Influence of sunshape and optical error on spillover of concentrated flux in solar thermal power tower plant

Abstract

It is important to calculate and evaluate the spillover of flux reflected by heliostats on the heat shields for the construction, operation and optimization of solar thermal power tower plant. By establishing a concentrated flux distribution model of power tower plant based on the real sunshape and taking haze, optical error, shadowing and blocking effect into consideration, the authors calculated the flux density distribution on the receiver and heat shields under various conditions. The results show that the radiation energy on heat shields can reach about 15–45 MW under typical conditions, accounting for 1%–8% of the total received energy of the system. The flux density on heat shields is between 30 and 70 kW/m2, which is equivalent to the flux level of trough solar concentrator system. The calculations and fitting results show that the energy proportion on heat shields is positively correlated with circumsolar ratio(CSR) and optical error. The effect of CSR on the energy proportion of heat shields is linearly increasing, while the effect of optical error is nonlinear. This indicates that the spillover flux on heat shields can compensate for the loss of the receiver caused by haze, optical errors of heliostats.