Composite number

Engineering

Heat transfer

Materials science

Power (physics)

Chemical engineering

Mass transfer

Thermodynamics

Physics

Organic chemistry

Potassium carbonate

Energy storage

Composite material

Chemistry

Thermal energy storage

Volume (thermodynamics)

Journal of Energy Storage

Salt hydrates are ideal for long-term thermochemical heat storage in a built environment, where K2CO3 is considered a promising thermochemical heat storage material. This class of materials continues to encounter certain technical bottlenecks in practical applications, and the enhancement of heat and mass transfer is a key challenge. Composite materials are a promising method to address this challenge because heat and mass transfer are coupled and material-dependent. In this study, a novel K2CO3-based composite material was synthesized from expanded graphite (EG), K2CO3, and octylphenol polyoxyethylene(10) ether (OP-10), and its structural information, reaction kinetic properties, thermodynamic properties, and cycling stability were determined. The results showed that the use of EG with OP-10 significantly enhanced mass and heat transfer. Compared to pure K2CO3, the thermal conductivities of the composites were increased by 9–15 times and their half-conversion time was shortened by approximately 3/4–4/5, indicating that their mass and heat transfer capacities were effectively improved. The mass and volume energy storage densities (ESDs) of K2CO3-based composites reached 429–563 kJ⋅kg−1 and 138–216 kWh⋅m−3, respectively, and these values depended on the content of K2CO3. In addition, the cycling stability results indicated that these K2CO3-based composites performed well and were suitable for medium-to-low-temperature thermochemical thermal storage applications.

Enhancement of heat and mass transfer of potassium carbonate-based thermochemical materials for thermal energy storage