Civil Engineering Reference
In-Depth Information
taking place within the material at constant temperature. Precisely, the usage of
terminologies pertaining to freezing and melting varies with the literatures, but in
this chapter, the convention followed for the freezing and melting is being
referenced to the process by which transfer of heat energy takes place between the
heat storage material and the heat transfer medium. Besides, the terms like
charging or solidification and discharging would also mean the same as that of
freezing and melting processes, respectively.
In reality, the LTES systems offer a huge potential to store thermal energy,
when compared to the SHS systems for building cooling and heating applications.
This is due to the fact that, the heat storage material in an LTES system possess
good thermophysical characteristics in terms of freezing and melting, which
provides more flexibility to store or release the thermal energy on demand.
Moreover, the volumetric capacity and handling of heat storage materials in
LTES systems would also benefit for its preference in modern building HVAC
applications. Both the sensible and latent thermal storage systems are capable of
offsetting the thermal load demand and can satisfy the energy redistribution
requirements in buildings. The forthcoming sections are dedicated to the SHS and
LTES systems, which would clearly highlight their effective contribution towards
meeting nearly zero energy in buildings that are being newly constructed or
refurbished.
2.3 Thermochemical Energy Storage
In the spectrum of TES technologies, the concept of utilizing the chemical
potential of certain materials for storing and releasing the heat energy on a long-
term basis has been gaining momentum in recent years. Basically, the thermal
energy can be stored or released by virtue of the reversible chemical reactions
occurring between the reactive components (or chemical compounds or materials)
with negligible thermal loss.
The endothermic reactions of the chemical compounds can be initiated by
supplying the thermal energy that is being captured from any heat source (solar
energy). For instance, the heat energy that is required to be stored and released
over time using two chemically reactive components can be defined by
C
1
C
2
þ
Heat input
,
C
1
þ
C
2
ð
3
Þ
Herein, the pair of chemical components (C
1
,C
2
) has got dissociated into
individual components with the supply of heat, which can be stored separately. On
the other hand, if they are combined together, the same paired components are
produced with the release of heat energy (exothermic reaction). The International
Energy Agency (IEA) during the Task 32 SHC programme proposed a prototype
system working on the principle of thermochemical reaction for storing heat
energy using the hydrates of magnesium sulphate.
