Energetic and Exergetic Analyses of Experimentally Investigated Hybrid Solar Air Heater

Abstract

Solar energy is a type of renewable energy that is readily available, but it must be converted to a usable form using a highly efficient method. The global energy problem that has surfaced in recent years shows the importance of both practical and scientific studies on using solar energy for space heating. Solar air heaters are large volume systems used for space heating. Research on the geometry and surface forms of solar air collectors is focused on reducing system volume and optimizing the use of solar energy. A photovoltaic (PV) module can be cooled with a fluid to prevent a decrease in efficiency due to heat while generating electrical power. The subject of this study is the idea of using the heat from cooling the modules to support a solar air heater. The improvement of the thermal performance of a solar air collector with a cooling thermal load of the concentrated photovoltaic thermal collector (CPV/T) was experimentally investigated. The heat exchanger, which removes the heat of the water-ethylene glycol circulating in the photovoltaic thermal collector, is mounted in the solar air heater’s chamber of one of the two identical solar air heaters, and the first hybrid unit was obtained (i.e., first unit). The ordinary one was called the second unit. Heated air left the first and second units at average temperatures of 45.87°C and 38.83°C, respectively. Although the airflow rates in the units are the same, the air temperature in the first unit was increased by 18.13%. The heat contribution of the heat exchanger to the first unit was 128.96 W. The first and second law efficiencies of the first and second units were calculated as 51.89%, 15.22%, and 45.4%, 10.34%, respectively. The energetic and exergetic improvement of the first unit was found to be 6.49% and 4.88%, respectively. The local solar utilization capability is 797.76 kW·h/year and 609.12 kW·h/year for the first and second units, respectively. The waste heat from the CPV/T collector cooling cycle, which is 188.64 kW·h/year, was recovered for heating air in the first unit. The recovery of waste heat for use in the first unit provided a significant performance improvement over the second unit. The environmental contribution of the waste heat recovery means 144 kg CO2 emission per year less in emission release. This study addresses the process of supporting the performance of a solar air heater with the waste heat obtained during the liquid cooling application of a CPV/T collector. The heat exchanger of a closed loop that cools a CPV/T collector was placed in the solar air heater’s chamber of the first solar air heater unit. The heat released from the heat exchanger increased the unit’s heating capacity. The improvement achieved with the first unit compared to the second unit is evaluated by comparing it to the second unit but without a heat exchanger attachment. While solar utilization in the first unit reached 525.19 W, the second unit provided 401 W of solar utilization. The energy and exergy values of the first and second units were found to be 51.89%, 15.22%, and 45.4%, 10.34%. When evaluating the use of solar energy instead of fossil fuel-based heating applications, it is predicted that the local gain can be 767.76 kW·h/year and 609.12 kW·h/year. In recent years, active cooling of PV modules is a popular method to prevent a decrease in module efficiency due to a rise in the PV module temperature. Gaining use of the thermal load removed from the PV module is another well-known subject. In this study, 188.64 kW·h/year of thermal load from the CPV/T collector was recovered to the heating air in the first unit. In this way, the efficiency of the first and second laws of the first unit increased by 6.49% and 4.88%, respectively, compared to the second unit. The idea of the hybrid solar air heater contributes to researchers working in this field and raises awareness among practitioners.