Design and research of removable secondary mirror in high concentrated photovoltaic technology

The direct fraction of sun irradiation is used to focus on Fresnel lens in High Concentrated Photovoltaic technology, electric energy is produced through photoelectric inversion. However, because of many factors in practice like the low tracking accuracy of tracker, structure vibration by winds and atmospheric scattering, the direct normal irradiation to the Fresnel lens can not be guaranteed. To solve this problem, a removable secondary mirror whose shape was a reverse cone with no top was added between the Fresnel lens and solar cells to increase the acceptance angle of the solar module. A design example was given, and analyzed by optical simulation with the software of Solidworks and Tracepro. The conclusion indicates the removable secondary mirror can increase the acceptance angle and improve the irradiance uniformity of the focus spot.