## 3 Studies on Using Organic PCM in Concrete for Thermal Energy Storage
(2020) [63] constructed a system consisting of a three-layer composite PCM/concrete wall, with the paraffin wax PCM having a thickness of e\({}_{\text{m}}\) = 2 cm and the whole wall having a length of L = 20 cm. A solar water heat absorber was physically connected to the outer layer. Both the sun's rays and the surrounding air's convection contribute to the boundary conditions on the glass's exterior. The hourly weather reports of Casablanca, Morocco, were consulted. The advantage of adopting latent heat storage methods in such solar thermal energy systems is attained when the transmitted heat causes the water's temperature to gradually grow, melting PCM within the concrete wall. With further paraffin removal from the wall-mounted solar absorber, the PCM's latent heat storage capacity decreases. The synthesis and characteristics of PCM composites integrating aerated/foamed geopolymer concrete (GFC) for improving heat storage capacity were described by [PERSON] et al. (2021) [64]. The chemical compatibility, mechanical characteristics, and thermal performance of aerated concrete with a form-stable PCM composite based on paraffin/hydrophobic expanded perlite were experimentally tested. Chemical compatibility and thermal stability with GFC have been confirmed by FT-IR and TGA testing of the PCM composite. The GFC incorporating PCM composite has a very high thermal energy storage capacity, as shown by experiments in simulated test rooms. The peak indoor temperature of the test room was lowered by 1.85 \({}^{\circ}\)C and 3.76 \({}^{\circ}\)C, respectively, when 15% and 30% PCM composite were included, while the thermal storage capability increased by 105% and 181%. Using lauryl alcohol (LA)-impregnated rice husk ash (RHA) composite polymer cementitious material (PCM), [PERSON] et al. (2022) [65] created a novel kind of environmentally friendly foam concrete (FC). The leaking issue with LA was solved by using RHA, an agricultural byproduct, as a carrier material. As a result, a leakage-free composite PCM (LFCPCM) was developed, and for the first time, an RHA-based LFCPCM was successfully merged with cementitious FC. The results of tests on the FC-LFCPCM50 wallboard's solar thermoregulation performance showed that it kept the interior about 1.29 \({}^{\circ}\)C warmer during the cold weather hours compared to the reference FC (RFC) and about 2.8 \({}^{\circ}\)C cooler in the centre of the room during the day in hot weather. FC-LFCPCM50 wallboard may reduce daily energy use by 14.28 kWh. This level of energy conservation is equivalent to avoiding releasing 38 kg of CO\({}_{2}\) from burning coal, 37.7 kg of CO\({}_{2}\) from burning natural gas, and 6.19 kg of CO\({}_{2}\) from using electricity. [PERSON] et al. (2023) [66] used a variety of organic PCMs with good thermodynamic characteristics for heat storage at subfreezing temperatures to construct low-cost thermal energy storage aggregates (TESA). Different mixtures of paraffin wax, soybean oil, and coconut oil were employed as PCMs. The latex coating of TESA served to stop any potential leaks. Paraffin wax and soybean oil together demonstrated the greatest improvement in heat storage and time to freeze. Reducing the use of deicing salts and other winter maintenance while minimising environmental consequences and safety problems may be possible with the use of TESA concrete, which requires no operational administration. Table 1 presents a summary of research on organic PCMs used in concrete for thermal energy storage. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Authors (Year)** & **Configuration/Composition** & **Type of Study** & **Studied Parameters** & **Results/Findings** \\