Thermal performance analysis of a fine sand solar geyser integrated with photovoltaic technology

Abstract

This experimental study evaluates the thermal performance of a photovoltaic-integrated fine sand solar geyser (PFSG) system. The system comprises a fine sand-based solar geyser (FSG), incorporating a nichrome wire heating rod (NHR) and a circular heat exchanger (CHX) to enhance thermal energy conversion, storage, and extraction. During the charging operation, the sand temperature increased from 25.2°C to 164.2°C on Day 1 and from 94.7°C to 211.9°C on Day 2. Correspondingly, the FSG stored 14.02 MJ and 11.81 MJ of thermal energy with charging efficiencies of 97.41% and 90.76%, respectively. In the discharging operation, cold water circulated through the CHX, absorbing heat from the sand and exiting as hot water at a flow rate of 0.67 LPM. The sand temperature decreased from 150.2°C to 74.6°C (Day 1) and from 168.5°C to 79.7°C (Day 2). The system achieved an average water temperature increase of 11.7°C for 140 L and 13.75°C for 152 L, with discharging efficiencies of 90.0% and 90.05%. The PFSG system demonstrated an energy cost of $0.0233/kWh, payback period of 4.45 years, and an expected operational lifespan of 25 years, offering a sustainable and cost-effective solution for domestic water heating, even during low solar radiation or nighttime conditions.