HPS2 – demonstration of molten-salt in parabolic trough plants – Design of plant

Molten Salt as alternative heat transfer medium for parabolic trough systems shows a potential for lowering the levelized cost of electricity (LCoE). Kearney et al [1] described that a reduction of LCoE greater than 10% depending on the salt mixture is possible. In order to demonstrate the feasibility of using molten salts as heat transfer fluid as well as thermal energy storage medium in a parabolic trough solar field (SF) a demonstration plant in Évora, Portugal is being engineered, procured and constructed. It consists of one loop of HelioTrough^® collectors summing up to a total irradiated length of 684 m. Safe operation is ensured by a solar field heating system comprising impedance heating and heat tracing. The thermal energy storage (TES) system thermally disconnects the solar loop from the steam generating system (SGS) for providing a solar-independent steam production. The SGS is designed to provide live steam parameters of 560°C at 140 bar by a single path once-through boiler design. In the HPS2 project the Yara MOST salt-mix will be used, it combines a low-melting temperature with high operation temperatures. The water-steam cycle is equipped with throttling equipment in order to simulate different steam turbine behaviors and allow the demonstration of sliding pressure operation in the subcritical once through-type boiler.