Energy Systems Engineering / Enerji Sistemleri Mühendisliği

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  • Article
    Citation - WoS: 4
    Küçük ve Mikro Ölçekli Enerji Yatırımı için Hibrit Enerji Modeli
    (Pamukkale Üniversitesi, 2019) Yıldız, Mustafa; Bingöl, Ferhat
    Türkiye çatı üstü güneş ve küçük ölçekli rüzgâr türbinleri gibi farklı olasılıklarda yeni düzenlemelere 2017 yılında gitmiştir. Her iki teknoloji için de ayrı çalışmalar yapılmış olmasına rağmen henüz hibrit sistem değerlendirme metodolojisi ve sonuçları ülke çapında yaygın değildir. Bu çalışma, verilen tesis alanın mikro ölçekli rüzgâr ve güneş esaslı toplam enerji kapasitesine göre iki kaynaktan üretilen enerjiyi azami noktaya ulaştırmak için önerilmiş, Hibrit Optimizasyon Aracı (Hybrid Otpimization Tool)-HOT-olarak isimlendirilmiş bir model içerir. Son kullanıcının basit aylık bilgileri girerek yıllık üretim tahmini yapmasına olanak verir. Modelin karşılaştırılması yaygınca kullanılan ve ticari yazılım HOMER ile yapılmıştır. Sonuçta yapılan tahminlerin mikro sistemlerin ekonomik modelini tehlikeye atmayacak belirsizlikte çalışarak fizibilite çalışmalarında ön-analiz için kullanılabileceği sonucuna ulaşılmıştır.
  • Article
    Citation - WoS: 5
    Rüzgar Enerji Sistemleri için Hava Yoğunluğunun Hesaplanması
    (Gazi Üniversitesi, 2018) Bingöl, Ferhat
    Rüzgar tarlaları son yıllarda dünyada ve Türkiye’de deniz seviyesindeki alanların yanı sıra yüksek rüzgar hızı kapasitesine sahip dağlık bölgelerde de kurulmaya başlamıştır. Ancak, dikkat edilmesi gereken en önemli nokta bu konumlarda hava yoğunluğunun azaldığı ve bunun da rüzgar türbinlerinden üretim gücüne doğrudan etkilediğidir. Küçük görünen farklar eğer fizibilite aşamasında yanlış hesaplanırsa uzun yıllar üretim göz önüne alındığında önemli farklar yaratabilirler. Bu çalışmada Türkiye'de 126 ölçüm yapılmış nokta için temelde iki farklı yöntem kullanılarak yoğunluk hesabı yapılmış ve karşılaştırılmıştır. Genel itibariyle, sonuçlar yıllık ortalamalar dikkate alındığında iki metotta da birbirine yakın çıkmakta ama aylık ortalamalarda %2 seviyelerine ulaşan üretim tahmininde hatalara yol açacak farklılıklar göstermektedir.
  • Article
    Omega type solar charge station
    (Croation Union of Mech. Engineers and Naval Architects, 2002) Atagündüz, Gürbüz
    Acid rains, greenhouse effect, smog and depletion of ozone layer arc some of the factors, which lead to the air pollution in big cities all over in the world. One of ways to reduce the air pollution in big cities is the introduction of electro or hybrid cars. The present work deals with a photovoltaic charge station, which could be installed on a garage roof with the dimensions about three meters by six meters in order to charge the battery of an electro car. The present work consists of two parts. First part deals with the theoretical design of the charge station, which has been started during a research stay of the author* in Germany. The second part is an experimental work, completed at Izmir Institute of Technology as a MS-Thesis. The present work bases on the original idea of the author, used in a previous work for the field of heliostats of the Solar Thermal Power Plant in the University Ege. The idea is to create a fix mirror area, which should acts as if it were a sun-tracking array. The theoretical design work and the results of the experiments have shown that the idea is applicable also to photovoltaic fields.
  • Article
    Citation - WoS: 8
    Citation - Scopus: 10
    Auditory Event-Related Potentials Demonstrate Early Cognitive Impairment in Children With Subclinical Hypothyroidism
    (Walter de Gruyter GmbH, 2019) Çatlı, Gönül; Kocaaslan Atlı, Sibel; Olgaç Dündar, Nihal; Bayazıt, Onur; Evirgen Esin, Nur; Erdoğan, Uğraş; Dündar, Bumin Nuri
    Background: The aim of this study was to examine the cognitive functions of children with subclinical hypothyroidism (SH) and healthy children with the use of auditory event-related potentials (AERPs) and neuropsychological tests. Methods: Twenty children aged between 8 and 17 wars, diagnosed with SH, and 20 age-matched healthy controls were included in this study. A classical auditory oddball paradigm was applied during the electroencephalography (EEG) recordings, and event-related potentials (ERPs) were evaluated between the 0.5- and 20-Hz frequency intervals. P1, N1, P2, N2 and P3 amplitudes and latencies were measured in Fz, FCz, Cz, CPz, Pz and Oz electrodes. Additionally, a number of neuropsychological tests evaluating the reaction time and various cognitive functions were carried out. Results: In children with SH, P3 amplitudes in FCz, Cz and CPz electrodes were significantly lower than those in controls (p <0.05). In addition to this, the P1N1 and N1P2 peak-to-peak amplitude values were also found to be smaller for children with SH than controls (p <0.05). With regard to the neuropsychological tests, no significant difference was observed between the SH and control groups on any of the cognitive test parameters, reaction time or correct response rates. Conclusions: In the present study, while children with SI I did not differ from controls with respect to their cognitive functions evaluated via neuropsychological tests, cognitive differences were detected via electrophysiological investigations. This result implies that implicit changes in cognition which are not yet overtly reflected on neuropsychological tests may be detected at an early stage in children with SH.
  • Article
    Citation - WoS: 33
    Citation - Scopus: 42
    Thermodynamic Assessment of Downhole Heat Exchangers for Geothermal Power Generation
    (Elsevier, 2019) Yıldırım, Nurdan; Parmanto, Slamet; Akkurt, Gülden Gökçen
    Downhole heat exchanger is a device to extract heat from geothermal fluid. While it is widely used for heating purposes, its use for power generation has not been reported. The aim of this study is to examine the feasibility of power generation from a 2500 m deep existing geothermal well with high temperature gradient and insufficient flowrate by using a downhole heat exchanger. For this purpose, a thermodynamic and an economic evaluation model are developed by the use of Engineering Equation Solver software. Additionally, the parametric studies have been carried out to identify the effects of insulation, geothermal well conditions, geometry of downhole heat exchanger, mass flowrate and type of working fluids on the performance of downhole heat exchanger system. Consequently, work output of the best alternative is computed as 2511 kW(e) with 64 kg/s mass flowrate of R-134a for 2500 m-deep downhole heat exchanger having inner pipe diameter of 0.127 m. Electricity generation cost and simple payback time are calculated as 46 $/MWh and 2.25 years, respectively. The obtained results showed that the downhole heat exchanger system can be a feasible alternative for wells with very low geothermal flowrate to generate power. (C) 2019 Elsevier Ltd. All rights reserved.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 13
    Assessment of Thermal Comfort Preferences in Mediterranean Climate a University Office Building Case
    (Vinca Inst Nuclear Sci, 2018) Turhan, Cihan; Gökçen Akkurt, Gülden
    This study aims at evaluating the perceived thermal sensation of occupants with respect to thermal comfort standards, ASHRAE 55 and ISO 7730, for office buildings located in Mediterranean climate. A small office building in Izmir Institute of Technology Campus Area, Izmir, Turkey, was chosen as a case building and equipped with measurement devices to assess thermal comfort of occupants with respect to predicted mean vote and actual mean vote. Both objective and subjective measurements were conducted. The former included indoor and outdoor air temperature, mean radiant temperature, relative humidity and air velocity that were used for evaluating the thermal comfort of occupants. Oxygen concentration which can play an additional role in thermal comfort/discomfort, health and productivity of the office occupants, was also measured. Furthermore, occupants were subjected to a survey via a mobile application to obtain subjective measurements to calculate actual mean vote values. Based on objective and subjective measurements, the relationships among the parameters were derived by using simple regression analysis technique while a new combined mean vote correlation was also derived but this time by using multiple linear regression model. Neutral and comfort temperatures were obtained using indoor air temperature and actual mean vote values which were calculated from subjective measurements. The results showed that neutral temperature in the university office building was 20.9 degrees C whilst the comfort temperature range was between 19.4 and 22.4 degrees C for the heating season. By applying new comfort temperatures, energy consumption of the case building located in Mediterranean climate, can be reduced.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 3
    Green Smart Cities: Living Healthily With Every Breath
    (Institute of Electrical and Electronics Engineers Inc., 2019) Turhan, Cihan; Atalay, Ali Serdar; Gökçen Akkurt, Gülden
    Fifty-four percent of the world's population lives in big cities and it is projected to increase to nearly 70% by 2050s. Rapid and dense urbanization leads to smart cities which improve the quality of lives of the citizens. Therefore, development of smart cities is becoming vital. The quality of the citizens is affected by many factors including poor air quality, increased pollutants and microclimates called urban heat islands. The URBAN GreenUP project, initiated in June 2017, is a project funded under the European Union's Horizon 2020 programme. The main objective of the project is the development, application and replication of re-naturing Urban Plans in a number of European cities. In this study, measurement of nature-based solutions for mitigation of urban heat island effect and improvement of air quality for Urban GreenUP project in Izmir, will be introduced.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 2
    Feasibility of Large Scale Wind Turbines for Offshore Gas Platform Installation
    (AIMS Press, 2018) Bingöl, Ferhat
    Although, offshore wind energy development emerged under way at the beginning of the millennium, Europe is planning to bring offshore wind energy capacity to over 11.6 GW until 2020. This is nearly 10 times todays installed offshore capacity and equal to nearly 50% of the new planned investment in the wind energy market. The North Sea and the Baltic Sea are the main investment areas due to the shallower sea depth. In this paper an approach to use old gas / oil platforms as the foundation for a wind turbine is examined. An off shore gas platform close to Istanbul Turkey with over 20 years more lifetime is taken as a real-life case, with the wind resource information extracted from the recent large-scale wind atlas study, Global Wind Atlas version 2. The study aims to combine recent offshore economical models with up-to-date scientific wind energy yield assessment models to have a more realistic look on the feasibility of such an approach. The results show that, with the assumption of no extra support structure and capital loan costs, a project can be feasible with bigger then 8MW wind turbines. These may involve a large initial investment but the return of the investment (ROI) can be as low as 8 years. With bigger turbines, profit can be increased, and ROI can be decreased while the Levelized Cost of Energy (LCOE) displays minor decrease after 10 MW.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 9
    Impact of Climate Change on Indoor Environment of Historic Libraries in Mediterranean Climate Zone
    (Inderscience Enterprises, 2019) Turhan, Cihan; Durmuş Arsan, Zeynep; Gökçen Akkurt, Gülden
    Most historic library buildings house valuable paper-based collections that are kept in unconditioned environments. This vulnerable cultural heritage is expected to be highly affected by climate change in the future. In this study, indoor microclimate of an unconditioned historic library, Necip Pasa Library (Izmir, Turkey) is analysed for existing conditions and future climate data. The measured and predicted indoor microclimate data from 'present' till 2080s are used to determine possible chemical degredation risk on library collection and human comfort. Comparison of periodic results of future climate data indicates an increase in temperature that could cause both an increase in chemical degredation risk on the library collection and a decline in thermal comfort conditions. Mitigation of climate change effects on library collection and human comfort requires taking some actions such as adding light and adaptive mechanical solutions.
  • Article
    Citation - WoS: 19
    Citation - Scopus: 27
    Reactive Power Capability Model of Wind Power Plant Using Aggregated Wind Power Collection System
    (MDPI Multidisciplinary Digital Publishing Institute, 2019) Sarkar, Moumita; Altın, Müfit; Sorensen, Poul E.; Hansen, Anca D.
    This article presents the development of a reactive power capability model for a wind power plant (WPP) based on an aggregated wind power collection system. The voltage and active power dependent reactive power capability are thus calculated by using aggregated WPP collection system parameters and considering losses in the WPP collection system. The strength of this proposed reactive power capability model is that it not only requires less parameters and substantially less computational time compared to typical detailed models of WPPs, but it also provides an accurate estimation of the available reactive power. The proposed model is based on a set of analytical equations which represent converter voltage and current limitations. Aggregated impedance and susceptance of the WPP collection system are also included in the analytical equations, thereby incorporating losses in the collection system in the WPP reactive power capability calculation. The proposed WPP reactive power capability model is compared to available methodologies from literature and for different WPP topologies, namely, Horns Rev 2 WPP and Burbo Bank WPP. Performance of the proposed model is assessed and discussed by means of simulations of various case studies demonstrating that the error between the calculated reactive power using the proposed model and the detailed model is below 4% as compared to an 11% error in the available method from literature. The efficacy of the proposed method is further exemplified through an application of the proposed method in power system integration studies. The article provides new insights and better understanding of the WPPs' limits to deliver reactive power support that can be used for power system stability assessment, particularly long-term voltage stability.