Flat-plate solar-collector performance evaluation with a solar simulator as a basis for collector selection and performance prediction

The use of a solar simulator for performance determination permits collector testing under standard conditions of wind, ambient temperature, flow rate and “Sun”. The performance results determined with the simulator have been found to be in good agreement with outdoor performance results.This paper reports the measured thermal efficiency and evaluation of 23 collectors which differ according to absorber material (copper, aluminum, steel), absorber coating (nonselective black paint, selective copper oxide, selective black nickel, selective black chrome), type of glazing material (glass, Tedlar, Lexan, anti-reflection glass), the use of honeycomb material and the use of vacuum to reduce thermal convection losses. The collectors are given performance rankings based on noon-hour solar conditions and all-day solar conditions. The determination with the simulator of an all-day collector performance is made possible by tests at different incident angles. The solar performance rankings are made based on whether the collector is to be used for pool heating, hot water, absorption air conditioning, heating, or for a solar Rankine machine.Another test which aids in selecting collectors is a collector heat capacity test. This test permits a ranking of collectors according to their heat capacity (and time constant), which is a measure of the rapidity of a collector's response to transient solar conditions. Results are presented for such tests.Final considerations for collector selection would of course be made on the basis of cost and the reliability of performance over the required life of a collector. Results of a cost-effectiveness study is given for conditions corresponding to those required for absorption or heating. These results indicate that the additional cost involved in the upgrading of collector performance (selective surfaces, anti-reflection glass, etc.) appears to be cost effective and therefore justified. Some data are also presented to illustrate a method for the determination of outdoor performance degradation by use of simulator tests carried out before and after a period of outdoor operation.