Studies On a Micro-Thermophotovoltaic Device with a H2-NH3-Fueled Micro-Emitter

The potential of hydrogen (H₂)-ammonia (NH₃) blends as a carbon-free, green fuel in a 1–10 W micro-thermophotovoltaic (micro-TPV) device is evaluated experimentally. When H₂-NH₃ blends are used directly (without any modification) in a micro-TPV configuration that was developed for hydrocarbon fuel, applying a heat-recirculation concept and having an installation of gallium antimonide photovoltaic cells, low temperature on the micro-emitter outer surface are observed, generating a secondary flame at the micro-emitter outlet. To remove the secondary flame, satisfying the primary requirements for designing the micro-emitter (stable burning in the small confinement and uniform and high temperature along the walls), cyclone and helical adapters are installed at the fuel-air mixture inlet and upstream the main combustion zone, respectively. Also, the micro-emitter is extended to enhance the heat-recirculation effects. The helical adaptor with a large helix angle yields better performance, increasing the micro-emitter temperature. Under optimized design and operating conditions, the micro-TPV device produces 5.2 W with an overall efficiency of 0.87% and an emitter efficiency of 14%, indicating the maximum temperature of the micro-emitter outer surface up to 1408 K. Thus, the feasibility of H₂-NH₃ blends in practical micro power-generation devices has been demonstrated, implying the potential of partial NH₃ substitution to improve the safety of H₂ use with no carbon generation.