Investigation of thermal behaviour of paraffins, fatty acids, salt hydrates and renewable based oils as PCM

Latent heat thermal energy storage (LHTES) using phase change materials (PCM) is a renewable energy source that is applicable for implementation in space cooling due to its high energy storage density. A novel thermal energy storage which will encapsulate a PCM layer to absorb the rejected heat from the building during occupied hours and release it to the ambient air during night-time is going to be developed. On the grounds of this development, a selection of seven PCMs are examined. The selected materials comprise the basic classes of PCM, namely: paraffins, fatty acids, and salt hydrates. The objective of this study is to identify experimentally the thermal properties of commercial PCM, renewable based oils, PCM in water emulsions, and PCM polymer blends. The supporting materials used in the polymerization of the PCM are polyethylene glycol diacrylate (PEGDA) and polyvinylpyrrolidone (PVP). The characterization of the thermophysical properties of the PCM is achieved by using differential scanning calorimetry (DSC) in dynamic operation mode. The values of the thermophysical properties for the commercial PCM and the renewable based oils provided by the manufacturers are compared with the experimental results. The long term stability of the thermophysical properties of PCM after 50, 100, 150, and 200 thermal cycles equivalent to a 6-month duty cycle in a real-life application is presented. The cases of the PCM emulsions and the PCM polymer blends are analyzed. The obtained results demonstrate the stability of the PCM under thermal cycling and the supercooling effect during the liquid-solid phase change.