Harvesting heat with thermo-mechanically bistable beams: working principle and theoretical performances

Abstract

The interest in miniaturizing heat engines to harvest low-grade heat has grown up with the development of wireless sensors requiring little energy to work. The bimetallic strip heat engines exploit the thermo-mechanical instability of composite membranes to convert heat into mechanical energy and have been proposed as an alternative to Seebeck thermoelectric generators based on the properties of semiconductors like bismuth tellurides. This article aims to describe the theoretical operation of these heat engines by explaining the nature and the conditions of occurrence of the thermo-mechanical instability of simply-supported beams. The thermodynamic cycle of the heat engine is explained and the performances of nine types of bimetallic beams are evaluated.