UCLA

Elemental sulfur is a promising storage material for low to high temperature thermal energy storage (TES) applications due to its high chemical stability, high heat transfer rate, and low cost. In this study, we investigate the performance of sulfur-based TES systems (SulfurTES) in the temperature range of 50-600 oC for single-tank and multi-tank configurations, as well as heat transfer fluid options, and have found a wide range of system configurations that provide attractive performance and cost.

For a single-tank thermal battery configuration, a 2D, transient-state numerical model was developed and validated using experimental results obtained from the thermal cycling of a 10kWh SulfurTES battery. In general, the results show that a moderate shell aspect ratio (i.e., L/D ~ 4-7) and standard tube diameters (i.e., diameter ~ 2-6”) can be used to provide a range of high performance and low-cost systems.

Multi-tank configurations were investigated and found to have many attractive aspects. The proposed cascaded configuration with two shell passes boosts system’s energetic efficiency, providing a versatile system that accommodates wide selections of applications with low cost.

Effects of heat transfer fluid (HTF) properties on performance parameters were studied using sCO2 and HITEC Solar salt as HTFs. The large density of sCO2 leads to negligible compressor work that is beneficial to exergetic efficiency. High thermal conductivity and large energy density of HITEC salt provides promising thermal performance, but its prohibitive cost and limited operating temperature range make it undesirable to use with SulfurTES.

Finally, the cost analysis of SulfurTES system was conducted assuming integration with concentrated solar power plants. The results demonstrate significant cost advantage of SulfurTES over Molten-salt TES. The capital cost of SulfurTES achieves 2020 Sunshot TES cost target of $15/kWh, providing a levelized cost of energy of less than �5/kWh that satisfies the Sunshot cost target of 2030.