Effect of Tank Size on the Temperature Distributions for Hybrid Photovoltaic/Thermal Water Heaters

In the present study an investigation was conducted on the temperature distribution effect for several tank capacities (100 L, 120 L, 150 L and 200 L) having two different aspect ratios (H/D) for each capacity. Hot water is supplied to these tanks by a Hybrid PV/T collector of 4 m² illuminating area. The circulation of water within PV cells cools its surface area to solve the problem occurred in PV cells, where each 1°C increase in the surface module 0.45% of the electrical efficiency decrease. A pump circulates water from the bottom of the tank to PV/T collector and then dropped it at the top of the tank in order to maintain thermal stratification. It was observed that tanks with a higher H/D ratio results a better performance, as hot water is stored in the tank at an earlier time (morning hours 6:00 until 9:00) than of tanks with a lower H/D ratios. It can be observed also that tanks with a higher H/D ratios, highly maintain thermal stratification occurred in the tanks than lower ratios. The tank for 100 L capacity having an H/D of 2.66 resulted the best performance at which stratification was highly maintained and the optimum tank is found to be for 150 L with an H/D of 2.97 as a larger capacity of domestic hot water is heated. The tank with 200 L tanks shall require a better insulation for conserving heat inside and prevent ambient losses. Keywords: Hybrid PV/T collector, storage tanks, thermal stratification, aspect ratio.