Civil Engineering Reference
In-Depth Information
while the latent thermal energy storage (LTES) makes use of the energy stored
when a substance changes from one phase to another. On the other hand, energy
being stored by virtue of the process reactions between the chemical constituents is
referred under the thermochemical energy storage.
2.1 Sensible Thermal Energy Storage
As the name signifies, thermal energy is stored in the material through sensible heat
supply, which in turn would raise the temperature of the material considerably.
In this kind, the thermal energy stored by the material is directly quantified to its
mass (m
s
), specific heat capacity (c
ps
) and the temperature gradient (DT) of the
material which is given by
Q
s
¼
m
s
c
ps
DT
ð
1
Þ
or,
Q
s
¼
m
s
c
ps
ð
T
h
T
i
Þ
ð
2
Þ
where T
h
—maximum temperature attained by the material in (K) and T
i
—initial
temperature of the material in (K). It can be observed that the energy storage
capacity of such materials largely depends on their density and specific heat. The
relatively low thermal capacities of these materials are usually compensated by
their
large
temperature
gradient
experienced
during
heat
storage
or
release
processes.
For high-temperature applications, SHS materials can be a good choice for the
aforementioned reasons. Thermal energy can be stored or released upon demand
by exchanging the heat energy by virtue of the temperature difference being
experienced within these materials.
2.2 Latent Thermal Energy Storage
In recent years, the usage of LTES systems has received increased interest. LTES
systems have been recognized as one of the effective measures for reducing the
energy consumption, especially applied to the HVAC systems in buildings. As
stated earlier, LTES system utilizes a heat storage material which is capable of
storing and releasing the thermal energy by changing its phase either from solid to
liquid or vice versa, at isothermal conditions. For instance, during freezing
process, the material would undergo a phase change process by absorbing the
energy from the heat source at constant temperature.
Likewise, in a melting process, the thermal energy stored would be released by
the material to the surrounding heat transfer medium with phase change process
