Liquid desiccant thermal storage driven by off-peak electricity: synergistic regulation of solution concentration and air humidity for building load shifting

Abstract

Building latent cooling and humidification loads are difficult to shift with conventional sensible thermal storage, which limits demand-side flexibility in humid climates. To address this challenge, this study proposes and experimentally evaluates a heat pump–driven liquid desiccant system with integrated preheating and precooling for humidity-based energy storage and peak load shifting. A detailed thermodynamic model and laboratory-scale platform were developed to analyze the coupled dehumidification and regeneration processes, and sensitivity studies were carried out to identify the influence of key operational parameters. Results show that enhancing regeneration effectiveness and internal solution heat exchanger efficiency significantly increases the usable concentration swing and round-trip performance. At the single-building scale, the system achieved peak latent load reductions of 5.4 kW in summer and 4.8 kW in winter with a round-trip effectiveness of approximately 53 %. At the district scale, coordinated operation across multiple buildings in Nanjing delivered an aggregated reduction of 1.54 MW, accompanied by substantial energy cost savings, demand-charge reductions, and carbon mitigation. These findings demonstrate that humidity-based energy storage provides a practical and high-impact pathway to enhance building–grid flexibility and accelerate low-carbon urban energy transitions.