Comparative Sustainability Assessment of Various Energy Storage Techniques in Hot Arid Climates

Energy storage systems critically assist in the implementation of sustainable energy sources. However, energy performance, water use and greenhouse gas emissions, which are essential for the implementation decision, have received inadequate attention especially for arid climates. Using energy storage methods in hot and arid climate regions is a sensitive matter. It is critical to consider appropriate storage technologies to implement to avoid unnecessary casualties caused by extreme weather conditions. This study initially compares 13 different energy storage methods, namely, pumped hydro, compressed air, flywheels, hot water storage, molten salt, hydrogen, ammonia, lithium-ion battery, Zn-air battery, redox flow battery, fuel cells, supercapacitors, and superconducting magnetic storage in terms of water usage, energy density, location dependency, and temperature degradation to be implemented in hot arid regions by conducting expert panel survey on hot arid climate criteria. The survey concludes that the highest rankings for energy storage techniques are Zn-air battery, superconductors, and flywheels, with overall rankings of 7.18, 6.73, and 6.61, respectively. Thermodynamic analyses are performed to assess these energy storage systems by fixing an electrical output of 100 kW. The energy efficiencies obtained for the considered energy storage methods vary between 10.9% and 74.6% whereas, the exergy efficiencies range between 23.1% and 71.9%. The roundtrip efficiencies for the electrochemical and electromagnetic storage systems range from 58% to 94%. Afterward, energy conversion efficiencies of renewable sources (solar, wind, ocean current, etc.) are also considered for the final roundtrip performances to calculate source-to-electricity performances. It is found that superconductors are among the most efficient storage method than the other systems, especially when utilizing ocean current source with an overall efficiency of 37.6%. The CAES shows a higher efficiency of 26.4% among the mechanical techniques when utilizing ocean current source. The molten salt system has the highest efficiency of 21.8% when using solar source whereas the CAES and redox flow battery efficiencies are 11.9% and 12.2%. A life cycle assessment study is conducted to evaluate and compare the environmental burdens associated with the selected three energy storage systems, namely; compressed air energy storage, vanadium redox flow battery, and molten salt thermal storage. The redox-flow battery has the highest global warming potential corresponding to 0.121 kg CO₂ eq./kWh, whereas the molten salt has0.0306 kg CO₂ eq./kWh global warming potential. In contrast, the system with the least harm to the ozone layer is the compressed air storage with the value of 7.24 × 10⁻¹³ kg R11 eq. In sensitivity analysis, it is found that using solar photovoltaics for energy storage inputs critically lowers the associated environmental impacts. A sustainability index calculation is performed to normalize the efficiency and environmental impacts to enable fair comparison and selection among the three methods. The overall sustainability index values for the molten salt, compressed air, and redox-flow battery are found to be 90%, 43%, and 33%, respectively when solar energy is considered.