Simulation and performance assessment of load-following CSP plants

Abstract

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.

The paper is focused on the modeling of Concentrated Solar Power (CSP) plants based on a steam Rankine cycle combined with two different solar field configurations: Parabolic Trough Collectors (PTC) and Heliostats with Central Receiver (HCR). The system is designed to operate as a load following power plant: a Thermal Energy Storage (TES) system allows to compensate fluctuations in solar energy and in power demand, and to operate also during nighttime hours. Commercial software and in-house developed computer codes are combined together to predict CSP plant performance under real operating conditions. The power block was modeled by Thermoflex® whereas Trnsys® was used to model the solar field operation all over the year. An optimization procedure interacting with Trnsys® model was used to size the two considered solutions for the solar fields. On the base of annual Trnsys® simulations, the optimization algorithm determined the minimum aperture area of the solar field assuring the required Heat Transfer Fluid (HTF) flow rate from TES. Charging and discharging cycles of TES are ruled by the HTF flow rate required for each hour of the year so as to match the electrical demand. Results of annual plant operation on a one hour basis are presented and discussed for Upington (RSA). Then the global results are compared with similar plants based in Sevilla (ES).