Browsing by Author "Yildirim, Nurdan"

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Citation - WoS: 26
Citation - Scopus: 29
A comprehensive evaluation of PV electricity production methods and life cycle energy-cost assessment of a particular system
(ELSEVIER SCI LTD, 2019) Huseyin Gunhan Ozcan; Huseyin Gunerhan; Nurdan Yildirim; Arif Hepbasli; Ozcan, Huseyin Gunhan; Yildirim, Nurdan; Hepbasli, Arif; Gunerhan, Huseyin
This paper presents the study about electricity generation from solar photovoltaic technology based on four different methodologies with some performance indicators namely performance ratio system efficiency fill and capacity utilization factors respectively. In this regard not only theoretical approach and simulation programs (PVSOL and TRNSYS) were used to determine annual production but also experimental studies were carried out for the validation. While annual sum of electricity generation was evaluated between 3913.84 and 4323.94 kWh the PVSOL program was determined to be the method that best reflected the experimental studies with a rate of 94.33%. Moreover while fill and capacity utilization factors were annually obtained to be almost similar annual values for the performance ratio and system efficiency were evaluated to be partially close to each other based on the theoretical approach and PVSOL program. Besides evaluation of the power production and performance indicators a life cycle energy analysis was also made for a particular system with a capacity of 2.55 kWp and energy payback periods were obtained to be between 1.99 and 2.54 years considering four different methodologies. Moreover the life cycle cost analysis was performed with or without battery option and some improvement proposals were presented for the energy market to become investable. (C) 2019 Elsevier Ltd. All rights reserved.
Citation - WoS: 92
Citation - Scopus: 101
Energy and exergy analysis of a milk powder production system
(PERGAMON-ELSEVIER SCIENCE LTD, 2017) Nurdan Yildirim; Seda Genc; Yildirim, Nurdan; Genc, Seda
Milk has been consumed since time immemorial because of its unique nutritional properties and produced almost 816 million tonnes in the year of 2016. Due to its highly perishable characteristic milk is processed into more stable milk products such as cheese yoghurt and butter and milk powder. Among them milk powder is distinctive for its longer shelf life and can be stored at ambient temperature. The other advantages of milk powder are less volume requirement during its transportation and higher selling price. Therefore it is widely used in many food products such as ice cream bakery products and sausages. According to a recent study on the statistics from Food and Agriculture Organization world production of whole dried milk was 3597015 tonnes in 2014: Oceania 36.5% Americas 36.1% and Europe 24.1% of the World production. Milk powder production is a process that requires high energy especially for evaporation. Recently reducing energy use has been gaining importance by increasing energy and exergy efficiency. Conventional energy analysis is performed based on the First Law of Thermodynamics. Unlike from the First Law the Second Law or exergy analysis (defined as useful work) has appeared in the literature while this analysis not only assesses quantity but also quality of energy. In this study exergy analysis of a milk powder production system mainly includes 3 processes (pasteurization evaporation and spray drying) which will be presented. The aim of the study is to apply a thermodynamic analysis including comprehensive exergy analysis by using different performance parameters such as exergy efficiency improvement potential rate sustainability index relative irreversibility and exergetic factor for the milk powder production system. As a result exergetic efficiencies of the system components were found in the range of 9-83%. The overall energy and exergy efficiencies of the whole milk powder production system were calculated as 85.4 and 57.45% respectively. Additionally it was found that the evaporator and the heater have a higher impact in improvement actions. (C) 2017 Elsevier Ltd. All rights reserved.
Energy exergy and economic assessments of wind turbine alternatives
(INDERSCIENCE ENTERPRISES LTD, 2024) Nurdan Yildirim; Levent Bilir; Bilir, Levent; Yildirim, Nurdan
In this study two wind turbine installation alternatives for a residential district of 20 detached houses in six different European cities are considered. Firstly the installation of an individual residential scale (5 kW) wind turbine for each house is considered. Secondly the installation of a single wind turbine having the same total installed capacity (100 kW) is evaluated. The alternatives are compared according to annual energy production exergy efficiencies and simple payback time. The results pointed that the use of a single wind turbine is better that the use of individual residential scale wind turbines for small communities or districts.
Citation - WoS: 99
Citation - Scopus: 110
Evaluation of a hybrid system for a nearly zero energy greenhouse
(PERGAMON-ELSEVIER SCIENCE LTD, 2017) Nurdan Yildirim; Levent Bilir; Bilir, Levent; Yildirim, Nurdan
Greenhouses are widely used in the World especially in the Mediterranean climate to provide suitable environment in cultivation of different agricultural crops. Significant amount of energy is necessary to produce process and distribute these crops. Various systems including steam or hot water radiation system and hot air heater system are being used in greenhouse heating. A ground source heat pump system generally seen as a favorable option since it can provide both heating and cooling energy is considered for a greenhouse in this study. The aim of this study is to evaluate a renewable energy option for the required total energy need of a greenhouse. Grid connected solar photovoltaic panels are selected to assist a ground source heat pump and generate sufficient electrical energy for lighting. In this way a nearly zero energy greenhouse concept is foreseen for three different agricultural products: Monthly and annual heating cooling and lighting energy load of the greenhouse for these agricultural products were computed. The monthly average electricity generation of 66 photovoltaic panels which cover 50% of the southern face part of the asymmetric roof was calculated. Annual photovoltaic electricity generation was found as 21510.4 kWh. It was observed that photovoltaic electricity generation can meet 33.2-67.2% of greenhouse demand in summer operation months. Nevertheless the coverage ratio calculated by dividing the photovoltaic panels electricity generation to the electricity demand of the greenhouse (heating cooling and lighting) for each crop were very high in winter operation months. Yearly coverage ratio values were 95.7% for tomato 86.8% for cucumber and 104.5% for lettuce. These high coverage ratio values justify the nearly zero energy concept for the considered greenhouse. Economic and environmental evaluation of the considered system were also accomplished. A simple payback time of the crop cultivations was computed between 7.0 and 7.4 years. The energy payback time of the system was found to be 4.9 years and the greenhouse gas payback time value of 5.7 years and 2.6 years were calculated based on natural gas and coal based electricity generation respectively. (C) 2017 Elsevier Ltd. All rights reserved.
Citation - Scopus: 5
Geothermal energy in developing countries–The dilemma between renewable and nonrenewable
(Elsevier, 2022) Nurdan H. Yildirim; Emin Selahattin Umdu; Umdu, Emin Selahattin; Yildirim, Nurdan
Geothermal energy the first application of which was based on heating of hammam and space by the Romans in ancient times is now widely used in 88 countries with total 15950 MWe power and 107727 MWt thermal installed capacity. Geothermal energy which takes its energy from the depths of the earth is not affected much by external meteorological factors and therefore its the most important advantage compared to other renewable energy sources can produce almost uninterrupted energy throughout the year. On the other hand extracting this resource and transferring it to the surface is long difficult and costly. In order for a geothermal resource to be a clean environmentally friendly and sustainable energy source the most important thing to do is to reinject the geothermal fluid used in various applications to underground. Only in this way geothermal energy can be considered sustainable. The usage areas of geothermal energy vary depending on the thermodynamic properties of the geothermal fluid. Combined systems should be expanded to increase the efficiency of geothermal systems. In this chapter firstly basic information about geothermal energy and usage areas are given then current technologies and status are presented. The dilemma: renewable or nonrenewable sustainability and future prospect for developing countries are discussed. In the last part basic approaches in the analyses of geothermal systems are illustrated with a case study. © 2022 Elsevier B.V. All rights reserved.
Isıl Konfor ve Enerji Tüketimi Açısından İki Üniversite Binasının İncelenmesi
(2021) Nurdan Yildirim; hacer sekerci oztura; Şadiye Birce Ongun; Oztura, Hacer Sekerci; Ongun, Şadiye Birce; Yildirim, Nurdan
Binalar ve sanayi toplam enerji tüketiminin en büyük payını kapsamaktadır. Binalardaki enerji tüketiminin dağılımına bakıldığında da en önemli kısmını iklimlendirme sistemlerinin oluşturduğu görülmektedir. Bu nedenle iklimlendirme sistemlerinin enerji tüketimlerinin iyileştirilmesi veya daha verimli sistemlerin kullanılması büyük önem taşımaktadır. İklimlendirme sistemlerinin enerji tüketimlerini etkileyen faktörlerin başında sistem tipi kapasitesi tasarım şekli işletme ve iklim koşulları ve kullanıcı müdahaleleri gelmektedir. Yaşar Üniversitesi 5 Ocak 2016 tarihinde TS EN ISO 50001:2011 Enerji Yönetim Sistem (EnYS) Standardı belgesini ülkemizde alan ilk üniversite olmuştur ve o günden bu yana enerji verimliliği ile ilgili araştırma ve çalışmalar artarak devam etmektedir. Bu kapsamda üniversitemizin kullanım alanı en büyük ve farklı iklimlendirme sistemleri ve tasarımına sahip olan iki binamız enerji verimliliğimizi arttırmak açısından öncelikli olarak ele alınmıştır. Binalarımızın birim kullanım alanına göre enerji performans değerleri hesaplanmış ve bu değerlerin analizinde binalardaki ısıl konfor koşullarının da dikkate alınması gerektiği anlaşılmıştır. Bu nedenle her iki binamızda bazı ofis ve sınıflarda sıcaklık nem CO2 ve basınç gibi ısıl konfor ve iç hava kalitesi parametrelerinin ölçümleri yapılmaya başlanmıştır. Bu çalışmada söz konusu mahallerden alınan ölçüm sonuçları analizörlerden elde edilen enerji tüketim değerleri ve meteorolojik veriler kullanılarak binalarımızdaki iklimlendirme sistemlerimizin birim ısıtma sıcaklığına karşılık enerji tüketim değerleri hesaplanmıştır. Böylelikle binalardaki enerji tüketimi ve ısıl konfor açısından performans göstergeleri ortaya çıkarılarak enerji verimliliğinin arttırılması amacıyla öneriler sunulmuştur.
Citation - WoS: 2
Citation - Scopus: 2
Life cycle assessment and life cycle costing approach for building decarbonization by design choices: A case study
(John Wiley and Sons Inc, 2024) Emin Selahattin Umdu; Nurdan H. Yildirim; Poyraz Güzel; Ebru Alakavuk; Duygu Çinar Umdu; Alakavuk, Ebru; Guzel, Poyraz; Umdu, Emin Selahattin; Yildirim, Nurdan; Umdu, Duygu Cinar; Cinar Umdu, Duygu
Decarbonizing the urban environment has two significant challenges: Increasing electricity demand due to the electrification of space heating and increased renewables share in the electricity supply. The European Commission defines a new grid support mechanism for peak-shaving products in renewed Electricity Market Design. This aims to enable a new market tool to stabilize electric supply and demand. This study examines a grid-integrated thermal storage device's technical feasibility and economic performance to meet net zero building (nZEB) definitions. Alternative scenarios considering current national nZEB targets present energy market options and regulations are compared using the life cycle cost and the global warming potentials over the building lifetime. The results show that better building performance is possible even with a low investment increase of 6.7% compared to minimum building standards based on regulations. This enables older building cases to perform similarly with new building targets for Turkish National nZEB. Building electrification using heat pumps and thermal storage systems gives similar economic performances in the long term when a dynamic electricity tariff is available. Adapting the life cycle approach to decision-making in construction contracts can lead to a 50% decrease in building emissions while staying within the same construction budget. © 2024 Elsevier B.V. All rights reserved.
Citation - WoS: 18
Citation - Scopus: 18
Modeling and performance analysis of a hybrid system for a residential application
(PERGAMON-ELSEVIER SCIENCE LTD, 2018) Levent Bilir; Nurdan Yildirim; Bilir, Levent; Yildirim, Nurdan
Hybrid systems which use more than one renewable energy sources are quite advantageous because they can eliminate or at least vitiate the interrupted characteristics of the renewable sources. In the present study a hybrid system which consists of a small scale wind turbine and photovoltaic panels was focused on. The system supplies the required electricity demand for a detached house with a 117 m(2) area in five different locations (Izmir Madrid Budapest Paris and Helsinki) according to European climate zones. A detailed dynamic hourly electricity generation analysis for the two components of the hybrid system was performed. As a result the coverage ratio of the hybrid system electricity generation for the total electricity demand of the house simple payback time and energy payback time of the system were calculated for each city. The results revealed that yearly electrical energy demand of the house can be entirely met by the evaluated hybrid system for each city. Maximum yearly coverage ratio of 176.6% was observed for Izmir Turkey while minimum coverage ratio was 103.1% for Helsinki Finland. The simple payback time and energy payback time of the hybrid system were determined in the range of 7-25.5 years and 4.6-6.8 years respectively. (C) 2018 Elsevier Ltd. All rights reserved.
Citation - WoS: 33
Citation - Scopus: 39
Optimization of microalgae panel bioreactor thermal transmission property for building façade applications
(Elsevier Ltd, 2018) Emin Selahattin Umdu; Ilker Kahraman; Nurdan H. Yildirim; Levent Bilir; Umdu, Emin Selahattin; Yildirim, Nurdan; Bilir, Levent; Kahraman, İlker
Microalgae has great potential reducing embedded CO2 emissions of buildings through their entire life cycles by both increasing energy efficiency and actively capturing CO2. The use of closed microalgae photo bioreactors as building components has the added benefits of acting as an effective insulation system. Additionally microalgae can give a dynamic appearance with living dynamic system that also works as an adaptive sunshade. In this study the thermal transmittance (U value) of different photo bioreactors is determined by using experimental design methods for parametric studies. Heat transfer behaviour of the manufactured panel bioreactors at different operational conditions which satisfy both thermal comfort in building and microalgae growth conditions is evaluated. U values between 3.84 and 53.19 W/m2 K are observed in the study. Results show that there is a significant interaction between all main factors (reservoir air layer and reservoir wall thicknesses) and U value. Yet a two-way interaction is observed for only between reservoir and air layer thicknesses. Further air layer thickness has the highest contribution to the U value in the developed model as both a main and synergetic factor. © 2018 Elsevier B.V. All rights reserved.
Citation - Scopus: 5
Performance Assessment of University Buildings Based on Provided Thermal Comfort
(Institute of Electrical and Electronics Engineers Inc., 2019) Nurdan H. Yildirim; Hacer Sekerci Öztura; Sekerci, Hacer; Yildirim, Nurdan
Buildings and industry cover the largest share of total energy consumption. When the distribution of energy consumption in buildings is examined it is seen that the most important part is air conditioning systems. Therefore improving the energy consumption of air conditioning systems or using more efficient systems have great importance. The factors affecting the energy consumption of air conditioning systems are system type capacity design operation and climate conditions and user interventions.Yasar University is the first University having the TS EN ISO 50001:2011 Energy Management System Standard Certification in Turkey. Since the buildings and their systems are different in the Campus the new performance indicators are necessary to evaluate energy performance of the buildings. In this regard addition to existing energy metering system thermal comfort measurement devices were installed in some classes and offices in the campus.In this study performance assessment of two buildings in the Campus of Yasar University has been done based on their specific energy consumption and provided thermal comfort to the classes. Thus the relationship between energy consumption and thermal comfort in buildings is revealed and suggestions are presented to increase energy efficiency. © 2020 Elsevier B.V. All rights reserved.
Performance evaluation of geothermal assisted VAC systems for residential cooling purposes
(Inderscience Publishers, 2024) Nurdan H. Yildirim; Yildirim, Nurdan
Nowadays renewable energy sources are being integrated to HVAC-R system to reduce energy consumption of the buildings since buildings have the biggest share of the total energy consumption of nearly every country in the world. In this study a geothermal assisted cooling system with a vapour absorption refrigeration system having ammonia water or lithium bromide-water solution pair is studied in order to meet 10 kW cooling demand of a 150 m2 detached house in Izmir Turkey. The thermodynamic performances of the refrigeration systems are compared by conducting detailed energy exergy analyses and parametric studies. The exergetic efficiency of the lithium bromide-water vapour absorption refrigeration system is determined as 30% while it is 19.8% for ammonia-water vapour absorption refrigeration system. The vapour absorption refrigeration system with lithium bromide-water working pair is a better alternative for the considered house at the base case operating conditions. © 2024 Elsevier B.V. All rights reserved.
Citation - WoS: 24
Citation - Scopus: 30
Photovoltaic system assessment for a school building
(PERGAMON-ELSEVIER SCIENCE LTD, 2017) Levent Bilir; Nurdan Yildirim; Bilir, Levent; Yildirim, Nurdan
The installation of photovoltaic panels (PVs) on the roof of residential and commercial buildings is getting widespread as these areas stand normally idle and can be used for another purpose without losing an inhabited space. Considering the solar potential of Turkey a significant amount of electricity generation is possible using current PV technology. For this reason a two-story detached school building located in Izmir Turkey was taken into consideration and monthly as well as annual coverage ratio of an on-grid PV system for its entire energy requirement (including heating cooling and lighting) was investigated. The PVs were installed on the south face of the school building roof. A heat pump with a typical coefficient of performance (COP) value of 2.5 was used for supplying required cooling and heating. The heating cooling and lighting loads were determined on a monthly basis. The average monthly electrical energy generation of the mounted PVs was calculated using a written code in Energy Equation Solver (EES) software. As a result the monthly as well as yearly electrical energy demand coverage ratio values for the school using the installed PVs were revealed. Since the school building has a large south faced roof the installation of PVs is very suitable to meet the cumulative electrical energy need of the heat pump and the lighting load. For Case 1 180 PVs which supply the entire yearly demand (with a 110% coverage ratio) were taken into consideration while for Case 2 265 PVs which cover 75% of the roof area were evaluated. The results showed that between November and March PV electrical energy generation is not sufficient to meet all energy need of the school for both cases. However significant coverage ratio values were observed for the rest of the year. In a yearly basis the PV generation exceeded the building demand by 62% for the Case 2. This conclusion points out that the school can meet its yearly electricity need with the considered PV system and can even have an additional financial profit by selling its surplus PV electricity to the grid. Economic and environmental payback time values as well as simple payback time value were also computed for both investigated cases. The results pointed out a simple payback time of 7.9 years for Case 1 and 7.6 years for Case 2. Energy payback time was determined as 5 years for both systems. The greenhouse gas payback time of 2.7 years and 5.9 years was encountered for coal based and natural gas based calculations. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Rüzgâr türbini ile fotovoltaik modüler sistemin karşılaştırılması: Ege Üniversitesi-İzmir örneği
(2020) Huseyin Gunerhan; LEVENT BILIR; HÜSEYIN GÜNHAN OZCAN; Nurdan Yildirim; Ozcan, Hüseyın Günhan; Yildirim, Nurdan; Bılır, Levent; Gunerhan, Huseyin
Bu çalışmada rüzgâr ve güneş enerjisi bakımından önemli potansiyele sahip olan İzmir’de bulunan EgeÜniversitesi Makina Mühendisliği Bölümü binası için yaklaşık aynı kapasiteye sahip bir rüzgâr türbini(55 kW) ile fotovoltaik modüler sisteminin (54 4 kW) enerji üretimi ve ekonomik olarak karşılaştırılmasıyapılmıştır. Makina Mühendisliği Bölümü binasının iklimlendirilmesinde klimalar kullanılmaktadır ve elealınmış olan rüzgâr türbini ve fotovoltaik modüler sisteminin bu klimaların elektrik kullanımının ne kadarınıkarşılayabilecekleri incelenmiştir. Her iki sistemin enerji üretimleri TRNSYS yazılımı ile hesaplanmıştır. Buhesaplamalarda Makina Mühendisliği Bölümü binasının çatısında kurulu bulunan ölçüm istasyonundanalınmış olan dakikalık rüzgâr hızı rüzgâr yönü dış hava sıcaklığı ve güneş ışınımı verileri saatlik veriyeçevrilmiş ve analizlerde kullanılmıştır. Sonuç olarak ısıtma sezonunda fotovoltaik modüler sistemin ihtiyacın%88 85’i kadar rüzgâr türbininin ise %72 15’i kadar elektrik üretimi gerçekleştirebileceği hesaplanmıştır.Soğutma sezonunda ise fotovoltaik modüler sistemin ihtiyacın %202 25’i rüzgâr türbininin ise %114 45’idüzeyinde elektrik üretimi yapabileceği belirlenmiştir. Fotovoltaik modüler sisteminin basit geri ödemesüresi 9 19 yıl rüzgâr türbinin basit geri ödeme süresi ise 14 52 yıl olarak hesaplanmıştır. Elde edilensonuçlar değerlendirildiğinde, Ege Üniversitesi Makina Mühendisliği Bölümü binası için fotovoltaikmodüler sisteminin kurulumunun enerji üretimi açısından ve ekonomik olarak rüzgâr türbini kurulumdandaha tercih edilir durumda olduğu görülmüştür.
The Effect of Window Openings on Energy Consumption of an University Building: A Case Study in Izmir
(Institute of Electrical and Electronics Engineers Inc., 2022) Nurdan H. Yildirim; Yildirim, Nurdan
Buildings have almost a third of total energy consumption. University buildings also have significant energy consumption because of their high usage floor areas and user numbers as they are heavily used buildings. In order to provide energy efficiency in such buildings the insulation of the buildings choosing the systems used in the building as energy efficient the most appropriate use / operation of these systems and the building are the main factors. On the other hand behavior of the users is also very effective in energy consumption. It is known that users frequently interfere with windows especially in buildings that serve a large number of users. The aim of this study is to determine the interventions made by the users on the windows and the effects of these on the energy consumption through the year-round measurements in the selected classes in a university building. Within this scope measurements of window opening indoor air temperature CO2 concentration and electricity consumption were made in selected classes throughout 2019. Energy consumption model has been developed with the help of measurement results and regression analysis to determine the suggestions and percentages of the building's energy consumption reduction. The measurement results show that the total opening time of the windows in the classes is up to 33.6% of the annual usage time. It has been determined that keeping the windows open for a long time increases the energy consumption of the building by 4.07% in heating mode and 2.63% in cooling mode. © 2022 Elsevier B.V. All rights reserved.
Citation - WoS: 3
Citation - Scopus: 4
Thermodynamic analysis and assessment of a geothermal cooling system for a house
(INDERSCIENCE ENTERPRISES LTD, 2019) Buket Ozcan; Ilkyaz Ekin Aykurt; Melisa Akpak; Tuna Tacer; Nurdan Yildirim; Arif Hepbasli; Huseyin Gunhan Ozcan; Ozcan, Huseyin Gunhan; Tacer, Tuna; Akpak, Melisa; Yildirim, Nurdan; Hepbasli, Arif; Aykurt, Ilkyaz Ekin; Ozcan, Buket
In this study a geothermal assisted cooling system with a vapour absorption chiller (VAC) was designed in order to meet the cooling demand of a 140 m(2) detached single-family house in Izmir Turkey. In the considered system the geothermal fluid is transported to the VAC where water and ammonia are used as an absorbent and a refrigerant respectively. Energy and exergy analyses methods are utilised to assess the performance of the whole system while some operational properties of the VAC such as pressure temperature ammonia concentration and flow rate are determined. Based on the parametric studies optimum operating conditions of the VAC are obtained to be 30 degrees C 90 degrees C and 2 degrees C for the condenser boiler and evaporator respectively. Under these conditions the system has a coefficient of performance (COP) value of 0.30 with a simple payback period of 6.4 years the highest exergy destruction occurs within the absorber with a rate of 38.2%.
Citation - WoS: 47
Citation - Scopus: 55
Thermodynamic analysis of a milk pasteurization process assisted by geothermal energy
(PERGAMON-ELSEVIER SCIENCE LTD, 2015) Nurdan Yildirim; Seda Genc; Yildirim, Nurdan; Genc, Seda
Renewable energy system is an important concern for sustainable development of the World. Thermodynamic analysis especially exergy analysis is an intense tool to assess sustainability of the systems. Food processing industry is one of the energy intensive sectors where dairy industry consumes substantial amount of energy among other food industry segments. Therefore in this study thermodynamic analysis of a milk pasteurization process assisted by geothermal energy was studied. In the system a water ammonia VAC (vapor absorption cycle) a cooling section a pasteurizer and a regenerator were used for milk pasteurization. Exergetic efficiencies of each component and the whole system were separately calculated. A parametric study was undertaken. In this regard firstly the effect of the geothermal resource temperature on (i) the total exergy destruction of the absorption cycle and the whole system (ii) the efficiency of the VAC the whole system and COP (coefficient of performance) of the VAC (iii) the flow rate of the pasteurized milk were investigated. Then the effect of the geothermal resource flow rate on the pasteurization load was analyzed. The exergetic efficiency of the whole system was calculated as 56.81% with total exergy destruction rate of 13.66 kW. The exergetic results were also illustrated through the Grassmann diagram. (C) 2015 Elsevier Ltd. All rights reserved.
Citation - WoS: 34
Citation - Scopus: 43
Thermodynamic assessment of downhole heat exchangers for geothermal power generation
(Elsevier Ltd, 2019) Nurdan H. Yildirim; Slamet Parmanto; Gülden Gökçen Akkurt; Parmanto, Slamet; Yildirim, Nurdan; Akkurt, Gulden Gokcen
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 kWe 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. © 2019 Elsevier B.V. All rights reserved.
Türkiye’nin Farklı İklim Koşullarında Isıl Konfor Sıcaklıklarına Bağlı Olarak Konutların Enerji Performanslarının Değerlendirilmesi
(2021) Nurdan Yildirim; Ebru Hancioglu; Gulden Gokcen Akkurt; Hancioglu, Ebru; Yildirim, Nurdan; Akkurt, Gulden Gokcen
Isıl konfor insanın yapısı yaşı cinsiyeti gibi kişisel parametrelerin yanı sıra çevresel parametrelere de bağlıdır. Isıtma soğutma ve havalandırma sistemlerinin çalışma şekli ve dış hava sıcaklıkları ısıl konfor içinönemli parametrelerdir. Fanger deneysel çalışmalar sonucu “tahmini ortalama oy (PMV)” olarak adlandırılan bir gösterge oluşturmuş ve PMV=0’ı konfor için en iyi değer olarak belirlemiştir. Bu çalışmada farklıiklim bölgelerinden dört il seçilerek her bir il için ısıl konfor sıcaklıkları belirlenmiş ve bu ısıl konfor sıcaklıklarındaki enerji performansları değerlendirilmiştir. Isıtma ve soğutma sistemi için kişisel kontrole izinverilmeyen tam mekanik kontrollü sistem seçilmiş kesikli ve sürekli rejim için hesaplamalar yapılmıştır.Çalışmada konfor koşullarının PMV=0 olması durumunda enerji tüketimleri incelenerek iller arasındakiısıl konfor memnuniyeti ve enerji tüketiminindeki farklılıklar saptanmaya çalışılmıştır. PMV değerlerininistatistiksel analizinde İzmir ili için kesikli rejimde çalışmanın sürekli rejime göre daha iyi olmasına rağmen İstanbul için sürekli rejimde konfor koşulları açısından daha iyi sonuçlar alınmıştır. Tüm illerde süreklirejim uygulandığında birim enerji tüketiminde artış olduğu belirlenmiştir. Sürekli rejim kesikli rejime göreısıtma enerji tüketiminde % 4 5-6 2 soğutma enerji tüketiminde ise % 9 1-23 2 daha yüksektir.
Yapıya Entegre Fotovoltaik Sistem İle Elektrik Üretilerek İklimlendirilen Sera Tasarımları
(2021) Nurdan Yildirim; HASAN HÜSEYIN OZTÜRK; Bekir CANSEVDİ; Kaan Kucukerdem; Cansevdi, Bekir; Yildirim, Nurdan; Oztürk, Hasan Hüseyın; Kucukerdem, Kaan
Bu çalışmada yapıya entegre fotovoltaik sistem (YEFS) ile kendi enerjisini üreterekiklimlendirilen sera yapılarının tasarım özellikleri incelenmiştir. Antalya yöresinde tasarımlanacak olan ve YEFS ile iklimlendirilecek olan bir cam sera için ısıtma ve soğutma yükleri değerlendirilmiştir. Bu amaçla cam seranın ısıtılma ve soğutulması amacıyla Tr=18 °C ve Tr=28 °C referans sıcaklıklar için Isıtma/Soğutma-Derece-Saat/Gün(HDH HDD ve CDH CDD) değerleri belirlenmiştir. Serada HDH değeri, en yüksekOcak ayında 6136 3 °C-saat en düşük Eylül ayında 1 1 °C-saat ve yıllık toplam 25053 5°C-saat olarak belirlenmiştir. Bununla birlikte HDD değeri en yüksek Ocak ayında255 7 °C-gün en düşük Haziran ayında 1 1 °C-gün ve yıllık toplam 1043 9 °C-gün olarakhesaplanmıştır. Serada soğutma uygulanacak olan yaz ayları için CDH değeri en yüksek Temmuz ayında 1985 5 °C-saat en düşük Ekim ayında 71 7 °C-saat ve yıllık toplam5148 7 °C-saat olarak belirlenmiştir. Bununla birlikte CDD değeri en yüksek Temmuzayında 82 7 °C-gün en düşük Ekim ayında 3 °C-gün ve yıllık toplam 214 5 °C-gün olarakhesaplanmıştır. Ortalama ısıtma yükü en yüksek Ocak ayında 356 2 kW en düşük Mayısayında 24 kW ve yıllık ortalama 147 46 kW olarak belirlenmiştir. Ortalama soğutma yüküen yüksek Temmuz ayında 251 kW en düşük Ekim ayında 27 2 kW ve yıllık ortalama138 52 kW olarak hesaplanmıştır. YEFS seralar için özgün bir tasarımla etkin alankullanımı sağlayacak altında gıda üzerinde ise enerji üreterek ülke ekonomisi için birkatma değer sağlayacaktır. Çok geniş yüzey alanına sahip olan tarımsal yapıların çatılarının enerji üretimi amacıyla kullanılması dağınık güç üretim sistemlerinin kullanılmasını yaygınlaştıracaktır.