J. Rushkoff
Electric Power Research Institute,
United States
Keywords: thermal energy storage, industrial process heat, dispatch optimization
Summary:
Energy systems transitioning to reduce sourcing energy from fossil fuels and increase supply of variable renewable energy develop a potential need for energy storage to match supply and demand of energy. Electrochemical energy storage has filled this niche early on, in large part due to modular designs, low cost for the 1 to 4-hour duration space, and high round-trip efficiency (RTE). Thermal energy storage (TES) is another candidate to take up energy storage services for the grid. TES technologies generally have high energy density and low marginal cost of storage, but power to power (P2P) applications have not been commercialized in part due to low P2P RTE and few compensation opportunities for long-duration grid services. Power to heat (P2H) applications are seen as a steppingstone for TES to reach commercial maturity as the RTE for P2H is much higher for TES and integration tends to be less demanding and less costly. While the P2H application appears to be a natural fit for TES, a technoeconomic assessment based on real market data needs to be developed to identify potential sites for first-of-a-kind TES and enable the financing of these projects. This study detailed a formulation of a dispatch optimization model that the Electric Power Research Institute (EPRI) developed for TES providing heat for an industrial process while providing services to a wholesale electricity market. The optimization model included bidding in the energy and ancillary services markets and offered heat service modes such as fuel switching with the site’s existing fuel supply and scheduled dispatch. By applying the optimization model, the study evaluated the value that the TES system could bring to the industrial process and the grid as a controllable load resource. The study considered several case studies applying the optimization model for applications at sites in MISO, ERCOT, PJM, and SPP each with sensitivities on TES sizing between the charge power capacity, energy storage capacity, and discharge power capacity.