ÖzRapid depletion of fossil fuel resources as well as concerns for foreign dependence in meeting energy needs have led researches for alternative fuels. Biodiesel, which can be obtained from many renewable resources such as vegetable oil and animal fat through transesterification, is the most attractive alternative fuel for cars, especially for being environmentally friendly. However, there are some cons, too. The presence of water and free fatty acids in the biodiesel makes it more corrosive than petrol-diesel, and this is an undesired feature. Corrosion induced by contact with biodiesel both reduces the life of metal parts and deteriorates the fuel properties, hence adversely affects engine performance. Therefore, the corrosive characteristics of biodiesel are very important for long term durability of engine components. In this study, we tried to investigate the corrosive effects of biodiesel and blends on engine parts by evaluating and comparing test results from earlier studies for different periods at different temperatures with different biodiesel fuels. Remedial measures to inhibit or mitigate corrosive effects of biodiesel by using additives are also tackled. Fosil yakıt kaynaklarının hızla tüketilmesi ve enerji ihtiyacının karşılanmasında dışa bağımlılık kaygısı, alternatif yakıt araştırmalarına yol açmıştır. Transesterifikasyon yoluyla bitkisel yağ ve hayvansal yağ gibi birçok yenilenebilir kaynağından elde edilebilen biyodizel, otomobiller için, özellikle çevre dostu olmak için en çekici alternatif yakıttır. Ancak bazı eksiler de var. Biyodizelde su ve serbest yağ asitleri varlığı onu petrol türevi dizelden daha korozif yapar ve bu istenmeyen bir özelliktir. Biyodizel ile temastan kaynaklanan korozyon hem metal parçaların ömrünü azaltır hem de yakıt özelliklerini kötüleştirir ve bu nedenle motor performansını olumsuz olarak etkiler. Bu nedenle, biyodizelin korozif özellikleri, motor bileşenlerinin uzun süreli dayanıklılığı için çok önemlidir. Bu çalışmada, farklı biyodizel yakıtlarıyla farklı sıcaklıklarda farklı dönemler için önceki çalışmaların test sonuçlarını değerlendirerek ve karşılaştırarak biyodizel ve harmanların motor parçaları üzerindeki korozif etkileri araştırılmıştır. Katkı maddeleri kullanarak biyodizelin korozif etkilerini önlemek veya azaltmak için düzeltici önlemler de ele alınmaktadır.

Recently new and renewable energy sources began to become prominent as alternatives to fossil fuels. Among these are wind, solar, hydraulic, biomass, geothermal and wave energies. As for Turkey, the least accounted and less applied of these sources is wave energy. The government has established a short-term outlook on utilization of renewable energy sources, named "National Renewable Energy Action Plan" which is a part of Vision 2023 targets. Nonetheless, there is no planned utilization of and/or investment into wave energy in Turkey's agenda up to the year 2023. This might be mainly because of the complex structure of wave energy conversion systems, marine conditions, mechanical difficulties and high initial investment costs. However, this type of energy is environmentally friendly, cheap and clean, and a great potential is available especially in Turkey which is surrounded on three sides by sea. Although Turkey has neither coasts to oceans nor a long stretch of west coastline, which have the highest energetic waves thanks to the prevailing west-to-east winds; the Black Sea basin, as well as the southwestern Mediterranean region, may offer a good potential for development as an energetic regime, often comparable to oceanic sites in terms of wave heights, induced by strong wind patterns. In this study, wave energy potential in Turkey and recent studies made on determination of suitable sites for evaluation of wave energy in Turkey are discussed.

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Today, energy generation from renewable energy sources is of great interest. Photovoltaic (PV) systems, in this regard, have much to offer, but they suffer from low efficiency, which further deteriorates due to overheating under insolation. So, they need removal of heat from their bodies for better efficiency, which resulted in the introduction of PV-Thermal (PVT) systems, which feature heat transfer fluids (HTF) to draw the heat and deliver it to other systems that make use of it. Nevertheless, the best HTF has yet to be developed. Water-based fluids with additives or nanoparticles seemed like a good choice until HTFs that featured the use of encapsulated phase change materials (ePCM) were proposed. The findings of early studies and subsequent research revealed that the use of ePCM slurries (ePCM-Ss) as the working fluid in PVT systems increased the thermal efficiency, electrical efficiency, and overall efficiency without a notable increase in pumping power. However, preparation of ePCM-Ss is much more complex in many aspects compared to conventional HTFs, as it involves numerous parameters, including but not limited to the use of various shell and core materials, the variety of production methods, the homogeneity of the resulting capsules, the use of additives, the core to shell ratio, and the mass fraction of ePCM in the slurry. All these require an extensive and exhaustive study with quite a lot of background knowledge and interdisciplinary collaboration, as the proper selection of PCM materials and synthesis methods, as well as the correct concentration in the best CF, involve several aspects and expertise in a number of other fields. These parameters also significantly diversify and differentiate ePCM-S by affecting its suspension stability, rheological properties, and thermal properties. In recent years, PCMs have become an attractive research field for researchers due to their advantages. Although there are quite a number of studies addressing ePCM-S, none provide a holistic approach, and they just deal with a certain aspect of this broad topic. This study, therefore, aims to constitute a fundamental guide to refer to from the very beginning to the final implementation of the ePCM-Ss as the working fluid in PVT systems by addressing all steps, aspects, and almost all effective parameters in terms of advantages, disadvantages, challenges, and opportunities.

The aim of the present study was to numerically investigate the effects of circular inserts placed inside a circular tube in order to evaluate the heat transfer characteristics under different operating conditions. Computational Fluid Dynamics methods were used to solve the model, which is a heat pipe with an outer diameter of 21 mm equipped with circular inserts with a distance of 20 cm. Different mass flow rates of the heat transfer fluid, including 25, 50, 75, 100, and 125 g/s were examined, and the thermal behavior of the turbulators and the flow structure were investigated. R19.0 version of ANSYS Fluent software was used as the CFD program to obtain the desired results and contours. From the results, it was found that circular inserts can be used in heat pipes to produce vortices and thus improve the heat transfer.