Development of a new flat stationary evacuated CPC-collector for process heat applications

For the economical supply of solar process heat at temperatures between 120 and 150 °C a new non-tracking, flat, low-concentrating collector has been developed. The new collector is an edge ray collector with a concentration of 1.8 and inert gas filling, existing of parallel mounted absorber–reflector units, aligned in east–west direction. The basic concept is the integration of an absorber tube and reflectors inside a low pressure enclosure. Asymmetrical reflectors below the headers with a concentration of 0.6X provide extra radiation and prevent longitudinal radiation losses. To suppress heat losses due to gas-convection inside, air or inert gas like krypton at a pressure below 10 mbar is used.A prototype, with an aperture area of 2.0 m2, was tested in Munich and showed efficiencies of about 50% for krypton at 0.01 bar at a temperature of 150 °C with a radiation of 1000 W/m2 (900 W/m2 direct, ambient temperature 20 °C).