A concentrating solar cell is a combination of [Concentrator Photovoltaic]+[Fresnel Lenes]+[Sun Tracker]. Its solar energy conversion efficiency can reach 31% ~ 40.7%, although the conversion efficiency is high, but due to the long sunward time, it has been used in space industry in the past, and now it can be used in the power generation industry with sunlight tracker, which is not suitable for general families. The main material of concentrating solar cells is gallium arsenide (GaAs), that is, the three five group (III-V) materials. General silicon crystal materials can only absorb the energy of 400 ~ 1,100nm wavelength in solar spectrum, and the concentrator is different from silicon wafer solar technology, through the multi-junction compound semiconductor can absorb a wider range of solar spectrum energy, and the current development of three-junction InGaP/GaAs/Ge concentrator solar cells can greatly improve the conversion efficiency. The three-junction concentrating solar cell can absorb energy of 300 ~ 1900nm wavelength relative to its conversion efficiency can be greatly improved, and the heat resistance of concentrating solar cells is higher than that of general wafer-type solar cells.
Energy conversion rate comparison:
Thin-film solar (7%-12%), wafer solar (12%-20%), traditional nuclear power plants (30%), thermal power (36.8%), concentrated solar (31%-40.7%), new nuclear power plants (42-57%)
Concentrating solar cells can increase efficiency of power generation by using a lens to focus light on a small area. However, the temperature rise caused by concentration of light will damage the solar cell and power generation system, so it is often necessary to inhibit the concentration rate. If you use a lens with a concentrator rate of 1000 times, the cost of solar cell unit module can be reduced to about 1/10 of crystalline silicon cell unit, and the required area is only 1/2.5 of silicon wafer, and the concentrator solar cell must be located near focus of lens to function. Therefore, in order to make the module always oriented towards the sun, it must be combined with the use of sun tracking system, although this design can improve the conversion efficiency, but there are lenses, condensing heat release trough and the weight and volume of sun tracking system is larger... Therefore, it is not suitable for installation on the roof of Japanese residential buildings.