COLLECTOR CHARACTERIZATION AND COLLECTOR THERMAL PERFORMANCE TESTING IN TASK III OF THE IEA SOLAR HEATING AND COOLING PROGRAMME

The thermal performance of solar collectors measured according to standard test methods is appropriate for only a narrow range of operational and environmental conditions. It is usually assumed that the test results are fully characterized by the familiar Hottel-Whillier-Bliss equation, but this relationship was developed for flat plate collectors and is inadequate for representing a large number of the collectors currently being produced. In many cases the performance determined by the test may differ from that obtained in actual operational conditions. The work of Task III on the characterization of collector performance is aimed towards evaluating the effect of atmospheric factors (irradiance level, ambient temperature, windspeed) and of operational conditions (collector mass flowrate, tilt) on the thermal performance of a variety of solar collectors. Its objective is the development of improved test procedures and performance representations that account for these effects.