Review: Enhancing building energy efficiency through the integration of phase change materials (PCMs) and Thermoelectric Generators (TEGs) into the building envelope

As demand for energy-efficient buildings grows, innovative strategies are essential to reduce energy consumption and reliance on non-renewable resources. This review explores the integration of Thermoelectric Generators (TEGs) and Phase Change Materials (PCMs) within building envelopes, focusing on how PCMs can affect TEGs' performance by influencing the surrounding thermal conditions. TEGs are solid-state devices that can directly convert temperature differences into electricity and can be used to recover waste heat in buildings. Their power output ranges from milliwatts in single modules with low temperature differences to several watts in multi-module systems with higher temperature gradients. The efficiency of TEGs depends on maintaining a sufficient thermal gradient and device quality. PCMs, on the other hand, stabilize indoor temperatures by storing and releasing thermal energy during phase transitions. This behavior reduces heat flux and mitigates temperature fluctuations. Studies have shown that PCMs can reduce heat flux by 25 %-75 % and heat transfer by 6.5 %-56 %, which helps maintain the thermal gradient necessary for effective TEG operation. Despite the extensive research on PCM applications, there remains a significant gap in integrating TEG and TEG-PCM systems within building envelopes. This review examines how different PCM parameters, such as materials, thickness, and placement, influence heat transfer and temperature fluctuations, which are key factors for optimizing TEG performance. A significant gap in the literature is identified concerning integrating multiple PCM layers and the long-term performance of TEG-PCM systems. The findings highlight the need for further research into optimizing TEG-PCM integration in building envelopes to maximize energy generation and support smart, net-zero buildings.