Phase change materials (PCMs) as thermal energy storage medium are proven to be effective to enhance the performance of solar thermal system. The degradation of the thermal properties due to thermal cycles is changeable and accordingly the performance of the solar thermal cycle may decline. In this study, the thermal reliability of paraffin wax was investigated to analyse the ability to be used as thermal energy storage (TES) for solar water heating purposes that subjected to many phase change cycles. The mixtures were subjected to 400 phase change cycles and the thermal properties were measured. Two samples were prepared; Sample 1 was paraffin wax without phase change cycles whereas Sample 2 was gone through 400 phase change cycles. Four hundred phase change cycles indicated the phase change cycles for 1 year 35 days as 1 cycle equivalent to 1 day. The comparison of samples with and without 400 phase change cycles showed slight changes in thermal conductivity, specific heat, melting point and solidification point. Fourier Transform Infrared Spectrometer and Thermogravimetric Analysis showed that after 400 phase change cycles there is no weight loss observed. The paraffin wax is hence found reliable to be use without any degradation, without any chemical reaction and slightly improvement of thermophysical properties as TES for solar water heating purposes.
Application of Phase Change Materials in Solar Water Heating Systems for Thermal Energy Storage