Optical design of an off-axis mirror based solar concentrator

It is presented the optical design of a mirror based solar concentrator operating at concentrating factors higher than 850suns with an optical efficiency greater than 83% and an angular acceptance of at least ±0.5°. The optical system consists of an off-axis primary mirror optimized to work in conjunction with a secondary optical element which homogenizes the light on the photovoltaic (PV) cell and also increases the acceptance angle of the solar concentrator. Since in a high concentrating system the collected optical radiation can impinge on the PV cell also at high incidence angles, during the optical design and optimization particular attention was paid to reduce the number of rays impinging on the PVcell at high incidence angle. Furthermore the angular response of the PV cell was included to calculate the efficiency value of the whole system and to calculate the spatial distribution of the photocurrent in the different subcells constituting the multi-junction solar cell.