High-Efficiency Thermophotovoltaic System That Employs an Emitter Based on a Silicon Rod-Type Photonic Crystal

Thermophotovoltaic systems in principle enable utilization of heat that is usually regarded as wasted energy. However, the wavelength selectivity of the thermal emitter required for high efficiencies is difficult to control with conventional designs. Here, we design a thermophotovoltaic system, comprising silicon rods as thermal emitter with a relatively narrow emission spectrum and photovoltaic cells with a band gap corresponding to 1.76 μm, and verify efficient power generation. By accurately measuring the heat flux that enters the emitter, the emitter temperature, and the electrical output power of the photovoltaic cells, we find that the actual system efficiency (ratio of output power to ingoing heat flux) is 11.2% at an emitter temperature of 1338 K and the output power density footprint is 0.368 W/cm 2 . The obtained efficiency is relatively high, i.e., 1.65 times that of the previously reported record value (6.8%). Further efficiency improvements may lead to development of distributed energy supplies using combustion heat.