An important class of solar cells are those made of thin films of semiconductors. These are cheaper because they use less of the primary material: a few micrometers rather than a fraction of a millimeter, but are generally of lower efficiency because recombination occurs at the grain boundaries. The grain size in polycrystalline films varies […]

A more elaborate, and surely more expensive, approach to multiple junctions has been described by Barnett et al. (see Figure 7.16) [96]. The new method involves splitting, by dispersive optics, the incoming light into “bins” ofhigh energy, mid energy, and low energy. (In principle, the triangular glass prism of Isaac Newton would serve this purpose, […]

A fuel cell takes hydrogen gas as input and produces electricity, with efficiency in the range of 50-70%, greater than the internal combustion engine, ~30-35%. Automaker Honda in 2008 [114] released its hydrogen-fuel cell powered sedan, the FCX. This vehicle has a 280 mile range, using pressurized hydrogen. Pressurized hydrogen is available only in a […]

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 […]