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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%.
ISI POMPALI VE PARABOLİK OLUKLU GÜNEŞ KOLEKTÖRLÜ AKIŞKAN YATAKLI KURUTUCULARIN DENEYSEL ANALİZİ
(Turkish Soc Thermal Sciences Technology, 2015) Gürel, Ali Etem; Ceylan, İlhan; Yılmaz, Sezayi
In this study, both a heat pump and parabolic trough solar fluidized bed dryer were designed and manufactured. They were experimentally analyzed by first and second laws of thermodynamics and a comparison was made between the two. Drying air temperatures were controlled as PID for 40 degrees C set temperatures. Drying air temperature was controlled with a sensitivity of +/- 0.254 degrees C in heat pump dryer system and +/- 0.369 degrees C in parabolic trough solar dryer. In the heat pump dryer system, whole system heating coefficient of performance (COPts) was calculated as average 1.91. In parabolic trough solar dryer, heating performance coefficient (IPK) was calculated as average 3. Exergy loss was found to be 203.97 J/kg in the heat pump dryer, and 32.08 J/kg in parabolic trough solar dryer. Average exergy efficiency was found to be 31.1% in the heat pump dryer, and 63.37% in parabolic trough solar dryer.
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
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.
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.
Hybrid pseudo-random number generator for cryptographic systems
(Springer, 2015) Avaroğlu, Erdinç; Koyuncu, İsmail; Özer, A. Bedri; Türk, Mustafa
For a powerful cryptographic system, high-quality random number streams are essential. Those raw pseudo-random number generators (PRNG) that are used to generate high-quality random numbers have some disadvantages, such as failure to meet the R4 security requirement. Therefore, use of random number sequences generated by these generators in a cryptographic system puts the entire system at risk. This study proposes a new hybrid PRNG by means of an additional input introduced to transition and output functions used in a raw PRNG system in order to eliminate this risk. The additional inputs to the designed system have been implemented via the true random number generator developed by using the Sprott 94 G chaotic system on FPGA. The random number streams obtained from the recommended hybrid structure have been subjected to the NIST 800.22 and FIPS statistical test, which have given good results. According to these results, it has been proved that the recommended hybrid PRNG system meets the R4 security requirement and can be used in cryptographic applications.
Histogram-based automatic segmentation of images
(Springer, 2016) Küçükkülahlı, Enver; Erdoğmuş, Pakize; Polat, Kemal
The segmentation process is defined by separating the objects as clustering in the images. The most used method in the segmentation is k-means clustering algorithm. k-means clustering algorithm needs the number of clusters, the initial central points of clusters as well as the image information. However, there is no preliminary information about the number of clusters in real-life problems. The parameters defined by the user in the segmentation algorithms affect the results of segmentation process. In this study, a general approach performing segmentation without requiring any parameters has been developed. The optimum cluster number has been obtained searching the histogram both vertically and horizontally and recording the local and global maximum values. The quite nearly values have been omitted, since the near local peaks are nearly the same objects. Segmentation processes have been performed with k-means clustering giving the possible centroids of the clusters and the optimum cluster number obtained from the histogram. Finally, thanks to histogram method, the number of clusters of k-means clustering has been automatically found for each image dataset. And also, the histogram-based finding of the number of clusters in datasets could be used prior to clustering algorithm for other signal or image-based datasets. These results have shown that the proposed hybrid method based on histogram and k-means clustering method has obtained very promising results in the image segmentation problems.
Hardware design and implementation of a novel ANN-based chaotic generator in FPGA
(Elsevier Gmbh, 2016) Alçın, Murat; Pehlivan, İhsan; Koyuncu, İsmail
This paper presents a novel hardware implementation of Artificial Neural Networks (ANNs) for modeling of the Pehlivan-Uyaroglu Chaotic System (PUCS) on Field Programmable Gate Array (FPGA). There are two main parts in the proposed work. In the first part, a 3-8-3 Feed Forward Neural Network (FFNN) has been created using Matlab R2015a. The training results show that FFNN trained with back propagation algorithm exhibits satisfactory precision for the direct implementation. In the second part, the hardware implementation of the trained network has been carried out. The designed architecture is presented using Very High Speed Integrated Circuits Hardware Description Language (VHDL) and is implemented on a Xilinx Virtex 6 (XC6VCX240T) chip. All related parameters are defined with IEEE 754 single precision floating point number format. For the approximation of Log-Sigmoid transfer function, Xilinx's COordinate Rotation Digital Computer (CORDIC) design has been employed. The design can be used with a clock frequency up to 266.429 MHz. Finally, chip statistics of FPGA and analysis results have been presented. The proposed work have showed that chaotic systems can be successfully modeled using ANNs on FPGA. In future, chaos-based engineering applications can be performed using ANN-based chaotic oscillators on FPGA. (C) 2016 Elsevier GmbH. All rights reserved.
Fuzzy tuning approach for adaptive exponential smoothing used in short-term forecasts
(Pamukkale Univ, 2017) Biçen, Yunus
Adaptive smoothing methods were suggested to improve forecast results on the characteristic changes of time series. The existing adaptive smoothing methods have been diversified over the years. Many of them are comprised of complicated logical or mathematical propositions for improving forecast accuracy, which are very different from the original simple method called Trigg and Leach method. A new method named Fuzzy Tuning Exponential Smoothing is introduced in this paper introduces. This method is successful in improving the forecast accuracy, especially for the time series including level shift or level shift with outlier deflection. The empirical application carried out on 'The M2-Competition Time Series'. The statistical analysis results demonstrate that the method outperforms classical adaptive smoothing method in terms of forecasting accuracy. In addition, the proposed method is relatively simple compared to other advanced adaptive methods.
Fuzzy logic-based user interface design for risk assessment considering human factor: A case study for high-voltage cell
(Elsevier, 2014) Aras, Faruk; Karakaş, Ercüment; Biçen, Yunus
This paper presents a novel risk assessment model considering human factor based on the fuzzy logic approach. For the contribution of the literature, not only the number of people is included in the process of risk assessment, but also with the human factor as a quantitative entry in this study. A flexible and user-friendly risk assessment interface is developed using LabVIEW program, which puts at disposal different applications for the course material. Designed interface gives an opportunity to users to assess risks in a wide range of consequences containing many different combinations and options. The interface is tested for a 100-kV high-voltage cell as a case study. As a result, it is seen that the interface assesses plenty of input elements and possibilities in a short time. For this reason, the fuzzy logic approach is suggested as a suitable method for risk assessment. (C) 2014 Elsevier Ltd. All rights reserved.
Effects of Thermal Modification of Oak Wood Upon Selected Properties Of Coating Systems
(North Carolina State Univ Dept Wood & Paper Sci, 2019) Gürleyen, Levent; Ayata, Ümit; Esteves, Bruno; Gürleyen, Tugba; Çakıcıer, Nevzat
In the last few years there has been an increased demand to change the natural color of valuable hardwoods without chemicals for use mainly in indoor parquet floors. In this study, wood samples from oak (Quercus petraea L.), one of the most used species for parquet, were heat treated (ThermoWood method) at 190 degrees C for 2 h and at 212 degrees C for 1 and 2 h. Untreated and heat treated wood surfaces were coated following two different applications: type 1, with a single layer of sealer (50 g/m(2)) and type 2 with two layers (35 g/m(2)) using a nanolacke varnishing system. The objective of this study was to investigate surface properties including adhesion, glossiness, pendulum hardness, and color (L*, a*, b*,Delta E*,Delta L*, Delta a*, and Delta b*). With heat treatment the lightness decreases, and its decrease is higher for higher temperatures and treatment times. Type 2 coated wood presented a slightly lower lightness decrease. The experiment showed a slight increase followed by a decrease in redness (lower a*) and a clear decrease in the yellow tone (b*). The total color variation increased with the intensity of the treatment, while the glossiness decreased (more for Type 1 coated wood). The adhesion strength and surface hardness decreased with the heat treatment in both the Type 1 and Type 2 coated wood samples. The decrease in adhesion was higher for Type 2, reaching 67%, while the decrease in surface hardness reached about 18%.
Effect of thermal treatment on the swelling and surface roughness of common alder and wych elm wood
(Northeast Forestry Univ, 2016) Aytin, Ayhan; Korkut, Süleyman
Wood heat treatment has increased significantly in recent years and is still growing as an industrial process to improve some wood properties. We studied the change of swellingand surface roughness of common alder (Alnus glutinosa (L.) Gaertn. ssp.glutinosa) and wych elm (Ulmus glabra Huds.) woods after heat treatment at two different temperatures and durations. The temperatures were 180 and 200 A degrees C and the durations were 2 and 4 h. A stylus method was employed to evaluate the surface characteristics of the samples. Roughness measurements by the stylus method were made in the direction perpendicular to the fiber on the wood surface. Four main roughness parameters, mean arithmetic deviation of profile (R (a)), mean peak-to-valley height (R (z)), root mean square roughness (R (q)), and maximum roughness (R (y)) were used to evaluate the effect of heat treatment on the surface characteristics of the specimens. Swelling and surface roughness parameters (R (a), R (z), R (y), and R (q)) differed significantly for two temperatures and two durations of heat treatment. Swelling and surface roughness values decreased with increasing treatment temperature and treatment times.
Effect of Heat Treatment of Wild Cherry Wood on Abrasion Resistance and Withdrawal Capacity of Screws
(Zagreb Univ, Fac Forestry, 2015) Aytin, Ayhan; Korkut, Süleyman; As, Nusret; Ünsal, Öner; Gündüz, Gökhan
In its wise use, many properties of wood are important. Among these properties, wood abrasion resistance (AR) and withdrawal capacity of screws (WCS) are deemed to be relatively significant. It is well know that heat treatment changes the resistance features of wooden materials by changing the structural characteristics of wood. Within the scope of this study, the effects were investigated of the temperature and duration of heat treatment of Wild Cherry (Cerasus avium (L.) Monench) on its AR and its WCS in the radial direction and tangential direction. The test results indicated that weight loss (WL) and thickness reduction (TR) remained almost the same in the radial direction specimen, but there was significant TR in the tangential direction specimen. As a result of these changes, the abrasion effect of the S-42 abrader diminished based on the increase in the number of cycles. However, in both the radial and tangential direction, the WCS decreased to a significantly greater extent in the heat-treated specimens than in the control specimens.
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
Design, modelling and simulation of a new nonlinear and full adaptive backstepping speed tracking controller for uncertain PMSM
(Elsevier Science Inc, 2012) Karabacak, Murat; Eskikurt, Halil İbrahim
In this study, a new nonlinear and full adaptive backstepping speed tracking control scheme is developed for an uncertain permanent magnet synchronous motor (PMSM). Except for the number of pole pairs, all the other parameters in both PMSM and load dynamics are assumed unknown. Three phase currents and rotor speed are supposed to be measurable and available for feedback in the controller design. By designing virtual control inputs and choosing appropriate Lyapunov functions, the final control and parameter estimation laws are derived. The overall control system possesses global asymptotic stability; all the signals in the closed loop system remain bounded, according to stability analysis results based on Lyapunov stability theory. Further, the proposed controller does not require computation of regression matrices, with the result that take the nonlinearities in quite general. Simulation results clearly exhibit that the controller guarantees tracking of a time varying desired reference speed trajectory under all the uncertainties in both PMSM and load dynamics without singularity and overparameterization. The results also show that all the parameter estimates converge to their true values on account of the fact that reference speed signal chosen to be sufficiently rich ensures persistency of excitation condition. Consequently, the proposed controller ensures strong robustness against all the parameter uncertainties and unknown bounded load torque disturbance in the PMSM drive system. Numerical simulations demonstrate the performance and feasibility of the proposed controller. (C) 2011 Elsevier Inc. All rights reserved.
Trend adjusted lifetime monitoring of underground power cable
(Elsevier Science Sa, 2017) Biçen, Yunus
Insulated power cables are the most critical devices used in electrical network for urban areas. Also, lifespan knowledge of these devices is the important information for decision-makers to make their investment planning. This study has presented a practical method for estimating the remaining lifetime of a power cable. The validation of the method has been tested under two different cases for 154kV XLPE insulated underground power cable system. Power cable thermal network has been modeled for a short-duration transient according to electrical analogy. Lifetime monitoring has been carried out by considering loss of life trend depending on the load raising an annual basis. The results show that the accuracy of the remaining service life estimation is related to receiving data with high sample-rate and determining loss of life trend curve belonging to the power cable. The realistic estimations are carried out using trend-adjusted exponential smoothing. (C) 2016 Elsevier B.V. All rights reserved.
Thermodynamic analysis of PID controlled fluidised bed dryer with parabolic trough collector
(Inderscience Enterprises Ltd, 2015) Gürel, Ali Etem; Ceylan, İlhan; Yılmaz, Sezayi
The aim of the current study was to investigate how to use hot water obtained by parabolic trough collector (PTC) in an air handling unit. The system consisted of a PTC, a water depot, a pump, an air handling unit, a fan, and control equipments. The purpose of the system was to maintain the set value without using an additional heater in the air handling unit. During the process, +/- 0.36 degrees C accuracy was achieved in a 40 degrees C set temperature. Uncertainty analyses were made for the measured temperature value and they were obtained as +/- 0.44 degrees C. The energy and exergy efficiency were calculated for the system. The heating performance coefficient (HPC) was defined as the ratio of the obtained energy from the system to the compulsory energy supplied to the system. The HPC was calculated as 3 on average. Heat energy of the water in the depot was converted to heat energy of the air in the system with an average 52 % exergy efficiency.
Thermal modelling and analysis of high-voltage insulated power cables under transient loads
(Wiley, 2013) Aras, Faruk; Biçen, Yunus
This article presents a simple thermal model for transient analysis of high-voltage underground power cables based on proper ladder diagram at MATLAB-Simulink software under various operating conditions for engineering students. Available commercial programs created with commercial worries are not suitable for students during the learning process, which involve different applications on power cable analysis. The model gives an opportunity for students to solve the often-faced transient problems in utilities. The transient model of the underground power cable system using the analytic procedures based on IEC60853 standards is presented with an example solution of the 154kV power cable in service in Turkish transmission system in this article. (c) 2010 Wiley Periodicals, Inc. Comput Appl Eng Educ 21: 516-529, 2013
The mathematical modeling of concentrated photovoltaic module temperature
(Pergamon-Elsevier Science Ltd, 2017) Ceylan, İlhan; Gürel, Ali Etem; Ergün, Alper
In this study, we examined the effect of the use of paraffin wax on the panel temperature of concentrated solar panels. Some tests were performed on various days for three months (including spring, summer, and winter months). With the help of the experimental results, new approaches have been made as concentrator ratio, area ratio, concentrator efficiency and power coefficient. As a result of this approaches the concentrator ratio was found to be 3. When the concentrator ratio was 3, the panel temperature of the system with paraffin was found to be between 80 and 100 degrees C, while that of the other system was found to be above 100 degrees C. Panel efficiency might be reduced down to 10% at these temperatures. The study also included the development of a mathematical model of the changes in the panel temperature of the concentrated systems in which paraffin was not used. The temperature at the back of the panels could be calculated by this mathematical model, depending on the ambient temperature and the concentrated solar radiation. The correlation coefficient of the mathematical model was found to be 0.929. The test results of two days, which were not included in the model, were used to determine the reliability of the model, and the panel temperatures were calculated using the correlation coefficients of 0.933 and 0.966. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
The impact of methanol fuelled spark ignition engines on engine performance and exhaust emissions
(Sila Science, 2011) Korkmaz, İbrahim; Çay, Yusuf
In this study, the performance and exhaust emission values of engine have been investigated according to the results obtained from the experimental study using gasoline and methanol fuels in spark ignition engines. In these experiments a regular automobile engine with 4 cylinders, 4 strokes and 1,3 liter volume was used. Without making any modifications on the engine, the engine performance has been determined for both fuels between the ranges of 1100-4000 rpm, 5-40 Nm torque values. In the experimental study, the rotation number, torque, strength, mean effective pressure, brake specific fuel consumption, fuel flow rate, exhaust temperature and exhaust emission values of the engine have been measured. According to the experiment results, if the engine works on gasoline, its minimum brake specific fuel consumption becomes 400 g/kWh, whereas if it works on methanol this value becomes 900 g/kW. The values of CO emission of the engine vary between 2 and 6% for gasoline, whereas the range for methanol is between 1 and 4%. Minimum HC emission values, on the other hand, have been observed as 330 ppm for gasoline and 250 ppm for methanol.

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