Thermal performance testing and analysis of a 1 MWth quartz tube bundle solid particle solar receiver using the energy balance analysis method

In this study, a method for testing and calculating the thermal efficiency of a 1 MW_th quartz tube-based solid particle solar receiver (SPSR) is proposed, utilizing the energy balance approach, and is validated through multi-condition experiments in Yanqing, Beijing. A heat transfer model is developed to quantify convective and radiative heat losses, while measured heat absorbed power is employed to systematically analyze the instantaneous thermal efficiency of the receiver and its influencing factors. Results from 26 completed experiments reveal that the receiver achieves a maximum outlet temperature of 699.6 °C, a peak thermal efficiency of 87.5 %, and a maximum heat absorbed power of 877.3 kW. Representative findings indicate that efficiency fluctuations are limited to less than 2.63 %, with a maximum efficiency of 72.41 %, demonstrating excellent operational stability. Increasing the particle mass flow rate significantly improves heat absorbed power and reduces heat losses. Variations in DNI directly influence the receiver's surface temperature, with thermal efficiency governed by the dynamic balance between heat absorption by particles and overall heat losses. Additionally, the thermal efficiency declines as particle outlet temperature and surface temperature rise.