Numerical study on optical performances of the first central-receiver solar thermal power plant in Korea

Abstract

In 2011, the first Korean central-receiver solar thermal power plant targeting the generation of 200 kWe was developed as a government research project. The project motivated us to develop an optical modeling program using the Monte Carlo ray-tracing method so that we are able to analyze performances of the solar concentration system in detailed and rigorous ways and to gain ideas to improve it. In the program, solar limb darkening without circumsolar radiation to model the sun shape was considered, and a clear-day insolation model to calculate Direct normal insolation (DNI) values was adopted. According to the breakdown of the optical efficiency, our program was developed to investigate the effects of six constituent efficiencies, i.e., cosine, shadowing, reflectivity, blocking, air transmission and spillage. On the other hand, a hierarchical screening algorithm to determine shadowing and blocking and a parallel computing technique were implemented for acceleration, which overcomes a major drawback of the Monte Carlo method and thereby enables to calculate annual performances. Comparisons with NREL’s SolTrace were made, and good agreements validated the development of our program. The hourly optical performances of the Korean solar thermal power plant on the summer and winter solstices and the autumnal equinox were simulated in terms of the solar flux and power distributions and the optical efficiencies. Basic parametric studies with the installation height and the tilt angle of the solar receiver were carried out based on annual performances. It is demonstrated that our program not only offers optical performance guidelines for operation confirms but also suggests improvement ideas that could enhance the efficiency and lead to a potential scale-up.