Porous materials in solar heat storage applications
Nataša Zabukovec Logar
National Institute of Chemistry, Hajdrihova 19, 1001 Ljubljana, Slovenia
Thermochemical heat storage (TCS) utilises the reversible chemical and physical
sorption of gases, mostly water vapour, in solids. It is considered the only
storage concept with a potential for long-term, also seasonal, low-temperature
(up to ~140 oC) thermal energy storage. Under the influence of a heat supply,
water is removed from the material that is then stored separately (activation of
material). When water vapour and sorbent are put into contact, there is a heat
release (material’s discharge or deactivation). The essential breakthrough that is
still needed to commercialise the storage concept is precise design and
engineering of new storage materials, as well as energy and resource efficient
and environmentally benign synthesis routes.
Current S&T activities are targeted at the development of porous adsorbents with
optimized physical-chemical properties for maximum heat storage capacity and
suitable interactions with vapours at applicable conditions (p,T). The quick and
fully reversible hydration processes in micro- and meso-porous materials is
considered superior to those in crystallohydrates, which are also attractive TCS
materials at a relatively low cost, but suffer from very slow sorption kinetics and
severe materials degradation. In the lecture, some recent studies of the
structure/sorption-behavior relationship in microporous solids with the aim of
improving the design of storage materials, will be presented. The highlights will
be on the role of chemical composition, pore size, hydrothermal stability and
thermal conductivity of selected microporous aluminophosphates and metalorganic framework materials.