Thermophotovoltaic performance metrics and techno-economics: Efficiency vs. power density

Thermophotovoltaics (TPV) are a promising new approach for converting heat to electricity. Their performance is primarily characterized by two metrics: efficiency and power density. While recent works have shown high efficiency, it is important to understand how both of these metrics impact the techno-economics of a TPV system as efforts to commercialize the technology advance. In this work, we develop the first unification of efficiency and power density into a single techno-economic metric based on the levelized cost of electricity (LCOE). We find that the LCOE can be broken into two parts: heating cost, including infrastructure and inputs for providing heat to the TPV cells, and cell cost, the capital cost of the TPV cells. We show that systems with high heating costs should prioritize TPV efficiency, while systems with high cell costs should prioritize power density. We then develop a model to identify the most impactful cell properties in improving the important performance metric and reducing system LCOE. Namely, improving spectral control with increased back-surface reflectance is the most effective to reduce LCOE in systems with high infrastructural costs, while increasing the view factor and reducing front-surface reflectance are most critical in systems with high TPV cell cost. Improving just one or two of these properties can reduce the LCOE by 25–75 %, reaching competitive values ∼8 ¢/kWh-e, less than the average cost of electricity in the US. This study thus elucidates which TPV performance metric is more important for system techno-economics and how to maximize it.