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    Biocomposite foams consisting of microencapsulated phase change materials for enhanced climatic regulation with reduced carbon dioxide emissions in buildings
    (Elsevier Sci Ltd, 2024) Gencel, Osman; Aydogmus, Ercan; Guler, Onur; Ustaoglu, Abid; Sari, Ahmet; Hekimoglu, Gokhan; Subasi, Serkan
    Using polyurethane foam (PUF) matrix-based phase change material-enhanced composites is crucial for improving energy efficiency, enhancing thermal regulation, and reducing environmental impact in buildings. Integrating bio-components into PUF production and using these bio-composite foams (BPUFs) as the matrix offers environmentally friendly and structurally advanced solutions. Microencapsulated phase change material (MPCM) further enhances these foams, creating innovative, high-performance, eco-friendly composites for building applications. In this context, the biocomponent castor oil (CO) to be used in BPUF production has been modified with epoxy. BPUF-MPCM biocomposites with different compositions were produced using MPCM in the range of 0-90 wt% and modified castor oil (MCO) in the range of 0.75-7.50 wt% in BPUF production. The addition of 90 wt% MPCM content in BPUF-MPCM biocomposites has facilitated the attainment of a melting enthalpy value of 176.8 J/g (at 25.4 C-degrees) while providing a solidification enthalpy value of 175.7 J/g (at 20.8 C-degrees). The advancements in the microstructure of BPUF-MPCM composites contribute to physical improvements, such as a more homogeneous cell structure and enhancements in thermal transformation properties, thereby contributing to their thermoregulatory characteristics. BPUF-MPCM 90 wt% composites have achieved 100 % energy savings and zero CO2 emission values by varying material thicknesses across all climate conditions.
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    Characterisation and energy storage performance of 3D printed-photocurable resin/microencapsulated phase change material composite
    (Elsevier, 2024) Er, Yusuf; Guler, Onur; Ustaoglu, Abid; Hekimoglu, Gokhan; Sari, Ahmet; Subasi, Serkan; Gencel, Osman
    The 3D fabrication of microencapsulated phase change material (MEPCM) doped resin polymer composites enables the creation of complex shapes and customized designs, opening doors for many applications in fields. This investigation fabricated a range of resin/MEPCM (20 %, 30 %, and 40 % by volume) composites using a mechanical mixing technique. This study investigates how the addition of MEPCM impacts resin matrix composite's mechanical strength, latent heat storage characteristics, and ability to regulate temperature effectively. With a 40 % MEPCM additive ratio, a pure resin porosity value of approximately 0.4 % increased to around 17 %. Thanks to the production of homogeneously dispersed MEPCM added resins with production with stereolithography (SLA), 40 % MEPCM additive enabled characteristic FTIR peaks of both MEPCM and resin to appear and, melting and solidification enthalpy values reached 87.15 j/g and 86.25 j/g, respectively. MEPCM addition enhanced the thermoregulatory properties of resin by absorbing or releasing heat during temperature fluctuations. On hotter days, 8 mm-thick composites create temperature differences exceeding 11 C, while this difference exceeds 6 C in the room center case. The produced 3D printed MEPCM/resin composite can be a potential material to effectively regulate the temperature of electronic devices, food packets, building materials, and electronic devices and automotive components.
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    Characteristics of cement-based thermo-concretes containing capric acid impregnated hemp for thermal energy storage and sound isolation in buildings
    (Pergamon-Elsevier Science Ltd, 2025) Gencel, Osman; Guler, Onur; Ustaoglu, Abid; Erdogmus, Ertugrul; Sari, Ahmet; Hekimoglu, Gokhan; Boztoprak, Yalcin
    Enhancing the lightweight structure, insulation, and thermal storage capacity of concrete is critical for energy efficiency and environmental impact reduction. The innovative application of using waste hemp shives as a phase change material (PCM) carrier in cementitious composites was performed in this study to enhance sustainable construction practices. Although previous studies have incorporated lightweight aggregates and PCMs, challenges such as PCM leakage and the reliance on synthetic materials have limited their effectiveness. This study utilized waste hemp shives as a natural porous support for capric acid (CA) PCM in diatomite-based lightweight concrete, offering an eco-friendly and leakage-resistant solution with improved thermal and acoustic performance. No leakage was observed in shape-stabilized hemp/CA composites with 45 wt% CA. The melting and solidification temperatures were determined as 30.6 degrees C and 28.7 degrees C, with corresponding enthalpy values of 80.9 and 80.8 J/g, respectively. Concrete composites containing hemp/PCM reduced indoor temperatures by up to 4 degrees C compared to control samples. Moreover, composites with 30 % hemp/PCM content achieved sound absorption coefficients up to 0.6 and transmission loss values exceeding 24 dB, demonstrating their dual functionality for thermal energy conservation and acoustic comfort in building applications.
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    Enhancing sustainability with waste hemp-shive and phase change material: Novel gypsum-based composites with advanced thermal energy storage properties
    (Elsevier Sci Ltd, 2024) Gencel, Osman; Guler, Onur; Ustaoglu, Abid; Erdogmus, Ertugrul; Sari, Ahmet; Hekimoglu, Gokhan; Boztoprak, Yalcin
    This study addresses the rising demand for sustainable construction by introducing composite materials from natural and renewable resources: gypsum, hemp, and phase change materials (PCMs). These materials cater to the growing preference for eco-friendly building solutions. Incorporating hemp enhances sustainability while integrating PCMs into the porous hemp structure ensures adequate thermal energy storage and release without leakage. Firstly, the agricultural waste hemp shives and lauryl alcohol (LA) PCM were mixed to create shapestabilized hemp/PCM composites. The highest PCM ratio was determined in shape-stabilized composites exhibiting non-leakage properties, which was 45 wt %. These composites were then incorporated into gypsum materials at loadings of 7.5 %, 15 %, 22.5 %, and 35 wt % to produce the final composites. Morphological, thermal, and chemical characteristics of shape-stabilized composites were examined using SEM, TGA, and DSC, while the solar thermoregulation tests assessed the gypsum matrix composites. The phase change temperature of PCM was determined as 20.24 degrees C with a melting enthalpy value of 224.4 J/g. The hemp/PCM shape-stabilized composites demonstrated an impressive melting enthalpy value of 100.2 J/g, with only a slight reduction to 99.5 J/g after 750 test cycles. When the ambient temperature exceeded 50 degrees C, the central temperature of the cabins containing PCM composites was found to be at least 4 degrees C cooler than those containing only gypsum. Conversely, when the ambient temperature dropped to around 20 degrees C, it was observed that the central temperature of the cabins with PCM composites was approximately 2 degrees C warmer than those with only gypsum. This study introduces a novel approach to creating environmentally friendly gypsum/hemp/PCM composites for thermal energy storage systems.
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    Production and assessment of UV-cured resin coated stearyl alcohol/ expanded graphite as novel shape-stable composite phase change material for thermal energy storage
    (Pergamon-Elsevier Science Ltd, 2024) Guler, Onur; Er, Yusuf; Hekimoglu, Gokhan; Ustaoglu, Abid; Sari, Ahmet; Subasi, Serkan; Marasli, Muhammed
    Expanded graphite -phase change materials (PCM) structures are reinforced to polymers with various methods to fabricate advanced thermal energy storage materials. However, these methods still suffer from processing time and product efficiency challenges. In this study, the UV-curing method was used to produce shape-stable EGPCM-reinforced resin composites with fast curing and low process temperature of the resin. The composite material, comprising UV -curable resin (30 %), stearyl alcohol (65 %), and Expanded graphite (5 %), was synthesized. This synthesis aimed to address the limitations of traditional PCMs, such as low thermal conductivity and leakage. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the materials ' phase change behavior and thermal stability. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analyses were conducted to elucidate the microstructure and crystallinity of composite materials. The composites, exhibiting near-perfect impermeability with leakage as minimal as 0.89 %, not only enable the attainment of cooler environments by 2 - 3 degrees C under hot air conditions but also demonstrate exceptional thermal stability up to 207 degrees C, as evidenced by TGA results. Additionally, they offer a remarkable melting enthalpy value of 153.1 J/g. These composites, with their shape-retention ability during phase transitions and high thermal energy storage capacity, are a versatile and efficient option for sustainable energy management. This research contributes to the development of innovative materials for renewable energy integration and reducing carbon emissions.
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    Thermal energy storage and mechanical enhancement of cement composites containing PCM-impregnated and cement-slurry coated pumice aggregates
    (Elsevier, 2025) Gencel, Osman; Ozguler, Alper Tunga; Guler, Onur; Ustaoglu, Abid; Hekimoglu, Gokhan; Sari, Ahmet; Emiroglu, Mehmet
    In the field of thermal energy management and building materials, PCM has been impregnated into aggregates and added to cement to produce composite concretes. However, challenges such as PCM leakage and poor interfacial bonding have limited their widespread application. To address these issues, this study utilized pumice aggregates with exceptional porosity, impregnated with PCM and coated with cement slurry, to develop enhanced composite concretes. The produced composites were characterized through compressive strength tests, thermal conductivity measurements, ultrasonic pulse velocity analysis, and detailed thermal regulation experiments under dynamic solar radiation. Thermal regulation experiments were conducted using thermal imaging under real-time heating and cooling processes. Results demonstrated that PCM-impregnated aggregates enhanced the thermal stability of concrete, with surface temperatures on PCM-based composites (MAL-2) being approximately 5 degrees C lower during heating compared to control samples (MAL-K). During the cooling process, MAL-2 exhibited delayed temperature reduction, stabilizing surface temperatures around 1 degrees C higher than MAL-K due to PCM's latent heat release. Experimental outcomes further presented that an increasing proportion of PCM-impregnated aggregates significantly reduced porosity from 13.55 % to 7.87 % and improved compressive strength from 12.7 MPa to 16.81 MPa. Thermal conductivity increased from 0.5706 to 0.7058 W/mK, while water absorption decreased from 13.94 % to 7.13 %. Ultrasonic pulse velocity values increased from 2.49 km/s to 2.58 km/s, indicating enhanced matrix integrity. This design, offering superior thermal regulation and mechanical performance, holds great promise for applications in energy-efficient building materials and sustainable construction practices.