Efficiency of solar collectors - a review

The progress of solar energy conversion technologies during the last few decades triggered the development of various types of collectors, thermal, photovoltaic (PV), or hybrid. In this paper, authors present the basic elements of thermal (energy and exergy) analysis solar collectors and their efficiency. The review of thermal analyses covers basic types of collectors and is extended to some constructive variations, e.g. with supplemental thermal elements (TEG). Thermal radiation proves to be the most important energy loss factor, due to the large temperature difference between the collector surface and the sky. To determine the total efficiency of solar collector operation, as a more complex analysis method of solar collector systems is proposed, to include economic, environmental and life-cycle analysis elements.