Size-tunable CaCO3@n-eicosane phase-change microcapsules for thermal energy storage

Phase-change materials can store and release tremendous amounts of latent heat energy in a single storage unit, and they have become a promising candidate for building comfort temperature regulation with a significant energy-saving effect. In this study, we developed a novel type of size-tunable phase-change microcapsules for high-efficient thermal management and temperature regulation in buildings. The phase-change microcapsules were based on an n-eicosane core and a CaCO3 shell and fabricated using an emulsion-templated self-assembly interfacial precipitation method. Their sizes were controlled through regulating the surfactant concentration, resulting in a desired capsule size as well as a well-defined core-shell microstructure and a regular spherical morphology. When the mass ratio of sodium dodecyl sulfate to sulfobetaine varied from 3/2 to 1/1 in the mixed surfactant system, the resultant phase-change microcapsules exhibited a tunable diameter from 740 nm to 1.54 µm together with a significant increase in latent-heat capacity from 100 to 131.5 J/g. The application investigation of the obtained microcapsules in building thermal regulation was performed through incorporating microcapsule samples into cement, employing the resultant cement composites as building envelopes for a model house. The cement composites presented a good ability to regulate the indoor temperature of the model house thanks to the thermal energy storage and latent heat release of the phase-change microcapsules. The model house coated with the cement composites on the roof exhibited a maximum indoor temperature of 47 °C after subjected to the simulated sunlight radiation for 4 h, leading to a decrease in indoor temperature by 5 °C compared to the model house with pure cement. With a rational combination of the phase-change microcapsules and cement, this study provides a promising approach to passive and efficient comfort temperature regulation for green energy-saving building applications.