Low-cost semiconductor cells with efficiency approaching 20% have evolved making use of alloys of selenides of copper, indium, and gallium (CuIn1_xGaxSe2, known as “CIGS”). These crystalline alloys are typically P-type semiconductors with appropri­ate bandgaps, high absorption coefficients, and quite large diffusion lengths. The cell is typically in the form of a thin N-layer placed near […]

In brief summary, the ideal single-junction cell at best captures only about 30% of the light energy. Going beyond the single-junction cell, a well-developed technology is to stack two or three junctions in series (tandem), engineered so that light not converted in the first junction may be converted in the second or third junction. This […]

Gaseous hydrogen can be piped as is natural gas, with preference for plastic pipe to avoid questions of hydrogen embrittlement of steel. Large volume storage of hydrogen (as is presently the case for natural gas) may be possible in favorable geological underground formations. Caverns presently sought for storing or “sequestering” unwanted CO2 underground may conceivably […]

The reasons for ascendancy of CIGS include efficiency and durability, but the main reason is that these cells can be manufactured, without vacuum equipment, on a roll- to-roll mass basis similar to a modern printing press. The next figure shows one possible step-by-step prescription for CuIn1_xGaxSe2 CIGS cell manufacture that does not require vacuum equipment. […]

A niche application of concentrating solar cells has been described [98] that exploits strengths and overcomes weaknesses of these devices. Solar cell efficiency decreases with temperature, which occurs in locations where the solar energy is strongest. Multijunction tandem devices definitely need cooling because of the concentration of energy, a factor of several hundred. Concentrating devices […]

Alternative possibilities for dense hydrogen storage are by reaction of hydrogen to form chemicals such as metal hydrides and by temperature-dependent adsorption of hydrogen onto lightweight high-area substrates, which may include decorated graphitic surfaces. Hydride storage tanks have been tested in connection with autos and trucks. A figure of merit of such a storage medium […]

The largest thin-film solar cell supplier is First Solar, manufacturing thin-film cells of CdTe. According to the New York Times [80], First Solar, an American firm based in Tempe, Arizona, has signed an agreement with the Chinese government for a 2 GW photovoltaic farm to be built in the Mongolian desert. The photovoltaic farm of […]

What can be done to make solar cells more efficient? We have already described the main classes of solar cells that are now available. These can be characterized in terms of the number of distinct energy gaps, according to the physical form, and according to the use for single sun illumination versus concentrated illumination. New […]