Temperature Dependent Performance of Solar Photovoltaic and Thermal Hybrid Systems
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erature Dependent Performance of Solar Photovoltaic and Thermal Hybrid Systems R. R. Vardanyana, *, V. K. Dallakyana, and M. G. Travajyana a
National Polytechnic University of Armenia, Yerevan, Armenia *e-mail: [email protected]
Received September 14, 2020; revised September 30, 2020; accepted October 15, 2020
Abstract—Solar photovoltaic-thermal (PVT) hybrid systems have the high potential to be an effective and viable method for producing electricity and thermal energy for low grade heating application. The hybrid system is highly energy efficient with improved electrical efficiency due to cooling of solar cells and gained thermal energy due to heat absorbed by the fluid from the heated cells. Nevertheless, the utilization of these systems is not growing rapidly due to the controversial operational problems, as well as installation and maintenance difficulties in comparison with general separated photovoltaic (PV) and thermal systems. In this paper the operating temperatures of solar cells in PV and PVT collectors in dependence of ambient temperature are investigated. On the base of comparison of operating temperatures of solar cells of PV module and PVT collector the effectivity of PVT system application is assessed. It is shown that there is a ‘critical’ minimum value of ambient temperature below which the PVT system cells have the higher temperatures than the cells in PV modules (‘reverse’ process) and the application of PVT system is not reasonable. The dependence of “critical” temperature on the type and thermal characteristics of PVT system is investigated. The proposed methodology for PVT hybrid systems effectivity assessment can be used by scientists and designers during the development of different hybrid PVT systems. Keywords: Solar, photovoltaic, thermal, hybrid, module, system DOI: 10.3103/S1068337220040180
1. INTRODUCTION Main technologies for use of solar radiation are the photovoltaic conversion of light directly into electricity, and the thermal conversion of solar rays into the heat. The market of solar thermal and photovoltaic (PV) electricity generation is growing rapidly [1]. It is known, that in PV systems most of the absorbed solar radiation by a solar cell (about 80%) is not converted into electricity but contributes to increase the temperature of solar cells, then reducing the electrical efficiency of cells. This is the inherent drawback feature of solar cells – degradation in performance due to temperature. Typical PV modules convert about 15% (at 25°C, Standard Test Condition-STC) of solar radiation into electricity; the rest heats the solar cell, and is dissipated as waste heat. On a bright sunny day, a PV panel can reach temperatures in excess of 100°C. This can reduce the efficiency as much as 37 or 0.5% for every 1°C temperature rise. As a result of heating the PV module conversion efficiency reduces up to 9.5% instead of 15% measured at STC. The PVT hybrid system combine a PV solar cell, which converts solar radiation into electricity, with a solar thermal collector, w
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