A novel form stable PCM based bio composite material for solar thermal energy storage applications

Abstract

• Development of PCM-water hyacinth biochar based form stable thermal energy storage material. • The thermophysical properties and thermal stability of the proposed composite material has been analysed and discussed. • Negligible leakage has been reported at 6:4 ratios (PCM: biochar). • The composite has good thermal conductivity and latent heat of fusion. • The developed material is suitable for solar energy applications. Phase change materials found to be a promising solution in the field of thermal energy storage. However, the low thermal conductivity and form stability over cycles of charging and discharging of PCM are challenges to address. In the proposed study, a novel and low cost biochar-PCM hybrid latent heat energy storage material have been developed and tested. The biochar is prepared from aquatic invasive weed plants by using a batch type pyrolyser. The characteristics and properties of the novel energy storage material have been evaluated using various experimental and analytical methods. The methods include Brunauer, Emmett and Teller (BET), Scanning electron microscope (SEM), X-ray powder diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT–IR) and thermal conductivity tester. The study also put forward the optimized proportion of biochar and PCM in hybrid thermal energy storage material. The new material shows superior thermal conductivity over pure PCM as well as better stability due to the high carbon content and porosity of the developed biochar. Simple Impregnation method has been used to prepare form stable composite material which has good thermal and structural stability. The best mixing ratio (PCM: biochar) is found to be 6:4 (wt/wt%) with minimum leakage of PCM from the composite. The sample prepared through this method yield all the desirable properties as compared to other developed samples. The chemical properties of the composite remain the same as the pure PCM, which confirms no chemical interaction between the PCM and biochar. The heat of fusion is calculated to be 179.4 J/g. The thermal conductivity of the PCM is enhanced up to 13.82 times with the addition of water hyacinth biochar as a supporting matrix. The addition of aluminum metal powder further increases the thermal conductivity by 17.27 times higher than that of PCM alone.