Experimental demonstration of the hybrid solar receiver combustor

We report the first-of-a-kind experimental demonstration of a direct hybrid between a solar cavity receiver and combustor, in which the functions of a solar receiver and a combustor are integrated into a single device. The device was built and tested at a nominal capacity of 20-kWth for all the three modes of operation, namely solar-only, combustion-only and mixed-mode (a combination of both solar and combustion). Here, a 5-kWel xenon-arc solar simulator and natural gas were used as the energy sources, while the combustion mode was operated in the Moderate or Intense Low oxygen Dilution (MILD) combustion regime to offer low NOx emissions and good heat transfer. The thermal efficiency, heat losses, heat flux distribution within the cavity and pollutant emissions are reported for the solar-only, combustion-only and mixed-modes of operation. The thermal performance was found to be similar in all modes of operation, assuming reasonable heat recovery from the exhaust gas. Since system losses are reduced by integration (e.g. by avoiding start-up and shut-down losses), this confirms that an overall benefit can be derived from the device. Nevertheless, there is a need to manage the significantly different heat flux distribution for the three modes of operation.