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Bu makaleye şu şekilde atıfta bulunabilirsiniz (To cite to this article): Ozcan H. and Seyıtoglu S. S., "Comparative thermodynamic assessment of various super-and trans-critical working fluids for low temperature power generation applications", Politeknik Dergisi, 20(4): 915-921, (2017). Politeknik Dergisi, 2017; 20 (4) : 915-921 Journal of Polytechnic, 2017; 20 (4) ABSTRACTRecently, energy need is exponentially increasing in the world while energy sources are decreasing rapidly. Therefore, this issue requires energy sources to be used more efficiently and urges professionals to utilize energy from low temperature energy sources such as waste heat and low temperature renewable sources. In this study, energy and exergy analyses of several clean working fluids are comparatively studied in several organic Rankine cycle configurations. CO2, N2O, and SF6 fluids are compared with the conventional R23 in three ORC configurations, namely the basic ORC cycle, regenerative ORC cycle, and reheat and regenerative ORC cycle, respectively. Effects of various selected system and environmental parameters on the system performances are comprehensively investigated. Even though R23 shows the best energy and exergy performances than those of other investigated working fluids at low-temperature applications, N2O and CO2 provide a clean solution to high GWP (global warming potential) R23 with similar performance characteristics at low and high temperature power generation applications.Keywords: Organic rankine cycle, energy, exergy, R23, CO2, N2O, SF6. ÖZSon zamanlarda, enerji ihtiyacı dünyada katlanarak artarken enerji kaynakları hızla azalmaktadır. Bu yüzden, bu konu enerji kaynaklarının daha verimli kullanılması ve uzmanları atık ısı ve düşük sıcaklık yenilenebilir enerji kaynakları gibi düşük sıcaklık kaynaklarının kullanmalarını gerektirir. Bu çalışmada, birbirinden farklı temiz akışkanların enerji ve ekserji analizleri farklı organik Rankine çevrim konfigürasyonlarında karşılaştırmalı olarak incelenmiştir. CO2, N2O ve SF6 akışkanları geleneksel R23 akışkanı ile sırasıyla temel organik Rankine çevirimi, ara buhar almalı organik Rankine çevrimi ve ara ısıtmalı-ara buhar almalı organik Rankine çevrimlerinde karşılaştırılmıştır. Çeşitli seçilmiş sistemlerin ve çevresel parametrelerin sistem performanslarına etkileri kapsamlı olarak incelenmiştir.Anahtar Kelimeler: Organik rankine çevrimi, enerji, ekserji, R23, CO2, N2O, SF6.

Summary Biomass energy sources consist of materials such as wood obtained from forests, wastes from agriculture and forestry processes, and industrial, human, and animal wastes. Biogas energy is generated as a result of the anaerobic decomposition of biomass. The analysis of biogas energy potential from animal waste plays a significant role in developing countries, which involves Turkey. Therefore, the work executed in this article presents a case study for such regions. A comprehensive analysis for the production potential of biogas from the wastes of breed animals in TR83 region in Turkey, which includes the provinces of Amasya, Çorum, Samsun and Tokat is presented in this study. The number of animals and their total waste generation were determined. Then the biogas potential, along with the electricity production and the reduction of CO2 emissions, were calculated accordingly. In addition, the amount of biogas that can be produced in the TR83 region has been determined to be 151.8 M m3 per year from cattle, 6.3 M m3 per year from small cattle, and 12.9 M m3 per year from poultry. As a result, the optimal location for biogas plants based on supply chains were determined. Accordingly, the electricity potential that can be generated for the TR83 region has been determined as 49.25 MW. In addition, it has been found that approximately 19 times more carbon emissions will occur if electricity is obtained from natural gas, and approximately 34 times more emissions will be given off if it is obtained from imported coal. Ultimately, the resulting facility placement points were found to be Suluova, Çorum, Sungurlu, Bafra, Çarşamba, Vezirköprü, Erbaa, Tokat and Zile.

Undoubtedly, energy plays a vital role in every sphere of life. Fossil energy sources such as coal and natural gas are generally used for energy production. People are looking for more efficient use of the source in recent years due to the rapid depletion in the fossil fuel resources. Gasification of coal is a useful method for produce clean and efficient energy. This study was carried out to find out the various trends in scientific studies that provide literature for the field of coal gasification on world. All data used in this study have been reached from Web of Science database. In this study, the coal gasification related to both bibliometric and historical analyses were investigated. The Web of Science database was scanned for the articles about coal gasification between the years of 1989 and 2020. The considered parameters in the bibliometric analysis are the number of citations and documents, authorships and ownerships, patterns of international collaborations and addresses.