Accelerated thermal cycle and chemical stability testing of polyethylene glycol (PEG) 6000 for solar thermal energy storage

Accelerated thermal cycle test of polyethylene glycol (PEG) of molecular weight 6000, an organic phase change material (O-PCM), has been carried out for 1500 melt/freeze cycles. The latent heat of fusion and melting temperature is measured using differential scanning calorimeter between 0th and 1500th melt-freeze cycles to study the changes in its thermal properties. Also, the changes in the compositional/functional groups of the material during the cycle test are also measured using FT-IR spectroscopy technique. The melting temperature is found to be stable in the quoted range of 55-60 °C with a maximum deviation of 6.5% when compared to that of at 0th cycle. However, a gradual drop in the latent heat of fusion with the increasing number of thermal cycles is measured. The FT-IR spectra do not show any noticeable changes in the peaks which confirm its compositional stability even after the higher number of thermal cycles. Thermal and chemical reliability tests of PEG 6000 along with the techno-economic analysis have shown that this PCM has a significant potential to be used as a thermal energy storage system.