Development and multiscale characterization of sensible/sorption bimodal heat storage for cooling tower applications

This study presents experimental results on so-called cTES (cold Thermal Energy Storage) in the specific configuration of coupled heat and moisture storage. An effective improvement in coupled sensible/sorption energy storage is presented through the development of a new sensible/sorbent material made of glass spheres coated with a mixture of AQSOA Z05 zeolite and PDMS Sylgard 184. The manufacturing process is described first. The new material is characterized from the material scale (a few milligrams, ATG-DAC) to the intermediate scale (hundreds of coated beads, controlled oven) and the TES prototype scale (hundreds of kilograms of coated beads). The main results show that the new coating is highly effective, with more than 95 % of the sorbent material being active. The measured kinetics are quite low and significantly lower than those of the pure adsorbent Z05, which has been attributed to the low permeability of the binder used during the manufacturing of the coating. The experimental characterization of the thermal behavior at the prototype scale (approximately 440 kg of coated spheres and 270 kg of uncoated spheres) highlights the effective operation of the cTES, i.e., water storage during adsorption and flattening of the ambient air temperature during desorption, and the low amplitudes of those phenomena due to the low kinetics. • A procedure to produce a polydimethylsiloxane/AQSOA-Z05 based composite for coupled heat storage applications is presented • Equilibrium isotherms show that the new coating is highly effective, with more than 95% of the sorbent being active • Lower kinetics than pure Z05 are observed • At TES scale, effective operation is observed: water storage during adsorption; flattening of temperature during desorption • Low amplitudes are observed, linked with the low kinetics