PCM Phase Change Material Energy Storage Material / PCM Phase
PCMs latent heat storage can be achieved through solid–solid,
solid–liquid, solid–gas and liquid–gas phase change. However, the
only phase change used for PCMs is the solid–liquid change.
Liquid-gas phase changes are not practical for use as thermal
storage due to the large volumes or high pressures required to
store the materials when in their gas phase. Liquid–gas transitions
do have a higher heat of transformation than solid–liquid
transitions. Solid–solid phase changes are typically very slow and
have a rather low heat of transformation.
Initially, the solid–liquid PCMs behave like sensible heat storage
(SHS) materials; their temperature rises as they absorb heat.
Unlike conventional SHS, however, when PCMs reach the temperature
at which they change phase (their melting temperature) they absorb
large amounts of heat at an almost constant temperature. The PCM
continues to absorb heat without a significant rise in temperature
until all the material is transformed to the liquid phase. When the
ambient temperature around a liquid material falls, the PCM
solidifies, releasing its stored latent heat. A large number of
PCMs are available in any required temperature range from −5 up to
190°C .Within the human comfort range of 20°C to 30°C, some PCMs
are very effective. They store 5 to 14 times more heat per unit
volume than conventional storage materials such as water, masonry