DSpace Arşivi :: by Yazar "Hepbasli A." değerine göre listeleniyor

Yazar "Hepbasli A." seçeneğine göre listele

Listeleniyor 1 - 20 / 51

Assessment of the energy utilization efficiency in the Turkish transportation sector between 2000 and 2020 using energy and exergy analysis method
(2006) Utlu Z.; Hepbasli A.
Energy and exergy utilization efficiencies in the Turkish transportation sector over the period from 2000 to 2020 are evaluated in this study. A comparison of the overall energy and exergy efficiencies of the Turkish transportation sector with the other countries is also presented. Energy and exergy analyses are performed for four transport modes, namely roadway, railway, airway and seaway, while they are based on the actual data for 2000 and projected data for 2020. Roadway appears to be the most efficient mode when compared with railway, air and seaway. It is projected that about 15% of total energy resources will be used in this sector during 2020. The energy utilization efficiencies for the Turkish transportation sector range from 23.71% in 2000 to 28.75% in 2020, while the exergy utilization efficiencies vary from 23.65% to 28.85% in the same years, respectively. Exergetic improvement potential for this sector is estimated to be 700 PJ in 2020, with an average increase rate of 4.5% annually between 2000 and 2020. Road transport and oil-fuelled combustion engines offer the principal scope for exergetic improvement in the coming decades. It may be concluded that the methodology used in this study is practical and useful for analyzing sectoral energy and exergy utilization to determine how efficiently energy and exergy are used in the sector studied. It is also expected that this study will be helpful in developing highly applicable and productive planning for energy policies. © 2004 Elsevier Ltd. All rights reserved.
Assessment of the Turkish utility sector through energy and exergy analyses
(2007) Utlu Z.; Hepbasli A.
The present study deals with evaluating the utility sector in terms of energetic and exergetic aspects. In this regard, energy and exergy utilization efficiencies in the Turkish utility sector over a wide range of period from 1990 to 2004 are assessed in this study. Energy and exergy analyses are performed for eight power plant modes, while they are based on the actual data over the period studied. Sectoral energy and exergy analyses are conducted to study the variations of energy and exergy efficiencies for each power plants throughout the years, and overall energy and exergy efficiencies are compared for these power plants. The energy utilization efficiencies for the overall Turkish utility sector range from 32.64% to 45.69%, while the exergy utilization efficiencies vary from 32.20% to 46.81% in the analyzed years. Exergetic improvement potential for this sector are also determined to be 332 PJ in 2004. It may be concluded that the methodology used in this study is practical and useful for analyzing sectoral and subsectoral energy and exergy utilization to determine how efficient energy and exergy are used in the sector studied. It is also expected that the results of this study will be helpful in developing highly applicable and productive planning for energy policies. © 2007 Elsevier Ltd. All rights reserved.
Assessment of wind characteristics for energy generation
(2004) Ulgen K.; Genc A.; Hepbasli A.; Oturanc G.
Wind technology in Turkey has gained considerable maturity over the last 5 yr, and wind energy projects are becoming commercially attractive in the country. In practice, it is essential to describe the variation of wind speeds for optimizing the design of the systems resulting in less energy generating costs. The wind variation for a typical site is usually described using the Weibull distribution. The two Weibull parameters of the wind speed distribution function, the shape parameter k (dimensionless) and the scale parameter c (m/sec), were computed from the wind speed data for Aksehir in Konya, in Central Anatolia in Turkey. The average wind speeds for the site ranged between 1 and 2 m/sec for most times the wind blows, while the maximum wind speed recorded was 17 m/sec. The yearly values of k and c at this site varied between 1.756-2.076, and 2.596-3.444, respectively. Rayleigh distribution gave a better agreement with the actual data than that of Weibull distribution. The results would give useful insights to engineers and scientists dealing with wind energy.
Avoidable and unavoidable exergy destructions of a fluidized bed coal combustor and a heat recovery steam generator
(Elsevier Ltd, 2015) Callak M.; Balkan F.; Hepbasli A.
Abstract Advanced exergy analysis was performed using the actual operational data taken from a fluidized bed coal combustor (FBCC) and a heat recovery steam generator (HRSG) in a textile plant located at TorbalI, Izmir. First, the conventional exergy analysis of the units was carried out. The exergetic efficiencies of the units were found to be 44.2% and 46.2%, respectively. Advanced exergy analysis was then performed by splitting the exergy destructions of the units into avoidable and unavoidable parts. The avoidable exergy destruction rates of the FBCC and the HRSG were determined to be 2999 kW and 760 kW according to the measurements. Correspondingly, the exergy efficiencies were modified to 53.1% and 48.1%, respectively. © 2015 Elsevier Ltd. All rights reserved.
A comparative study on exergetic performance assessment for drying of broccoli florets in three different drying systems
(2010) Icier F.; Colak N.; Erbay Z.; Kuzgunkaya E.H.; Hepbasli A.
This article deals with the exergy analysis and evaluation of broccoli in three different drying systems. The effects of drying air temperature on the exergy destruction, exergy efficiency, and exergetic improvement potential of the drying process were investigated. The exergy destruction rate for the drying chamber increased with the rise in the drying air temperature at 1.5 m/s, both in the tray and the heat pump dryer. The highest exergy efficiency value was obtained as 90.86% in the fluid bed dryer in comparison to the other two drying systems and the improvement potential rate was the highest in the heat pump dryer during drying of broccoli at the drying air temperature of 45°C and the drying air velocity of 1.0 m/s. © 2010 Taylor & Francis Group, LLC.
Comparison of Turkey's sectoral energy utilization efficiencies between 1990 and 2000, part 1: Utility and industrial sectors
(2004) Utlu Z.; Hepbasli A.
Turkey's demand for energy has been rapidly increasing as a result of factors like industrialization, urbanization and rapid population growth. In meeting the increased demand, the efficient utilization of energy in all Turkish sectors plays an essential role. The present study, consisting of two parts, analyzes sectoral energy utilization in Turkey over an 11-yr period from 1990 to 2000. In order to calculate sectoral energy utilization efficiency values, Turkey is subgrouped into four main sectors, namely, utility, industrial, transportation, and commercial-residential. Part I of this study investigates the first two subsectors, while the remainder is treated in Part 2, where all the sectors considered are discussed in detail. Turkey's overall first law efficiencies for the entire utility sector are found to vary from 30.10 to 35.21%, while those for the whole industrial sector are obtained to range from 61.20 to 68.97%, with average values of 31.82 and 63.57%, respectively. It is anticipated that the present study will provide useful insights into the Turkish energy use and the planned studies towards increasing energy efficiencies in the sectors studied.
Comparison of Turkey's sectoral energy utilization efficiencies between 1990 and 2000, part 2: Residential-commercial and transportation sectors
(2004) Hepbasli A.; Utlu Z.
Turkey's energy consumption and imports are experiencing rapid growth, as is the Turkish economy. Hence, rational and efficient utilization of energy resources is very essential. Therefore, knowledge of the Turkish energy utilization efficiencies is of paramount importance in establishing the energy policy of the country. The present study, consisting of two parts, analyzes sectoral energy utilization in Turkey over an 11-yr period from 1990 to 2000. In order to calculate sectoral energy utilization efficiency values, Turkey is subgrouped into four main sectors, namely, utility, industrial, residential-commercial and transportation. Part 1 of this study investigated the first two subsectors, while the rest is studied here. Turkey's overall first law efficiencies for the entire residential-commercial sector are found to vary from 54.19 to 57.76%, while those for the whole transportation sector are obtained to range from 20.15 to 23.88%, with average values of 56.21 and 21.70% for 11 years, respectively. Total energy utilization efficiencies are calculated to vary from 43.24 to 45.81%, with an average value of 44.66% for the same years. It is anticipated that the results obtained can assist national government for future planning studies. However, a good energy management system should be installed throughout the country for the optimum use of these resources.
Development of geothermal energy utilization in Turkey: A review
(2004) Hepbasli A.; Ozgener L.
The development of geothermal energy (GE) utilization in Turkey with viewing its historical development and opportunities is discussed. GE is used for electric power generation and direct power utilization in Turkey, which is among the first five countries in the world in geothermal direct use applications. Direct use of geothermal resources has expanded from space heating of single buildings to district heating, greenhouse heating, industrial usage, and physical treatment facilities. It is expected that GE development will increase in the country if the geothermal law becomes effective.
Energetic and exergetic analysis of building cogeneration systems
(2009) Yoru Y.; Karakoc T.H.; Hepbasli A.; Turgut E.T.
This study deals with types of micro cogeneration (or micro combined heat and power, MCHP) systems and reviews energetic and exergetic analysis of MCHP systems, which are also called building cogeneration systems. These are classified as micro and macro cogeneration systems and figured within subgroups. Previously conducted studies on exergy and energy analyses of internal combustion engines (micro turbines), external combustion engines (Ericsson engines), fuel cells (solid oxide fuel cells) and thermophotovoltaic systems are treated in this paper. The main objectives of this study are to classify MCHP systems used in building cogeneration systems, to introduce types of MCHP systems and to better define micro cogeneration systems in the light of previously conducted studies. In this regard, energetic and exergetic efficiencies of various MCHP systems are graphically obtained. Under grouping presented MCHP systems, internal combustion engines based MCHP systems are defined to be the best choice with energetic and exergetic efficiency values of 86.0% and 40.31%, respectively. Micro gas turbines and Ericson engine based micro cogeneration systems are also obtained as valuable systems with the energetic values of 75.99% and 65.97% and exergetic values of 35.8% and 38.5%, respectively. However, in this building cogeneration group, energetic and exergetic efficiencies of the thermophotovoltaic systems have 65.0% and 15.0%, respectively. It may be concluded that system choice depends on the type of the system, energy flow of the system, system parts and developments, while building, system capacity, comfort and maintenance are the other factors to be considered. Copyright © 2008 by ASME.
Energetic and exergetic assessment of the industrial sector at varying dead (reference) state temperatures: A review with an illustrative example
(2008) Utlu Z.; Hepbasli A.
One of the keystones for obtaining sustainable development is the use of exergy analysis. The present study deals with the assessment of energy and exergy utilization efficiencies in the industrial sector. Attempts have also been made at understanding the effect of varying dead (reference) state temperatures on these efficiencies. In this context, the methodology used is presented first. It is then applied to Turkey, which is selected as an application country, based on the actual data for 2003. Finally, the results obtained are evaluated and discussed. The Turkish industrial sector (TIS) considered includes iron-steel, chemical-petrochemical, petrochemical-feedstock, cement, fertilizer, sugar, non-iron metal industry and others such as textile and yarn, glass and glassware production, paper, beverage and cigarette, food, wood, leather, etc. All activities in this sector are produced by using electricity and heat energy. Parametric expressions of energy and exergy efficiencies are developed as a function of the dead-state temperature. The energy and exergy efficiency values for the TIS are found to vary from 51.95% to 80.82% and 25.30% to 29.50% at the dead-state temperature variations between 0 and 25 °C, respectively. It is expected that this study will be very beneficial in developing energy policies of countries from the exergy management point of view. © 2007 Elsevier Ltd. All rights reserved.
Energy and exergy analyses of combined thermochemical and sensible thermal energy storage systems for building heating applications
(2012) Caliskan H.; Dincer I.; Hepbasli A.
In this study, energy and exergy analyses are conducted to model novel integrated systems, combining thermochemical and sensible thermal energy storage (TES) systems, for building heating applications, and their performance is assessed for three various dead state temperatures of 8 °C, 9 °C and 10 °C. The present overall system consists of a floor heating system (FHS), System-A and System-B. The FHS is accommodated in the building floor and supported with a floor heating unit (FHU), a pump and an energy receiver unit (ERU). The System-A includes a thermochemical TES (TTES), a solar collector, a heat exchanger, a pump and a hot well of aquifer TES (ATES). Also, the components of System-B are a cold well of ATES and a HP unit. The system is designed to have the aquifer and thermochemical TES systems supplying the necessary heating for buildings. The FHS in the building can be operated with System-A (the TTES and hot well of ATES) and the System-B (the cold well of ATES and HP) to provide the same heating load in a more efficient manner. The maximum exergy efficiency is calculated for the hot well of ATES to be 88.78% at 8 °C dead state temperature, while the minimum one is obtained for the charging process of TTES as 21.69% among the TES systems considered. If all the system components are considered, the FHU has the highest exergy efficiency as 98.08% at a dead state temperature of 8 °C. Among the TES systems, the exergy efficiencies for the aquifer TES (ranging between 56.38% and 88.78%) are generally higher than the corresponding thermochemical TES efficiencies (ranging from 46.71% to 84.80%). Thus, the results show that the aquifer TES system is exergetically more efficient than the thermochemical TES system. © 2011 Elsevier B.V. All rights reserved.
Energy and exergy efficiencies of a real CHP integrated ceramic factory
(Brazilian Society of Mechanical Sciences and Engineering, 2009) Yoru Y.; Karakoc T.H.; Hepbasli A.
This study investigates the energy and exergy efficiency results of a cogeneration system in a ceramic factory based on the results of energy and exergy analysis. The considered ceramic factory located in Izmir, Turkey has 3 gas turbines, 6 spray dryers and 2 heat exchangers. Gas turbines produce electricity by using natural gas as a fuel. All spray dryers are fueled by both natural gas (NG) and exhaust gases of gas turbines. Exhaust gases are also utilized in the heat exchangers. Although all spray dryers are fueled by natural gas during the investigated month, June 2007, only 2 spray dryers were operated by both NG and exhaust gases of gas turbines, other spray dryers were able to oparete by only exhaust gases. Based on the 720 hour data pattern (including 43200 data), the mean energetic and exergetic efficiency values of the cogeneration system are found to be 82.3% and 34.7%, respectively.It was obtained that 53.67% of energy was discharged to the atmosphere through the exhausts of spray dryers and heat exchanger. Total electricity production was found to be 28.6% of total energy supplied. This means that 71.4% of total energy supplied would be thrown if gas turbines could be used only for generating electricity during the period studied. © 2009 by ABCM.
Energy conservation studies on residential heating systems: An application for Izmir, Turkey
(2001) Hepbasli A.
Energy conservation through improvement of the efficiencies of end use devices such as boilers and stoves used for space heating is one of the most effective ways to provide immediate relief for the energy problem in the residential sector of Turkey. For this reason, during the 1995-96 winter period, the campaign 'Saving the Environment Begins at Home' was launched by the branch office of the Chamber of Mechanical Engineers in Izmir (CMEI) and the Metropolitan Municipality of Izmir (MMI). The study was carried out by a team consisting of 18 persons from both organizations to improve the combustion systems of boilers and stoves for space heating. In 2,600 buildings, 3,178 boilers for space heating were inspected and also their gas components measured by ten mechanical engineers using flue gas analysers. During the study implementation, special computer software was used. The data collected by expert controllers were evaluated through computers. Missing and faulty points were reported to apartment managers in charge of building services and they were asked to fulfil the requirements. In addition to these, courses for improving boiler operators were given to 1,553 operators in Izmir. 1,838 houses heated by stoves were inspected and technical rules for efficient use of stoves were explained to users on site. Furthermore, during the 1996-97 winter period, a total of 303 randomly selected boilers were inspected, and also their flue gas measurements were carried out by the same team. In this paper, the application steps of the study performed, for the first time, on a large scale for Izmir in Turkey, are explained and results obtained are presented.
Energy demand estimation based on two-different genetic algorithm approaches
(2004) Canyurt O.E.; Ceylan H.; Ozturk H.K.; Hepbasli A.
Energy modeling is a subject of widespread current interest among engineers and scientists concerned with problems of energy production and consumption. Energy planning is not possible without a reasonable knowledge of past and present energy consumption and likely future demands. In this study, two forms of the energy demand equations are developed in order to improve energy demand estimation efficiency for future projections based on the genetic algorithm (GA) notion. The genetic algorithm energy demand (GAEDM) model is used to estimate Turkey's future energy demand based on gross domestic product, population, import, and export figures. Both equations proposed here are non-linear, of which one is exponential and the other is quadratic. The quadratic form of the GAEDM model provided a slightly better fit solution to the observed data and can be used with a high correlation coefficient for Turkey's future energy projections. It is expected that this study will be helpful in developing highly applicable and productive planning for energy policies.
Energy utilization needs in Turkish mixed feed industry
(WFL Publisher Ltd., 2012) Boyar S.; Hepbasli A.; Akdeniz R.C.
The first feed factory in Turkey was put into operation by a private company in 1955. Since then, the mixed feed sector has continued to grow rapidly. Today, feed manufacturing industry has become one of the most important agricultural sectors in Turkey, with 712 factories at capacities varying from 5 to 100 ton/h. In the literature, there are very limited studies on the energy use of Turkey's feed manufacturing industry and the extruder pellet line having popularity in recent years in the mixed feed factories. The main objective in doing the present studywas to investigate the energy use of the Turkish mixed feed sector and the necessity of energy management system in the light of the studies performed in the mixed feed factory located in Izmir, Turkey. Taking into account Turkey's total mixed feed production of 11,501,123 tons/yr determined by the Turkish Feed Manufacturers' Association and assuming an average value of the factory studied with 0.005 tons of oil equivalent (toe) per tons of feed production, the total energy consumption of the mixed factories in Turkey is estimated to be about 57,506 toe annually. It was well determined that an energy management system should be built not only in the feed factory studied but also in all factories in Turkey.
Environmental impacts from the solar energy systems
(2009) Gunerhan H.; Hepbasli A.; Giresunlu U.
Solar energy technologies offer a clean, renewable, and domestic energy source, and are essential components of a sustainable energy future. Solar energy systems (i.e., photovoltaics, solar thermal) provide significant environmental benefits in comparison to the conventional energy sources. It is known that these systems have some minor negative impacts on the environment during their production and operation. This study presents an overview of some positive impacts of the solar energy systems and negative impacts covered by environmental impact assessment.
Exergetic analysis and assessment of industrial furnaces
(2010) Caliskan H.; Hepbasli A.
This study presents exergy analysis of a natural gas-fired radiant tube-heating furnace. In the analysis, actual data over a test period of 3 h were used. Exergy efficiencies, destructions, losses, and entropy generation of the furnace were determined. For an average furnace temperature of 666.6°C, average exergy efficiency value was calculated to be 9.6%. The exergy destruction rate was obtained to be 5.34 kW while exergy rates of the flue gases, exergy losses, and exergy steel were 12.53 kW, 44.28 kW, and 6.6 kW, respectively. On the other hand, the exergy rate of the product (steel) was found to be between 4.61 kW and 9.88 kW over the 15 min test periods, and it reached a maximum rate at the end of the second hour. Copyright © 2010 by ASME.
Exergetic analysis of textile convective drying with stenters by subsystem models: Part 1-exergetic modeling and evaluation
(2010) Cay A.; Tarakçioglu I.; Hepbasli A.
This study, which consists of two parts, deals with the exergy analyses and assessments of the direct gas-heated (DGHS) and hot oil-heated (HOHS) stenters. In the first part, a new model for the exergetic analysis of the convective drying of textiles at stenters was presented and the variations of exergetic parameters for each chamber of the stenter were examined. It was emphasized that the exergy efficiency of the last chambers decreased drastically due to the lower evaporation rate of the falling rate period of drying. Additionally, the subsystems of the chambers were analyzed. For this purpose, the detailed control volume models were conducted for the stenters. It was determined that the combustion chamber and mixing unit of the DGHS and the hot oil boiler of the HOHS led to higher exergy destruction rates. Furthermore, total exergy destruction and loss rates of the HOHS were higher compared to those with the DGHS. The exergy efficiency values of each chamber of the DGHS were calculated to be 10.9, 14.9, 15.3, 12.2, 9.8, and 5.3%, respectively. © 2010 Taylor & Francis Group, LLC.
Exergetic analysis of textile convective drying with stenters by subsystem models: Part 2-parametric study on exergy analysis
(2010) Cay A.; Tarakçioglu I.; Hepbasli A.
In this study, the effects of exhaust air humidity ratio, the residual moisture content of fabric outlet, and the temperature of the drying air on the exergy destruction and efficiency of stenters were investigated. The exergy efficiencies of the direct gas heated stenter (DGHS) and hot oil heated stenter (HOHS) were calculated to be varying from 8.5 to 17.5% and from 6.8 to 14.0%, depending on the exhaust air humidity ratio, respectively. The increase in the drying air temperature led to an increase in the exergy efficiency, especially in the constant rate and second rate period of the drying. On the other hand, the application of the gradual temperature method caused the highest total exergy efficiency due to the highest drying rates in the first chambers where considerably high air temperatures were set. Overdrying resulted in the higher irreversibility due to the increase in the fuel consumption in the falling rate period of drying. Thus, the exergy efficiency decreased drastically. © 2010 Taylor & Francis Group, LLC.
Exergetic assessment of direct-expansion solar-assisted heat pump systems: Review and modeling
(2008) Kara O.; Ulgen K.; Hepbasli A.
Although the idea of using a solar collector as the evaporator in the traditional heat pump cycle was first proposed in the year 1955, studies on the subject began in the late 70s. One of the keystones for obtaining sustainable development is also the use of exergy analysis. In this regard, the main objectives in doing the present study are twofold, namely (i) to review studies on direct-expansion solar-assisted heat pump systems (DX-SAHPs) and (ii) to present a mathematical model along with an illustrative example, which is used for heating an office space in Solar Energy Institute of Ege University, Izmir, Turkey, by floor heating with a DX-SAHP system. The system uses a 4 m2 bare flat-plate collector as the evaporator, while the working fluid is chosen to be R-22. Water is heated by the heat pump and heat is delivered to the office space by floor heating. Exergy equations for the system are derived, while exergy calculations are made. The exergy efficiency values for the individual components of the DX-SAHP system are found to range from 10.74% to 88.87%. It is expected that this study will be very beneficial to everyone involved or interested in the exergetic design, analysis and performance assessment of DX-SAHPs. © 2007 Elsevier Ltd. All rights reserved.

Yazar "Hepbasli A." seçeneğine göre listele

Sayfa Başına Sonuç

Sıralama seçenekleri