Phase Change Materials: Limitations and Improvements

Phase Change Materials: Limitations and Improvements

By Shehwar Ali

Phase change materials are considered to be ideal products for thermal management solutions. These materials are capable of storing and releasing thermal energy while melting and freezing, hence the name phase change.

Phase change materials, when in the process of freezing, release a large amount of energy (latent energy), also known as the energy of crystallization. On the other hand, when melted, these materials absorb an equal amount of energy from the environment.

Types of Phase Change Materials & Limitations

There are various types of phase change materials. The most commonly used ones include salt hydrates, fatty acids, esters, and paraffin.  Ionic liquids are considered to be more of the newer ones.

Each type of material bears some disadvantages or limitations. For instance, the difficulty with ice is that it is good only when maintained at a minimum temperature of 0oC; same is the case with gel packs. Gel packs have a predominant compound called sodium polyacrylate. With its addition, the whole crystal structure of ice is changed and therefore, ice loses its ability to work as an active phase change material.

Another example is a salt hydrate. Some problems occur when the salt hydrate is used as a phase change material. The main issue is that salt hydrate melts incongruently when melting into a saturated aqueous phase and a solid phase. Because of the differences in density, a phenomenon called decomposition occurs, which in most cases is irreversible. Other issues of salt hydrates include their poor nucleating properties (which can be adjusted by adding a nucleating agent). Also, change in volume along with their destructive nature and toxicity are one of the prominent issues of using salt hydrates.

Paraffin is a traditional phase change material and also bears some limitations. Pure paraffin products are thought to have very high latent heats. Petroleum-based paraffin has geopolitical consequences because of the release of an excess amount of carbon which contributes to the global warming crisis.

PCM Improvements – A Reality!

Vegetable-based phase change materials are gaining popularity because of their safety and environmental benefits. Paraffin is thought to be toxic and has laxative effects when ingested. Moreover, when disposed of in a landfill, it poses environment problems.  The material that makes up paraffin, long chain alkanes, will not decay for decades. On the other hand, vegetable-based phase change materials degrade within six months. Considered cost-effective, vegetable-based materials are environmentally friendly and also renewable with the capability to be microencapsulated.  Biodegradable, higher latent heat, longer ignition rates, longer horizontal flame propagation rates are all the new properties that vegetable-based phase change materials have to offer.

The role of phase change materials in stabilizing the temperature of the environment is significant. A system that saves energy while providing comfort is what these products have to offer are main advantages. Even though many disadvantages still exist, research is ongoing to overcome hurdles holding back phase change materials.

Learn more about Phase Change Materials in PreScouter’s webinar.

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