Performance characteristics of a Hybrid Solar Receiver Combustor fed with Hydrogen and operating in the MILD combustion regime

This study describes the performance characteristics of a Hybrid Solar Receiver Combustor operated in the Moderate or Intense Low oxygen Dilution (MILD) combustion regime, in which the functions of a solar receiver and a combustor are integrated into a single device. The device was tested at a nominal capacity of 12-kWth for both the combustion-only (MILD) and mixed-mode (a combination of both solar and combustion simultaneously), using hydrogen (H2) as fuel. A 5-kWel xenon-arc lamp was used to simulate solar radiation into the device. The influence of the mode of operation on the thermal efficiency, heat losses, heat flux distribution within the cavity and pollutant emissions are reported for a range of values of the heat extraction. It was found that MILD combustion can be successfully stabilised within the HSRC over a wide range of operating conditions, and in the mixed-mode of operation, providing ultra-low NOx and uniform temperature/heat flux. The thermal performance was found to be similar for both the combustion-only (MILD) and mixed modes of operation, despite the different nature of the two energy sources, confirming that an overall benefit can be derived from the device. Overall, this study highlights that, if renewable H2 (which can be produced by different renewable energy sources, including solar, wind or biomass) is used as fuel, the device can efficiently operate in all the modes of operation employing 100% renewable energy.