Simulations of energy storage of ultra-low-grade-heat with liquid desiccant solutions

Ultra-low-grade heat from industrial processes remains an underutilised energy resource that could significantly aid decarbonisation if suitable recovery and storage technologies are identified. This study assesses the techno-economic feasibility of using liquid desiccant solutions to recover heat between 25 °C and 40 °C from a manufacturing plant producing radiation detectors, store it in a thermochemical form and deliver it to an end user by truck. A comprehensive modelling framework evaluates the performance of aqueous solutions of lithium chloride, calcium chloride and potassium formate under varying operating conditions and system configurations, including systems with single and double regenerators, different flow rates, storage tanks and frequency of the transport cycles. The analysis covers 466,560 design scenarios and investigates energy storage capacity, dehumidification potential and cost-effectiveness. Results indicate that 25% wt. aqueous calcium chloride regenerated in a system with double regenerator using a hot-solution approach offers the best overall trade-off, delivering up to 994 MWh of thermochemical energy per year when heat is available at 40 °C. Multi-criteria decision analysis confirms that this configuration performs optimally for several end users, including archives and indoor swimming pools. Sensitivity analysis identifies transport cost, energy prices and cycling frequency as key economic drivers, with payback periods being highly dependent on these factors. This study demonstrates the potential of liquid desiccant-based thermochemical storage for utilising ultra-low-grade thermal energy in decentralised energy networks, especially in applications where temperature and humidity control are critical.