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Photocell Provides Both Heat And Electricity

November 27, 2001

In 1969, scientists at the Ioffe Physico-Technical Institute, St. Petersburg made heterostructured photoelectric cells based on the elements of the third and the fifth group of the periodic table (for example, gallium arsenide). Now the photocells can find application not only in space, but also on Earth. To make them working the sunlight is not necessary, because they can use radiation from any heated substance. The ordinary dynamo with petrol drive also converts heat to electricity, but the Ioffe scientists have offered a more sophisticated device.
      
If someone lives in the mountains, where there is neither heat plants nor power lines, it is enough to have the photocell super-heater and a gas cylinder to get warm, cook food and play on a notebook. A device with a size about a small case works using a gas-jet, which heats the emitter - a small metal plate - up to 1200-1400 C. That is not much hotter than burning coal. At such temperature the plate becomes light-orange, but emits mainly long-wave radiation - with wavelengths higher than 1 micron. The emitter is surrounded by photocells, which absorb this light.
      
The photocell in the heater is a gallium-stibium alloy. Such heterostructured conductor catches long-wave radiation, so it gives a higher current than usual cadmium photocell, which can only convert radiation with wavelengths of less than 1.1 micron. Stibium-gallium photocell with a square of 2 sq. cm is able to produce 10A current. The super-heater has 30 photocells in a series-connection and they give 12 V voltage. With such a source of electricity , one can use a notebook, a small TV or an economic lamp.
      
Electricity is the main benefit of the device, but it also heats well. The heated emitter radiates extensively, some part of energy is taken by photocells, but about 70% of photons are reflected back to the emitter. The device is being cooled by a fan, which drives the hot air away from the heater and a room gets warm fast.
      
The physicists have made only a pilot device. It costs much, but it is possible to choose such materials and dimensions that it would be profitable to put it on a production line. It could be of use for geological parties and polar explorers: with the photocell heater you do not have to wind up a diesel engine at 40 C frost, just burn a gas-jet. There are neither pistons nor crankshafts. There it is, noiseless, standing in the corner, giving both heat and electricity.

Informnauka (Informscience) Agency