Developing and Testing Solar Collectors

Patay, István and Erdélyi, Miklós and Gulyás, László (2009) Developing and Testing Solar Collectors. Progress in Agricultural Engineering Sciences, 5 (1). pp. 55-74. ISSN 1786-335X

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Abstract

A relatively new trend is the development of concentrator-type solar collectors and cells for the use in micro-concentrators. The geometry of these concentrators is simple, the reflexion surfaces or mirrors are usually flat-plate surfaces. The relations of radiation in the inner spaces of these collectors are complicated. The OSLO optical edition software can be used to study and simulate the light paths in the concentrator elements and resonators, using the laws of geometrical optics. Based on the results of study and simulation, a pilot collector was built for energetic testing. In the applied arrangement, the absorber surface was the heated tube itself and fitted exactly to the inlet concentration surfaces. By this way, the relation of the absorber surface and collecting surface was reduced to 0.25. Since the radiation losses decreased, the efficiency of the pilot collector was relatively high even at high outlet temperature conditions (50% at 50 °C outlet temperature and Δ T = 18 °C). The optical concentration of solar radiation energy is a possible way to increase the liquid heat transporter collector efficiency and the outlet temperature. Importance of air solar collectors is lower, but their application in some agricultural post-harvest processes (drying, desiccating) may be useful and profitable. A flat-plate-plate solar air collector was built and tested, with special absorber geometry and material. The results of tests are also shown in this study. The proved daily ΔT-asymmetry at both of pilot collectors is an important result for the practice. Practically it means that the afternoon hours are more favorable for the energy production than the morning hours. Since this effect probably exists in all types of solar collectors, the practice of horizontal direction of collectors needs modifying.

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