Dynamic Investigation of a Coupled Parabolic Trough Collector–Phase Change Material Tank for Solar Cooling Process in Arid Climates

Abstract

The use of solar energy for cooling processes is advantageous for reducing the energy consumption of conventional air-conditioning systems and protecting the environment. In the present work, a solar-powered cooling system with parabolic trough collectors (PTC) and a phase change material (PCM) tank is numerically investigated in the arid climates of Saudi Arabia. The system contains a 160-kW double-effect absorption chiller powered by solar-heated pressurized water as a heat transfer fluid (HTF) and a shell and tube PCM as a thermal battery. The novelty of this paper is to investigate the feasibility and the potential of using a PTC solar field coupled to a PCM tank for cooling purposes in arid climates. The numerical method is adopted in this work, and a dynamic model is developed based on the lumped approach; it is validated using data from the literature. The functioning of the coupled system is investigated in both sunshine hours (charging period) and off-sunshine hours (discharging period). The PTC area in this work varies from 200 m2 to 260 m2 and the cooling capacity of the chiller ranges from 120 kW to 200 kW. Obtained results showed that the 160-kW chiller is fully driven by the 240 m2-solar PTC during the charging period and about 23% of solar thermal energy is stored in the PCM tank. It was demonstrated that increasing the PTC area from 220 m2 to 260 m2 leads to a reduction in the PCM charging time by up to 45%. In addition, it was found that an increase in the cooling loads from 120 kW to 200 kW induces a decrease in the stored thermal energy in the PCM tank from 450 kWh to 45 kWh. During the discharging period, the PCM tank can continue the cooling process with a stable delivered cooling power of 160 kW and an HTF temperature between 118 °C and 150 °C. The PCM tank used in the studied absorption chiller leads to a reduction of up to 30% in cooling energy consumption during off-sunshine hours.