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    Thermal energy storage performance evaluation of bio-based phase change material/apricot kernel shell derived activated carbon in lightweight mortar
    (Elsevier, 2023) Hekimoglu, Gokhan; Sari, Ahmet; Gencel, Osman; Onal, Yunus; Ustaoglu, Abid; Erdogmus, Ertugrul; Harja, Maria
    The synergy between phase change materials (PCMs) and activated carbon (AC) obtained from biomass is an energy-efficient method for creating composite materials with enhanced thermal performance. This study presents such a leak-proof composite with enhanced properties through the impregnation of bio-based lauric acid (L)-capric acid (C) eutectic mixture (LCEM) as a PCM in the AC derived from apricot kernel shells (AC-AKS) framework. The manufactured AC-AKS/PCM composite was subsequently incorporated into cement-pumice based mortar (CPM) in various proportions. This was done to produce energy-efficient construction materials aimed at increasing the thermal performance of buildings. Morphological, physical, thermal stability, mechanical strength, thermal energy storage (TES) and solar thermoregulation performances of the obtained leak-proof composite PCM were experimentally determined. The compressive strength of CPM samples with TES ability (TESCPM) was found 6.8 MPa, 4.3 MPa and 2.1 MPa for TESCPM1, TESCPM2 and TESCPM3, respectively. The relatively lower mechanical strength values can be accepted when considering their thermal regulation performances. The apparent porosity was around 26 %, while water adsorption around 24 % for TESCPM3. FTIR results proved the presence of well chemical compatibility between AC-AKS and PCM. The DSC results exposed that the AC-AKS/PCM composite had a melting temperature and a latent heat capacity of 21.58 degrees C and 126.8 J/g, respectively, while these values were within the range of 18.93-20.51 degrees C and 10.55-30.32 J/g for the TESCPMs. TGA results exposed that the functioning temperature of the AC-AKS/PCM was greatly lower than the limit temperature value measured for its thermal degradation. The solar thermoregulation performance test indicated that the fabricated TESCPM exhibited noteworthy advantages by providing the cooling effect throughout the daytime as well as the heating effect throughout the nighttime. All of these favorable properties make the proposed AC-AKS/PCM-integrated CPM promising materials for innovative TES applications in construction elements.
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    Utilization of waste apricot kernel shell derived-activated carbon as carrier framework for effective shape-stabilization and thermal conductivity enhancement of organic phase change materials used for thermal energy storage
    (Elsevier, 2022) Hekimoglu, Gokhan; Sari, Ahmet; Onal, Yunus; Gencel, Osman; Tyagi, V. V.; Aslan, Enes
    In this study, low-cost and eco-friendly AC obtained from waste apricot kernel shells (ACAS) was utilized to simultaneously solve the inherited drawbacks and enhance thermal conductivity of (Capric-Myristic acid (CA-MA), Lauryl alcohol (LAOH), n-Octadecane (OD) and Polyethylene glycol (PEG)) as different type organic PCMs. The ACAS/PCM composites had high PCM loading rates of up to 75 wt%, hence a high latent heat capacity of up to 193.7 J/g. Their melting and freezing temperatures varied in the range of 20.21-26.61 degrees C and 18.37-28.78 degrees C, respectively. All the prepared composites exhibited high thermal degradation resistance as well as high cycling stability even after 1200 melting-freezing cycles. The thermal conductivity of ACAS/CA-MA, ACAS/LAOH, ACAS/OD and ACAS/PEG was measured approximately 2.61, 2.40, 2.27 and 1.75 times higher than that of pure CA-MA, LAOH, OD and PEG, respectively. The advantageous TES characteristics of leak-proof composites make them favourable PCMs for low-temperature thermal management of buildings. (C) 2022 Elsevier B.V. All rights reserved.