Low-cost, high efficiency, energy storage is needed for the future electric grid which will include more variable energy resources, such as wind and solar. Substantial penetration of wind and solar resources into the electric power grid is challenged by their intermittancy, as well as the dynamic response limitations of central utility plants. Storing electric energy directly into batteries is one of the most efficient ways to preserve the energy generated from renewable resources, but capacity limitations of conventional batteries are too great at present to economically store enough energy at utility-scales. Energy storage for concentrating solar power (CSP) is also a critical enabling technology as it enables higher capacity factor power plants and unlike other renewables, its integration actually lowers the levelized cost of energy. However, in CSP plants, energy storage involves amassing thermal/thermochemical energy at high temperatures as a reserve for use during times when the sun is not shining.
In this talk, advancements in both a novel thermochemical energy storage (TCES) concept based on redox cycling of reducible, doped calcium manganite (doped CaMexMnO3-δ) perovskite particles and in the development of low-cost regenerative heat exchangers for supercritical CO2 (s-CO2) power cycles will be presented. The TCES concept utilizes the fact that perovskite oxides (with chemical structure ABO3-δ) can undergo endothermic partial reduction to store solar heat at temperatures as high as 900°C. By providing excess reduced oxide during periods of high insolation, the combined thermochemical and sensible energy in the partially reduced perovskites can provide total storage of nearly 750 kJ/kg such that < 1.5 m3 of particles can be re-oxidized to produce a MWh of electricity for a 50% power cycle. The presentation highlights modeling efforts that seek to develop tools for adequate capture of the reacting, multi-phase (gas-solid) flow phenomena occuring within both high temperature solar receivers and heat rejection heat exhangers. A brief overview of a synergistic effort to develop regenerative heat exchangers for s-CO2 power cycles that are to be employed within CSP plants is also given. Strategies and progress towards enabling these concepts are presented in the context of meeting U.S. DOE Sunshot targets of high temperature storage at <$15/kWht.