Thermal characterisation of isotopic heat sources for enhanced thermophotovoltaic systems

Radioisotope thermophotovoltaics (RTPVs) are playing an increasingly important role in the energy supply for deep space exploration. The output performance of RTPVs can be significantly improved by increasing the surface temperature of isotopic heat sources and reducing the high-temperature degradation effect of the thermophotovoltaic cells. This work proposes methods such as selective emission coating and adjusting heat source structure to improve heat source temperature and optimize heat distribution. Results showed that the surface temperature of the heat source could generally reach more than 1000 K by using the selective coating when the thermal power of the isotopic heat source was 500 W. The use of selective coatings can also make the thermophotovoltaic cells closer to the heat source, and the volume of RTPVs could be reduced from 1.23 × 10⁻³ m³ to 0.49 × 10⁻³ m³, with a reduction of ∼60 %. Under the condition of W@SiO₂ selective coating and 500 W heat source, RTPVs could produce the maximum output power of 22 mW/cm² when the distance between the InGaAs cell and the heat source is 2 cm. The results provided effective guidance for the design of the heat source and miniaturization of RTPVs in space applications.