The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
Fatih Evrendilek - One of the best experts on this subject based on the ideXlab platform.
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Quantifying spatio-temporal dynamics of solar radiation Exergy over Turkey
Renewable Energy, 2010Co-Authors: D. Alta, Can Ertekin, Fatih EvrendilekAbstract:Abstract The insensitivity to energy quality is one of the disadvantages of an energy analysis when compared to an Exergy analysis. It is only the Exergy analysis that clearly reveals the degradation of energy quality in the processes of absorption and emission of solar radiation. The national spatial distribution of mean monthly Exergy Values of solar radiation over Turkey was mapped at 500-m resolution using universal kriging based on solar radiation data from 152 geo-referenced locations. Mean Exergy Value of solar radiation in Turkey was estimated at 13.5 ± 1.74MJm −2 day −1 , with a mean annual Exergy-to-energy ratio of 0.93.
Ming Zhai - One of the best experts on this subject based on the ideXlab platform.
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Conventional and microwave-assisted pyrolysis of gumwood: A comparison study using thermodynamic evaluation and hydrogen production
Fuel Processing Technology, 2019Co-Authors: Ashak Mahmud Parvez, Muhammad T. Afzal, Sannia Mareta, Ming ZhaiAbstract:Abstract The application of microwave energy in biomass pyrolysis has gained increasing interest due to its fast, volumetric, selective and efficient heating. However, the dominance may be levelled off if the energy and Exergy efficiencies of overall system are taken into consideration. Hence, based on the lab-scale experimental data (at 600, 700 and 800 °C), energy and exergetic assessment of pyrolysis-derived gas, char and oil from gumwood under conventional and microwave heating were investigated in this work. The results showed that at each temperature, the corresponding energy and Exergy rates of gas under microwave heating were found to be 23% and 26%, respectively, higher than those of conventional one. Meanwhile, the Values for char were around 46%. This was mostly because microwave-derived pyrolysis product contained more gaseous and char products compared to the conventional process. In contrast, opposite trend was noticed for bio-oil due to the reduction of oil yield in pyrolysis product. It was demonstrated that the total energy and Exergy Value of individual pyrolysis products were significantly influenced by the energy and Exergy content of individual component. For example, the increment rate of energy and Exergy Values of H2 and CH4 were sufficiently higher than the decrement rate of energy and Exergy Values of CO and CO2 with the increase of temperature; the total Values were consequently increased at the elevated temperature. For the case of char and oil, the energy and Exergy rate were decreased with temperature due to the reduction of individual product yield. Pyrolysis system efficiency (PSE), the overall performance indicator used in this study, of the microwave-assisted process was 13.5% higher than that of the conventional process. Moreover, the experimental results were further analysed with the conduct of a hydrogen plant simulation using Aspen Plus™ whose results confirmed that an improved performance of microwave heated system was achieved by producing 120 gH2/kg gumwood, 15% higher compared to that of conventional system.
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Energy and Exergy analysis of rice husk high-temperature pyrolysis
International Journal of Hydrogen Energy, 2016Co-Authors: Xinyu Wang, Li Guo, Ming Zhai, Peng DongAbstract:Abstract Based on a two-stage fixed bed high-temperature pyrolysis system, the influence of temperature (800–1200 °C) on total energy and Exergy, as well as Exergy and energy efficiency of unreacted carbon, tar and pyrolysis gas were analyzed. The results indicate energy and Exergy of each component in the pyrolysis gas as well as the total energy and Exergy increase with temperature. Energy Value and Exergy Value contributions of the components in the pyrolysis gas at 800 °C and 900 °C are CO > CH 4 > H 2 > CO 2 . From 1000 °C to 1200 °C, the rank turns into CH 4 > CO > H 2 > CO 2 . The energy efficiency and Exergy efficiency of pyrolysis gas are in the range of 64.57–72.68% and 52.93–60.64%, respectively. The increasing rate of energy Value and Exergy Value of the pyrolysis gas reaches maximum at 1000 °C. The energy efficiency and Exergy efficiency of unreacted carbon and tar decrease with temperature. The consumption of energy for tar collection and loss of energy and Exergy carried by tar can be reduced by increasing temperature. The loss Exergy efficiency increases slightly below 900 °C and decreases from 38.8% to 34.6% above 900 °C.
Yaning Zhang - One of the best experts on this subject based on the ideXlab platform.
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An expeditious methodology for estimating the Exergy of woody biomass by means of heating Values
Fuel, 2015Co-Authors: Yaning Zhang, Xiaoyan Gao, Haochun ZhangAbstract:Abstract Determination of the Exergy of woody biomass is the first step to evaluate and study the material characteristics, transfer processes, and utilization systems of woody biomass from Exergy aspect. This study supplies an expeditious methodology for estimating the Exergy of woody biomass based on studying the LHVs (lower heating Values), HHVs (higher heating Values), and Exergy Values of sixty-four woody biomass. The results obtained from this study show that the higher LHV and HHV the woody biomass has, the higher Exergy it has. A positive linear relationship between the Exergy Value and LHV with relative errors of −2.78% to 1.98% and a positive linear relationship between the Exergy Value and HHV with relative errors of −4.80% to 4.80% are obtained. These two relationships can be used to achieve an expeditious estimation of the Exergy of woody biomass for engineering purposes.
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Influences of Physical and Thermochemical Properties on the Exergy ofCereal Straws
Journal of Fundamentals of Renewable Energy and Applications, 2014Co-Authors: Abdel E. Ghaly, Yaning ZhangAbstract:Exergy is a measurement of how far a material deviates from a state of equilibrium with the environment. The Exergy Values of the barley, oat, rye and wheat straws were determined and the influences of LHV, moisture content, ash content, S, C, O, H and N on the Exergy of cereal straws were evaluated. The moisture content of the four cereal straws varied from 10% (oat straw) to 17% (rye straw). The moisture related Exergy Value of the four cereal straws varied from 283.954 kJ/kg (oat straw) to 479.747 kJ/kg (rye straw), accounting for 1.376-2.275% of the total Exergy of cereal straws. A positive linear relationship between the Exergy Value and moisture content of cereal straws was observed. The ash content of the four straws varied from 1.635% (rye straw) to 4.554% (oat straw). The ash related Exergy Value varied from 25.912 kJ/kg (rye straw) to 111.061 kJ/kg (oat straw), accounting for 0.123-0.538% of the total Exergy of cereal straws. A negative linear relationship between the Exergy Value and ash content of cereal straws was observed. The S content of the four straws varied from 0.058% (rye straw) to 0.144% (oat straw). The S related Exergy Value varied from 5.626 kJ/kg (rye straw) to 13.944 kJ/kg (oat straw), accounting for 0.027-0.068% of the total Exergy of cereal straws. A negative linear relationship between the Exergy Value and S content of cereal straws was observed. The results showed that the combined contribution of the Exergy Values of moisture, ash and S contents to the total Exergy of cereal straws (1.982-2.424%) is very small and can be neglected. The O/C, H/C and N/C atomic ratios varied from 0.7184 to 0.7780 (8.30%), from 1.4214 to 1.5457 (8.74%) and from 0.0026 to 0.0254 (876.92%), respectively. The correlation factors varied from 1.133 to 1.142 (0.8%). The Exergy Values of the four cereal straws varied from 20.631 MJ/kg (oat straw) to 21.156 MJ/kg (wheat straw). They were mainly determined by the correlation factors and the LHVs. A positive linear relationship between the Exergy Value and LHV of cereal straws was observed.
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Determination of the Exergy of Four Wheat Straws
American Journal of Biochemistry and Biotechnology, 2013Co-Authors: Yaning Zhang, Abdel E. GhalyAbstract:Exergy is a measurement of how far a certain materi al deviates from a state of equilibrium with the environment. It is a useful tool for improving the efficiency of energy-resource use. The Exergy Value s of four wheat straws (Absolvant, Max, Monopol and Vuka) were determined in this study. The effects of physical and chemical properties (moisture content, ash content, LHV and S, C, O, H and N contents) were evaluated. The moisture related Exergy varied from 281.834 kJ kg -1 (Monopol) to 366.766 kJ kg -1 (Absolvant), accounting for 1.311-1.734% of the tot al Exergy of wheat straws. A negative linear relationship between the Exergy Value and moisture content was observed. The ash related Exergy varied from 53.468 kJ kg -1 (Absolvant) to 117.675 kJ kg -1 (Vuka), accounting for 0.253-0.556% of the total e xergy of wheat straws. A negative linear relationship bet ween the Exergy Value and ash content was observed. The S related Exergy ranged from 6.817 kJ kg -1 (Max) to 11.077 kJ kg -1 (Vuka), accounting for 0.032-0.052% of the total Exergy of wheat straws. A positive linear relationship between the Exergy Value and S conten t was observed. The O/C, H/C and N/C atomic ratios and the correlation factors varied in ranges of 0.7133-0.7537, 1.3475-1.5457, 0.0063-0.0225 and 1.133-1.138, respectively. The Exergy Values of the fo ur wheat straws were between 21.156 MJ kg -1 (Absolvant) and 21.503 MJ kg -1 (Monopol). They were mainly determined by the correlation factors and the LHVs. A positive linear relationship between the Exergy Value and LHV was observed. The combined contribution of ash, moisture and S related Exergy to the total exe rgy was very small (1.694-2.212%) and can be neglected.
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Comprehensive Investigation into the Exergy Values of Six Rice Husks
American Journal of Engineering and Applied Sciences, 2013Co-Authors: Yaning Zhang, Abdel E. GhalyAbstract:Exergy is a measurement of how far a certain system or material deviates from a state of equilibrium with the environment and it is a useful tool for improving the efficiency of energy-resource use. Based on the previous work, the Exergy Values of six rice husks were investigated in this study. The effects of physical and chemical properties were also detailed. These included moisture content, ash content, S, C, O, H and N contents. The moisture related Exergy of the six rice husks ranged in 241.432-290.304 kJ per kg rice husk, accounting for 1.563-1.758% of the Exergy of rice husks. An exponential relationship between Exergy Value and moisture content was observed. The Exergy of ash varied between 37.419 kJ per kg rice husk and 61.217 kJ per kg rice husk, making up 0.233-0.401% of the Exergy of rice husks. An exponential linear relationship between Exergy Value and ash content was observed. The S related Exergy ranged from 1.217 kJ per kg rice husk to 2.993 kJ per kg rice husk, accounting for 0.007-0.018% of the Exergy of rice husks. The O/C, H/C and N/C atomic ratios varied in ranges of 0.592-0.662, 1.404-1.730 and 0.008-0.011, respectively, whereas the correlation factors varied slightly in the range of 1.118-1.127. The Exergy Values of the six rice husks ranged in 15.053-18.407 MJ/kg. They were mainly determined by the correlation factors and the LHVs. A positive linear relationship between Exergy Value and LHV was observed.
Javier Uche - One of the best experts on this subject based on the ideXlab platform.
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Assessment of Water Resources by Exergy Cost
Thermodynamics for Sustainable Management of Natural Resources, 2017Co-Authors: Javier Uche, Amaya Martínez, Beatriz CarrasquerAbstract:This chapter presents the application of Exergy analysis to water bodies focusing the attention on the assessment of the Exergy cost. It comprises three different but clearly connected sections: Exergy cost of water technologies, Exergy Value of the hydrological cycle and fundamentals, and application and results of the Physical Hydronomics methodology. The Exergy cost is a key parameter to be included in any water analysis regarding Exergy efficiency. It measures the goodness of the considered technological process when it is compared with the ideal one and it is used to translate the objective Exergy measurements into economic figures. The unit Exergy cost of water technologies is introduced both in the analysis of the Exergy Value of the natural hydrological cycle and in the calculation of water costs. In particular, Physical Hydronomics is defined as the application of the Exergy analysis to the assessment of costs of water bodies and it has presented interesting results when considered in the European Water Framework Directive implementation for Spanish and European watersheds. The background and main results of these three mentioned issues are presented along this chapter.
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The hidden Value of water flows: the chemical Exergy of rivers
International Journal of Thermodynamics, 2012Co-Authors: Amaya Martínez-gracia, Antonio Valero, Javier UcheAbstract:The hydroelectricity potential of rivers is a very well-know parameter used to characterize the availability of a river as a function of its flow and its altitude. However, the chemical potential of water flowing through the rivers is commonly ignored. In its source, water presents high quality and, therefore, it owns an important availability that can be expressed through its chemical Exergy Value. On the opposite, when it flows into the sea and reaches the thermodynamic equilibrium, it can not be further used and it is converted into a null Exergy Value. Within these two limit Values, the Exergy state of the river at its different stages can be assessed. On the other hand, water availability for specific uses depends on its quality. In this way, the almost always hidden Value of water, its chemical potential, is highlighted and can be compared to the potential component, since they are expressed in the same units (energy units). In this paper, it is shown that potential and chemical Exergy Values of rivers rise up with Values with the same order of magnitude. That is, the chemical Value of a river is, from a thermodynamic perspective, as much as its potential Value. The main difference lies in the current available technologies to take advantage of those physical disequilibrium: while hydro-power turbines are a completely proved technology, there are not yet commercial devices to take advantage of the hydro-chemical potential. Results of those estimations for a small Spanish river, the Muga river, are presented in this paper in order to prove the accuracy of the methodology. It is shown that the potential Exergy of that river ranges from 2.37 to 7.15 MW, while its chemical Exergy is comprised between 2.30 and 8.78 MW for the present state of the river. In addition, several Exergy indexes are defined as basic parameters to provide information about the advantage taken from the river, that is, about the water uses within the watershed.
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The hidden Value of water flows: the chemical Exergy of rivers
International Journal of Thermodynamics, 2012Co-Authors: Amaya Martínez-gracia, Antonio Valero, Javier UcheAbstract:<p class="PSAbstractCxSpFirst" style="line-height: normal; margin: 0cm 1cm 0pt; mso-add-space: auto;"><span style="mso-bidi-font-size: 9.0pt; mso-bidi-font-family: Arial; mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: x-small;"><span style="font-family: Arial;">The hydroelectricity potential of rivers is a very well-know parameter used to characterize the availability of a river as a function of its flow and its altitude. However, the chemical potential of water flowing through the rivers is commonly ignored. In its source, water presents high quality and, therefore, it owns an important availability that can be expressed through its chemical Exergy Value. On the opposite, when it flows into the sea and reaches the thermodynamic equilibrium, it can not be further used and it is converted into a null Exergy Value. Within these two limit Values, the Exergy state of the river at its different stages can be assessed. On the other hand, water availability for specific uses depends on its quality.</span></span></span></p><p class="PSAbstractCxSpMiddle" style="line-height: normal; margin: 0cm 1cm 0pt; mso-add-space: auto;"><span style="mso-bidi-font-size: 9.0pt; mso-bidi-font-family: Arial; mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: x-small;"><span style="font-family: Arial;">In this way, the almost always hidden Value of water, its chemical potential, is highlighted and can be compared to the potential component, since they are expressed in the same units (energy units). In this paper, it is shown that potential and chemical Exergy Values of rivers rise up with Values with the same order of magnitude. That is, the chemical Value of a river is, from a thermodynamic perspective, as much as its potential Value. The main difference lies in the current available technologies to take advantage of those physical disequilibrium: while hydro-power turbines are a completely proved technology, there are not yet commercial devices to take advantage of the hydro-chemical potential.</span></span></span></p><p class="PSAbstractCxSpLast" style="line-height: normal; margin: 0cm 1cm 0pt; mso-add-space: auto;"><span style="mso-bidi-font-size: 9.0pt; mso-bidi-font-family: Arial; mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: x-small;"><span style="font-family: Arial;">Results of those estimations for a small Spanish river, the Muga river, are presented in this paper in order to prove the accuracy of the methodology. It is shown that the potential Exergy of that river ranges from 2.37 to 7.15 MW, while its chemical Exergy is comprised between 2.30 and 8.78 MW for the present state of the river. In addition, several Exergy indexes are defined as basic parameters to provide information about the advantage taken from the river, that is, about the water uses within the watershed.</span></span></span></p>
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Assessment of Environmental Water Cost Through Physical Hydronomics
Water Resources Management, 2011Co-Authors: Amaya Martínez, Javier Uche, Antonio Valero, Carlos RubioAbstract:The Georgescu-Roegen’s statements about the connexion between the Economy and the Thermodynamics, together with the Eco-integrator approach introduced by Naredo and its relation with the water cost definitions given in the European Water Framework Directive (WFD), are the outline backgrounds of the work presented in this paper. Assuming that the physical laws are called to be the objective and universal tools to assess water costs, Physical Hydronomics (PH) has been developed as the accounting tool for the WFD application, regarding its physico-chemical objectives. PH is defined as the specific application of the Thermoeconomics to physically characterize the degradation and correction of water bodies. The Second Law of Thermodynamics, through the Exergy loss calculation, is the basic working tool in this study. The final objective of PH is to use those calculated physical costs of water as a guide to allocate the environmental and resource costs introduced by the WFD. In this paper, the general framework and the basic accounting principles of PH are explained. First, from the quantity and quality measurements in the river (they give the Exergy Value to water bodies), the Exergy profiles of the river at different statuses (those defined by the WFD) are obtained. Then, the environmental cost of water is obtained (in energy units) as the Exergy needed to cover the gap between the current state of the river and the objective state defined by the applicable legislation to fulfil the European requirements. To do it, thermodynamic efficiency of water treatment technologies was introduced in the analysis. Then, the physical cost are translated into monetary units. To illustrate the application of the PH’s methodology, the example of the Spanish Muga Basin, sited in the Inland Basins of Catalonia, is summarized at the end of this paper. The results show that similar results to conventional Measurements Plans to fulfil the WFD objectives are obtained. However, PH presents an important advantage: costs could be allocated according to the degradation (Exergy costs) provoked by the different water users in the water bodies.
D. Alta - One of the best experts on this subject based on the ideXlab platform.
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Quantifying spatio-temporal dynamics of solar radiation Exergy over Turkey
Renewable Energy, 2010Co-Authors: D. Alta, Can Ertekin, Fatih EvrendilekAbstract:Abstract The insensitivity to energy quality is one of the disadvantages of an energy analysis when compared to an Exergy analysis. It is only the Exergy analysis that clearly reveals the degradation of energy quality in the processes of absorption and emission of solar radiation. The national spatial distribution of mean monthly Exergy Values of solar radiation over Turkey was mapped at 500-m resolution using universal kriging based on solar radiation data from 152 geo-referenced locations. Mean Exergy Value of solar radiation in Turkey was estimated at 13.5 ± 1.74MJm −2 day −1 , with a mean annual Exergy-to-energy ratio of 0.93.