Annual performance of photovoltaic-thermal system under actual operating condition of Dire Dawa in Ethiopia

Abstract

As cooling of Photovoltaic panel by water improves the electrical conversion efficiency and produces warm water as a by-product, photovoltaic thermal system is being used for cogeneration of electrical energy and hot water. In this study, the annual performance of a glazed photovoltaic thermal system (combination of PV module and solar flat plate collector) with storage tank was investigated by the dynamic computational model. The model was developed using MATLAB under actual hot water demand condition for co-generation electrical energy at Dire Dawa in Ethiopia. The computational model determines the electrical energy production and temperature of water at different points and other components of the PV-T system within a given time interval. In addition summaries of monthly and annual incident solar irradiance, electrical energy generation, thermal energy transported to storage and thermal energy supplied as hot water to end users are computed, considering the hourly hot water consumption pattern and storage size effect. The simulation, which is conducted for 20 m2 PV-T system, consists of 12 panels with each 1.64 m2 module areas resulted in generation 803 kWh/year thermal energy and 310 kWh/year electrical energy. The annual average electrical efficiency, thermal efficiency, hot water end use overall efficiency and co-generation (PV-T) efficiency of the system were 15.4%, 50.4%, 38%, and 65.8% respectively. The fraction of solar energy in meeting the heating load for hot water generation was 44.5% for 60℃ hot water supply temperature. Hence, that PV-T system can only be used for water preheating meeting at maximum half of the heating load in tropical area.