Thermal Energy Storage for a Dish Stirling Concentrated Solar Power System

摘要

A phase change salt Thermal Energy Storage (TES) device has been designed and built for use with a Stirling engine in a concentrated solar power system. A eutectic blend of NaCl and NaF was used for the latent heat energy storage medium, with a melt temperature of 680C and energy storage capacity of 43 MJ (12 kW*h). A sodium heat pipe integrated the heat transport function from the solar receiver surface to the Stirling heater head and the molten salt canister during charge mode and from the salt canister to the heater head during discharge mode. The heat pipe was an elaborate hybrid structure with interconnected vapor chamber regions at the receiver and heater head, with extension tubes into the salt canister. Multiple extension tubes were used to maximize contact area with the salt. A sintered powder wick was used to accommodate the high fluxes at the receiver and multilayer screen wick throughout the rest of the heat pipe. The assembly was mostly Inconel 625, with Haynes 230 at the receiver. The layout of the multi-chambered heat pipe required careful analysis and design. A CFD tool was used to evaluate wick heat transport capability in a variety of orientations. Fabrication of the welded heat pipe & salt canister assembly required careful sequencing. In order to suppress corrosion, processing of the salt charge was done in a manner that minimized residual moisture. A basic heat pipe functional test was done before delivery of the system to the customer for thorough performance testing (which is described in a related paper).