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Adyabatik Soğutma Sistemlerinde Nozul Yapısının Soğutma Performansına Etkilerinin Teorik ve Deneysel İncelenmesi
(2016) Gürel, Ali Etem; Yıldız, Abdulaziz; Deniz, Emrah
Küresel ısınma, yaşam standartlarındaki artış vb. etkenler soğutma ve iklimlendirme sistemlerine olan talebi her geçen gün artırmaktadır. Bu sistemlerin performanslarının artırılmasına yönelik farklı yöntemler kullanılmaktadır. Bu yöntemlerden biri de soğutma sistemlerinde evaporatif kondenser kullanımıdır. Bu çalışmada, soğutma sistemlerinde evaporatif kondenser kullanımının sistem performansına olan etkileri deneysel olarak analiz edilmiştir. Deneysel sistemin kondenser ünitesi adyabatik nemlendirme yöntemi ile soğutulmuştur. Adyabatik nemlendirme işlemi 0.2, 0.3 ve 0.4 mm çaplarında nozullar kullanılarak gerçekleştirilmiştir. Sistem, hava soğutmalı kondenser kullanımı ve farklı nozul çapları için termodinamik olarak analiz edilmiş, sistemin soğutma performansları karşılaştırılmıştır. Elde edilen veriler evaporatif kondenser kullanımıyla, kompresör işinde %8.48 azalma, soğutma sistemi COP değerinde %32.92 ve tüm sistemin COP değerinde ise, %18.43 artış olduğunu göstermiştir
The artificial neural network model to estimate the photovoltaic modul efficiency for all regions of the Turkey
(Elsevier Science Sa, 2014) Ceylan, İlhan; Gedik, Engin; Erkaymaz, Okan; Gürel, Ali Etem
Artificial neural network (ANN) is a useful tool that using estimates behavior of the most of engineering applications. In the present study, ANN model has been used to estimate the temperature, efficiency and power of the Photovoltaic module according to outlet air temperature and solar radiation. An experimental system consisted photovoltaic module, heating and cooling sub systems, proportional integral derivative (PID) control unit was designed and built. Tests were realized at the outdoors for the constant ambient air temperatures of photovoltaic module. To preserve ambient air temperature at the determined constant values as 10, 20, 30 and 40 degrees C, cooling and heating subsystems which connected PID control unit were used in the test apparatus. Ambient air temperature, solar radiation, back surface of the photovoltaic module temperature was measured in the experiments. Obtained data were used to estimate the photovoltaic module temperature, efficiency and power with using ANN approach for all 7 region of the Turkey. The study dealing with this paper not only will beneficial for the limited region but also in all region of Turkey which will be thought established of photovoltaic panels by the manufacturer, researchers and etc. (C) 2014 Elsevier B.V. All rights reserved.
Assessment of a novel defrost method for PV/T system assisted sustainable refrigeration system
(Pergamon-Elsevier Science Ltd, 2022) Karaağaç, Mehmet Onur; Ergun, Alper; Gürel, Ali Etem; Ceylan, İlhan; Yıldız, Gökhan
Energy consumption has continuously increased depending on the rapidly growing human population, enlarging economies, advancing technologies, and improving living standards. A noteworthy share of the energy consumption has been arising from the buildings all across the world. Refrigeration, heating, and air conditioning systems have accounted for a significant portion of the energy consumption in the buildings. Therefore, it is possible to both reduce energy consumption, and mitigate the carbon footprints by efficiently designing, constructing, and operating these systems. In this framework, the present research has centered on the refrigeration systems, and aimed to develop a novel defrost method for photovoltaic thermal (PV/T) assisted sustainable refrigeration systems. In the conventional refrigeration systems, the frost process occurs when air condenses on the evaporator surface as a result of the evaporator surface temperature being below the freezing point of water or the dew point temperature of the air in the conditioned space. Differently in the present work, PV/T system is used to prevent the frost process in the refrigeration system, unlike the conventional systems. Accordingly, the efficiency loss caused by the temperature increment will be prevented by cooling the PV module, and it is aimed to be more efficient by reducing the daily power consumption as an alternative solution method to the frost that occurred on the evaporator in refrigeration systems. On this purpose, a novel evaporator design is developed, and used for defrosting in this study. Accordingly, this novel design includes a refrigerant line inside the evaporator and a hot water line from the PV/T in this design. In the results, it is noticed that the system designed for winter conditions could be used for defrosting. While an average of 605 W for heat energy was used for each defrost process, the average defrost duration was recorded to be approximately 4 min. While the average electrical efficiency of the PV module was found to be 13.6%, the average total efficiency was found to be 38%. Besides, Average PV module surface temperature was determined as 36.4 degrees C, average water storage tank temperature was determined as 26.4 degrees C. In addition, the coefficient of performance (COP) of the refrigeration system is calculated to be 4.18. COP increased by an average of 9% during defrosting. Furthermore, the environmental economic cost was calculated to be 14.6 $/h. In the conclusion, it is proven that the novel defrost method proposed in the present work can be used for refrigeration systems, and contribute to both the reduction of energy consumption and mitigation of carbon emissions arising from the buildings.
Assessment of a solar-assisted infrared timber drying system
(Wiley, 2017) Aktaş, Mustafa; Ceylan, İlhan; Ergün, Alper; Gürel, Ali Etem; Atar, Musa
This study investigates convective-infrared drying characteristics of timber. The biggest disadvantage of infrared heating systems is the uncontrollable rise of the surface temperature up to extremely high values, which causes damage to the product. In this study, the power of an infrared system was controlled and adjusted according to the surface temperature of the product. In doing so, the surface temperature of the infrared heater was prevented from reaching up to values that could damage the product. During the analysis, the surface temperature of the timbers was kept at an average of 65 degrees C, while the bottom temperature was kept at an average of 45 degrees C. The air collector used in the system was found to be 50% efficient. At the end of a 13-h drying period, the moisture content of pine timbers could be reduced from 1.42 to 0.0948 g water/g dry matter. During the system analysis, parameters such as moisture content, mass diffusion coefficient, and useful energy rate were taken into consideration. (c) 2017 American Institute of Chemical Engineers Environ Prog, 36: 1875-1881, 2017
Cooling of a photovoltaic module with temperature controlled solar collector
(Elsevier Science Sa, 2014) Ceylan, İlhan; Gürel, Ali Etem; Demircan, Hüsamettin; Aksu, Bahri
The efficiency of photovoltaic modules decreases with heating, so there has been an increase with regard to the solution of the problem. Photovoltaic module converts the incoming solar radiation into heat and electric energy. Due to this heating feature of photovoltaic modules, it is likely to produce heat energy from PV modules as well. Such systems are called as both a photovoltaic and thermal systems in the literature. A lot of experimental studies were done by special processing on the PV module. Since the studies require special processing on the module, they remain as laboratory work only. In this study, different PV/T systems were experimentally analyzed for the cooling photovoltaic modules. A simple pipe was placed on PV module as a spiral heat exchanger in order to provide active cooling. Also, the system can easily be applied to large-scale systems. As a result of experimental research, the module efficiencies with cooling were calculated as 13%, and the module efficiencies without cooling were about 10%. As the set temperature increased, module temperature can be increased or decreased. The module temperature was changed according to solar radiation and set temperature. As the solar radiation increased the module temperature decreased in this experimental system. The solar radiation has nothing to do with set temperature for this system. (C) 2014 Elsevier B.V. All rights reserved.
Current practices, potentials, challenges, future opportunities, environmental and economic assumptions for Türkiye's clean and sustainable energy policy: A comprehensive assessment
(Elsevier Ltd, 2023) Ağbulut, Ümit; Yıldız, Gökhan; Bakır, H.; Polat, Fikret; Biçen, Yunus; Ergün, Adem; Gürel, Ali Etem
In today's world, most countries including Türkiye have met their electricity demand at a dominant rate by burning fossil-based fuels in thermal power plants. However, fossil-fuel reserves have been rapidly depleted, resulting in high volatility in these fuels’ markets, as well as alarming environmental, and economic problems for the governments. In recent years, many governments have started to face these problems and have rapidly transitioned to renewable and alternative carbon-free energy sources in their electricity production variety. However, these belated steps have failed to mitigate the increment in global greenhouse gas emissions against the rapid growth of population and energy demand. In recent years, Türkiye has put a noteworthy challenge to mitigate its dominant use of fossil fuels, reducing its energy dependence, sustaining its economic development, and mitigating the carbon footprint. From this point of view, it is witnessed that many power plants have been established, many of them are currently under construction, especially to produce more electricity in a sustainable way. Accordingly, the present study aims to comprehensively discuss Türkiye's energy production policy, energy potential and reserves, challenges, future opportunities, and the impacts of the energy sector on the economic and environmental issues for the country. In this framework, it is well-noticed that the country's future energy production policy has been reasonably changed in order to achieve positive economic and environmental outcomes in the medium and long term. © 2023 Elsevier Ltd
Determination of optimum insulation thickness, energy savings, and environmental impact for different climatic regions of Turkey
(Wiley-Blackwell, 2013) Çay, Yusuf; Gürel, Ali Etem
In this study, optimum insulation thicknesses, energy savings, and payback periods have been investigated based on life-cycle cost analysis for an external wall in four various cities from four climate zones of Turkey. Also, the study have been analyzed the effect of insulation thickness on release of CO2 and SO2 emissions. The results show that insulation thicknesses vary between 0.045 and 0.195 m, life-cycle energy savings between 13.26 and 248.9 $/m2, payback periods between 1.19 and 1.97 years when used extruded polystyrene as insulation material. When the optimum insulation thickness was used, emissions were reduced by 6292% depending on the city, fuel type, and insulation material. (c) 2012 American Institute of Chemical Engineers Environ Prog, 32: 365-372, 2013
Determination of the heat transfer coefficient of PV panels
(Pergamon-Elsevier Science Ltd, 2019) Ceylan, İlhan; Yılmaz, Sezayi; İnanç, Özgür; Ergün, Alper; Gürel, Ali Etem; Acar, Bahadır; Aksu, Ali İlker
In this study, the efficiency of the rear-panel air velocity in cooling was investigated based on the temperature and solar radiation in the environment where the panels are located. During the cooling of the panels, the rear-panel temperature decreases, and accordingly, the open-circuit voltage of the panels increases. At present, the most important losses in panels are due to the increase in panel temperature depending on the solar radiation and outdoor air temperature. In this study, the rear-panel temperature changes were observed at 0-5 m/s air velocities and 10-40 degrees C. The calculations reveal that in winter weather conditions, the temperature of the panels did not increase at a level that would require cooling. This study investigated the heat transfer from the surface depending on the outdoor air temperature of the rear-panel air velocity and the changing rear-panel temperature. The effect of different outdoor air temperatures on the rear-panel heat transfer is minimal. When the air velocity was 5 m/s and the outdoor air temperature was 10-40 degrees C, the heat transfer in the Poly Crystal Solar panel was calculated as 11.6 W/m(2)K. (C) 2019 Elsevier Ltd. All rights reserved.
Economical and environmental effects of thermal insulation thickness in four different climatic regions of Turkey
(2011) Gürel, Ali Etem; Daşdemir, Ali
In the countries which supply big amount of their energy needs by import like Turkey using the energy economically is important. Thermal insulation technologies in buildings are the main method for using energy economically. However, choosing the thickness of the insulation material redundant causes high insulation costs. For this reason, an optimum point provides the highest gain in insulation applications is the subject. In this study, for Antalya, Manisa, Ankara and Sivas in the four climate regions in Turkey and optimum insulation thickness, energy saving and payback period in using two different insulation materials (extruded polystrene and rock wool) and five different kinds of fuel (coal, natural gas, fuel-oil, LPG, electricity) were calculated. In addition to this, an analysis of insulation thickness of the harmful emissions of the gas like CO2 and SO2 was made. The results of the study showed that the optimum insulation thickness vary between 0.016 and 0.145 m, energy savings vary between 1.79 $/m2 and 103.44 $/m2 and the payback period vary between 1.268 years and 6.022 years depending on the city and type of fuel. Environmental impacts of high used coal fuels were observed during the combustion, and emissions of CO2 and SO2 revealed decreases between 67%-75%.
Energetic, exergetic, and thermoeconomic analyses of different nanoparticles-added lubricants in a heat pump water heater
(Elsevier, 2022) Yıldız, Gökhan; Ağbulut, Ümit; Gürel, Ali Etem; Ergün, Alper; Afzal, Asif; Saleel, C. Ahamed
The heat pumps are frequently used in domestic and industrial applications for hot water supply. The present paper aims to thermodynamically investigate the impacts of the nanoparticle-addition into the lubricants on the energetic, exergetic, and thermoeconomic aspects of a heat pump. In the experiments, air to the water heat pump is separately charged with various metal oxide-based nanoparticles (Al2O3, CuO, and TiO2)-added oils at a constant mass fraction of 0.5%. Polyolester (POE) and 134a are used as a lubricant, and refrigerant, respectively. The mass flow rates of the water passed through the condenser are varied from 10 to 25 g/s with an interval of 5 g/s. In the results, it is observed that the thermal conductivity value noteworthy increases with the presence of nanoparticles in POE. The highest increment in thermal conductivity is found to be 39% for POE + CuO in comparison with that of pure POE. Furthermore, with nanoparticles addition, it is noticed that the COP value generally improves, and the highest improvement for COP value is noticed to be 8% for POE + TiO2 nanolubricant at the mass flow of 25 g/s. Furthermore, exergy efficiency enhances by 3.6%, 1.8%, and 4.5% for POE + Al2O3, POE + CuO, and POE + TiO2, respectively. The lowest heating cost is calculated to be 3.465 c/kWh at 20 g/s flow rate for POE + Al2O3. In conclusion, this paper clearly reports that usage of nanoparticles along with lubricants is presenting better energetic, exergetic, and thermoeconomic results rather than the usage of lubricant alone in the heat pumps.
Energy Analysis of a New Design of a Photovoltaic Cell-Assisted Solar Dryer
(Taylor & Francis Inc, 2013) Ceylan, İlhan; Kaya, Metin; Gürel, Ali Etem; Ergün, Alper
In this study, a new type of solar dryer was designed and manufactured. This new solar dryer is composed of a heat pipe collector, a drying chamber, a load cell, an air circulation fan, photovoltaic cells (PvC), batteries, and halogen lamps. In this experimental study, tomatoes were used to test the drying process. The drying air was heated by the heat pipe collector and forced through the tomatoes by a blower fan during the daytime. The photovoltaic cells, which were used to run the fan, were also used to charge the batteries during the day. These charged batteries were used for running the halogen lamps during the night, when the halogen lamps were used to heat the drying-air-assisted photovoltaic cells. During the drying period, the drying air temperature, relative humidity, air flow rates, solar radiation, and loss of mass were measured in the solar dryer. Then, the measured data were used for energy analysis.
Environmental and economic assessment of a low energy consumption household refrigerator
(Elsevier B.V., 2019) Gürel, Ali Etem; Ağbulut, Ümit; Ergün, Alper; Ceylan, İlhan
Energy consumption is the biggest obstacle in the economic growth of a country. In recent years, Turkey has imported around at the rate of three-quarters of its total energy demand. Upon the past 10-years running, Turkey paid nearly half a trillion dollars for its total energy bill. The big share of energy consumption has emerged from buildings. Therefore, energy savings have great importance, particularly in the buildings. A refrigerator is responsible for the most dominant electrical energy consumption rate with 32% in a house. Therefore, this paper proposes a novel household refrigerator design for reducing energy consumption. In the proposed design, the necessary air for the cooling process will be provided from outdoor ambient in appropriate weather condition. The compressor work will, thus, be decreased via this way, and contribute to a reduction in energy consumption. The results indicated that this system in 63 provinces can be effectively used between 1 and 4 months and help to reduce 36 million $ in Turkish electric energy bill with the use of only 1 year period. Additionally, a reduction of approximately 850,000 tons of CO2 annually in Turkey can be achieved by applying the proposed design in this study. Hereby, Turkey can contribute not only to be sustained economic growth but also to reduce harmful gas emissions arising from electricity generation methods in the country. © 2019 Karabuk University
Estimation of global solar radiation on horizontal surface using meteorological data
(Sila Science, 2012) Gürel, Ali Etem; Ergün, Alper
In the present study, the methods of Artificial Neural Networks (ANN) and Regression Analysis were used in estimating monthly average daily global solar radiation arriving on horizontal surface in Rize with the help of meteorological and geographic data like monthly average daily extraterrestrial radiation, monthly average daily hours of bright sunshine, day length, relative humidity, wind speed, temperature and declination angle. Mean bias error (MBE), root mean square error (RMSE) and t-statistic methods were used to evaluate performance of the estimation. It was seen at the end of the study that the equation obtained through multi-regression analysis method yielded better performance than that of obtained through ANN method.
Exergetic analysis of a new design photovoltaic and thermal (PV/T) System
(Wiley, 2015) Ceylan, İlhan; Gürel, Ali Etem
Photovoltaic (PV) module converts the incoming solar radiation into heat and electric energy. Due to this heating feature of photovoltaic modules, it is likely to produce heat energy from PV modules as well. Such systems are known as photovoltaic and thermal systems in the literature. In this study, a new design PV/T system was experimentally analyzed for cooling photovoltaic modules while heating water at the same time. PV/Tis a forced circulation system without pump. Therefore, these systems are different from those described in the literature. For all PV/T system, step-by-step exergy analysis has been performed according to obtained experimental results. PV module thermal exergy, solar collector thermal exergy, and PV module electrical exergy variations have been calculated for this exergy analysis. Overall, exergy efficiency was obtained as about 17% for 45 degrees C set temperature and 21% for 55 degrees C set temperature. (c) 2015 American Institute of Chemical Engineers Environ Prog, 34: 1249-1253, 2015
Exergetic assessment of a concentrated photovoltaic thermal (CPV/T) system
(Inderscience Enterprises Ltd, 2016) Gürel, Ali Etem
Photovoltaic module efficiency can be increased by concentrating the solar radiation that is captured. This approach, however, may increase cell temperature and decrease the efficiency of the module. Such conditions can be prevented by cooling down the photovoltaic modules. Currently, this operation is generally performed with water or air. To improve cooling, this study presents the design, manufacture and analysis of a concentrated photovoltaic thermal (CPV/T) system utilising paraffin wax, which is a novel method, to cool down photovoltaic cells and to store thermal energy. Exergy analysis was done for various system states of this system in which a concentrator was used and not used, and results were compared. Even with the use of a concentrator in the system, the average temperature of the photovoltaic cells was measured as 30 degrees C. The average electrical efficiency of photovoltaic cells in the system was calculated as 14.67%.
Exergetic, economic and environmental analysis of temperature controlled solar air heater system
(Elsevier Ltd, 2022) Gürel, Ali Etem; Yıldız, Gökhan; Ergün, Adem; Ceylan, İlhan
Solar energy systems are widely utilized to obtain environmentally friendly and sustainable electrical and thermal energy that able to be used in many applications. Temperature-controlled solar air heater (SAH) system with a zigzag finned plate and flat plate was designed, manufactured, and tested experimentally in this study. It was determined that the set temperature was 15% higher than the flat plate SAH outlet temperature. The most important cause for this increase, the air is exposed preheating in the first collector. As the heat transfer surface area raised thanks to the zigzag fins in the second collector, the temperature of the air increases even more. SAH system's energy efficiency was found to be 71.15% on average. SAH system's maximum exergy efficiency was determined as 3.7%. The SAH system's average exergy destruction is calculated to be 651.58 W on average. According to the enviroeconomic analysis of the system, hourly CO2 mitigation was found to be 1.04 kg CO2/h and the environmental cost was 1.508 ¢/h. The energy cost was calculated as 0.0834 $/kWh, while the exergoeconomic parameter was calculated as 0.1931 kWh/$. In addition, the energy payback period was determined as 1.35 years, while the exergy payback period was determined as 45.9 years. © 2021
Exergy, sustainability and performance analysis of ground source direct evaporative cooling system
(Elsevier, 2022) Yıldız, Gökhan; Ergun, Alper; Gürel, Ali Etem; Ceylan, İlhan; Ağbulut, Ümit; Eser, Servet; Afzal, Asif
A significant portion of global energy consumption is due to energy consumption in the buildings. Heating, cooling, and air conditioning systems have the largest share in this energy consumption. Evaporative cooling systems, which have the advantage of being economical, zero pollution, and easy maintenance are preferred to reduce energy consumption in buildings. These systems are used in many areas such as greenhouses, broiler houses, and warehouses. In this study, analyzes of exergy, sustainability, and cooling efficiency in four different situations of a ground source direct evaporative cooling system were made. The system was studied in four different cases. While the highest exergy efficiency was obtained in case 3 with 20.83%, the exergy efficiencies in other cases were obtained as 16.83%, 17.49%, and 18.36%, respectively. In addition, the highest specific exergy loss was determined as 100.51 J/kg in case 2, while it was calculated as 73.08 J/ kg, 80.23 J/kg, and 73.05 J/kg for the other cases, respectively. It is seen that the sustainability values are in parallel with the exergy efficiency when the evaporative cooling system is examined for four different cases. The sustainability values were determined as 1.20 for case 1, 1.21 for case 2, 1.26 for case 3, and 1.22 for case 4. It is determined that the exergy efficiency gives precise information about the usability and sustainability of the system when these situations are evaluated. The exergetic improvement potential (EIP) was determined as 0.061 for case 1, 0.082 for case 2, 0.063 for case 3, and 0.059 for case 4, respectively. Although the highest exergy efficiency is obtained in case 3, it has a higher recovery potential than case 1 and case 4. In addition, cooling efficiencies for four different cases were obtained as 33.70%, 34.81%, 41.69%, and 36.95%, respectively. The temperature differences between the room and ambient temperatures were determined as 1.45 degrees C, 1.21 degrees C, 1.6 degrees C, and 1.48 degrees C for each case, respectively.
Forecasting of future greenhouse gas emission trajectory for India using energy and economic indexes with various metaheuristic algorithms
(Elsevier Sci Ltd, 2022) Bakır, Hüseyin; Ağbulut, Ümit; Gürel, Ali Etem; Yıldız, Gökhan; Güvenç, Uğur; Soudagar, Manzoore Elahi M.; Hoang, Anh Tuan
The accelerating increment of greenhouse gas (GHG) concentration in the atmosphere already reached an alarming level, and nowadays its adverse impacts on the living organisms, environment, and ecological balance of nature have been well-understood. India is one of the top countries that contribute the most to global GHG emissions. Therefore, it is of great significance to forecast the future GHG trends of the country in advance and accordingly take measures against the parameters that cause these emissions, considerably. In this direction, the present research has centered on forecasting the greenhouse gas trajectory of India with various metaheuristic algorithms. In this framework, marine predators algorithm (MPA), lightning search algorithm (LSA), equilibrium optimizer (EO), symbiotic organisms search (SOS), and backtracking search algorithm (BSA) are used for modeling the future GHG emission trajectory of India. Accordingly, the significant economic and energy indicators of India such as renewable energy generation, electricity generation from coal, electricity generation from gas, electricity generation from oil, gross domestic product, and population between 1990 and 2018 are collected to make a nexus with GHG emissions. As GHG emissions, CO2, CH4, F-gases, N2O, as well as total GHG emissions are separately forecasted by the year 2050. To make a better comparison, each GHG emission data in the last year five years is used for the testing phase of the algorithms, and then statistically discussed in terms of R2, MBE, rRMSE, and MAPE benchmarks. In the results, it is found that the R2 value changes between 0.8822 and 0.9923 for CO2, 0.2855-0.9945 for CH4, 0.9-0.9904 for F-gases, 0.4655-0.9964 for N2O, and 0.9016-0.9943 for total GHG emission, and the results in terms of rRMSE are very satisfying for all algorithms. In the study, it is forecasted that the two greenhouse gas emissions with the highest increase rate in 2050 will be between 2.5 and 2.87 times for CO2 emissions and between 2.8 and 3.5 times for F-gases, compared to today's data. According to the results of the present paper, the total GHG emission for India is forecasted to be 2.1-2.4 times higher in the year 2050 as compared to today. Given all forecasting results together, it is seen that the MPA algorithm generally gives the best results according to the statistical metric results, while the LSA algorithm generally gives the worst results. Consequently, the present paper strongly reports that the decision-makers and policy-makers
Güneş Enerjisi Santrallerinin Türkiye ve Avrupa’daki Geri Ödeme Sürelerinin Karşılaştırması
(Düzce Üniversitesi, 2023) Gyam, Mohannad; Ceylan, İlhan; Gürel, Ali Etem; Yıldız, Gökhan
Dünya’da enerjinin önemi her geçen gün artmaktadır. Ülkelerin büyük bir bölümü ihtiyaç duydukları enerji gereksinimini fosil yakıtlar tarafından karşılanmaktadır. Fosil yakıtların tükenecek olması, artan fiyatı ve çevreye vermiş olduğu zararlardan dolayı araştırmacılar alternatif enerji kaynaklarına yönelmişlerdir. Yenilenebilir enerji kaynaklarına son yıllarda alternatif enerji olarak talep büyük oranda artmıştır. Güneş enerjisi, yenilenebilir enerji kaynakları arasında en popüler ve tüm dünyada yaygın olarak kullanılan enerji kaynaklarından birisidir. Bu sebeple, Türkiye ve Avrupa ülkelerinde güneş enerjisi kullanımı artırılmaya çalışılmaktadır. Türkiye güneş ışınım miktarı yüksek olmasına rağmen beklenen seviyelere ulaşamamıştır. Bu çalışmada, Türkiye ile Avrupa ülkeleri arasındaki şebekeye bağlı 1 MW’lık bir güneş enerjisi santralinin geri ödeme süreleri karşılaştırılmıştır. Karşılaştırılan ülkeler, kendilerine özgü solar radyasyon değerlerinde %22,6 verimliliğe sahip bir monokristal güneş panellerinin kullanıldığı varsayılmıştır. Ayrıca, Rusya-Ukrayna savaşının enerji fiyatlarına etkisi nedeniyle güneş enerjisi santralinin geri ödeme süresi iki senaryo üzerinden değerlendirilmiştir. Elde edilen sonuçlara göre, birinci senaryoda en yüksek geri ödeme süresi 2,75 yıl ile Karaman’da, ardından 3,17 yıl ile Türkiye gelmektedir. İspanya, Fransa ve Almanya’daki geri ödeme süreleri sırasıyla 3,6, 5,6 ve 5,7 yıl olarak hesaplanmıştır. İkinci senaryoda ise (Rusya-Ukrayna savaşı sonrası), en yüksek geri ödeme süreleri 2,22 yıl ile Almanya ve 3,27 yıl ile Fransa olarak belirlenmiştir. İspanya, Karaman ve Türkiye’de geri ödeme süreleri sırasıyla 2,41, 2,75 ve 3,17 yıl olarak tespit edilmiştir.
Havalandırma sistemlerinde kanal çapları ve basınç kayıplarının bilgisayar destekli hesaplanması
(2010) Gürel, Ali Etem; Ketrez, Mustafa
Havalandırma sistemlerinin en önemli parçaları olan kanallar ve bağlantı parçalarına ait hesaplamalar uzun, karışık ve zaman alıcı hesaplamalardır. Bu çalışmada, havalandırma sistemlerinde kullanılan kanal çaplarının ve basınç kayıplarının hesaplamalarını yapabilen bir bilgisayar programı hazırlanmıştır. Hazırlanan program kanal hidrolik çapını, sürtünme kayıplarını ve bağlantı parçalarının dinamik basınç kayıplarını tablo kullanma zorunluluğunu ortadan kaldırarak hesaplayabilmektedir.

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