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Thermal energy storage radiatively coupled to a supercritical Rankine cycle for electric grid support

Meroueh, Laureen, Chen, Gang
Renewable energy 2020 v.145 pp. 604-621
carbon dioxide, coal, electricity, greenhouse gas emissions, heat transfer, phase transition, power plants, renewable energy sources, silicon, storage technology, temperature, thermal energy
Frequent variation in electricity demand strains power plants, thereby increasing CO2 emissions. Grid integration of intermittent renewables exacerbates this problem. Energy storage can mitigate demand fluctuations. Yet, common grid-scale storage technologies are geographically limited or prohibitively expensive. Storing electricity as heat, although thermodynamically counter-intuitive, can be cheaper and nonrestrictive. To do so, high temperatures are desired according to the second law of thermodynamics. Here, we analyze electricity storage through the phase change of solid to molten silicon and discharge the stored heat radiatively to a working fluid, allowing system flexibility. We use heat transfer analyses to determine whether radiative discharge of a thermal energy storage system to supercritical water is a viable method. Our analysis shows a system cost of $45 ± 10 per kWhe and 12-hr round-trip efficiency of ∼38%–43%. Rather than constructing additional gas-fired peaker plants to address peak loads, the proposed system can be implemented and use existing infrastructure from retired coal power plants. This approach is compatible with current power plants as well as renewable energy, providing a segue from fossil fuels to renewable energy dependent power plants.