Beyond the combustion chamber: Heat transfer and its impact on micro-thermophotovoltaic systems performance

Conversion of thermal radiation into electrical current in thermophotovoltaic devices is directly influenced by the heat transfer, since the cell efficiency depends on the temperature. For micro-scale devices, heat management is yet more important due to the proximity between the components. A detailed study in these systems needs to considers the presence of wavelength-selective optical filters, used to reflect undesired radiation. In this study, we propose a model where the dependence of the physical parameter with the radiation wavelength is taken into account through a discretization of the radiation spectrum into several bands and estimation of average values. By coupling this procedure with a computational fluid dynamics solver, the cell efficiency as a function of geometrical and operational parameters can be estimated. The results indicate the existence of an optimal emitter/cell distance, depending on the emitter temperature and the heat transfer coefficient between the cell and the external medium. A secondary cooling mechanism, the air flow between the emitter and the filter, can also help to reduce the cell temperature. While the emitter average temperature has a strong impact on the cell efficiency, the temperature distribution in the emitter surface has no significant influence, allowing the use of average values.