Silicon and GaAs/Ge concentrator power plants: a comparison of cost of energy produced

Until now virtually all of the development of terrestrial concentrator PV power plants has utilized silicon cell technology. If silicon concentrator technology achieves its predicted potential performance and cost, it would be very close to commercial viability as defined by DOE goals of 12 c/kWh. Also until now, GaAs cell technology has not been a viable alternative for these power plants, largely due to the cost of cells grown on GaAs substrates. The ability to grow high-efficiency GaAs solar cells on germanium substrates presents the strong possibility of reducing their cost of energy produced. The cost of large-grain, optical-grade, polycrystalline germanium substrates is potentially 15 times less than single-crystal GaAs substrates, and cell conversion efficiencies approaching 35% are likely for tandem-junction GaAs cells. This analysis shows that for comparable 50 MW Fresnel lens plants, the 30-year, levelized cost of energy (COE) from GaAs/Ge cells can be $0.118/kWh compared to $0.140/kWh for a 27.4% Si back-contact cell