Solar Cells Washington DC
Lowering the Cost of Solar Energy
A minute's worth of sunlight that reaches the earth's surface has enough energy to supply all our power needs for a year. But solar power is still a lagging technology -- not refined enough for widespread acceptance and requiring equipment that is too expensive for most end-users who can't secure state and federal financial incentives. In fact, it still costs two to five times as much to get power from the sun as it does to derive it from traditional fossil fuels.
But researchers are charging full-steam ahead, trying to reduce the manufacturing costs of solar equipment and increase efficiencies. Most of their research is concentrated on two fronts: making cheaper versions of crystalline silicon cells (which comprise 80 percent of the current solar market) and creating less expensive photovoltaic technologies with the reliability and efficiency of crystalline silicon.
In a traditional solar cell, a single material (silicon) performs three essential functions: It absorbs sunlight, converting photons into electrons and "holes, which occur when electrons leave their normal positions; it withstands the electric field needed to separate electrons and holes; and it conducts the electrons and holes to the cell's collecting contacts. To perform these three functions simultaneously and efficiently, the semiconductor material must be very pure -- and very expensive. With the purchase and maintenance price amortized over the typical 20-year life span of a solar cell, a single produced watt of electricity costs about $4. By contrast, energy currently can be extracted from oil and gas for about $0.40 per watt.
To lower costs, companies and researchers are experimenting with different materials, such as amorphous silicon, gallium arsenide and copper indium diselenide. These are often called thin-film solar cells, and can be sprayed on or otherwise bonded to other materials such as traditional-looking shingles. But the catch with these materials is their efficiency, since they harness about 8 to 10 percent of the total energy in sunlight, compared with 15 to 20 percent efficiency of typical solar cells. So while you're paying less for them, you're currently getting only about half as much energy from them as you would with silicon.
But STMicroelectronics, Europe's largest semiconductor maker, has stated that it expects to introduce its first prototypes of a revolutionary new solar cell that should cost as little as $0.20 per generated watt. The company says it expects to demonstrate 10 percent efficiency and move from prototype to production by the end of this year.
Our target price per watt is fixed at $0.20, says Dr. Salvo Coffa, the lead researcher in ST's solar development group. And I don't expect any technological difficulties in going from prototypes to mass-produced products.
ST is conducting its research in two different arenas: using cheaper organic materials -- such as plastic -- as opposed to silicon, and developing the more futuristic (and further from production) solar nanotechnology.
Solar nanotechnology involves the use of nanosize (one nanometer is about 1,000 times smaller than the diameter of a human hair) semiconductors that are arranged through chemical reactions in a matrix of plastic-like materials. In these cells, each essential function is performed by a different substance (as opposed to silicon, which performs all three). An organic dye absorbs light and creates electron-hole pairs, a nanoporous (high-surface area) metal-oxide layer transports the electrons, and the hole-transporting material is typically a liquid electrolyte.
The cost of production is expected to be drastically lower than the cost to produce today's solar cells. In fact, these nanocomposite solar cells can be manufactured in a fashion similar to producing photographic film. Some industry experts even predict that the efficiency of such nanocomposite products should be on par with traditional silicon in as little as three years, but those involved are more hesitant to venture guesses as to when the products will actually come to market.
Solar advocates are quick to point out that even with today's expensive initial costs, most solar systems eventually pay for themselves, and they often save money when tax incentives and rebates are factored in. The technological advances described above only serve to increase their optimism.
For more information about solar-cell research and development, visit STMicroelectronics website at http://www.st.com , or you can check out a couple of U.S. Department of Energy sites: the Energy Efficiency and Renewable Energy site at http://www.eere.energy.gov and the National Renewable Energy Laboratory site at http://www.nrel.gov .