Preparation and characterization of binary and ternary composite PCMs with two phase transition temperatures for solar water heating system

This paper presented a novel binary or ternary composite phase change material (CPCM) composed of two or three single phase change materials (PCMs), which can be used for solar water heating system (SWHS) to accomplish the demand for seasonal thermal energy storage. Five single PCMs, capric acid (CA), lauric acid (LA), stearic acid (SA), 62# paraffin (62#) and octodecyl alcohol (OA), are selected to make CPCMs. Samples with different combination of single PCMs and different mass ratios are properly prepared and investigated. The thermal properties of CPCMs are analyzed via Schrader equation and series experiments, such as step cooling curve, differential scanning calorimetry (DSC), thermal cycling and Fourier-transform infrared (FTIR) spectroscopy tests. Investigation shows that the proposed CPCMs with 2 phase transition temperatures (PTTs) have stable properties, higher latent heat and lower price compared with their components. Especially the proposed ternary CPCM with a eutectic mixture as its low temperature component can demonstrate more excellent thermal characteristics. For example, compared with LA-62# (1:1), LA-OA-62# (3:1:4), with the same mass ratio of high and low temperature components as LA-62#, can increase its latent heat of the low temperature phase transition process and the whole phase transition process, maximum by 17.6%. The proposed CPCMs are suitable for seasonal thermal energy storage.

Automated summary

This paper presents a novel binary or ternary composite phase change material (CPCM) for seasonal thermal energy storage in solar water heating systems. The thermal properties of the CPCMs are analyzed and compared with their single phase change material components. The results show that the proposed CPCMs have stable properties, higher latent heat, and lower price, making them suitable for seasonal thermal energy storage.