In this work, energy and exergy analyses are applied to a thermal energy storage system employing a storage medium in the two-phase or supercritical regime. First, a numerical model is developed to investigate the transient thermodynamic and heat transfer characteristics of the storage system by coupling conservation of energy with an equation of state to model the spatial and temporal variations in fluid properties during the entire working cycle of the TES tank. Second, parametric studies are conducted to determine the impact of key variables (such as heat transfer fluid mass flow rate and maximum storage temperature) on both energy and exergy efficiencies. The optimum heat transfer fluid mass flow rate during charging must balance exergy destroyed due to heat transfer and exergy destroyed due to pressure losses, which have competing effects. Similarly, the optimum maximum storage fluid temperature is evaluated to optimize exergetic efficiency. By incorporating exergy-based optimization alongside traditional energy analyses, the results of this study evaluate the optimal values for key parameters in the design and operation of TES systems, as well as highlight opportunities to minimize thermodynamic losses.
- Advanced Energy Systems Division
Exergy-Based Optimization of Sub- and Supercritical Thermal Energy Storage Systems
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Tse, LA, Lakeh, RB, Wirz, RE, & Lavine, AS. "Exergy-Based Optimization of Sub- and Supercritical Thermal Energy Storage Systems." Proceedings of the ASME 2014 8th International Conference on Energy Sustainability collocated with the ASME 2014 12th International Conference on Fuel Cell Science, Engineering and Technology. Volume 2: Economic, Environmental, and Policy Aspects of Alternate Energy; Fuels and Infrastructure, Biofuels and Energy Storage; High Performance Buildings; Solar Buildings, Including Solar Climate Control/Heating/Cooling; Sustainable Cities and Communities, Including Transportation; Thermofluid Analysis of Energy Systems, Including Exergy and Thermoeconomics. Boston, Massachusetts, USA. June 30–July 2, 2014. V002T12A001. ASME. https://doi.org/10.1115/ES2014-6302
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