Peak sun? Peak sugar?

It strikes me as common sense that if you need nothing more than a magnifying glass to start a fire, there's free solar power anywhere. Yet concentrating solar power in such a manner is not what ordinary solar collectors do. Until recently, that is. IBM seems to have figured out how to use the magnifying glass principle to dramatically shrink the amount of space and number of components needed to build a solar farm:

By mimicking the antics of a child using a magnifying glass to burn a leaf or a camper to start a fire, IBM scientists are using a large lens to concentrate the Sun's power, capturing a record 230 watts onto a centimeter square solar cell, in a technology known as concentrator photovoltaics, or CPV. That energy is then converted into 70 watts of usable electrical power, about five times the electrical power density generated by typical cells using CPV technology in solar farms.

If it can overcome additional challenges to move this project from the lab to the fab, IBM believes it can significantly reduce the cost of a typical CPV based system. By using a much lower number of photovoltaic cells in a solar farm and concentrating more light onto each cell using larger lenses, IBM's system enables a significant cost advantage in terms of a lesser number of total components.

For instance, by moving from a 200 sun system ("one sun" is a measurement equal to the solar power incident at noon on a clear summer day), where about 20 watts per square centimeter of power is concentrated onto the cell, to the IBM Lab results of a 2300 sun system, where approximately 230 watts per square centimeter are concentrated onto the cell system, the IBM system cuts the number of photovoltaic cells and other components by a factor of 10.

While this seems like a no-brainer, the reason it hadn't been done before was because only recently did they realize that computer chip technology could be used for cooling solar collectors:
The trick lies in IBM's ability to cool the tiny solar cell. Concentrating the equivalent of 2000 suns on such a small area generates enough heat to melt stainless steel, something the researchers experienced first hand in their experiments. But by borrowing innovations from its own R&D in cooling computer chips, the team was able to cool the solar cell from greater than 1600 degrees Celsius to just 85 degrees Celsius.

The initial results of this project will be presented at the 33rd IEEE Photovoltaic Specialists conference today, where the IBM researchers will detail how their liquid metal cooling interface is able to transfer heat from the solar cell to a copper cooling plate much more efficiently than anything else available today.

Yahoo article here. I hope this pans out. As to why it would take so long for someone to put two and two together and figure out how to harness solar magnification in a practical way, I'm not sure. (According to this article the technology is being described as "cheap and efficient," and already in use in Australia.)

While using this techology to build solar farms is commendable, I wonder how soon it will be before they start selling home units.

(And speaking of energy, with the price of gasoline continuing to escalate, I wonder how long it will be before people resort to home distillation or ethanol. Sugar is still cheap, and this unit will produce 35 gallons of car fuel per week, at $1.00 a gallon. More here, and remember, "home ethanol production was advocated and used by Henry Ford when he created the Model T.")

posted by Eric on 05.22.08 at 05:16 PM


"cool the solar cell from greater than 1600 degrees Celsius to just 85 degrees Celsius."

What do they do with the rejected heat?

dre   ·  May 22, 2008 5:25 PM

Why don't we just go back to whale oil? Petroleum replaced whale oil in the 19th century, but petroleum isn't a renewable resource and whales are. Can cars run on whale oil? I don't see why they couldn't.

chocolatier   ·  May 22, 2008 8:07 PM


The rejected heat is probably wasted in the air.


There is a severe shortage of whales for the purpose.


Concentrated solar photo voltaics have been done before. There are a few problems. Cell life for one. Typically such cells produce 1/2 volt. That means getting about 450 amps out of a 1 cm sq chip. Not easy.

Also the more concentrated the light the more closely the reflector must track the sun. Also there are only a few liquid metals suitable sodium and potassium and they are very corrosive and cant stand contact with the water vapor in the atmosphere. Woods metal might work but it contains lead and other toxic metals. The IBM folks have a few more problems to solve to make this commercial.

M. Simon   ·  May 22, 2008 9:17 PM

If you're going to make your own ethanol for fuel, you wouldn't start with sugar, at least in the US. The subsidized price is WAY higher than high fructose corn syrup.

Richard R   ·  May 22, 2008 11:26 PM

I wish they'd figure out a way to cool my Xbox360...

Mr. Bingley   ·  May 23, 2008 7:12 AM

Hell, there is probably more energy to be captured in the heat than any sort of photovoltaic conversion.

Phelps   ·  May 23, 2008 10:28 AM

Sugar takes many forms.

What I like about these technologies is that I enjoy seeing things I might be able to actually buy and use in the near future.

Eric Scheie   ·  May 23, 2008 11:43 AM

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