Efficient, Low Cost Dish Concentrator for a CPV Based Cogeneration System

Zenith Solar Ltd has developed efficient electricity and heat co-generation system based on segmented-parabolic dish of total aperture area of 11 m(2) and water cooled dense array module combined of triple junction cells. Conventional parabolic dishes are inherently inefficient in the sense that the radiant flux distribution is non uniform causing inefficient generation by the PV array. Secondary optics improves uniformity but introduces additional complexity and losses to the system. Zenith's dish is assembled of 1200 flat mirrors of approximately 100 cm(2) each. Every mirror facet has a unique shape such that the geometrical projection from each mirror on the focal plane is essentially the same. When perfectly aligned, the projected radiation from all mirrors overlaps uniformly on the PV surface. The low cost construction of the dish utilizes plastic mount supported by a precise metal frame. The precision of the metal frame affects the overall optical efficiency of the mirror and hence the efficiency of the system. State of the art dish of 11 m2 active aperture results in output of 2.25 kWp (900 W/m(2)) electrical and 5 kWp thermal power from one dish system representing 21% electrical and 50% thermal conversion efficiency adding to 71% overall system efficiency.