Thermally responsive flexible phase change materials with high themal conductivity for thermal energy storage

Table $1.$ Classfication of FDMs $-$ FDMs used for primary enesgy storage

The FDM groups shown in this table have some advantages and disadvantages in practice. Parameters such as phase change enthalpy, phase change temperature, thermal conductivity and thermal conductivity in solid and liquid state should be taken into account when selecting FDMs$.$ Candidate materials for use as FDMs are those that show phase change in the $0-120C$ range. These materials are classified as organic, inorganic and their mixtures. Examples of inorganic FDMs are salt hydrates and clathrate hydrates. Their advantages are: high melting temperature, good thermal conductivity, cheap and non$-$flammable, while their disadvantages are: corrosiveness, supercooling, phase distortion and reduction in the number of hydrates. Examples of organic FDMs are paraffins and fatty acids. Their advantages are: chemically stable, little or no supercooling, non$-$corrosive and non$-$toxic, high melting temperature and low vapor pressure, while their disadvantages are low thermal conductivity, large volume change during phase change and flammability. Thermal energy storage is defined as high or low thermal energy stored for later use. It is a property that acts as a transition between the time interval between energy requirement and energy utilization. Latent Heat storage is a technique that utilizes the phase change latent heat of FDMs for energy storage. This phenomenon occurs during phase change in a certain temperature range. This is why this technique is called latent heat storage technique.

Dimensions in FDM selection

$1-$Thermodynamic critena: Suitable melting temperaturerange

$-$Have a high melting temperature per unit volume or mass to store a high percentage of energy using less FDM

$-$It should have a high heat storage capacity, and its density should be high so that it can be placed in small volume storages.

$-$The thermal conductivity should be high $($in order to reduce the time required for storage and recovery$).2-$As kinetic criteria, the solid should show little or no supercooling effect during solidification. For successful crystallization, the nucleation rate of the substance should be high and the crystal formation rate should be large.

$3-$It should show chemical stability as chemical criteria. The melting and solidification process must be completely reversible. It should not undergo chemical degradation after a large number of melting and solidification processes, that is$,$ it should be long$-$lasting.

High concentration of HCHO $($formaldehyde$)$ as a coating was found to be very effective for solving liquid leakage problems. Ali Karaipekli and Ahmet Sari impregnated a eutectic mixture of capric acid$-$myristic acid $($CA$-$MA$)$ into a porous vermiculite. The results showed that the CA$-$MA eutectic blend could be retained in the vermiculite pores at a rate of $20wt\%,$ without the need for molten PCM SIZInt$$s$.$ Ye Hong and Ge Xinshi studied the encapsulation of five different types of high$-$density polyethylene $($HDPE$)$ into paraffin and found that composite PCMs based on HDPE$5$ had the best shape stability.

However, while the development of shape$-$stabilized composite PCMs has greatly improved the problem of pure PCMs$,$ thermal contact resistance between PCMs and the controlled device and poor installation are two growing problems that greatly hinder their further application in practical energy storage and thermal control engineering. In particular, conventional shape$-$stabilized PCMs offer strong stiffness without any flexibility even if the internal phase change matrix completely melts into liquid, which directly leads to high installation difficulty, easy brittle failure and poor surface contact with the device. To solve the installation challenge, researchers have to adopt more complex installation process and extra add$-$ons, which greatly increase economic costs and reduce application feasibility.

For composite PCMs$,$ the macroscopic physical properties of the composite depend mainly on the supporting materials, as the supporting materials have larger molecular chains than pure phase change matrix materials. If thermoplastic polymers have excellent flexibility, composite PCMs obtained by physically blending PCM matrix into polymers will have a chance to offer a certain flexibility. This is because when the temperature of composite PCMs is higher than the melting point of the internal $PCM$ matrix, i$.$e$.$ when the matrix turns into a liquid, the mechanical properties of composite PCMs have a certain relationship with the supporting materials. When the temperature is lower than the melting point, there will be macro mechanical stiffness.

The search for new technologies to save energy and reduce environmental impact has always been a scientific.

Could you please write the references in the literature summary section about Synthesis of flexible latent heat storage material and examination of its thermal performances, prepare the reference list and send it to me$?$