Exploiting the Potential of Pyroelectric-Piezoelectric Hybrid Devices for Low-Grade Thermal Energy Harvesting

This study proposes a separate and combined (pyroelectric + piezoelectric) energy harvesting system using a bimetallic beam. Hybrid energy harvesting is achieved by waste thermal energy using thermal expansion mismatch of the bimetallic beam. In this regard, four types of design are proposed, along with various heating/cooling cycles. Auxetic layers in a bimetallic beam are used to enhance the power. The best-performing design and heating/cooling cycle are considered for further power increment. Two models are simulated based on low (model C3) and high heat consumption (model C5). The load resistance, frequency, bimetallic beam and pyroelectric/piezoelectric layer thickness are varied and maximum power is obtained at 175 M omega (C3), 75 M omega (C5), 0.02 Hz (C3 and C5) and 0.4 mm (C3 and C5) as 20 mu W (C3) and 40 mu W(C5), respectively. The piezoelectric, pyroelectric and combined power variation is the effect of stress and temperature fluctuations on H-PEH layer. Additionally, five well-known higher pyroelectric/piezoelectric coefficient materials are studied and found that La-NBT-BT-Ta gives the maximum power of 0.811 and 1.99 mW for combined (pyroelectric + piezoelectric) effect in low (C3) and high (C5) heat consumption model, respectively. The stress generated in both models is analyzed to look at practical feasibility. The present study uses a cantilever-based structure in which the substrate bimetallic beam is made of two different alloys with differences in coefficient of thermal expansion. A pyroelectric material (H-PEH layer) is attached over the bimetallic beam and a heating source is placed below it. This hybrid structure is used for piezoelectric, pyroelectric, and combined energy harvesting.image (c) 2023 WILEY-VCH GmbH