PROCESS CONTROL AND DESIGN ISSUES IN A CONCENTRATED SOLAR POWER TROUGH PLANT WITH THERMAL STORAGE

The power block for a conventional Concentrated Solar Power (CSP) Plant without thermal storage follows standard power block design practices. A closed loop heat transfer fluid (HTF) is heated in the solar field, which consists of multiple solar collector assemblies (SCAs). Heat exchangers use the heat from the HTF to generate and superheat steam. The steam is sent to a steam turbine, which generates electricity. The cooled HTF is recirculated back to the solar field. In an effort to shift the period of power generation or to maintain full power output during non-peak periods of operation, a thermal energy storage (TES) system can be added. This entails adding a second closed loop fluid that is heated by the HTF during sufficient radiation hours, which in turn can heat the HTF that is supplied to the power block during periods of non-peak radiation. This article discusses the process control and design issues for the integrated solar field, TES system and power block for these plants. The article will address the following: 1) Operations with the Solar field on-line, TES system off-line, and STG on-line. 2) Operations with the Solar field on-line, TES system charging, and STG on-line. 3) Operations with the Solar field on-line, the TES system discharging, and STG on-line. 4) Operations with the solar field off-line, the TES system discharging, and the STG on-line. 5) Operations with the Solar field on-line, the TES system charging, and STG off-line. 6) Steam Turbine Issues. 7) Freeze protection. 8) HTF/TES Heat Exchanger. 9) Circulating Water and Surface Condenser.