Thermo-electrical performance modeling and experimental validation of a water-cooled single-axis tracking photovoltaic–thermal system

Fixed photovoltaic systems suffer from reduced irradiance capture and temperature-induced efficiency losses. This study presents the design, experimental evaluation, and numerical modeling of a water-cooled single-axis tracking photovoltaic–thermal system under tropical climate conditions. The system integrates east–west solar tracking with rear-surface water cooling to improve irradiance capture, regulate photovoltaic temperature, and recover useful heat. Outdoor experiments were conducted using a fixed photovoltaic panel as the reference system, and a semi-empirical model was developed and validated using independent test days. Results showed that the tracking system improved irradiance capture, with off-peak irradiance gain reaching 34.6%. The tracking photovoltaic–thermal system maintained surface temperatures within 38.6–60.5 °C under irradiance levels of 91.75–1090 W/m 2 . The system achieved peak electrical, thermal, and gross combined efficiencies of 11.9%, 70.42%, and 82.22%, respectively. After deducting the 5 W cooling-pump demand, the peak combined efficiency remained 76.72%. Second-law analysis showed a peak exergy efficiency of 12.82% and maximum entropy generation rate of 0.244 W/K. Model validation showed strong outlet water temperature prediction, with root mean square error below 0.08 °C, mean absolute percentage error below 0.20%, and coefficient of determination above 0.96. Combined efficiency was predicted with root mean square error of 1.48–3.62% and mean absolute percentage error of 1.90–4.58%. Break-even analysis showed that the additional electricity generation required to recover the added tracking and cooling cost decreased from 293.09 kWh/year at a 5-year recovery period to 94.28 kWh/year at a 25-year recovery period. The corresponding net carbon dioxide mitigation decreased from 211.48 to 64.37 kg CO 2 e/year over the same period. These results confirm that integrating single-axis tracking with rear-surface water cooling improves photovoltaic–thermal performance under variable tropical outdoor conditions.