Phase change materials (PCMs) are applied in heat storage units, as they are able to accumulate the energy in the form of the latent heat of fusion. Thus, they can be used in recovering the excess of heat from various industrial processes. Their main weakness is their low thermal conductivity coefficient, which strongly limits their usage. In this paper, the benefits of the application of metallic inserts in heat storage PCM-based units were elaborated. Two kinds of Al–Si spatial elements (foams and honeycomb structures) were produced with the use of means of the investment casting method. Key factors influencing the technological process were established. The surface’s roughness was measured in order to compare the obtained structures with their patterns in terms of the casting’s accuracy. The compressive strength of the samples was tested, and their fatigue resistance was considered. The thermal performance of manufactured inserts in the PCM (paraffin)-based accumulator, supported by the calculation of heat fluxes, was analyzed and adjusted. Finally, further optimization was conducted in terms of the volume ratio of the metal insert to the PCM. Metallic inserts were found to significantly affect the performance of the entire energy storage system, as their use results in reduced charging time, a longer heat release time, increased maximum temperature, and a significant reduction in the temperature gradient in the heat storage unit.

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.

Composites based on the AlSi12 aluminum alloy reinforced with Saffil^TM fibers (Composite I) and with both Saffil^TM fibers and nickel-coated graphite flakes (Composite II) were developed using the squeeze casting method in the fabrication process. The objective of this work was to evaluate the influence of the employed reinforcements on the mechanical properties and corrosion behavior of the obtained materials. To achieve this, investigations were conducted, including SEM analysis, flexural strength testing, Brinell hardness testing, linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Corrosion measurements were performed in a 3.5% NaCl solution at room temperature. Mechanical investigations revealed a significant increase in flexural strength and hardness for Composite I compared to the plain matrix alloy. In contrast, Composite II’s flexural strength was reduced by the weakening effect of graphite flakes. Performance under bending improved by 46% for Composite I and 25% for Composite II compared to the AlSi12. The corrosion resistance of the tested materials followed the order AlSi12 > Composite I > Composite II. The LSV and EIS results indicate that the explanation for this may be differences in the properties of the protective oxide/hydroxide layer. Furthermore, SEM images showed a weak bond between nickel and graphite.