On-sun performance of an improved dish-based HCPV system

The University of Arizona has developed a new dish-based High Concentration Photovoltaic (HCPV) system which is in the process of being commercialized by REhnu, Inc. The basic unit uses a paraboloidal glass reflector 3.1 m x 3.1 m square to bring sunlight to a high power point focus at a concentration of ~20,000x. A unique optical system at the focus reformats the concentrated sunlight so as to uniformly illuminate 36 triple junction cells at 1200x geometric concentration. The relay optics and cells are integrated with an active cooling system in a self-contained Power Conversion Unit (PCU) suspended above the dish reflector. Only electrical connections are made to the PCU as the active cooling system within is completely sealed. Eight of these reflector/PCU units can be mounted on a single two axis tracking structure2. Our 1 ^st generation prototype reflector/PCU unit consistently generated 2.2 kW of power normalized to 1kW/m² DNI in over 200 hours of on-sun testing in 20113. Here, we present on-sun performance results for our 2 ^nd generation prototype reflector/PCU unit, which has been in operation since June 2012. This improved system consistently generates 2.7 kW of power normalized to 1kW/m² DNI and has logged over 100 hours of on-sun testing. This system is currently operating at 28% DC net system efficiency with an operating cell temperature of only 20°C above ambient. Having proven this system concept, work on our 3^rd generation prototype is underway with a focus on manufacturability, lower cost, and DC efficiency target of 32% or better.