International Journal of Exergy (48 papers in press)
Comprehensive investigation of using n-butanol/gasoline blends in a port-fuel injection spark-ignition engine
by Murat Kadir Yesilyurt, Hayri Yaman
Abstract: In this study, butanol was examined mixing with gasoline at different ratios (Bu0, Bu5, Bu10, Bu20, and Bu30) in a single-cylinder, four-stroke, PFI SI engine for monitoring engine characteristics at various loads to perform thermodynamic analyses. It can be reported that the maximum efficiencies were calculated at the highest load for tested fuels. Accordingly, the maximum thermal efficiencies were computed to be between 35.85-40.60% meanwhile corresponding exergetic efficiency results were found to be between 33.33-37.85% for tested fuel samples. In addition, the maximum SIN values were achieved between 1.500-1.609.
Keywords: Butanol; Economic; Emissions; Exergy; Higher alcohol; Performance; Sustainability.
DEVELOPMENT OF EMPIRICAL MODELS FOR ESTIMATION DIFFUSE SOLAR RADIATION EXERGY IN TURKEY
by Nurullah Arslanoglu
Abstract: In this study, exergy of diffuse solar radiation is estimated using empirical models. Long-term meteorological data (1983-2005) consisting of monthly mean diffuse solar radiation for 7 selected stations were available from from NASA Langley Research Center. Empirical models were developed by correlating diffuse solar radiation exergy in terms of relative sunshine period. Three different regression models (Linear, quadratic, cubic) are presented to predict diffuse solar radiation exergy. The empirical models performance is determined with the most frequently utilized statistical methods. The performance ranking of the models is carried out by using the global performance indicator method (GPI). The maximum diffuse solar radiation exergy value (53 MJ/m2year) belongs to Adana for selected provinces . Quadratic type is the best predictive method for Bursa, Ankara, Adana, Gaziantep provinces located in Turkey, and Igdir and Trabzon regions are excellently predicted by Cubic type. Linear type is then used for the best prediction of the Izmir city of Turkey. Consequently, The empirical models obtained in this study can successfully predict diffuse solar radiation exergy. Therefore, it is easy to apply for other places with similar climatic conditions all over the world. In this way, it will be possible to design solar systems correctly by scientists and industrialists.
Keywords: Diffuse solar radiation; exergy; empirical models; clearness index; sunshine period.
Exergy Analysis of a HDH-VCR Cycle for Water and Air Conditioning
by Tangellapalli Srinivas
Abstract: The fresh water and space conditioning are the human needs for the comfort living. Humidification dehumidification vapour compression refrigeration (HDH-VCR) cycle for combined portable water and air conditioning (A/C) has been studied with exergy approach. HDH-VCR cycle has been studied with thermodynamic exergy approach for efficient operation of the cycle. The focused options in this work are dehumidification with normal water (HDH), dehumidification with chilled water (HDH-VCR 1) and dehumidification with VCR (HDH-VCR 2). The exergy losses of the components are compared for these three units. As per the exergy analysis, HDH-VCR 2 has been highlighted with higher exergy efficiency compared to the others.
Keywords: air conditioning; HDH-VCR; exergy; psychrometry; second law of thermodynamics.
Maximization of Energy and Exergy Efficiencies for a Sustainable Thermoelectric Cooling System by applying Genetic Algorithm
by JITENDRA MOHAN GIRI, Pawan Kumar Singh Nain
Abstract: The efficient thermal management of thermoelectric cooler (TEC) as a sustainable cooling technology is important. The energy loss, electrical power requirement, and irreversibility of the TEC system need to be minimized. Hence, the loss of energy and energy quality (exergy) are two significant points of concern. Thus, energy and exergy efficiency can be used as the key indicators to optimize TECs performance. Through this work, authors separately optimized TEC energy efficiency (?I) and exergy efficiency (?II) considering thermoelectric elements geometry and electric current by using the genetic algorithm (GA). The effects of electrical contact resistance and thermal resistance are considered in the mathematical model of this work. Unlike previously reported works, the authors have used junction temperatures different from surface temperatures at the respective cold and hot sides of TEC. This study reveals that maximum energy and exergy efficiencies are obtainable at the same values of electric current, length, and cross-sectional area of thermoelectric elements. It is significant as these identical optimum design variables assert maximum ?I and ?II. At cold surface temperature (Tc) of 20?, the maximum energy efficiency of 4.11 and the maximum exergy efficiency of 0.0715 are obtained. Exergy efficiency can be used as the basis to choose TEC since it assures better energy quality and connects with sustainable development. The genetic algorithm optimization result is validated through ANSYS
Keywords: thermoelectric cooler; energy efficiency; exergy efficiency; genetic algorithm; optimization; finite-element simulation.
EXERGETIC PERFORMANCE ANALYSIS OF HIGH PRESSURE AIR SYSTEMS ON SHIPS
by Asim Sinan KARAKURT, Ibrahim OZSARI, Veysi BASHAN
Abstract: Energy consumption, energy/exergy efficiency, and being more ecologically issues are among the most scientifically researched topics today. These three important aspects also attract attention to ships that have many high energy consumption systems. One of the highly energy consumed system in ships is high pressure start air systems with relatively have high capacity consuming compressors. In this study, energy and exergy analyses are made to optimize the use of a ship high pressure air system according to performance outputs such as power consumption, exergy destruction, and ecological coefficient of performance (ECOP). Exergy destructions caused by the power consumed by the main compressors and the improper use of the air stored at high pressures are calculated. And also, the ECOP criterion was used to compare 3 different models according to the first and second laws of Thermodynamics. The general results obtained from the analysis are as follows. The power consumption of models are 1530, 1283, and 1276 kW (38%, 31%, and 31%); the exergy destruction values are nearly 250, 471, and 450 kW (21%, 40%, and 39%); ECOP values are 6.15, 2.72, and 2.84 (53%, 23%, and 24%), respectively. Moreover, the effects of different sea water temperature, ambient temperature, and isentropic efficiencies of compressors on the power consumption, exergy destruction, and ECOP values are presented.
Keywords: Air storage; ECOP; Exergy analysis; Ship compressed air system.
Why brain functions may deteriorate with aging: A thermodynamic evaluation
by Cennet Yildiz, Mustafa Özilgen
Abstract: Loss of the brain functions with ageing is related to decrease of its oxygen utilization in the literature. Although we have much more limited data obtained with the brain, when compared with the muscles, at the present level of our knowledge, we may say that the loss of ageing damage to the brain functions may be caused by the brain work performance caused by deterioration of the energy generation capacity of the mitochondria and work performance ability of the warned out ion pumps upon ageing. Thermodynamic assessment points the muscle work performance as the place to look at. Nature has equipped the muscle cells with healing capability, in terms of fixing the damage to the mitochondria or multiplying their numbers. If the same natural healing technologies may be implemented to the brain cells, ageing damage to the brain cells may be at least partly recovered.
Keywords: Ageing in the brain; mitochondrial energy; entropy generation; Gibbs free energy utilization; ion pumps; work performance efficiency.
Thermodynamic analysis of a new multi-generation plant based on the waste heat from the cement industry for improved energy management
by Mehmet Altinkaynak, Murat Ozturk, Ali Kemal Yakut
Abstract: In this paper, the hydrogen production and liquefaction option by utilizing the waste heat from the raw material preheating sub-unit of cement facility are investigated thermodynamically. The gas turbine plant and Rankine cycle are chosen to generate power and, also in order to generate hydrogen, a part of the produced power is used for PEM electrolysis. In these conditions, the hydrogen generation from analyzed integrated plant is computed as 0.028 kg/s. The energetic and exergetic effectiveness of Brayton and Rankine cycles integrated with the waste heat recovery process in the cement facility are computed as 58.24% and 42.17%, respectively, for the chosen working condition. It is also asserted that increasing the input temperature of gas turbine depended on the cyclone gas temperature increases the exergy efficiency of investigated system.
Keywords: Waste heat; cement facility; energy; exergy; efficiency; hydrogen production and liquefaction.
Development of exergy maps as a tool for assessing solar energy potential in Iraq
by Abdul Hadi Khalifa, Fadhil Kareem
Abstract: This work aims to develop three sets of maps for solar intensity and the exergy efficiency of the solar and PV systems for Iraqi cities. The first is for the global solar radiation that falls on a horizontal surface; the second is solar exergy efficiency. In contrast, the third set is for the exergy efficiency of a 20 kW hybrid-connected PV system installed at the Middle Technical University's presidency, Iraq- Baghdad. The development of the solar exergy and the exergy efficiency map sets are based Petela model; the model equations were programmed depending on the Iraqi weather data and solved using the Engineering Equation Solver (EES) software. Meteonorm package was used to collect the weather data for 48 sites inside and outside Iraq to cover this country's entire area. From the weather data and the theoretical model, it is found that: The average daily global solar intensity in January is varied from 275 to 375 W/m2, while it is varied from 530 to 710 W/m2 in July. The western regions of Iraq, which are often desert lands, suffer from the low intensity of solar radiation due to the dusty weather that characterizes this region. The solar exergy is 70 to 138 W/ m2 in January, and this range in July is 260 to 330 W/ m2. The higher average exergy efficiency ranges from 15 to 19.3 % in the winter, while the lower is 7.5 to 13.8% in the summer. Finally, the site at lower latitudes has more global solar radiation. On the other hand, higher latitudes have more exergy efficiency than those for the sites at lower latitudes.
Keywords: Solar radiation; Solar exergy; PV exergy efficiency; Exergy maps.
EXERGY ANALYSIS OF A NATURAL GAS COMBINED CYCLE POWER PLANT: A CASE STUDY
by Gabriel Marques Pinto, Christian Jeremi Rodriguez Coronado, Tulio Augusto Zucareli De Souza, Eudes Muller D’Oliveira Santos
Abstract: This work performs energetic and exergetic analysis of a CCPP, by using a full-scope simulator, which faithfully reproduces the operation of a real Brazilian CCPP. The analyses are performed for design and off-design conditions. The results present, for the design condition, a power generated of 820.6 MW, a first law efficiency of 51.54% and a second law efficiency of 49.32%. The equipment responsible for the main irreversibilities were: the combustion chamber (70.24%), gas turbine (10.75%) and heat recovery steam generator (7.37%). In the off-design scenario, the first and second law efficiencies were decreased by 2.65% and 2.54%, respectively.
Keywords: Combined cycle; Exergy; Efficiency; Exergy destruction rate.
Exergoeconomic analysis of a solar CCHP with partially porous material filled collector
by Navid Tonekaboni, Hesamoddin Salarian, Majid Eshagh Nimvari, Jahanfar Khaleginia
Abstract: In this research, a parabolic solar collector is analyzed in solar combined cooling, heating and power cycle by adding porous materials in five stages are investigated. This research focus on use of flat plate collectors in solar CCHP. Following this study, the exergoeconomic analysis of the system was performed for financial analysis and calculation of the payback period. The average enhancement of collectors efficiency and solar CCHP cycle using porous media is 16% and 11% respectively. By using flat solar collector fully filled porous media, the cost of the cogeneration cycle reduces up to 38% in comparison with other CCHP.
Keywords: Solar collector; exergoeconomic; porous materials; partially porous; payback period.
Investigation of effects of several design parameters on exergo-sustainability metrics for two-spool turbojet engine at different flight conditions
by Hakan AYGUN
Abstract: In this study, performance and exergy analyses of twin-spool turbojet engine (TS-TJE) were carried out at different flight conditions (sea level-zero Mach (phase-I) and altitude of 11000 m-0.8 Mach (phase-II)). According to performance analysis of TS-TJE, the rising of turbine inlet temperature (TIT) leads to increase thrust and specific fuel consumption while the increase in low pressure compressor pressure ratio (LPC PR) results in decreasing of these parameters. Moreover, overall efficiency of turbojet becomes higher due to rising LPC PR. However, the higher is the TIT, the overall efficiency the lower. On the other hand, amongst the components, exergy efficiency of the combustor has the lowest value. Considering variation of LPC PR from 2.4 to 3.4 as well as constant TIT at 1240 K, exergy efficiency of the combustor varies from 70.87 % to 73.07 % at phase-I and from 75.3 % to 76.7 % at phase-II. On the other hand, exergetic sustainability index of TSTJE experiences an increase from 0.265 to 0.299 at phase-I and from 0.28 to 0.302 at phase-II. It is thought that the current analysis may seem to yield new insight so as to enhance energetic and exergetic performance of turbojet engine by considering optimum design parameters.
Keywords: Two-spool turbojet; exergy; turbojet performance; exergo-environmental; exergo-sustainability.
Energy and exergy analyses of a cryogenic reverse Brayton cycle with waste heat recovery
by Shanju Yang, Qi Wang, Jie Hao, Bao Fu, Lina Wang, Yu Hou
Abstract: In a typical reverse Brayton cycle (RBC), a great amount of compression heat is just wasted, for which there exit two different temperature levels. The basic organic Rankine cycle (ORC) and the regenerative ORC with improvement were then applied to recover waste heat. Considering that the waste gas after ORC was reused, the total exergy efficiency was defined to evaluate different cycles. A simulation method was conducted to predict cycle performances and the coupling between RBC and ORC was clarified. The feasibility of replacing the after cooler with the evaporator was analyzed. Compared with the typical RBC, a relative improvement of 18.2% was achieved for COP in the combined system, and the cooling exergy efficiency was increased by 16.8%. The correspondence of the total exergy efficiency and the COP of whole system exited in different cycle layouts. Proper organization of the RBC with ORC could promote the energy efficiency.
Keywords: cooling; expander; energy utilization; exergy efficiency; organic Rankine cycle; reverse Brayton cycle;.
Multi-Objective Optimal Design of Solar-Gas Turbine Driven Polygeneration System based on 4E Analysis
by Khodadoost Rostami Zadeh, Seyed Ali Agha Mirjalily, Seyed Amir Abbas Oloomi, Gholamreza Salehi, Mohammad Hasan Khoshgoftar Manesh
Abstract: In this paper, a novel polygeneration system for an office building based on an integrated flat plate solar collector and gas turbine to produce simultaneous power, freshwater, cooling, and heating has been introduced. The proposed system includes a heat recovery steam generator, a Multi-Effect Desalination (MED), Reverse Osmose (RO), a steam turbine, a solar plate collector, and an absorption chiller. The transient simulation and analysis for the solar system have been done in TRNSYS software. Also, a computer code was built to compute Energy, Exergy, Exergoeconomic, and Exergoenvironmental (4E) analysis dynamically. Furthermore, multi-objective optimization process using Genetic Algorithm (MOGA) and Water Cycle approach (MOWCA) to maximize the exergy efficiency, minimize the total cost of exergy, and minimize the total environmental impacts of exergy has been conducted simultaneously. Genetic Programing has been employed to generate correlations for objective function estimation with high accuracy for reducing computation time. Results show the overall exergetic efficiency, which is improved by 12.65 % and 12.67% using MOGA and MOWCA. Also, the overall exergoeconomic cost of power and water is reduced by 27.66%, 32.97%, 27.83%, and 32.96% using MOGA and MOWCA, respectively.
Keywords: Polygeneration; Exergetic; Exergoeconomic; Exergoenvironmental; Water Cycle Algorithm.
Thermodynamic and exergo-environmental assessment of the organic Rankine cycle and S-CO2 Brayton cycle for heat recovery in a gas turbine
by Mehmet Altinkaynak
Abstract: The general purpose of this study is to make feasible the recovery of waste heat in gas turbines. An integrated power generation system consisting of a gas turbine-powered by supercritical carbon dioxide closed Brayton cycle and organic Rankine cycle working with n-pentane is designed. The actual operating conditions of combined system are examined thermodynamically to establish the limiting states. Thermodynamic examination is performed for all elements of integrated system. The total net power generation of overall system is found to be 2789 kW. The energetic and exergetic efficiencies of combined plant are found to be 44.71% and 42.05%, respectively. As a result of thermodynamic analyses, the irreversibility amount of system is also calculated and found to be 13810 kW. System equipment with the highest exergy destruction is found in the heat exchangers with 56%. The temperature and pressure of turbine inlet conditions have considerable impact on the whole system performance.
Keywords: S-CO2 power plant; energy; exergy; efficiency; waste heat.
Investigation of Maximum Performance Characteristics of Seven-Process Cycle Engine
by GÜVEN GONCA, Bahri Sahin, Ibrahim Genc
Abstract: Emissions released from internal combustion engines (ICEs) should be minimized due to environmental harmful effects and engine performance should be maximized owing to economical concerns. In the recent years, it has been indicated that the Miller cycle applications into the ICEs could provide a remarkable abatement in emissions. Combustion temperatures during heat addition to engine cylinder can be held constant by applying Takemura cycle. This study investigates the maximum performance characteristics such as power, power density and thermal efficiency for the combinationof the Miller cycle and the Takemura cycle in seven processes depending on engine speed and ratios of compression, equivalence, exhaust temperature, Takemura cycle, cut-off, cycle pressure, cycle temperature. An Artificial Neural Network (ANN) modeling approach is also investigated as an alternative and simpler method. The results acquired could be utilized by engine modelers in order to determine the performance characteristics.
Keywords: Maximum power; Maximum power density; Takemura cycle; Dual Miller cycle; Optimization; Performance analysis.
Irreversibility analysis of various components in a supercritical thermal power plant
by Naveen Kumar Gavirineni, Edison Gundabattini
Abstract: Supercritical coal-based 660 MW plant is analyzed to estimate the irreversibility at different atmospheric conditions. The overall outcomes indicated that the boiler has the highest exergy destruction in the system followed by the condenser. The exergy destruction increases with the increase in the atmospheric temperature and decreases with the decrease in the atmospheric temperature. The exergy destruction of the boiler is 1198 MW followed by the exergy destruction of turbine 50.7MW at 35oC, in Indian climate condition. At 20oC atmospheric temperature exergy destruction of boiler decreases at the rate of 2% while at 40oC it increases at the rate of 0.67%. Similarly, at 20oC atmospheric temperature exergy destruction of turbine decreases at the rate of 12.6% while at 40oC the value increases at the rate of 7.9%.
Keywords: Plant load factor; Auxiliary power; Energy; Exergy; Specific coal consumption.
Entropy Generation and Hybrid Fluid-Solid-Fluid Heat Transfer in 3D Multi Floors Enclosure
by Mohammad Mohsen Peiravi, Javad Alinejad
Abstract: The innovation of this paper is fins shape and arrangement effects on entropy generation and hybrid fluid-solid-fluid heat transfer in 3D multi floors enclosure with heat flux boundary condition by lattice Boltzmann method (LBM). The results signified that maximum and minimum of mean nondimensional temperature on the wall (z=0)were in enclosure with 22 rectangular fins in hot and cold zones that was equal to 0.503 (%15.1) and 5 horizontal ellipse fins in hot zone that was equal to0.445 (%1.8), respectively.
Keywords: Different fins arrangement; Entropy generation; Fluid-solid-fluid interface; Heat flux; Hybrid thermal field; Lattice Boltzmann model.
Thermodynamic analysis of novel absorption type pressure reducing station
by Rahul Patil, Sunil Bhagwat
Abstract: Steam is an important utility in the process industry such as oil refinery, paper mill etc. In industries, boiler generates utility steam at high pressure and distribute it through different pressure headers as per the pressure requirements of the process. The distribution of steam from high pressure header to low pressure header is done by pressure reducing station. It was found that in the depressurization process a significant amount of exergy destruction happens up to 42 %. The present work proposes the novel absorption type pressure reducing station which addresses the exergy destruction issue. In this work, the mathematical model and simulation of absorption type pressure reducing station (APRS) and absorption-ejector type pressure reducing (AEPRS) station has been done in Scilab (open source software) using highly accurate thermodynamic correlations available in the literature. Sensitivity analysis has been done for various operating parameters. The performance of both APRS and AEPRS is compared with conventional PRS and steam ejector system and it was found that APRS and AEPRS have low exergy destruction up to 9.5 %.
Keywords: Absorption; Pressure reducing station; LiBr-water; Exergy destruction.
ENERGY AND EXERGY ANALYSES OF HYDROGEN ADDITION IN A DIESEL ENGINE
by Kubilay BAYRAMOGLU, Semih Yilmaz, Mustafa Nuran
Abstract: In the study, the effect of hydrogen addition with air taken from the intake manifold at different rates on performance and emissions in a single-cylinder, four-stroke diesel engine has been numerically investigated. The first and second law analyses of thermodynamics are performed for each hydrogen addition condition. Numerical analysis has been performed with Ansys-Forte, energy and exergy calculations have been carried out according to the analysis results. The results of the analysis show that with the addition of hydrogen, CO emissions decrease while the engine performance and NOx emissions increase.
Keywords: Diesel engine; Chemical exergy; Combustion; Hydrogen addition.
Effect of Pilot injection and Injection pressure on Combustion, Performance, Exergy and Exhaust Emission of Bioethanol-Diesel Fueled Common-rail Direct Injection Engine
by Abhishek Paul, Subata Bhowmik, Nirupam Pal, Rajsekhar Panua
Abstract: This investigation highlights the preeminence of Bioethanol-Diesel blended fuels on the combustion, performance, exhaust emission and exergy paradigms of a common-rail direct injection engine under varying pilot fuel mass share, fuel injection pressure and load conditions. The investigation begins with a Fourier-transform infrared spectroscopy followed by a stability estimation of Bioethanol on Bharat stage-IV Diesel. The engine is operated with 0%, 10% and 20% pilot fuel mass for 5% and 10% (by volume) Bioethanol blended Diesel fuel at 300 bar and 500 bar fuel injection pressure and 50%, 75% and 100% of full load conditions. The pilot fuel with higher fuel injection pressure and Bioethanol addition advances the position of combustion parameters of the engine. The pilot fuel and Bioethanol addition also improves the brake thermal efficiency, brake specific energy consumption, oxides of nitrogen, unburned hydrocarbon, carbon monoxide and smoke opacity of the engine. This investigation consequently made a substantial approach to deal with the economic and environment contribution by concomitantly addressing to the effective energy utilization, energy extraction and reasonable exhaust emissions under Diesel-Bioethanol strategies.
Keywords: FT-IR spectroscopy; Bioethanol; Pilot fuel strategy; Exergy; Combustion.
An Analysis Approach for Entropy Generation in Bounded Solids Subject to Sudden Heat Flux
by M. Sunar
Abstract: This work addresses the problem of entropy generation rate due to conduction for a one-dimensional bounded solid onto which a sudden heat flux is applied from one of its surfaces and the other surface is insulated. A theoretical procedure is presented using the infinite series to solve for temperature distribution with different forms of the applied heat flux. The considered cases include, but not limited to, constant, ramp and sinusoidal types of heat fluxes. The theoretical temperature results are found to be closely matching with those available in literature for one case and with those obtained by the finite element approach for all the cases. Entropy generation rate due to thermal field is presented in all the 3 cases with the conclusion that an energy balance is attained at some depth below the surface.
Keywords: Bounded Solid; Conduction; Heat Flux; Entropy Generation Rate; Theoretical; Finite Element Method.
Energy Efficient Distillation Column Configuration: An Exergy Analysis
by Laxmi Patil, Vinay Amte
Abstract: The column targeting tools and exergy analysis are used to set energy targets and improve energy efficiency in distillation column. The combination of process options like feed stage location, reflux ratio, feed conditioning, side-reboiler and side-condenser greatly improves thermodynamic efficiency and reduces exergy loss throughout the column. The converged base-case simulation for propane-propylene binary mixture obtained from Aspen Plus was evaluated with both column targeting tools and exergy loss analysis. The study reveals significant decrease in reboiler (~29%) and condenser (~15%) duties, and increase in thermodynamic efficiency by ~33% as compared to base-case design by reduction in total exergy losses.
Keywords: Column targeting; Exergy analysis; Distillation column; Reflux ratio; Side-reboiler; Side-condenser; Thermodynamic efficiency.
3D CFD modelling and exergy loss minimization within a high-pressure vortex tube
by Abbas Aghagoli, Mikhail Sorin
Abstract: In the present study, 3D CFD simulation of vortex tubes at high operating pressure is investigated. The impact of inlet pressure and the cold mass fraction is investigated in terms of the exergy losses within the vortex tube. The results show that the minimum exergy losses occur at cold mass fraction equals 0.5, meanwhile, the exergy efficiency achieves its maximum at cold mass fraction equals 0.9. It is illustrated that friction has a major impact on the entropy generation rate near the wall and at the center of the vortex tube.
Keywords: Entropy generation rate; Vortex tube; Exergy loss; CFD.
Energy and exergy analysis of co-gasification of crude glycerol and animal fat mixtures
by Ana Almeida, Rosa Pilão, Elisa Err@isep.ipp.pt, Carlos Pinho
Abstract: This work presents an energy and exergy analysis of co-gasification tests of crude glycerol and animal fat mixtures, in order to obtain first and second law efficiencies, the last ones representing a novelty in the field of gasification technology. Mixtures with 5 % (w/w) of dry animal fat, 57 % (w/w) of dry treated crude glycerol and 38 % (w/w) of water were studied in a fixed bed down flow gasification reactor at 800
Keywords: animal fat; co-gasification; crude glycerol; energy; exergy.
6E Analysis of a Direct Steam Generation PTC-based Solar Power Plant
by Mohammad Hasan Khoshgoftar Manesh, Mohsen Yazdi, Saeed Kabiri
Abstract: The present study focuses on the energy, exergy, exergoeconomic, exergoenvironmental, Emergoeconomic, and Emergoenvironmental (6E) analyses, besides advanced exergy-based analysis, for a solar thermal power plant with Direct Steam Generation (DSG). The solar filed is is considered and verified based on the DISS test facility. In this regard, computer code has been developed for 6E analysis with high accuracy. The thermodynamic simulation has been verified with Thermoflex software and also the primary reference data with high accuracy. Results show that the overall Emergoeconomic factor of the DSG solar power plant is 85.34%, and its total Emergoenvironmental factor is 85.56%. After the solar field, low-pressure and high-pressure turbines are the preferred priority. Advanced exergy analysis reveals that the avoidable percentage of the Emergoenvironmental rate allocated to exergy destruction of the solar field, low-pressure turbine, and high-pressure turbine is 10%, 42%, and 34%, respectively. These values are equal to 11%, 45%, and 38%, respectively, for the Emergoeconomic rate allocated to exergy degradation. Therefore, it is essential to improve the low and high-pressure turbines economically and environmentally.
Keywords: PTC Solar Power Plant; Exergoeconomic; Exergoenvironmental; Advanced exergy analysis; Emergy.
Effects of various long-chain alcohols as alternative fuel additives on exergy and cost in a spark-ignition engine
by Battal Dogan, Murat Kadir Yesilyurt, Dervis Erol, Hayri Yaman
Abstract: This paper deals with exergy and exergoeconomic analyses of gasoline-hexanol and gasoline-heptanol blends as alternative additives were performed in a spark-ignition engine at a constant speed (1600 rpm). Fuel cost rate, cost per unit of exergy for power, cost rate of total exergy loss, exergonomic factor, and relative cost difference were calculated. The lowest cost of the power acquired from the engine for G100, HEX20, and HP20 at 5 kW was 0.122, 0.656, and 1.042 $/MJ, respectively, and the corresponding fuel cost rates were 1.07, 5.2, and 8.26 $/h, respectively.
Keywords: Spark-ignition engine; Hexanol; Heptanol; Exergy; Exergoeconomic.
Exergy analysis of a diesel hydrotreater and mild hydrocracking unit in a petroleum refinery
by Cagatay Yaylaci, Mahmut R. Bayramoglu
Abstract: The aim of this research work is to analyse the exergy efficiency of the Diesel Hydrotreater and Mild Hydrocracking unit of Turkish Petroleum Refineries Corporation Izmit Refinery (TUPRAS). For this purpose, the process was simulated by using Aspen HYSYS
Keywords: exergy efficiency; exergy destruction; diesel hydrotreater; mild hydrocracking; Aspen HYSYS; feed heater.
AN APPLICATION OF EXERGY ANALYSIS OF THE ENERGY USE IN CAMEROON
by TALLA KONCHOU Franck Armel, ALOYEM KAZÉ Claude Vidal, NGOUATEU WOUAGFACK Paiguy Armand, TCHINDA René
Abstract: In this work, the concept of energy and exergy used applied to Cameroon is analysed. The analysis of the exergetic flux is applied to various sectors (residential, industrial, transport, agricultural and others) in order to bring the various points of exergetic losses and to propose some means to remedy these losses. It is observed that other sectors (hotels and restaurants, administrative buildings, hospitals ...) are less efficient. An analysis of the situation in the whole Cameroon for the year 2010 gives 37.9% and 10.81% for the energetic and exergetic efficiency respectively. The results are compared with those of other countries.
Keywords: Cameroon; Energy analysis; Exergy flow; Exergy efficiency; Fossil Energy.
Exergy analysis of an electric grain drying system with internal circulation of the drying medium of corn
by Guiying Wang, Wenfu Wu, Wen Xu, Yan Xu, Yaqiu Zhang, Daping Fu
Abstract: In recent decades, exergy analysis has become an important tool to assess drying systems and optimize drying processes. This research work uses a corn drying experiment to analyse the exergy performance of a newly developed drying system, where, all exhaust air recirculated is dehumidified by condensation to achieve energy savings and environmental protection. The results show that under the experimental conditions, the exergy efficiency of the drying process was 34.03-64.90%, and the drying rate of corn was stable at 0.3-0.4% when the condensation intensity was 1.1-4.9 g/m3. The improvement potential rate of the drying process was 109-115 kJ/s and 37-52 kJ/s when the drying temperature was 90-100
Keywords: exergy analysis; electric grain drying system; internal circulation of the drying medium; drying characteristics; condensation characteristics.
Multi-objective Optimization of Supercritical CO2 Combined Cycles Based on Energy-Exergy-Economy balanced Analysis
by Chunlei Li, Qitai Eri
Abstract: In this paper, the supercritical CO2 (sCO
Keywords: supercritical CO2; combined cycle; SPECO; Multi-objective-Optimization.
Exergy analysis and optimisation of a two-stage thermoelectric generator with tapered legs
by Mkpamdi Eke, Chika Maduabuchi
Abstract: Numerous previous studies indicate that the performances of thermoelectric generators are enhanced by incorporating legs with variable area geometries. However, there is a dearth of comprehensive optimisation studies on these new thermoelectric generator designs. More so, the few optimisation studies that exist have rather employed unrealistic isothermal boundary conditions in their numerical models. Furthermore, these new leg geometries have not been applied to multi-stage systems. Accordingly, to address these gaps, a numerical optimisation, using ANSYS 2020 R2 software, is performed on a two-stage thermoelectric generator with variable area leg geometries; with optimisation parameters that include: leg geometry (height and area), intensified insolation with external load resistance, i.e., geometrical, thermal and electrical operation of the device. An exergy/irreversibility analysis is also carried out and techniques of minimising thermodynamic losses while allowing for the useful exergy output after solar energy conversion are proposed. Results indicate that, for an optimum leg height, area, concentrated solar radiation intensity and load resistance of 10 mm, 0.7 mm2, 20 suns and 1.3 , respectively. Maximum energy and exergy efficiencies of 7.03% and 7.55% respectively, were obtained for the proposed system. This improves the energy and exergy efficiencies of the standard device by 23.44%.
Keywords: Irreversibility analysis; solar power generation; variable leg geometry; two-stage thermoelectric generators; exergy optimisation; thermodynamic analysis.
Energy, exergy and environment analyses of a hybrid PV-system district heating system for a new household settlement in Germany
by Khaoula Daghsen, Dorra Lounissi, Bouaziz Nahla, Kallert Anna, Young Jae Yu
Abstract: This work presents an exergetic and environmental assessment of a hybrid district heating system(HDHS)analysed within two supply temperature levels. Energetic, exergetic and environmental performances are investigated. Results indicate that different scenarios have a lower degree of exergy efficiency in comparison to energy efficiency. The HDHS has a higher exergy efficiency (around 2%) and lower primary exergy demand (around 3%) compared to the normal district heating system (NDHS).Moreover, the combination of photovoltaic (PV) modules and low supply temperature reduces around 90 % of the exergy losses. Results of the environmental study confirm that the lower supply temperature added to the PV modules reduce CO2 emissions. In general, exergy analyses of the district heating systems should be conducted to make the exergo-environmental model, the matching of the quality level of demand and supply and the environmental impact, more known to the public and decision-makers in the context of multi-grid energy systems.
Keywords: CO2 emission; District heating; Exergy; Hybrid energetic systems,PV-modules.
Exergy cost analysis of Soil- Plant system
by Masoumeh BararzadehLedari, Yadollah Saboohi, Antonio Valero, Sara Azamian
Abstract: In this paper, inspired by a gas turbine power plant, the interaction between plant-soil processes has been simulated. This study indicates that solar energy in the photosynthesis process is equivalent to the fuel in combustion chambers. \r\nIn the glucose production process, when solar exergy is considered as a fuel, 99.4 percent of total exergy cost is supplied with solar exergy and only 0.6 percent of the exergy cost is provided by nutrients content. In general, 30% of the total exergy entering the Calvin cycle is consumed in glucose production and the remaining 70% is related to biomass generation. Moreover, 98% of the total exergy cost of the soil box is related to nutrient supply (due to the decomposition process), and only 2% percent is due to soil\'s nutrition. This happens because the decomposing processes include numerous energy-intensive chemical reactions and therefore, a high level of exergy cost.\r\n\r\n
Keywords: plant-soil process; exergy; Thermoeconomic analysis; exergy cost.
Exergy versus Labor in Aggregate Production Functions: Estimates for Ten Large Economies
by Ivan Savin, Jeroen Van Den Bergh, Robert Ayres, Lu Hao
Abstract: One can distinguish active (machines) from inactive (infrastructure) capital. Active capital consumes useful energy (or exergy) to do thermodynamic work that muscles and brains usually do. We use data for ten large economies and find that exergy performs just as well as, and hence can replace, labor in a Cobb-Douglas production function. This result is robust for each country separately and for all countries estimated together. Furthermore, when estimating a three-factor model (capital, labor and exergy), the coefficients of all three factors are positive and significant when all countries estimated together. When testing for each country separately the coefficient of exergy, unlike that of labor, is significant for China and Japan, while the opposite holds for the US and the UK. Our findings underpin the essential role of energy behind GDP growth, and the relevance of exergy as either a substitute or complement for labor in aggregate production functions.
Keywords: GDP; Cobb-Douglas function; energy; capital.
Effects of the dissimilarity of water depth on energy and exergy efficiencies and productivity of solar energy
by R.K. Yadav, Mukesh Kumar, Jay Singh, Desh Bandhu Singh, Navneet Kumar
Abstract: This research work investigates the effect of dissimilarity of water depth on energy and exergy efficiencies and productivity of solar still of double slope type coupled to N alike evacuated tubular collectors. The analysis has been done for archetypal days of June and January for complex climatic situation of New Delhi using computer codes inscribed in MATLAB-2015a. It has been concluded that values of average daily efficiencies and productivity increase first and then become almost constant beyond water depth of 0.56 m.
Keywords: Exergy; Efficiency; productivity; ETC; double slope solar still.
Greenhouse gas emissions within the exergoenvironmental assessment of a compact combined cooling, heating and power system
by Monica Carvalho, Adriano Marques, Raphael Abrahao
Abstract: Because of the significant public concern regarding climate change (and global warming), greenhouse gas (GHG) emissions have been successfully employed to communicate environmental impacts. This study develops a Life Cycle Assessment of the equipment and energy flows of a combined cooling, heating and power system system, expressing the environmental impacts as GHG emissions. Environmental data was used as input to an exergoenvironmental assessment, based on the SPECO methodology. The GHG emissions associated with the consumption of natural gas and grid electricity are 0.258 and 0.227 kg CO2-eq/kWh, respectively. The internal combustion engine is responsible for the highest share of GHG emissions (15.95 kg CO2-eq/h), of which 15.80 kg CO2-eq/h is due to the formation of pollutants and the remainder refers to equipment. From the combined analysis of exergoenvironmental parameters, strategies that increase energy use and decrease irreversibilities should focus on the absorber heat exchanger, the steam generator, and heat recovery unit. Some of the recent energy policy responses to the COVID-19 crisis include the deployment of energy solutions such as combined energy systems, and exergoenvironmental assessments can promote the adoption of these more efficient systems.
Keywords: Thermoeconomics; SPECO; Carbon footprint; Absorption refrigeration; Allocation of emissions.
Sensitivity investigation of N similar evacuated tubular collectors having series connection by incorporating exergy analysis
by Desh Bandhu Singh
Abstract: This research work deals with the sensitivity investigation of N similar evacuated tubular collectors (N-ETCs) having series connection taking computer codes inscribed in Matlab-2015a considering a normal day of May for New Delhi complex climate. The sensitivity with respect to N for N-ETCs from exergy as well as heat gain viewpoints is maximum with mean sensitivity figure values as 0.92 and 2.11 respectively. This analysis will help the designer to focus on particular input parameter as per the requirement of user.
Keywords: sensitivity analysis; sensitivity figure; N; evacuated tubular collector; OAT; efficacy.
The exergoeconomic optimization and economic sensitive analysis for flash-binary and double flash geothermal power systems
by Chao Luo
Abstract: The flash-binary and double flash power technologies are proposed to exploit the geothermal resources in Tibet and western Sichuan, China. The exergoeconomic optimization and economic sensitive are simulated by genetic algorithm. The results show that the levelized cost of electricity for flash-binary and double systems are 0.07052 US$/kWh and 0.0838 US$/kWh respectively before exergoeconomic optimization, and 0.06803 US$/kWh and 0.07331 US$/kWh respectively after exergoeconomic optimization. When the geofluid mass flow rate and power plant capacity are more than 50 kg/s and 1100 kW respectively, the plant cost per unit capacity maintains between 2000 US$/kW and 3500 US$/kW.
Keywords: Geothermal power generation; Flash-binary system; Double flash system; Exergoeconomic; Sensitivity.
Examination and thermodynamic modeling of a geothermal energy power plant for sustainable development; a case study
by Oguzhan Akbay, Fatih YILMAZ
Abstract: The new design article aims to assess the thermodynamic performance modeling of the geothermal power generation plant using real process data. This advised model comprises a steam turbine, high and low-pressure organic Rankine cycles, and also these plants are working by n-butane refrigerant. Moreover, with energy and exergy efficiencies, this proposed study is compared with different refrigerants. Looking at the consequences, the ORC-1's energy and exergy efficiencies are 14.49% and 19.03%, while the ORC-2's energetic and exergetic efficiencies are 10.75 %and 14.69%, respectively. Analysis results specified that the energy and exergy performances of the investigated power plant are 10.33% and 39.03%, respectively.
Keywords: Energy; exergy; geothermal power plant; thermodynamic; Organic Rankine cycle.
Exergetic assessment of a concentrated photovoltaic-thermoelectric system with consideration of contact resistance
by Aminu Yusuf
Abstract: Despite extensive studies on concentrated photovoltaic-thermoelectric systems, exergy analysis has not been given much attention. Herein, a comprehensive exergy analysis of a concentrated photovoltaic-thermoelectric system is presented. The results showed that increasing the number of thermoelectric modules in the system reduces the exergy destruction in the system, thereby improves the exergy efficiency. Likewise, performance of an individual thermoelectric module reduces with increase in the number of thermoelectric modules in the system. While increasing the contact resistance from 0% to 100% of internal resistance of the thermoelectric modules reduces the exergy efficiency of the thermoelectric modules by 50%.
Keywords: Contact resistance; performance evaluation; exergy efficiency; thermoelectric modules; concentrated photovoltaic; thermodynamic system; exergy destruction; solar energy; electrical energy; heat transfer; water cooled-system; one-dimensional model.
Exergy study of co-firing processes of low-grade coal with oil palm kernel shell (as received, torrefied, pyrolyzed), in a brick furnace, using aspen plus.
by Edward Siza Antolinez, Carlos Alirio Diaz Gonzalez, Nidia Juliana Caceres Garcia, Angie Karina Castro Jerez
Abstract: Exergy analysis of substitution of low-grade coal by raw, pyrolyzed or torrefied oil palm kernel shell (PKS) was developed using simulation software. Different cases were carried out, comparing coal combustion base-case with co-firing cases with raw and pre-treated PKS. Exergy efficiencies values of pyrolysis and torrefaction processes agree with the reported data. An increase in the energy density of PKS after these processes leads to a decrease in fuel consumption compared to the base coal combustion case. Furthermore, an increase in air requirements for co-firing cases with pyrolyzed and torrefied PKS shows that using a high air excess, compared to the base case, high thermal power values can be obtained with lower flame temperatures, decreasing irreversibilities in combustion and burning bricks processes. However, considering pretreatment processes, total irreversibilities in pyrolysis cases are average 30% greater than the case base, contrasting with torrefied cases, where total irreversibilities are about 20% greater than the case base. Finally, the lower specific fuel consumption of torrefied cases, added to a lower increase in irreversibilities, suggests that torrefaction of PKS may be an option to replace low-grade coal in this type of furnace. An extension with environmental analysis is recommended to obtain a more comprehensive decision criterion.
Keywords: Exergy study; coal substitution; biomass; cofiring; pyrolysis; torrefaction; Aspen plus.
Energy, exergy, and economic analyses of an innovative hydrogen liquefaction process utilizing liquefied natural gas regasification system
by Saman Faramarzi, Seyed Mojtaba Mousavi Nainiyan, Mostafa Mafi, Ramin Ghasemiasl
Abstract: A novel hydrogen liquefaction cycle integrated with the liquefied natural gas (LNG) regasification system is proposed. The novelty of this study is based on two parts: first, the proposed cycle is a process integration of LNG regasification, steam methane reforming (SMR), and hydrogen liquefaction systems, and second, the proposed model is more efficient in terms of energy consumption than other similar cycles mentioned in the literature. The specific energy consumption (SEC) and the capacity of the optimized proposed model are 6.59 kWh/kg_LH2 and 371 tones per day, respectively. The sales price of liquid hydrogen as the product of the proposed cycle is $ 2/kg in 3 years payback period, making it economically viable. Energy, exergy, and economic analyses are implemented to analyze the proposed hydrogen liquefaction cycle. The optimized case undergoes 30% better performance by the genetic algorithm (GA) optimization method in terms of SEC than the base case.
Keywords: Exergy analysis; Hydrogen liquefaction; Economic analysis; Genetic algorithm; LNG regasification; Mixed refrigerant.
Analysis of a Kalina Cycle Integrated with a Reheat Furnace
by Sevgi Aslan, Cuma Karakus, Yildiz Koc, Huseyin Yagli, Ali Koc
Abstract: In the present paper, parametric optimisation, energy and exergy analyses of KC was performed together with economic and environmental analyses. After parametric, energy and exergy analyses of KC, maximum net power production, thermal efficiency and exergy efficiency of KC were calculated as 389.44 kW, 33.86% and 68.96% at 430
Keywords: Reheat furnace; Kalina cycle; waste heat recovery; economic analyses; environmental analyses; energy; exergy.
Conventional and enhanced exergy analyses of a parallel integrated thermal management system for pure electric vehicles
by Meijie Gao, Moran Wang, Kunfeng Liang, Chunyan Gao, Bin Dong, Lin Wang
Abstract: To improve the efficiency of the integrated thermal management system (ITMS) of pure electric vehicles, an enhanced exergetic analysis method was proposed. According to enhanced exergetic analysis, the exergy destruction distribution of main components of ITMS was detected in-depth, the internal factors arousing the exergy destruction of each component and the priority of component optimization can be recognized. The results indicate that the priority order of improving components of ITMS is the condenser, the battery evaporator, and then the cabin evaporator. The exergy destruction within the evaporator is entirely belonged to the endogenous part, and the exergy destruction of the condenser is mainly caused by the condenser itself, its endogenous exergy destruction (78.8%) is greater than the exogenous exergy destruction (21.2%). Meanwhile, the enhanced exergetic analysis suggested that the avoidable exergy destruction of the system accounts for about 68.7% of the total exergy destruction of the system, the potential for improvement of the system is huge. The interaction among the components is not strong, due to the 72.38% of exergy destruction in the system is endogenous.
Keywords: thermodynamics; ITMS; enhanced exergetic analysis; exergy destruction; pure electric vehicles
Special Issue on: CPOTE2020 The Energy System Beyond 2020 - Exergy Application in Assessment and Optimisation
Characterization of the Effect of Water Content on the Methanol Spray Combustion
by Chih-Yung Wu, Bo-Yi Hu
Abstract: The methanol spray combustion in the laboratory-scale combustor was experimentally studied in the present study, especially for the effect of the water content in methanol on the flame phenomena. The results showed that as the water content in the fuel mixture was less than 10%, and the flames can be sustained stably. The appearance of the flames was not significantly different for various water contents in the fuel mixture. However, the flame length was reduced by increasing water contents, but there was no apparent change in the flame lift-off height. The exergy efficiency was in the range of 18-21%. In addition, near flame extinction, the increase of specific exergy destruction can be found. As the water content in the fuel mixtures was increased by 10%, the exergy efficiency reasonably decreased by 9.98%, but the thermal efficiency reduced by 26.61%.
Keywords: spray combustion; methanol economy; exergy analysis.
Simultaneous thermodynamic and economic enhancement of heat pumps based on a new method for avoidable irreversibility assessment
by Volodymyr Voloshchuk, Paride Gullo, Olena Nekrashevych
Abstract: The paper presents a new method aimed at the simultaneous thermodynamic and economic enhancement of air-source and water-source heat pumps. The novel approach allows estimating the avoidable parts of the exergy destruction and investment expenditures by avoiding the need for ideal process introduction, being the most critical issue associated with the application of the existing advanced exergy-based methodology. In fact, within the proposed new method the values of the avoidable parts of investment expenditures of the k-th component belonging to the considered heat pumps are determined assuming a greatly efficient component rather than not an extremely inefficient one. The proposed approach was applied to domestic hot water heat pumps using R410A and R134a to evaluate its potential. The results obtained suggested that at the investigated operation conditions the condenser and the evaporator are components for which minimizing irreversibilities can provide simultaneous thermodynamic and economic enhancement.
Keywords: exergy analysis; avoidable exergy destruction; Heat pumps; component interactions; thermodynamic improvement; economic improvment; exergoeconomic analysis.
Energy and exergy analyzes of a cogeneration unit in an oil refinery: a case study
by Luiz Fernando Ferreira, Waldyr Gallo
Abstract: This case study performed energy and exergy analyses of a cogeneration plant in an oil refinery, generating 97.8 MW of electrical power and 885 t/h of steam at 485
Keywords: Energy Analysis; Exergy Analysis; Cogeneration Operation; Industrial Indicators.
Improving the operation of heat exchanger networks through exergy analysis
by Bahar Saeb Gilani, Tatiana Morosuk
Abstract: In this paper a procedure is introduced to compare alternative control configurations for the optimal operation of heat exchanger networks. The novelty of the proposed method lies on the exergy-based formulation of the optimization problem. The method uses the advantage of exergy analysis in quantifying the thermodynamic inefficiencies of heat exchangers and mixers as the fundamental elements of heat exchanger networks. Two different bypass placements are compared for an example heat exchanger network at steady state to illustrate the advantage of exergy analysis in understanding and improving the performance of the system. It is shown that in some cases solving the optimization problem based on energy does not indicate any differences between alternative design configurations. Whereas solving the optimization problem aiming at the minimum exergy destruction provides the missing information. For the studied heat exchanger network, while both designs require the same amount of heat utility, one design demonstrates around 25% less exergy destruction. It is also shown for the first time in this paper that applying exergy-based optimization reveals further room for the improvement of the heat exchange network operation. By readjusting the manipulated variables of the control system, the total exergy destruction of the heat exchanger network can be reduced by over 6% for both studied design configurations.
Keywords: Heat Integration; Heat Exchanger Network; Exergy Analysis; Optimal Operation; Control Configuration; On-line Optimization.