Volume 21: Sustainable Energy Solutions for a Post-COVID Recovery towards a Better Future: Part IV

A mechanism study of optimal spectral selectivity of solar absorbing coating and thermal performance potential of solar power tower Qiliang Wang, Guiqiang Li, Gang Pei, Hongxing Yang

Abstract

The solar power tower (SPT) is one of the most common applications of concentrating solar power technology. The tower receiver is the core component in a SPT system, responsible for solar absorption and solar conversion by depositing one single solar selective-absorbing coating (SSC), which usually has a fixed spectral selectivity characteristic. Owing to highly non-uniform optical distribution on the receiver surface, the tower receiver is riddled with complex physics coupled with optical, thermal and mechanical problems. The SSC exerts crucial roles in the activity in the physical process of optical-thermal conversion. However, given the complex physics on the surface of the tower receiver, the common SSCs used in the tower receiver are far from the optimal design of SSC in terms of spectral selectivity, which leads to the less efficient solar-thermal conversion in the tower receiver. In this paper, a comprehensive spectral heat transfer model of the tower receiver was first established and verified. The calculation accuracy of the proposed model was significantly improved by 10% compared with the conventional model. In this context, the mechanism of optimal spectral selectivity of SSC in response to the different concentration ratios and service temperatures was fully revealed. Dunhuang 10 MW SPT was selected as a study case, and the tower receiver covered with a variety of SSCs with optimal spectral selectivity was analyzed. The potential performance in the solar-thermal conversion of the tower receiver was analyzed as well. The results showed that the optimal spectral selectivity of SSC varied dramatically with the solar irradiance density and receiver surface’s temperature, revealing the mismatches problem of the current SSC on the next-generation SPT system. The tower receiver with optimal SSCs exhibited the largest improvement potential in receiver efficiency and pointed out the development direction for the next-generation tower receiver.

Keywords Concentrating solar power, Solar power tower, Solar absorbing coating, Spectral selectivity, Solar energy conversion, Spectral heat transfer.