Energy, economic, and environmental assessment of a standalone hybrid renewable system for sustainable buildings with phase change materials and rooftop PV shading

Improving energy efficiency and power supply reliability in standalone buildings is essential for sustainable development. Enhancing building envelopes with phase change materials (PCM) can address economic challenges and reduce peak power demand issues for Heating, Ventilation, and Air Conditioning (HVAC) systems. This study proposes an optimized approach to determine the ideal location and thickness of PCMs across the roof. It also analyzes the impact of rooftop PV shadow on the thermal performance of PCM-enhanced roofs for a building designed in accordance with ANSI/ASHRAE Standard 140-2017. Furthermore, effective Building Evaluation Model (BEM) strategies are incorporated into a techno-economic assessment to optimize a PV, fuel generator, and battery energy system, with the goal of minimizing the cost of energy (COE). Utilizing a BioPCM with a melting temperature near the building's comfort zone (25 °C), the study finds that a single layer (1.12 cm) of PCM on both sides of the roof insulation delivers the best performance. The proposed method achieves over 4.79% annual energy savings without PV shading and 8.75% with PV shading, reduces energy costs to $0.15/kWh, supplies over 50% of energy from renewable resources, and lowers CO2 emissions by 41–54% compared to the reference case without roof enhancements. Additionally, implementing PV shading reduces heating and cooling demands by 14.3% and 7.2%, respectively, when standard roof insulation is applied, and by 6.9% and 2.3%, respectively, when roof insulation is poor. These findings provide valuable insights for various stakeholders in designing rooftop PV system strategies that enhance building power supply and support sustainable development goals.