Civil Engineering Reference
In-Depth Information
The desorption-adsorption reaction of hydrates of magnesium sulphate which is
capable of storing 2.8 GJ/m3 of energy was identified during the aforementioned
Task 32 of IEA. The associated reaction is as follows:
MgSO
4
7H
2
O
ðÞþ
heat input
,
MgSO
4
ðÞþ
7H
2
O
ðÞ
ð
4
Þ
The term 'sorption' usually refers to the phenomenon of capturing of a vapour
or a gas by a substance that is available in the condensed state (either in solid or
liquid state). The former is known as 'sorbate', and the latter is called as 'sorbent'.
The phenomenon of sorption generally comprises of both thermochemical and
thermophysical criteria, which also includes the aspects related to the absorption
and adsorption processes. The absorption in terms of TES literally means the
process of absorption of a gas into the liquid medium (or the absorbent). Likewise,
adsorption refers to the binding of a gas or vapour on the surface of the solid or
porous material.
The aspects of adsorption are more related to the surface phenomenon of one or
more materials undergoing reactions either through the physical (physisorption) or
chemical (chemisorption) routes. The physisorption is more pronounced, when the
reaction occurs due to the effects of Van der Waals forces, but the chemisorption is
realized by virtue of the valence forces. The heat of sorption is usually high for the
chemisorptions when compared to the physisorption, but the reaction may be
sometimes irreversible for the former case.
Sorption processes for acquiring TES can be further divided into the open-loop
and closed-loop systems. In the open-loop systems, the working fluid vapour
(water vapour) is usually exhausted to the open atmosphere, whereas in the closed-
loop systems, the working fluid is separated out from the neighbourhood subsys-
tems. The circulating working fluid capable of catering higher heat storages would
characterize the operating efficiencies of the closed-loop systems.
The energy density of various storage methods (N'Tsoukpoe et al.
2009
),
the volume reduction in the storage containment using various TES technologies
(Pinel et al.
2011
), classification of the chemical storage (Pinel et al.
2011
) and the
combination of working materials of thermochemical energy storage (Gores et al.
2012
) are depicted in Fig.
1
a-d.
3 Incorporation of TES in Buildings
The increasing energy demand and security of energy supply worldwide has
indubitable necessities for conserving energy at every step of economic develop-
ment of a nation. The buildings are identified to be one of the major sectors, which
would account for 30-40 % of primary energy consumption. The construction of
value-added building structures would in one way help to elevate the economy and
societal status of a country, but on the other hand, they would have a higher
proportion of energy consumption being derived from primary energy sources.
