A lot of researchers get giddy when talking about thermal energy storage; primarily because there are a lot of areas you can research. One topic that has graced the minds of several academics is called Phase Change Materials. I admit I am equally guilty of investing quite some time into this phenomenon, because it is quite fascinating, and I will tell you why in this article.
Thermal energy storage-a trendsetter
Thermal energy storage (TES) has been battling a certain amount of scepticism because of doubts concerning the availability of fast and dispatchable energy which a lot of other storage systems can boast about. Despite concerns, TES has been promising because more than 90% of the energy generation is wasted as heat. So, it has been a long quest to harvest this wasted heat and reuse it for energy generation through TES systems, which is pretty smart don’t you think?
It is also helpful to note that TES is not constrained by geographical locations like how pumped hydro systems are. It can also be modulated in size to fit the generation capacity. It also has the flexibility to make use of sustainable materials in its fabrication while also proving to be a relatively safe form of storage, unlike batteries and flywheels that may release energy destructively. TES systems comprise sensible heat storage which means that the temperature changes that a system undergoes are without a phase change. Another TES system is thermochemical heat storage which makes use of a bunch of chemical reactions to store chemical energy with the use of heat. However, in my opinion, the most interesting one is called latent heat storage which comprises the technology known as Phase Change Materials (PCM).
PCM-It’s all in the name
The concept of PCM is super easy to understand! They are basically substances which can absorb, store and release heat energy while undergoing a change of phase from solid to liquid or liquid to gas and vice versa. Usually, temperature increases with an increase in the input heat energy but for latent heat storage materials, after a certain temperature point is reached, heat input increases but the temperature remains constant. The melting point of that material usually acts as the point when temperatures do not change, and storage takes place. Correspondingly, when the material starts to solidify, the heat that was absorbed by the material is released to the surroundings.
PCMs are usually made from organic materials, inorganic materials, or a combination of both. They can be dry, wet, have a protective shell or even not have one. It is quite versatile and compatible with many compounds which helps in improving its properties and making it useful for a wide variety of applications.
Is it really worth it?
These materials also activate at different temperatures depending on the material used. For example, paraffin wax is a PCM. Depending on the number of carbons present in different ‘grades’ of PCM, it has different melting temperatures. There are different thermal analyses such as Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) which can help identify the melting point, latency, and other properties of the PCM.
Let us say that you want to warm your hands with a thermal glove, PCMs can help with that by choosing a material that is close to the body temperature of 37°C-38°C. If you want to cool your laptop because you have been binge-watching shows all day, PCMs can still help with that by absorbing the heat from the device thereby cooling it. In this manner, PCMs can also be scaled to energy storage applications in buildings and even smart cities.
I was re-introduced to it in detail when I took the Energy Storage course at IST, Portugal. Studying about various storage technologies enabled me to understand that there is a lot of scope for thermal storage systems. Also, with the European Green Deal promoting storage as one of the key future developments, I definitely think it is worth it!
Final thoughts
A lot of research is going on in the field of PCM based applications and coming up with appropriate, cost-effective solutions, especially for predictive modelling is yet to be finalised. The testing methods are an area that requires a lot of focus, especially when determining the life of PCMs and whether it’s financially feasible in the long run.
Currently, it’s not widely commercialised yet because of the initial challenges mentioned above. The good thing is, that Europe is boosting the growth of research and development with policies like the Green Deal. So, I believe that PCMs will gain significant traction in the coming years!
By Sharon Santhosh, EIT InnoEnergy Master’s in Energy Storage Student