Phase-Change Millicapsules with Highly Conductive and Adsorptive Radial Frameworks for Efficient Thermal Energy Management

Abstract

In conventional thermal energy network (TEN) systems, heat loss and fouling in long pipelines reduce energy efficiency and hinder sustainable operation. Phase-change capsules (PCCs) are promising dispersoids for flexible energy storage and delivery; however, their thin shells compromise structural stability, limiting their fabrication to the micro- or nano-scale and restricting practical applications. Herein, we introduce hydrophilic milliscale PCCs (HMPCCs) as a pragmatic solution for efficient thermal energy delivery and antifouling in TENs. HMPCCs feature a thin shell and internal three-dimensional radially conductive and adsorptive frameworks with hierarchical pores (80% porosity), which provide enhanced thermal conductivity; a high adsorption capacity for Ca²⁺, Mg²⁺, and Fe³⁺ ions; and efficient phase-change material encapsulation without leakage. Incorporating clinoptilolite nanoparticles into the HMPCCs further increases the thermal conductivity, supplements the adsorption capability for Ca²⁺ and Mg²⁺ ions, and optimizes the bulk density for stable dispersion in water. HMPCCs achieved 100% removal efficiency for scaling cations (0.1–1.0 mg L^–1) and exhibited excellent durability, maintaining structural integrity after 1000 phase-change cycles. A thermodynamic analysis confirmed that the adsorption process was endothermic, spontaneous, and thermodynamically favorable. Regeneration via low-energy desorption ensures its reusability and economic viability. These findings suggest that HMPCCs represent a scalable and sustainable solution for advanced TEN applications and have outstanding thermal management and antifouling capabilities.