System integration analysis of a zeolite 13x thermal energy storage

Nowadays a major energy transition aimed at cutting CO2 emissions has begun, with the ambitious goal of drastically reducing the dependence on fossil fuels and promoting the use of renewable energy sources. In this context, energy storage systems play a key role in ensuring a stable, secure and time-aligned energy availability. Open sorption thermal energy storages (TESs) can contribute to such transition, since they are simple and cheap devices able to provide a hot airflow with a high energy density and to store energy for long time. In this work, open sorption TES systems operated with Zeolite13X are investigated with a focus on the integration in practical applications. First, the experimental analysis and modelling of the sole TES system is described. Then, the integration of the TES at system level is carried out. The analysis evidences that a significant reduction of storage capacity occurs if air humidification is necessary before the adsorption process or afterwards to keep adequate indoor comfort conditions for the occupants. For the exemplary case study considered, an energy density of 150 kWhm−3 can drop to 40 kWhm−3 in case of complete compensation of the adsorbed water through a humidifier. This paper provides useful guidelines for evaluating the performance of a TES integrated system in terms of specific energy and efficiency. It also identifies applications involving high latent loads (e.g., swimming pools, locker rooms) or for which low relative air humidity is required (e.g. interior of vehicles to prevent condensation on windows) as particularly beneficial for using a TES system.