Abstract
In the present study, the evaluation of potential improvement of the overall efficiency of a common PV panel, valorizing the heat extracted by a heat exchanger that is integrated on its back side, either into work using an endoreversible Carnot engine or into cold by using an endoreversible tri-thermal machine consisting of a heat-driven refrigeration machine operating between three temperature sources and sink (such as a liquid/gas absorption machine), was carried out. A simplified thermodynamic analysis of the PV/thermal collector shows that there are two optimal operating temperatures T˜h and Th* of the panels, which maximize either the thermal exergy or the overall exergy of the PV panel, respectively. The cold produced by the endoreversible tri-thermal machine during the operating conditions of the PV/thermal collector at T˜h is higher with a coefficient of performance (COP) of 0.24 thanks to the higher heat recovery potential. In the case of using the cold produced by a tri-thermal machine to actively cool of an additional PV panel in order to increase its electrical performances, the operating conditions at the optimal temperature Th* provide a larger and more stable gain: the gain is about 12.2% compared with the conventional PV panel when the operating temperature of the second cooled panel varies from 15 to 35 °C.
Highlights
Accepted: 6 January 2022Photovoltaic (PV) technology is currently one of the most widely used technologies for producing renewable electricity with 20.6% of the 6523 TWh renewable electricity generation worldwide in 2018 [1]
The results of the analyses described are performed considering the actual characteristics of the PV panels manufactured by SUNPOWER (SPR-Max2-360-COM)
The PV panel temperature evolves from a maximum temperature the stagnation temperature (Tst) varying from 81 ◦ C to 40 ◦ C
Summary
Photovoltaic (PV) technology is currently one of the most widely used technologies for producing renewable electricity with 20.6% of the 6523 TWh renewable electricity generation worldwide in 2018 [1]. The PV conversion for a simple Si-based p-n junction is, limited by the theoretical Shokley–Queiser limit: only a maximum of 31% of the non-concentrated solar radiation can be converted into electricity [2]. The produced heat increases the temperature of the cells, which in turn reduces the ability of the PV panel to generate electricity.
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