Thermal performance was tested during cycling work for latent heat storage systems based on KNO₃ and NaNO₃ (weight ratio 54:46). For heat transfer improvement, cast aluminum honeycomb-shaped structures were produced via 3D printing of polymer model and investment casting. Different wall thicknesses were tested at 1.2 mm and 1.6 mm. The obtained results were compared to working cycles of pure PCM bed. The use of enhancers is reported to improve the rate of charging and discharging of the deposit. In the next step, the structures were examined with numerical simulation performed with ANSYS Fluent software. The wall thicknesses taken into consideration were the following: 0.8, 1.2, 1.6, and 2.0 mm. An insert with a greater wall thickness allows for smaller dT/dt and better heat distribution in the vessel. The investment casting process enables the manufacturing of complex structures of custom shapes without porosity and contamination.

For improving heat transfer in the thermal energy storage system (TES), cast aluminum cellular structures were designed, optimized, and produced by investment casting. The pattern was 3D printed from polylactide (PLA) polymer and then subjected to molding and heat treatment. Selected casting parameters, i.e. temperature of the mold and poured metal, as well as low pressure (vacuum), allowed to production of a complex, thin-walled casting. To evaluate the effectiveness of the structures (enhancers), a lab-scale heat accumulator was constructed and filled with phase change material (PCM) composed of KNO3 and NaNO3 salts. Thermal cycling, including charging and discharging of the accumulator, was analyzed and compared between systems with pure PCM bed and the one equipped with the produced enhancer. To protect aluminum casting against corrosion with molten salts, nickel plating was applied. Process parameters, such as plating process time and nickel subcoating application time, were determined. Microscopic observations confirmed high-quality, continuous coating on aluminum casting surfaces with characteristic microgrooves remaining after the printed pattern.

The research aims to determine whether a protective oxide coating obtained by plasma electrolytic oxidation (PEO) will prevent unfavourable changes occurring on the surface of aluminium heat enhancers for thermal energy storage (TES) based on phase change materials (PCMs). For domestic purposes (short-term, solar energy), salt hydrates are widely utilised as PCMs. Their low thermal conductivity makes the application of metal enhancers necessary to improve heat transfer in the unit. Due to the chemically aggressive nature of MgCl₂·H₂O, aluminium enhancers can be negatively affected during working cycles. PEO was proposed to overcome corrosion issues in the units. Cast samples, coated with PEO for a short time in KOH-Na₂SiO₃ electrolyte, were subjected to a molten MgCl₂·H₂O environment. Mass change and the surface were studied via SEM, EDS, and XRD measurements. A thin layer of aluminium oxide prevented castings from changes occurring on the surface of the enhancer.