Everyone is working on a better way to get more energy out of photovoltaic solar cells, from using quantum dots to fiber optics. Now a Swiss company has decided on a brute-force method, hit a photovoltaic cell with the equivalent of 2,000 suns. Airlight Energy, partnering with IBM Research, ETH Zurich and Switzerland’s Interstate University of Applied Sciences, is developing a way to use parabolic reflectors to concentrate sunlight onto a set of solar cells, each only a half inch on a side.
It’s called a High Concentration PhotoVoltaic Thermal (HCPVT) system and so far, the test plant is capable of generating 25 kiloWatts of electricity. The parabolic dish tracks the sun as it moves across the sky, so it always gets the maximum amount of light. As a result, the solar cell chips receive 2,000 times as much light energy as they normally would. Even though they’re small, each cell pumps out up to 250 Watts, and there are hundreds of them.
Photovoltaic panels, though, start losing their efficiency if they get too hot. To keep the chips cool, a network of tiny tubes carries water between and around them. The water reaches temperatures of about 194 degrees, which can be used to heat water in a building or to heat salty water, which is passed through a membrane that removes the salt to make the water drinkable.
The photovoltaic plant operates at 30 percent efficiency, much higher than the less than 20 percent one might expect from a typical roof-mounted setup. And a parabolic dish of about one square yard would be able to generate about two kilowatt-hours per day and purify seven to nine gallons of salt water. Right now there are several prototypes being built, with one being tested in Switzerland. Airlight said that they envision this kind of solar power in countries where there’s lots of sun but little fresh water.