Development and performance evaluation of a photovoltaic-integrated thermic solar geyser for domestic water heating

This study presents the performance evaluation of a photovoltaic-integrated thermic solar geyser (TSG) using energy analysis. The TSG system incorporates a nichrome wire heating rod and flexible pipe heat exchanger with aluminum fins. Therminol VP1 (thermic oil) is used as the thermal energy storage medium to ensure effective heat retention. During the charging operation, the average oil temperature increases from 32.67 °C to 101.83 °C over four days. The recorded average efficiencies are 12.32 % for the PV, 89.69 % for the TSG, and 11.05 % for the overall system. Operating under ambient temperatures ranging from 19 °C to 39 °C, the system receives an average solar radiation of 562 W/m² and generates a PV power output of 804 W. In the discharging operation, the system operates continuously for 12 h, reducing the oil temperature from 103.63 °C to 48.39 °C and supplying 720 L of hot water at a flow rate of 1 LPM, with an average temperature rise of 16.4 °C. The system effectively heats 240 L of water daily for two consecutive days and retains heat efficiently overnight, achieving thermal retention efficiencies of 94.15 %, 93.84 %, and 86.68 % for 80L, 120L, and 240L discharge cases, respectively. Over a 25-year operational lifespan, the system mitigates 77.92 tons of net CO₂ emissions, supporting environmental sustainability. The system has levelized cost of energy of $0.051 per kWh and payback period of 5.24 years. Although the initial cost of the proposed system is higher than the conventional systems, its enhanced thermal storage capability ensures reliable, efficient, and environmentally friendly domestic water heating.