Enhancing energy efficiency of walls in summer and winter with novel phase change storage concrete design.

Energy storage technology can effectively reconcile the imbalance between energy supply and demand, offering significant potential for applications in areas such as waste heat recovery and utilization, as well as building energy efficiency. For this purpose, three types of hollow glass microspheres with varying particle sizes were employed as the base materials in this study. Paraffin was incorporated into the porous aggregates using three methods: porous aggregate adsorption, vacuum adsorption, and negative pressure circulation adsorption, to fabricate paraffin-based composite phase change aggregates. A novel phase change energy storage concrete was developed by incorporating composite phase change aggregate and copper powder into ordinary concrete, based on the experimental evaluation of thermal conductivity and compressive strength of the composite phase change aggregate. The thermal and mechanical properties of the resulting concrete were systematically investigated. Finally, by taking the weather conditions in Hunan Province, China as the reference operating scenario, a numerical simulation model of the phase change energy storage concrete test chamber was developed using Fluent software. Research indicates that among the three adsorption methods evaluated, the negative pressure circulation adsorption method demonstrates the most effective adsorption performance. When the particle size ranges from 0.85 to 1.56 mm, the paraffin adsorption rate in the phase change aggregate is 20 to 35% higher compared to that of the other two particle sizes. When the composite phase change aggregate has a volume replacement rate of 20%, the compressive strength of C30 concrete reaches 31.4 MPa, which complies with the specified requirements. Increasing the dosage of composite phase change materials can significantly improve the energy storage efficiency and thermal conductivity of concrete, however, it may lead to reductions in apparent density, compressive strength, and thermal performance. With increasing copper powder incorporation rate, the thermal conductivity and compressive strength of phase change energy storage concrete exhibit a linear increase. Compared with conventional concrete test chambers, phase change energy storage concrete test chambers demonstrate a more pronounced capability in mitigating indoor temperature fluctuations through effective peak load reduction and valley filling, as well as significantly delaying the occurrence of peak temperatures.