Pcm Advantages And Disadvantages

Phase change materials (PCMs) are “latent” thermal storage materials. They use chemical bonds to store and release heat. The thermal energy transfer occurs when a material changes from a solid to a liquid or from a liquid to a solid. This is called a change in state, or “phase”. Initially, these solid-liquid PCMs perform like conventional storage materials; their temperature rises as they absorb solar heat. [6]

When PCMs reach the temperature at which they change phase (their melting point) they absorb large amounts of heat without getting hotter. When the ambient temperature in the space around the PCM material drops, the PCM solidifies, releasing its stored latent heat. PCMs absorb and emit heat while maintaining a nearly constant temperature.

There are several options with distinct advantages and disadvantages. The phase change solid-liquid by melting and solidification can store large amounts of heat or cold, if a suitable material is selected. Melting is characterized by a small volume change, usually less than 10 %. If a container can fit the phase with the larger volume, usually the liquid, the pressure is not changed significantly and consequently melting and solidification of the storage material proceed at a constant temperature. Upon melting, while heat is transferred to the storage material, the material still keeps its temperature constant at the melting temperature, also called phase change temperature (figure

In the case of solid-liquid phase change, it is called solid-liquid phase change enthalpy, melting enthalpy, or heat of fusion. Materials with a solid-liquid phase change, which are suitable for heat or cold storage, are commonly referred to as latent heat storage material or simply phase change material (PCM).

Some solid-solid phase changes have the same characteristics as solid-liquid phase changes, but usually do not possess a large phase change enthalpy. However, there are exceptions and they are used in a few applications. Further on, even materials with a solid-liquid phase change can be combined with other materials in a way that they do not show the liquid properties any more (section 2.3.4.1). For this reason, whenever talking about phase change in general, the terms phase change temperature Tpc and phase change enthalpy Δpch are used, instead of the terms melting temperature and melting enthalpy.

Another major advantage with latent heat storage is that heat is stored under isothermal conditions, which means they can deliver or store energy at a constant temperature