13 Review on PCM Application for Cooling Load Reduction …
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13.2.2 Latent Heat Storage Materials
These materials have high specific heat capacity thus high concentration of energy
is stored per unit mass due to latent heat involved. Another main advantage of using
these materials is that they operate between small temperature differences while
storing or retrieving the energy. These undergo solid- liquid or liquid-gas phase transition, in working range of temperature. The volumetric transition during liquid-gas
phase change is quiet high as compared to solid-liquid PCM, hence are less suitable
for building storage applications. Thus, solid-liquid transition storage systems are
focused in this chapter. The heat stored within PCM storage is given in Eq. 13.2.
Q = m
T melt
T i
C ps .dT + m.L + m
T f
T melt
C pl .dT
(13.2)
The solid-liquid PCMs are further classified as inorganic and organic. Example
of organic latent heat storage materials are paraffins, sugar alcohols, fatty acids etc.
and example of inorganic PCMs are water, hydrated salts, molten salts, aqueous
solutions etc. Moreover, two more miscible pure PCM constituents, having single
melting/solidifying temperature are referred as eutectic mixtures. Use of hydrated
salts as thermal energy storage materials is preferred, as they possess high energy
density owing to higher density and latent heat. However, they show tendency of
sub-cooling (or super-cooling) due to low nucleation rate thus, diminishing their
usability significantly. Different PCMs are studied as potential TES materials, for
temperature reduction within buildings and are illustrated in Table 13.2.
A significant number of researchers are working on organic PCMs i.e. on methods
to increase their thermal conductivity which is a major drawback of using organic
PCM. The research is going on to dope the nanoparticles into the PCM matrix to
enhance their thermal conductivities. The methodology of mixing and characterizing
the nano-enhanced PCMs is discussed in detail under Sect. 13.6.
13.2.3 Chemical Heat Storage Materials
Research is still under process to explore materials storing thermal energy as enthalpy
change of a reaction. For e.g.:
A + B + energy → C + D
(13.3)
In this interaction A and B absorb energy and convert into C and D thus the energy
is stored as enthalpy change. It is important for reaction to be reversible so that energy
can be retrieved when required. The challenge lies in finding such reactions that may
hold true, must be stable and can be triggered as and when required. A perfect
251
13.2.2 Latent Heat Storage Materials
These materials have high specific heat capacity thus high concentration of energy
is stored per unit mass due to latent heat involved. Another main advantage of using
these materials is that they operate between small temperature differences while
storing or retrieving the energy. These undergo solid- liquid or liquid-gas phase transition, in working range of temperature. The volumetric transition during liquid-gas
phase change is quiet high as compared to solid-liquid PCM, hence are less suitable
for building storage applications. Thus, solid-liquid transition storage systems are
focused in this chapter. The heat stored within PCM storage is given in Eq. 13.2.
Q = m
T melt
T i
C ps .dT + m.L + m
T f
T melt
C pl .dT
(13.2)
The solid-liquid PCMs are further classified as inorganic and organic. Example
of organic latent heat storage materials are paraffins, sugar alcohols, fatty acids etc.
and example of inorganic PCMs are water, hydrated salts, molten salts, aqueous
solutions etc. Moreover, two more miscible pure PCM constituents, having single
melting/solidifying temperature are referred as eutectic mixtures. Use of hydrated
salts as thermal energy storage materials is preferred, as they possess high energy
density owing to higher density and latent heat. However, they show tendency of
sub-cooling (or super-cooling) due to low nucleation rate thus, diminishing their
usability significantly. Different PCMs are studied as potential TES materials, for
temperature reduction within buildings and are illustrated in Table 13.2.
A significant number of researchers are working on organic PCMs i.e. on methods
to increase their thermal conductivity which is a major drawback of using organic
PCM. The research is going on to dope the nanoparticles into the PCM matrix to
enhance their thermal conductivities. The methodology of mixing and characterizing
the nano-enhanced PCMs is discussed in detail under Sect. 13.6.
13.2.3 Chemical Heat Storage Materials
Research is still under process to explore materials storing thermal energy as enthalpy
change of a reaction. For e.g.:
A + B + energy → C + D
(13.3)
In this interaction A and B absorb energy and convert into C and D thus the energy
is stored as enthalpy change. It is important for reaction to be reversible so that energy
can be retrieved when required. The challenge lies in finding such reactions that may
hold true, must be stable and can be triggered as and when required. A perfect