A new low-cost high-temperature shape-stable phase change material based on coal fly ash and K2CO3

The shape stable phase change materials (SSPCMs) consisting of coal fly ash (CFA) and potassium carbonate (K 2 CO 3 ) are promising candidates for high temperature thermal storage applications, owing to their low price, high melting enthalpy and low corrosivity of K 2 CO 3 . Nevertheless, the chemical reactions between K 2 CO 3 and CFA at high temperature limit its application. To solve this problem, in this work, a new two-step method for preparing SSPCMs containing K 2 CO 3 and CFA was proposed. Firstly, the CFA was successfully modified by K 2 CO 3 with a mass ratio of 3:2. The main phase of the modified CFA was changed into potassium aluminum silicate (KAlSiO 4 ). Then the SSPCMs were synthesized using the modified CFA and K 2 CO 3 . The latent heat and thermal conductivity of the prepared SSPCMS increased with the increase of salt content. The SSPCMs with potassium carbonate contents of 50 wt% (SSPCM-55) and 60 wt% (SSPCM-46) maintained good shape without cracks after the sintering processes . In addition, they showed a good cyclic stability in the 150 times thermal cycle tests in terms of mass, latent heat and chemical compatibility. The SSPCM-46 showed the best performance considering both heat transfer and energy storage density , and is promising to be used as a low-cost high-temperature PCM.