Civil Engineering Reference
In-Depth Information
The transport of thermal energy inside the PCM can be faster enough with the
presence of nanoparticles, by which the rate of heat transfer of PCM is augmented
and the energy consumed during charging (freezing) process can be reduced.
However, the addition of nanomaterials to the PCM may alter the latent heat of
fusion and phase change temperature, but the shift in these parameters has to be
kept minimum, which ultimately depends upon the thermophysical aspects of the
dispersed nanomaterials.
The term supercooling refers to the temperature drop experienced by the PCM
with respect to its phase change temperature during the freezing process. That is,
the PCM would still remain in the liquid state even when it is cooled below its
freezing point. By supplying the cold energy continuously (activation energy), the
PCM would tend to achieve the state of crystallization. The supercooling in PCM
would actually lead to the energy consumption, considerably.
In order to reduce the effect of supercooling, various heat enhancement tech-
niques have been proposed widely, in recent years. Of having such methods, the
incorporation of nanomaterials has proved to effectually reduce the supercooling in
PCMs (Parameshwaran et al.
2013
and Zhang et al.
2012
). The fast response
exhibited by the nanomaterials towards the change in the heat energy requirements
has invariably contributed to the reduced energy consumption with better heat
storage and release characteristics of PCMs.
The thermal stability of PCMs is much more important for them to be heat
resistant and stable when subjected to elevated temperatures. The thermal stability
of PCMs can be increased with the incorporation of nanomaterials that have higher
melting temperature. The physical amalgamation of the nanoparticles with the
PCM as well as the interbonding linkages of the PCM structure can together
contribute to achieving higher temperature of decomposition of PCM.
On the other hand, the nanoparticles can also keep the PCM to be stable enough
when tested for several thousand repeated thermal cycles. This may be due to the
physical adsorption of nanoparticles with the PCMs or through the capillary
action, and the nanoparticles may get into the minute porous structure of the
PCMs, thereby giving them a better mechanical strength towards thermal or shock
disturbances on the long-term basis.
10 Sustainable Aspects of Thermal Energy Storage System
The effective energy redistribution and enhanced energy conservation that can be
achievable through the TES systems offer a great potential for gaining the sus-
tainable merits for the new and refurbished buildings. The integration of thermal
storage systems with the HVAC systems in buildings can help to shift the on-peak
load demand to off-peak conditions as well as minimize the overall primary energy
consumption.
