Solar cells and thermoelectric generators as finite-time chemical heat engines

This paper shows a fundamental thermodynamic similarity between thermoelectric and photovoltaic energy converters which, at open circuit, can be represented as isochoric engines generating a finite chemical potential which appears as voltage at the terminals of the device. We show that, allowing for the temperature variation of the Seebeck coefficient, the maximum energy efficiency is intrinsically lower than the Carnot efficiency, as assumed in most of the literature, although more sophisticated strategies may exist to recuperate this loss. At finite current, further losses can be modelled in terms of finite-time thermodynamics.