Description of the performances of a thermo-mechanical energy harvester using bimetallic beams

• Thermo-mechanical instability of bimetal thermostats is modeled using a Ritz method.
• Demonstration of the operation of the bimetallic strip heat engine is made.
• Heat engine’s output mechanical energy is evaluated.
• Heat engine’s Carnot efficiency is evaluated.

Many recent researches have been focused on the development of thermal energy harvesters using thermo-mechanical or thermo-electrical coupling phenomena associated to a first-order thermodynamic transition. In the case of the bimetallic strip heat engine, the exploitation of the thermo-mechanical instability of bimetallic membranes placed in a thermal gradient enables to convert heat into kinetic energy. This paper is a contribution to the modeling and the comprehension of these heat engines. By restraining the study to the simply-supported bimetallic beams and using a Ritz approximation of the beam shape, this paper aims to give an analytical solution to the first mode of the composite beams and then to evaluate the efficiency of the harvesters exploiting these kinds of instability.