Novel Method to Design Non-Ideal Parabolic Dish Concentrator for Concentrated Photovoltaic Application; Its Theoratical Analysis and Experimental Characterisation for Design Validation

A concentrating photovoltaic (CPV) system concentrates solar radiation onto a photovoltaic (PV) cell using optics to replace the high cost of PV cell with inexpensive concentrator material. Parabolic dish concentrators (PDC) offer the highest optical and thermal efficiencies of all the current concentrator options. True paraboloidal geometry results in a point focus PDC while a non-ideal PDC produces a spatially distributed image at the focal plane. A simple and novel method is devised to design a non-ideal PDC to achieve a spatially distributed focus for a flat target plane for use in CPV systems. A basic geometrical parabolic curve construction method was modified to distribute the solar flux without geometrical power loss and a non-ideal PDC was built for a geometrical concentration ratio of 100. The design of the PDC was analysed by a ray tracing method employing principles and laws of geometrical optics. An analytical investigation of the built PDC enabled calculation of an energy efficiency of 59%. The resulting energy concentration ratio shows a beam uniformity of 72.3% across the cell. A parametrical analysis was also performed by varying the PDC surface reflectivity and the PDC geometry to predict a maximum energy efficiency of 85.5% and a uniform beam profile across the cell without geometrical power loss.