A Novel Modular and Dispatchable CSP Stirling System: Design, Validation, and Demonstration Plans

This paper summarizes the preliminary results from the on-going development of a novel modular dispatchable solar power plant concept. The work encompasses techno-economic feasibility assessment, concept design, full scale subsystem tests and validation work, and ultimately plans for a fully integrated demonstration of the system. The proposed solar power plant concept consists of a heliostat field that powers a latent heat thermal energy storage (TES), fitted on a small tower. The solar receiver located underneath the TES tank, is an optical cavity with a small aperture that enables the concentrated sunlight to be emitted directly on the solar absorber surface while ensuring low convective and radiative losses. The stored thermal energy is provided to the engine, in proximity to the latent heat storage, with a pumped heat transfer fluid (HTF). The Stirling engine with a rated power of 13 kW has been modified and optimised for the operational conditions that the eutectic aluminum-silicon latent heat storage provides. For example, a new engine tubular gas heater has been developed for the HTF (i.e. sodium) and the expansion cylinder has been enlarged to improve both efficiency and power output as the temperature of the working gas is somewhat lower than in previous dish Stirling application. The choice of eutectic aluminum-silicon as TES media resulted from a thorough assessment of several phase change materials throughout the design phase of the project. Indeed, such a TES media selected would benefit from a suitable melting temperature of around 580 degrees C, high energy density, high thermal conductivity, and low cost.