Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleAçık Erişim2026Scopus SJRQ2Production and Thermal–Structural Characterization of Nano-Oxide-Doped Paraffin-Based Phase Change Composite Materials for Thermal Storage Applications
Yücel, Halit Lutfi; Özdemir, Osman; Kahraman, Gökhan
Paraffin-based composite phase change materials (PCMs) have been synthesized for thermal energy storage applications to enhance thermal conductivity and stability while maintaining latent heat storage capacity. In this study, RT42 paraffin was modified with inorganic nano-oxides (Al2O3, CuO, SiO2, and ZnO) in the presence of sodium dodecyl sulfate (SDS) as a surfactant. The incorporation of SDS improved nanoparticle dispersion and reduced agglomeration, resulting in enhanced phase-change behavior and improved structural homogeneity. Differential scanning calorimetry (DSC) analysis revealed slight variations in melting and crystallization temperatures, while the ZnO-doped composite retained up to 92% of the latent heat storage capacity of pure RT42. Among all the investigated composites, the Al2O3-doped sample exhibited the highest thermal conductivity and specific heat capacity. Thermogravimetric analysis (TGA) indicated an increase of approximately 15–20°C in the decomposition temperature, demonstrating enhanced thermal stability. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the preservation of the crystalline structure and improved microstructural uniformity. The developed SDS-assisted nano-oxide/RT42 composites exhibit significant potential for passive thermal regulation in renewable energy and building applications.
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İncele - MakaleYalnız künye2026Scopus SJRQ2Experimental ınvestigation of hybrid passive cooling strategies for photovoltaic modules using nano-enhanced PCM and graphene-coated finned structures under hot climate conditions
Özdemir, Osman; Yücel, Halit Lutfi; Kahraman, Gökhan
This study experimentally investigates the use of several passive cooling techniques to enhance the electrical performance of photovoltaic (PV) modules under high ambient summer temperatures in Elazığ, Turkey. Throughout the trial period of July, August, and September, a system comprising four photovoltaic panels, one designated as a reference, was developed. The first passive cooling arrangement utilized a paraffin-based phase change material (PCM) RT42HC. In the second configuration, a nano-enhanced PCM (NePCM) composite was employed, prepared by dispersing 1 mass% of Al2O3 nanoparticles into the paraffin matrix and stabilizing them with 3 mass% of sodium dodecyl sulfate (SDS) to ensure homogeneous distribution. The third, hybrid configuration integrated 14 graphene-coated parabolic pin-tipped fins mounted externally onto the aluminum enclosure housing the NePCM composite. Experimental results demonstrated that the implemented passive cooling techniques markedly decreased the panel surface temperature, thereby enhancing electrical power output and photovoltaic efficiency. The hybrid graphene-coated fin-NePCM system demonstrated superior performance, achieving a maximum surface temperature reduction of 12.65 °C, a sustained electrical efficiency increase of 6–13%, and an average daily electrical energy gain of 26.23 Wh day−1 compared to the reference module. These findings demonstrate that the integrated hybrid design is an effective and reliable passive cooling method for sustaining photovoltaic system performance under hot climate conditions.
- MakaleAçık Erişim2025Elazığ İli Örneğine Ait On-Grid Çatı Üstü Güneş Enerji Santralinin Yıllık Gerçek Üretim Verilerinin PV*SOL Simülasyon Değerleri ile Karşılaştırılması
Celik, Ertugrul; Özdemir, Osman
Geçmişten bugüne kadar insanoğlunun temel gereksinimlerinin karşılanması için enerjiye ihtiyaç duyulmaktadır. Dünyada nüfusun hızlı bir şekilde yükselmesi, teknolojik faaliyetlerin gelişimiyle birlikte enerji tüketimi gün geçtikçe artmaktadır. Günümüzde artan enerji talebini karşılamak için fosil yakıtlar ve yenilenebilir enerji kaynakları kullanılmaktadır. Yenilenebilir enerji kaynakları, doğal süreçler aracılığıyla sürekli olarak yenilenen ve fosil yakıtlarla karşılaştırıldığında düşük emisyon değerlerine sahip olan çevre dostu enerji üretim kaynaklarıdır. Güneş enerjisi sistemlerindeki teknolojik ilerlemeler, maliyetlerin düşmesi ve verimliliğin artması, güneş enerjisini yenilenebilir enerji kaynakları arasında güçlü bir alternatif haline getirmektedir. Özellikle arazi ve çatılara kurulan Güneş Enerji Santrallerinin (GES) sayısı gün geçtikçe artmaktadır. Bu çalışmada Elazığ ili sınırları içinde sanayi bölgesinde bir işletmenin çatısına kurulmuş şebekeye bağlı çatı (on-grid) üstü GES sistemi ele alınmıştır. Çatı üstü GES toplam 165 adet, 545 Watt gücünde monokristal panellerden oluşmakta olup toplam gücü 89,9 kWp’tir. Sistem performansını artırmak amacıyla seçilen alan için en iyi yönelimi ve eğim açısını bulmak amacıyla PV*SOL yazılımı kullanıldı. Bu çalışmada mevcut GES sisteminin bir yıllık enerji üretim verileri aylara göre incelenerek, PV*SOL simülasyonunda elde edilen benzetim sonuçları ile karşılaştırılarak PV*SOL yazılımının doğruluk oranı değerlendirilmiştir. Çalışma sonucunda PV*SOL simülasyon programından elde edilen veriler ile çatı üstü GES gerçek verileri arasında %0,03 fark olduğu tespit edilmiştir. Bu sonuçlar göz önüne alındığında, uygulaması yapılan enerji sisteminin teknik ve ekonomik olarak uygun olduğu söylenebilir.
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İncele - MakaleYalnız künye2023Scopus SJRQ1Mathematical modeling of vibration failure caused by balancing effect in hydraulic turbines
Kahraman, Gökhan; Özdemir, Osman
This article discusses the causes of vibrations depending on unbalanced hydraulic forces in rotating and non-rotating equipment in hydraulic plants within the scope of vibration measurement standards. The radial and axial positions of the turbine shaft, normal operating conditions, the absolute vibration of the signal output velocity during startup and shutdown during unbalance condition of the turbine, the proximity probes have been measured by TMO 793 accelerometer sensor and TMO 793 velocity sensor. The results obtained from the monitoring are analyzed and the first discussion is over the comparison of the current operating levels and vibration standards. Secondly, the comparison is analyzed in order to examine the improvement in vibration level of the elimination of hydraulic imbalance more comprehensively, considering the stability of the hydro turbine-generator unit, a proportional row damping force, proportional-order oil-film force and a hydraulic force and by creating a new non-linear proportional-order mathematical model. Changes in vibration levels and spectral bands for failure types are stated as well. The solution of this integrated and accurate mathematical model shows that it is useful and concise in the diagnosis and prediction of faults in hydropower plants.
AtıfScopus13WoS13OpenAlex16İncele - MakaleAçık Erişim2020Faults Caused by Cavitation in Hydraulic Power Plants and Solution Methods
Kahraman, Gökhan; Özdemir, Osman
Hydraulic energy is one of the richest and most useful renewable energy sources in the world. For this reason, hydraulic turbines must be operated at optimum efficiency levels against multiple transient situations such as starting and stopping that shorten their useful life and cause fatigue damages in order to generate energy continuously. Pressure variations occur due to flow irregularities in Francis turbines operating at non-optimal partial loads. If the sepressure variations coincide with the natural frequency of a hydraulic, mechanical or structural component, they create high vibrations due to resonance, causing the turbine to operate in an unbalanced (balanced) manner. In this study, the high vibrations of the Francis turbine were monitored with the help of a continuous (online) vibration monitoring system via the cavitation sensor mounted on the turbine adjustment blade and the cavitation vibration effects of the operation in the case of unbalance and the cavitation vibration effect after the imbalance was eliminated. Vibration caused by the cavitation phenomenon in different operating conditions of hydraulic turbines has been shown graphically. In the the graphic given in the last part of the article, it is seen that vibration magnitude is reduced from 2 mm s-1 to 0.5 mm s-1 after the bearing failure is eliminated. This is an important consequence for the hydraulic turbines to be operated in the safe cavitation zone to avoid high vibration levels.
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