## 4 Studies on Using Inorganic PCM in Concrete for Thermal Energy Storage
In addition, the effectiveness of the PCM-mortar matrix as well as the PCM-TRC slabs' mechanical performance are affected by the temperature and, by extension, the PCM state (solid or liquid). When comparing the thermal effectiveness of a 10 wt.% PCM-TRC slab (4.5 cm thick) to that of the reference TRC slab, the former yields a 37% saving of energy as well as a 4 \({}^{\circ}\)C drop in peak temperature. Microencapsulated bio-based phase change material (MbP) incorporated into a micro-concrete composite (MbPMC) was created by [PERSON] et al. (2021) [76] for use in thermal energy storage in buildings. According to the surface morphology data, the newly generated MbP particles were almost spherical and ranged in size from 2 nm to 10 nm. X-ray diffraction research verified the shell material's amorphous structure and  
Figure 8: Concrete mixture compressive strength with time [72]. the extremely crystalline character of the bio-based PCM chains. The chemical steadiness between the material of the shell and the core (phase change material) is further established by the Fourier transform infrared (FTIR) spectra. The MbP has shown excellent latent heat potential behaviour, with a value of 47.31 J/g, and consistent phase change behaviour. Rebound hammer test results for indicative compressive strengths of MbPMC specimens showed a pattern that was consistent with values determined from the Compressive Testing Machine (CTM) for varying amounts of MbP. These findings show that MbP included in micro-concrete composites (MbPMCs) may store thermal energy as well as provide passive cooling during construction without compromising their structural integrity during testing. [PERSON] et al. (2022) [77] used experimental and computational methods to study the thermal performance of PCM-concrete wallboards. In the first step, PCM-concrete mixes were made in the lab using varying PCM concentrations. To conduct a thermal examination of the compounds, an original bench test was developed using the transient plane source theory. In addition, a finite-element-based numerical simulation was performed, and its findings were compared favourably to those obtained from actual experimentation. The interior temperatures and thermal fluctuations of the various PCM wallboards were found to be significantly reduced in the numerical simulations. Additionally, the postponement of temperature peaks highlighted the improvement in the energy efficiency of PCM wallboards over conventional concrete, particularly in the case of the bilayer wallboard. A novel PCM (concrete thermal energy storage system) was introduced by [PERSON] et al. (2022) [78]. The PCM-enhanced mixture allows the system to work at temperatures up to 400 \({}^{\circ}\)C, making it ideal for use in industrial settings. Diatomite, a porous fossil flour, was utilised to absorb the PCMs, which were a salt combination consisting of 40% KNO\({}_{3}\) and 60% NaNO\({}_{3}\). In the lab experiments, the authors compared two different concrete recipes: one containing PCM (5 wt.%) and one without PCM. Joule's effect was used to power the charging phase, and compressed air was sent via the pipe to cool the module. The findings demonstrated that the inclusion of the PCM into the storage system significantly enhanced thermal performance. The greatest PCM integration percentage simulated was 40%, and this resulted in a doubling of the quantity of thermal energy stored and released. The effectiveness of PCMs as a thermal energy storage medium was evaluated by [PERSON] et al. (2023) [79]. The concrete was made using a mix of water, sand, cement, and lightweight aggregate. In the concrete specimens (50 mm \(\times\) 50 mm \(\times\) 50 mm), copper tubes of varying shapes and sizes (12.7 mm in diameter and 50 mm in length) were embedded. Copper tubes were arranged in three different patterns: four squares, four crosses, and six rectangles. After that, the authors waited 28 days at room temperature to cure the concrete.