Design and experimental characterization of a CPC solar collector

Medium temperature solar thermal applications have received remarkable interest in the recent years in both residential and industrial sectors. These applications, typically in a temperature range of 80 - 250°C, require thermal collectors coupled to solar concentrators. Concerning these applications, a prototype of Compound Parabolic Concentrator coupled to an Evacuated Tube solar collector, was developed and built. The instantaneous efficiency of the prototype was measured according to the suggestions of the European Standard EN 12975-2. The "Outdoor steady-state" test method, well accepted for testing flat plate and evacuated tubular collectors, was used. The specific useful power extracted from the prototype was also derived. The measured performance is in line with theoretical derivations. However, when using the instantaneous efficiency of the Outdoor steady state test method some discrepancies arise in simulating the daily behavior of the collector, suggesting a different testing approach