Convective heat loss under windy conditions and effects of porous shroud for large scale cavity receiver

The cavity receiver is considered suitable for the next generation Concentrating Solar Power (CSP) systems. However, due to the extreme working temperature and varying environmental conditions, convective heat losses in the cavity receiver are high and fluctuates over time, challenging its solar-thermal conversion efficiency and long-time operation. In the present study, a solar-thermal-fluid flow coupled numerical model was first established for the cavity receiver, and the convective heat loss under different wind directions was investigated. The effects of the wall shroud were investigated, leading to a novel porous shroud proposal for the cavity receiver. The results showed that origin of turbulence inside the cavity receiver varied for different wind directions, resulting in a non-steady convective heat loss. The porous shroud mitigates wind effects reducing heat loss, and proved effective for various cavity receiver shapes. The performance of the porous shroud primarily relies on the medium inertial loss coefficient and thickness of the porous wall. The cavity geometry also had influence on the optimal medium inertial loss coefficient and optimal wall thickness. With the porous shroud, variation trends of convective heat loss and the detrimental wind direction changed. For cavity receivers with optimal porous medium parameters, reduction rate of convection heat loss remained nearly the same (about 50.0%).