mirrors" cost exponentially less than any other solar concentrator on the market.

The rounded mirror backing focuses the sun on a small area of photovoltaic material. The result is that the same amount of sunlight can be captured with significantly less of the (expensive) photovoltaic material. Making the concentrating mirror cheap just further reduces the costs.

Because the devices would be very light, they could be easily mounted on wire structures that would be used to keep them perpendicular to the sun's light. They're hoping to be able to produce power at roughly the costs of natural gas. With California's subsidies that would actually make it one of the cheapest sources of power available. They're already in discussions with several utility companies about the possibility of selling power to them. The $21M will likely only be enough for one pilot plant. But if that's successful, it won't take long for at least one zero to get added on to that total.

That's some seriously clever engineering right there. Lets just hope they can stand up to the elements.

Via CNet Green Tech

Comments (10)

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written by Alaya, February 19, 2008

After checking out the website, I noticed that they install these solar bubbles in mid-air -- suspended by wires. Not only would the bubbles be more exposed to the elements, and therefore more likely to rupture, but all of the wires in the air is pretty unfortunate in terms of bird habitat. Any thoughts from others on the matter?

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written by EV, February 20, 2008

Birds seem to not have problems with wires. A bird-chipper (wind mill) on the other hand, seems to mow them down.

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written by David, February 20, 2008

Regarding the durability of the balloons, if you dig down into the companies website, you learn they are designed to be replaced every 12 months, interestingly.

On the subject of birds and wind power, modern wind turbines are a relatively low risk to birds. The little old ones were a more significant threat, but the ones being installed now are so high and turn relatively slowly, so the birds seem to avoid them.

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Wind
written by Steve, February 20, 2008

Seems like wind would be a significant problem. They probably wouldn't cut it in the plains states (that's where the bird chippers come in).

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Why isn't this tech used in AirShips?
written by So..., February 20, 2008

Seems to me that if you filled that biatch with some helium, and hooked the power up to a couple fans, you'd have yourself a solar powered airship. But that's just me.

Can I open liscence the idea in a blog post? If so, consider it done.

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Plenty of high wires already in existenc
written by Chris, February 20, 2008

When I saw this I thought that they could be a great addition to the guy wires holding up cell phone and radio towers. It might be a challenge getting the devices up there, but it's a space that's already in use.

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Hmmmmmm
written by Bob, February 23, 2008

Great idea, but I have a couple questions. Such a light-weight object would seem to cause alot of issues when it comes to wind, especially if it is not "locked down", and since the inflated, concave, reflective backing is used as a parabolic reflector, it must be moveable in order to be properly oriented to the sun, it can't be anchored in a stationary position. I'm sure there is a way, but it may be an issue.
Also, the effectiveness of a parabolic reflector is dependent on the curve of the parabola and the focal point being correct. As the sun heats the air in the bubble, it will expand, causing the focal point of the parabola to change, and basically making the position of the (apparently) stationary PV panel wrong. Maybe the low cost of the unit is a fair trade for the "touch and go" aspect of the focal point?

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PV calibration w.r.t. temperature
written by 672, February 25, 2008

Good comment about the focal point. However it wouldn't be hard to move the PV cell with respect to focal point. The focal point could be calculated based on expansion of the air with respect to temperature. The PV cell location could then be adjusted on the fly with feedback from a thermocouple. It might add a few bucks to the bottom line but it can be done relatively easily.

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written by hassan, December 12, 2008

i think it is good .. if replaced the flex plastic with polycarbonat .. i think it will be 100 year servesability.. thanks

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written by Sly, April 04, 2009

I've been offgrid for years now and the solar panel manuals all say not to use concentrators on the panels. I have some used ones from the Carrizo power plant in New Mexico and they used concentrators on the panels. After 20 some years of operating at the plant, the concentrators led to browning of the plastic laminates between the cells and the outer tempered glass, reducing the output power by at least 25%. I still got a good deal on the panels. What have you done to prevent the PV cells from cooking in the extreme heat that the concentrators would produce?
Thanx
Sly

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