CPV generator with dish reflector and fly’s eye receiver

Abstract

We describe a CPV generator in which an off-axis paraboloidal dish reflector powers a small receiver near the focus, housing many individually illuminated multijunction cells. The receiver entrance window doubles as a field lens that forms a reduced scale image of the reflector, at concentration of ∼30×. The image has a sharp boundary, and its position is stable against tracking errors. A fly’s eye lens array divides the image into equal portions, and further concentrates it to ∼500× onto the cells. This approach is in contrast to nearly all previous PV and CPV, where sunlight is equal apportioned (for simple series electrical connection) directly on entering the system. In our approach, small multijunction cells are packaged into a small receiver module that will be less expensive (per watt) to manufacture than large conventional PV or CPV modules, and can be economically upgraded for 40 year lifetime. Our concept differs from REhnu’s dish/receiver design [1] in its lack of obscuration and simpler cooling, using forced air convection rather than pumped liquid coolant, this made possible by the lower heat density at the cell array. In preliminary on-sun system data with a 2.4 m2 prototype powering 5.2 mm cells at 500× concentration, we demonstrate good tolerance to mispointing (90% at 0.5° off-axis), good air cooling (cell mounting plate at 19°C above ambient) and uniform division of light between the cells (scatter of 3.3% rms).