<p dir="ltr"><i>Membrane processes are used to desalinate seawater and surface water into potable water. The undesired byproduct of these processes is a stream of brine with high salt concentrations. In this project, the repurposed concentrate salt was studied as a potential storage medium for Thermal Energy Storage (TES), in effect preventing a harmful waste from being released to the environment while introducing a novel and low-cost alternative for energy storage. In this study, heat transfer behavior of an ROC-based thermal energy storage system is studied using CFD. A computational model is developed, verified, and validated to simulate the phase change process and buoyancy-driven flow in a square ROC-based thermal energy storage element. The computational results provide a predictive model for charge and discharge cycles of an ROC based thermal energy storage system. The results obtained from the CFD simulations were used in conjunction with a techno economic cost analysis, focused on the transportation, processing and containment cost of the energy storage, that aims to determine the economic feasibility of ROC technology in large scale, commercial applications. This cost analysis is based on a unique, existing salt composition. The total cost of TES was estimated by considering costs associated with transportation of brine, evaporation of remaining water, grinding the solid salt content, additives added, and containment costs while considering a positive financial gain from obtaining the concentrate from water treatment facilities. It was observed that operating the concentrate salt at high temperatures facilitated a solid to liquid phase change, which provides an increase in energy density and a reduction in TES cost. The results show a financial benefit using concentrate salt as a storage medium for heat making it a feasible material to meet the U.S. Department of Energy’s SunShot Initiative goals for TES, i.e., $15/kWh. Depending on the source of the brine, zero liquid discharge method, and operating temperature TES costs as low as (-$14.53), i.e., positive revenue was observed. In addition to containment material, the thermophysical properties and chemistry of feedwater sources significantly impacts the thermo-economics of the proposed concept. The concentrate salt exhibits a variable salt composition depending on the feedwater source. The occurrence of phase change within the operating temperature of the application significantly increases the energy storage density and reduces the cost of the thermal energy storage. The results also show that the concentrate salt that does not go through phase change may still be a feasible solid-state thermal energy storage in higher temperatures.</i></p>

Thermal Energy Storage Using Reverse Osmosis Concentrate

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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