A Critical Review of Solid Materials for Low-Temperature Thermochemical Storage of Solar Energy Based on Solid-Vapour Adsorption in View of Space Heating Uses

Abstract

The present report deals with low-temperature thermochemical storage for space heating, which is based on the principles of vapour adsorption onto solid adsorbents. With the aim of obtaining comprehensive information on the rationalized selection of adsorbents for heat storage in open sorption systems operating in the moist-air flow mode, various materials reported up to now in the literature are reviewed by referring strictly to the possible mechanisms of water vapour adsorption, as well as practical aspects of their preparation or their application under particular operating conditions. It seems reasonable to suggest that, on the basis of the current state-of-the-art, the adsorption phenomenon may be rather exploited in the auxiliary heating systems, which provide additional heat during winter’s coldest days.

Hydration mechanism in Ce-exchanged zeolites and heat release performances upon adsorption of water vapour in support of their potential use in thermochemical storage of energy under mild conditions of adsorbent regeneration and saturation

“…Nowadays, renewable energy sources are considered as a key issue for sustainable development and climate change, especially in the building sector which is responsible for approximately 40% of the energy consumed in the EU countries resulting in strong greenhouse gases emissions [1]. In attempts to circumvent issues due to the intermittent nature of the renewable energy, many studies have focused on converting it into more useful forms such as thermal energy or electricity [2][3][4][5][6]. Amongst the numerous possibilities for energy conversion, solar energy harvested in abundance during summer may be exploited to increase the internal energy of an appropriate storage material (i.e., charging step) and thus be stored until cold days in winter when the heating supply system is under pressure.…”

“…Amongst the numerous possibilities for energy conversion, solar energy harvested in abundance during summer may be exploited to increase the internal energy of an appropriate storage material (i.e., charging step) and thus be stored until cold days in winter when the heating supply system is under pressure. Converted subsequently into heat during the discharging step, it may be used as a supplemental source of space heating [6].…”

“…In view of future uses in low-temperature thermochemical storage of solar energy, solid materials capable of releasing much heat during adsorption of vapours have the potential to yield high storage densities [5,6]. With the open sorption systems operating in the moist-air flow mode, the heat released upon the adsorption of water vapour may serve to increase the temperature of the dry air leaving the reactor.…”

“…The warm gas is subsequently directed to the space heating loop of the heated building. Various kinds of solid materials with a propensity for being reversibly dried and hydrated, and additionally characterised by good hydrothermal stability, have been already tested as adsorbents for the thermochemical storage (TCS) uses [6][7][8][9][10][11][12][13][14][15]. Porous zeolites and zeolite-based structures commonly stand out from the others as combining high specific surface areas, pronounced hydrophilic character of their surface, and good thermal/hydrothermal stability [16,17].…”

“…By the way, zeolite 13X was the first adsorbent practically applied in a short-term low-temperature thermochemical storage for daily heating of a school building in Germany [18,19]. Nevertheless, the handling of zeolites as effective adsorbents of water vapour may pose some practical problems [6].…”