Overcoming thermal energy storage density limits by liquid water recharge in zeolite-polymer composites

Abstract

Water-adsorbent pairs for thermal energy storage (TES) show promise due to their high heat of adsorption and stable adsorption/desorption process at near-room temperature. However, their overall energy storage capacity is limited by the adsorbent’s water adsorption capacity and slow recharge rate. To address this, we propose a liquid water recharge strategy for composite TES materials featuring high-adsorption-capacity zeolite particles (silicoaluminophosphate-34 [SAPO-34]) bound by a hydrophilic polymer. This innovation achieves TES densities exceeding 1.6 kJ g⁻¹, facilitated by liquid water retention and polymer hydration. The composites exhibit stability through more than 100 recharge/discharge cycles up to 150°C. Post-recharge, liquid water spontaneously segregates into three populations, each linked to a distinct heat storage temperature. This approach overcomes traditional limitations in adsorption-based TES, paving the way for rapidly recharged open-system thermal energy storage.