Characterisation and comparative analysis of zeotype water adsorbents for heat transformation applications

This paper presents the experimental characterisation of three zeotype materials, namely, AlPO-18, FAPO-34 and SAPO-34, suitable for adsorption heat transformation applications, employing water as refrigerant. Morphological and thermo-physical analyses were performed on each sample. In particular, the adsorption capacity of each material was evaluated by measuring a complete set of water vapour adsorption/desorption isotherms, in order to investigate the hysteresis effect. The obtained equilibrium data were fitted by means of Dubinin-Astakhov equation, both for adsorption and desorption branches. Finally, a thermodynamic analysis of the achievable performance of these three working pairs was performed under three main operating conditions, namely, thermal energy storage, air conditioning and heat pumping. The achieved results confirmed the potentiality of these adsorbents, showing promising cooling and thermal COP, up to 0.80 and 1.60 respectively, and heat storage capacities both for daily and seasonal operation.