Research on dolomite-based shape-stabilized phase change materials for thermal energy storage: Feasibility study of raw and calcined dolomite as skeleton support materials

Abstract

Mid and high-temperature inorganic salts have limited applications due to their corrosiveness and low thermal conductivity. Shape-stabilized phase change materials (SSPCMs) can ease these issues. This study explored using dolomite, an affordable and abundant mineral with good thermal properties, in SSPCMs. We developed SSPCMs using raw and calcined dolomite at 700 °C, 750 °C, and 800 °C (700Do, 750Do and 800Do) as skeletal support materials (SSMs) and NaNO3-KNO3 as the phase change materials (PCMs). Calcined dolomites had a porous structure compared to raw dolomite (RawDo). 700Do, 750Do and 800Do require a minimum of 50 wt%, 40 wt% and 30 wt% to stabilize the shape of the sintered material by 100 cycles. RawDo was unsuitable for SSM during cycling. XRD confirmed chemical compatibility between components, and SEM showed an even distribution of SSMs within the PCMs. The thermal conductivity of SSPCMs ranged from 1.09 to 1.27 W/(m·K), compared to 0.52 W/(m·K) for NaNO3-KNO3. The NaNO3-KNO3 has a latent heat of about 110.60 J/g and a supercooling degree of 5.84 °C. The latent heat of SSPCMs depends on the proportion of SSMs, slightly lower than the theoretical value by 0.01 %–2.37 %, and the supercooling degree of SSPCMs varies between 4.75 °C and 6.25 °C. The SSPCMs were chemically stable with little latent heat change after 100 cycles, showing excellent cycling stability. The thermal decomposition temperature of SSPCMs containing 700Do was about 580 °C, while SSPCMs containing 750Do and 800Do exhibited a minor decomposition onset at around 380 °C, attributed to Ca(OH)2 decomposition. The best-performing SSPCM contained 30 wt% 800Do, offering a thermal conductivity of 1.27 W/(m·K) and thermal energy storage density of 359 kJ/kg in the 100–320 °C range. In general, calcined dolomite-based SSPCMs offer excellent thermal energy storage performance at a low cost compared to many SSPCMs.