Developments of CPC solar evacuated glass tube collector with a novel selective coating

摘要

This paper describes the development of a novel CPC (compound parabolic collector) evacuated tube solar collector, using a medium-temperature selective coating. The medium-temperature selective coating was obtained by co-sputtering titanium and aluminum targets. The absorptance and the thermal emittance of the heat treated coating is 0.95, and 0.04 at 80 degrees C respectively. The collector was optimized, using a manifold of copper Utube with anti-oxidized coating and aluminum fin. An anti-reflection layer is added on the cover glass tube, and non-flash getter are used for maintaining the vacuum of the collector tubes. Thermal test results shown that the instantaneous efficiency based on gross area eta G can reach 0.46 at the temperature of 150 degrees C and the normalized temperature difference Tm* is 0.13 [(m2-degrees C)/W]. The experimental steam system application showed that the novel CPC solar collector can produce steam from water with temperatures about 108-145 degrees C during sunny days. It was also shown that the thermal performance of the solar collector did not degraded significantly.