Thermal Impact of A 35.2 KW Grid-Connected Rooftop Solar PV Power Plant on Space Cooling

Abstract

Rooftop photovoltaic (PV) systems can generate renewable electricity while shading building roofs and reducing solar heat gain. This study evaluated the electrical and thermal performance of a 35.2 kWp grid-connected rooftop PV system installed on the reinforced cement concrete roof of the College of Agricultural Engineering and Technology, Dediapada, Gujarat, India (21.63°N, 73.59°E). The system comprised 110 photovoltaic modules and shaded approximately 700 m² of roof area. Electrical generation, meteorological conditions, and indoor temperatures beneath the PV-covered and exposed roof sections were monitored from January 2019 to December 2022. The system generated an average of 50,581.5 kWh of electricity annually, corresponding to a specific yield of 1,437 kWh kWp⁻¹ year⁻¹. The measured data indicated an average annual indoor temperature reduction of 0.726°C, with maximum reductions of approximately 2–3°C during peak summer months. Using the steady-state heat-transfer equation, Q = UAΔT, the cooling-load reduction for the experimental room, with a roof area of 136.2 m², was estimated at 0.277 kW, equivalent to an annual cooling-energy reduction of approximately 1,011 kWh. Extrapolation to the entire 700 m² PV-covered roof yielded an estimated annual cooling-energy reduction of 5,194 kWh. At an air-conditioning coefficient of performance of 3.5, this represented approximately 1,484 kWh of electrical energy savings and an annual reduction of 1.22 tonnes of CO₂ emissions. The findings indicate that rooftop PV systems can provide combined electrical-generation and passive-cooling benefits in hot and humid climates.