Exergy Research Papers - Academia.edu (original) (raw)

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- Engineering, Mechanical Engineering, Aerospace Engineering, Exergy
- by Canan Acar
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- Hydrogen, Energy efficiency, GHG Emissions, Global Warming

Multicrystalline (multi-Si) photovoltaic (PV) technology is increasingly common throughout Australia and the developed world, as renewable energy technologies become viable electrical generation alternatives to coal and nuclear power. We have examined the cradle-to-grave life cycle of a 3kWp multi-Si PV system within Australia. The highest contribution of environmental impacts results from the usage of fossil fuel energy resources and their emissions at the pre-production and manufacturing stages. We analyze the impacts of multi-Si technology on ecosystem goods and services (EGS) and compared it with impacts resulting from coal power electricity. For 3kWp multi-Si system, coal, crude oil and iron ore were the critical resources consumed from the lithosphere while the public supply of water was consumed from the hydrosphere. For coal power electricity, coal and water were the resources most consumed from both the lithosphere and hydrosphere. However the resource consumption from coal power electricity is significantly larger than that of multi-Si PV. Coal power electricity is also responsible for much greater energy and exergy consumption compared to multi-Si PV. The main ecosystem disturbances resulting from the lifecycle of a 3kWp multi-Si unit affect supporting and regulating services though these disturbances are considerably lower than the services impacted from coal power electricity. The study concludes that similar analysis performed on another PV technology would provide a greater understanding to the Eco-LCA results for multi-Si PV technology, particularly with relation to exergy analysis.

- by Lifescience Global Canada and +1
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- Exergy
- by Rafael Souza
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- Engineering, Optimization, Dependability, Exergy

In this paper, the exergy analysis of “(56MW) the rmal power plant Raipur (India); a case study” are presented. The main objectives of this paper are to analyze the plant’s component separately and to id entify the parts having largest exergy losses. This paper will also justify the major sources of losses and exergy dest ruction in the power plant. According to the study, percentage rat io of the exergy destruction to the total exergy de struction was found to be maximum in the boiler system (57 %) followed by the turbine (33.3%), and then the condense r (5.34%). the exergy efficiency of the power plant was 31.12% . Which are low compared to modern power plants. According to analysis found that boiler is the major source o f irreversibility in the power plant, but exergy de struction rate in boiler can be reduced by reheating the system. It i s a suitable technique for decrease boiler’s irreve rsibility. How reheating is the best tool for improvement of overa ll performance and com...

- by Sahil Suryvanshee
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- Exergy, Exergy Analysis, Thermal Power Plant, Organic rankine cycle

Hybrid photovoltaic-thermal (PVT) collector has been developed by combining photovoltaic (PV) technology and solar thermal collector in one module. The combination of two technologies in the same module has the potential to reduce cost of materials and the required space also improves performance of collectors. The hybrid PVT collectors were designed to generate electrical and thermal energy simultaneously. PV technology converts solar radiation into electrical energy while solar thermal collector will be converting solar energy to thermal energy. The main components of PVT collectors are PV panel, absorber plate, working fluid and insulator. According to the previous research, PVT collectors were developed by using air and water as a heat transfer medium. The benefits of heat removal are increasing PV panel efficiency by removing excessive heat from module. Parameters affecting the overall performances of PVT collectors included mass flow rate, area of collector, irradiance and PV cell materials. This paper presents a review of energy and exergy analysis of air-based and water-based PVT collector with different designs. The performances of PVT collectors were studied using First Law and Second Law of Thermodynamics. This study has found that generally the energy and exergy efficiency are range from 40%-70% and 5%-25%, respectively.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2020 The Authors. Energy Science & Engineering published by the Society of Chemical Industry and John Wiley & Sons Ltd. Department of Mechanical Engineering, University of Mazandaran, Babolsar, Iran

- by Reza Babaei
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- Environmental Science, Malaysia, Energy and Environment, Optimization

A conceptual trigeneration system is proposed based on the conventional gas turbine cycle for the high temperature heat addition while adopting the heat recovery steam generator for process heat and vapor absorption refrigeration for the... more

- by Khushi Choudhary
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- Engineering, Mechanical Engineering, Environmental Science, Thermodynamics

Although water is a cheap and effective medium for thermal energy storage, other options are currently being studied, to increase the storage density or to reduce the cost of the storage. The authors have been developing a system which combines the advantages of stratified sensible heat storage and latent, phase change heat storage; i.e. a hot water storage tank with stratification where a phase change material (PCM) is included into a spiral tube installed in the top of the tank. The PCM used was a granular PCM–graphite compound of about 90 vol.% of sodium acetate trihydrate and 10 vol.% graphite. This paper presents the results of an experimental investigation of the performance of the new storage concept, and of a conventional hot water storage tank for comparison. The data are further analysed with respect to the energetic and exergetic performance of the two systems. Copyright © 2007 John Wiley & Sons, Ltd.

- by Marc Medrano
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- Mechanical Engineering, Chemical Engineering, Energy, Exergy
- by Ismail Hasan
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- Mechanical Engineering, Modeling, Heat Transfer, Performance

The black liquor is a byproduct of the kraft pulping process that contains more than half of the exergy content in the total woody biomass fed to the digester, representing a key supply of renewable energy to the pulping process. In this work, the conventional scenario of the black liquor use (i.e., concentration and combustion) is compared with the black liquor upgrading (via) gasification process for ammonia production in terms of economics, exergy efficiency and environmental impact. The combined energy integration and exergy analysis is used to identify the potential improvements that may remain hidden to the energy analysis alone, namely, the determination and mitigation of the process irreversibility. As a result, the exergy efficiencies of the conventional and the integrated cases average 40% and 42%, respectively, whereas the overall emission balance varies from 1.97 to −0.69 tCO2/tPulp, respectively. The negative CO2 emissions indicate the environmental benefits of the proposed integrated process compared to the conventional kraft pulp mill.

- by Daniel Flórez-Orrego and +1
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- Thermodynamics, Biorefinery, Biomass gasification for thermal and power application, Exergy
- by B. Michel
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- Mechanical Engineering, Civil Engineering, Energy, Green Computing

Exergoeconomic (thermoeconomic) analysis is performed on Alkhoms steam power plant. The nominal power of the plant is 120 MW. The analysis is based on real-time data and performed for three different loads. The main factor of load variation is the variation of the steam mass flow rate. These loads are 120 MW (full load), 60 MW (part load), and 100 MW (real-time operation). It is worth to mention that high-pressure heaters are out of service these days. A systematic and general methodology for defining and calculating exergetic efficiencies, exergy destruction, and exergy related to costs in thermal systems is presented. The methodology is based on the Specific Exergy Costing (SPECO) method. Results of the exergy analysis showed the exergetic efficiency (effectiveness) increases from 34.74% at the real-time operation to 40.96% at full operating load, and hence the ratio of the total exergy destruction to fuel input exergy decreases from 64.46% at a real-time operation to 59.6 at part load up to 57.88% at full operating load. The exergoeconomic analysis results the average specific cost is 0.177 /kWhatreal−timeoperationand0.113/kWh at real-time operation and 0.113 /kWhatreal−timeoperationand0.113/kWh at part load, and 0.102 /kWhatfulloperatingloadtakingintoconsiderationtheescalationoffuelprice(levelizedfuelcost).Itisfoundthatthecostofexergydestructioninthesteamgeneratorpresentsthemaincontributiontothetotalcostofexergyloss;itsvaluevariesinthesteamgeneratorfrom8296/kWh at full operating load taking into consideration the escalation of fuel price (levelized fuel cost). It is found that the cost of exergy destruction in the steam generator presents the main contribution to the total cost of exergy loss; its value varies in the steam generator from 8296 /kWhatfulloperatingloadtakingintoconsiderationtheescalationoffuelprice(levelizedfuelcost).Itisfoundthatthecostofexergydestructioninthesteamgeneratorpresentsthemaincontributiontothetotalcostofexergyloss;itsvaluevariesinthesteamgeneratorfrom8296/h at the real-time operation to 6560 /hatfulloperatingload,whileexergydestructioncostatpartloadisatanotablevalueof3495/h at full operating load, while exergy destruction cost at part load is at a notable value of 3495 /hatfulloperatingload,whileexergydestructioncostatpartloadisatanotablevalueof3495/h due to low fuel consumption. The contributions and the variation of exergy destruction cost with load are lower for the other components.

- by HAITHAM ELHEJAJI
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- Exergoeconomics, Exergy, Thermoeconomic Analysis, Exergy Destructions

These notes aim to increase the awareness of the concept of Bejan Number among the readers of International Communications in Heat and Mass Transfer. They refer to the paper of Zimparov et al. because the authors, in their outstanding commentary on Bejan number neglect both the possible confusion which may arise between Hagen Number and Bejan number and the more recent outcomes which opens a new direction for future research.

- by Michele Trancossi and +1
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- Thermodynamics, Fluid Dynamics, Entropy, Navier-Stokes Equations

An industrial-scale molasses-based bioethanol production system was modeled and studied by conducting exergy, exergoeconomic, and exergoenvironmental analyses. The entire process was represented by a control volume, and its exergoeconomic and exergoenvironmental parameters were determined using the specific exergy costing (SPECO) approach. These exergy-based analyses were carried out to measure the overall exergy dissi-pation, cost, and environmental impact of the bioethanol production process based on actual operational ther-modynamic, economic, and environmental data. Natural gas showed the highest contribution to the total input exergy (61.1%) and total environmental impact rate (56.6%) of the process, while the highest contribution to its total cost rate (75.7%) was from molasses. The exergetic efficiency determined for the process was 35.9%, while the exergy dissipation accounted for 60.8% of its total input exergy. The unit exergoeconomic costs of the fuel and product were determined to be 6.2 and 20.9 USD/GJ, while the unit exergoenvironmental impacts of the fuel and product were 15.5 and 31.5 mPts/GJ, respectively. The exergoeconomic factor of the process was found to be 29.4%, while the exergoenvironmental factor was 0.74%. Overall, natural gas consumption was the most significant exergetic hotspot of the process, and hence more exergetically-sustainable alternatives should be considered to improve the process. Low-cost waste feedstocks need to be utilized to improve the economic viability of the process.

- by Mohammad Rehan and +1
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- Environmental Engineering, Chemical Engineering, Civil Engineering, Environmental Science

The increase of waste presents a challenge for organizations and societies pursuing sustainable development. In this context, recycling is widely recognized for being a friendly strategy to the environment and the proper approach to effectively manage waste and minimize the negative impact on the environment and the economy. However, since the available recycling technology requires both raw materials and energy, it ultimately contributes to the depletion of natural resources. Therefore, it is vital to assess the energy efficiency of recycling processes to determine their real benefit. The scientific literature suggests a series of approaches , requirements and practices, which may be, at first sight, confusing. The present study focuses on efficiency evaluation of recycling processes by means of exergetic analyses. It performs a systematic review, based on nine significant factors in recycling processes, of the relevant literature concerning the evaluation of recycling processes through the exergetic approach. The review makes two important contributions. First, it presents an approach for assessing such diverse literature by means of a single structure. In addition, it allows the identification of improvement opportunities and reveals future research opportunities.

- by Milton Borsato and +1
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- Energy, Recycling, Exergy, Efficiency

In this study, we study and evaluate a zero emission integrated system, as taken from the literature, for coproduction of electricity and methanol. The investigated integrated system has three subsystems: water electrolysis, Matiant power plant (oxy-fuel combustion of pure methane), and methanol production unit. The system and its components are analyzed energetically and exergetically. The rates of exergy destructions, relative irreversibilities, and sustainability indexes of each subunit of each subsystem, as well as the overall system are analyzed to identify the greatest exergy losses and possible future research directions. The total rate of exergy destruction of the overall system is calculated to be around 280 MW. The greatest rate of exergy destruction, therefore the greatest irreversibility, occurs within the power plant unit (about 60 % of the total rate of exergy destruction). The energy efficiencies of electrolysis, power plant, and methanol synthesis unit are found to be 30 %, 76 %, and 41 %, respectively. The exergy efficiencies of electrolysis, power plant, and methanol synthesis unit are found to be 30 %, 64 %, and 41 %, respectively. Depending on the utilization of the heat rejected from the different units of each subsystem, the overall system could have energy and exergy efficiencies up to 68 % and 47 %, respectively.

- by Canan Acar
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- GHG Emissions, Clean energy technologies, Exergy, Exergy Analysis
- by S A. Moneim
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- Mechanical Engineering, Performance Evaluation, Exergy, Exergy Analysis
- by Zafer Utlu
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- Thermodynamics, Architecture, Energy, Natural Gas

This study reviews gas engine-driven heat pump (GEHP) systems for residential and industrial applications in terms of energetic and exergetic aspects for the first time to the best of the authors’ knowledge. These systems are novel heat pump systems (one of today's promising new technologies). Although the first investigations had been performed at late 1970s, the first merchandized GEHP was produced and introduced in the market in 1985. Gradually, it has become widespread all over the world for various purposes. Main application of GEHPs are for space and water heating/cooling purposes. However, they can be integrated to industrial applications, especially to drying processes.In this study, historical development of GEHP systems was briefly given first. Next, the operation of these systems was described, while studies conducted on them were reviewed and presented in tabulated forms. GEHPs were then modeled for performance evaluation purposes by using energy and exergy analysis methods. Finally, an illustrative example was given, while the results obtained were discussed. In addition, a new project on integration of GEHP systems to food drying processes in Turkey initiated by the authors was introduced. It is expected that this comprehensive study will be very beneficial to everyone involved or interested in the energetic and exergetic design, simulation, analysis and performance of assessment of GEHP systems.

- by Neslihan Colak
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- Engineering, Sustainable Development, Performance, Sustainable Energy
- by Antonello Barresi
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- Coffee, Food Engineering, Quality by Design, Exergy
- by Mithat Direk
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- Performance Evaluation, Exergy, Air Conditioning, Heat pump
- by Renwei Mei
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- Thermodynamics, Water, Performance, Energy Consumption

ABSTRACT Thermo–economic analysis of Heat Pipe Heat Exchanger (HPHE) for waste heat recovery in thermal systems using the P1–P2 and NTU methods is presented. The optimum effectiveness of a HPHE is given as a polynomial equation, whereas the net savings and payback period are given in closed form to enable the HPHE designer to determine the optimised values directly. In addition to this, exergy analysis of HPHE for waste heat recovery in thermal systems is formulated. The variation of exergy efficiency with respect to change in inlet temperature is also presented.

- by Anirudh Bhaskaran
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- Mechanical Engineering, Thermoeconomics, Exergy, Exergy Analysis
- by Abdul Khaliq
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- Mechanical Engineering, Chemical Engineering, Energy, Performance
- by Husain Almuslim
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- Mechanical Engineering, Chemical Engineering, Thermodynamics, Energy
- by Umit Unver
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- Mechanical Engineering, GAS TURBINE, Energy efficiency, Exergy
- by Canan Acar
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- Exergy
- by D. Berstad and +1
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- Engineering, Hydrogen, Liquefaction, Comparative Study

An exergy modeling and optimization of an industrial ammonia unit based on steam methane reforming (SMR) process is presented. The base-case unit produces about 1000 t NH3/day [1], as well as power and steam, with no auxiliary exergy use. Some critical operation parameters are analyzed and the base-case and optimal operating conditions of the major components are compared. Since the ammonia synthesis process is highly exothermic, higher per-pass conversions in industrial adiabatic reactors are often achieved by using various sequential catalyst beds, where a near-optimum profile of reaction rate vs temperature can be attained by regulating the inlet temperature of each bed. This is performed via internal heat recovery, either by preheating reactor feed gas or by using waste heat boilers, which results in an increase of the steam production and a smaller fuel consumption. But, although such near-optimum operation conditions may lead to higher reaction rates and, thus, lower catalyst volumes could be required, it is found that the optimal design of the ammonia loop is rather determined by the performance of each component and their interdependencies. Moreover, since the proposed objective function (exergy destruction minimization) is very sensitive to specific process variables, the convergence of the solution algorithm is sometimes hindered. The exergy destruction breakdown shows that the ammonia converter and the refrigeration system are together responsible for more than 71e82% of the total exergy destruction in the ammonia loop, which in turn varies between 25.6 and 38.8 MW for optimal and base-case operation conditions, respectively.

In the second part of this study, heat-pump drying systems were comprehensively reviewed in terms of applications and performance evaluations. In this regard, these systems were classified in terms of type of heat pump systems, type of dryer and product types first. The performance assessments included coefficient of performance (COP), specific energy consumption (SEC) and specific moisture extraction rate (SMER), while types of energetic, exergetic and cost analyses were covered. It may be concluded that the most preferred method used to determine the HPD efficiency is SMER, while in recent years exergetic analysis method has been widely used.

- by Neslihan Colak
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- Energy, Performance Assessment, Performance Evaluation, Exergy
- by Harun Kemal Ozturk
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- Mechanical Engineering, Chemical Engineering, Energy, Fuel Cell
- by Valeriy Maisotsenko
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- Engineering, Thermodynamics, Energy, Refrigeration

This study involved the performance of energy and exergy analysis on a 200 MW Steam cycle power plant (SCPP). The aim is to investigate the effect of using different number of feed water heaters (FWHs) on the cycle performance. Several simulation analyses were conducted in this study on a MATLAB platform. The computer model used was based on natural gas combustion, enthalpy balances, energy balances, and entropy changes of the SCPP. The real case study was simulated on a validated model of the SCPP for Shahid Montazeri Power Plant. The exergy destroyed within each components system and the exergy efficiency are determined to study the irreversibility of the system and identify the chances for the enhancement of the power system. Based on the result of the analyses, the energy and exergy efficiencies of the SCPP were determined to be about 37.52 % and 41.7 %, respectively. In the SCPPs, the combustion chamber (boiler) contributes the highest exergy destruction rate (around 48 % of the exergy value of the gas) among the main components of the power system.

- by Ahmed Al-Sammarraie
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- Energy, Exergy, Optimisation of Steam Cycle
- by Daniel Favrat
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- Mechanical Engineering, Renewable Energy, Energy, Heat Transfer
- by George Tsatsaronis
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- Mechanical Engineering, Civil Engineering, Thermodynamics, Methodology

The Second Law of Thermodynamics talks about the entropy and exergy of a thermodynamic system in its own state of internal thermodynamic equilibrium. It is an empirical finding that has been accepted as an axiom of thermodynamic theory. This law is explained through Statistical thermodynamics either classically or through quantum formulation. Although the firstlaw aspects of thermodynamics readily understood & accepted, people fail to comply with the secondlaw aspects. It is viewed as a topic more of theoretical interest rather than being an important engineering tool well applicable to our life aspects. In view of human efficiency, the second law discussion disregards the availability of time to a person being a problem and rather focuses upon its effective utilization. The irreversiblity of a process cast the difference between the actual work delivered and the maximum work (reversible work) that could have been derived from the system. Here we try to identify the major sources of irreversibilities and the way to minimize them in order to maximize performance.

- by Chandan Sinha
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- Thermodynamics, Exergy, Second Law of Thermodynamics

This paper presents an exergy and environmental assessment of a 1000 metric t/day ammonia production plant based on the steam methane reforming (SMR) process, including the syngas production, purification (CO 2 capture) and compression units, as well as the ammonia synthesis and purge gas treatment. An integrated heat recovery system produces power and steam at three pressure levels, besides exporting hot water, CO 2 and fuel gas, with no additional heat or power consumption being required. Two configurations for ammonia refrigeration process (À20 C) are compared in terms of power consumption. Exergy cost data for upstream processing stages of natural gas is used to calculate the extended exergy cost of the products of the plant, namely ammonia, CO 2 and fuel gas. Moreover, an appropriated methodology is employed to properly allocate the renewable and non-renewable exergy costs, as well as the CO 2 emissions of the reforming, shift and furnace stack among the products of the plant. By considering that the cost reduction of the combustion gases is a linear function of the exergy flow rate reduction in each component of the heat recovery system, an improved allocation of the CO 2 emission cost along the convection train is performed. A breakdown of the total exergy destruction rate of the plant (136.5 MW) shows that about 59% corresponds to the reforming process followed far behind by the ammonia synthesis and condensation (18.3%) and the gas purification units (13.2%). The overall exergy efficiency of the ammonia plant is calculated as 66.36%, which is enhanced by recovering the hydrogen-rich and fuel gases in the purge gas treatment process. The total and non-renewable exergy costs and CO 2 emission cost of the ammonia produced are calculated as 1.7950 kJ/kJ and 0.0881 kg CO2 /MJ, respectively. In addition, a rational exergy cost of 1.6370 kJ/kJ and CO 2 emission cost of 0.0821 kg CO2 /MJ are allocated to the CO 2 gas, which can be supplied as feedstock to an associated chemical plant (urea, methanol, polymers, etc.).

- by syed shabbar raza
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- Energy Conversion, Exergy, Plasma, Electrical And Electronic Engineering
- by Eunice Sefakor Dogbe
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- Mechanical Engineering, Energy, Process Engineering, Exergy
- by Maziar Arjomandi
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- Engineering, Refrigeration, Analysis, Exergy
- by Roberto Pisano
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- Engineering, Coffee, Process Optimization, Food Engineering

In this study, we investigate the economic, environmental and social impacts of various hydrogen production methods,
based on fossil fuel and renewable energy resources with a special emphasis on hybrid photoelectrochemical systems perform
comparative assessments of these methods for applications. The sources considered for hydrogen production in this
study are water, fossil hydrocarbons, and biomass. Furthermore, the primary energy sources considered in this study are
natural gas, coal, biomass, wind and solar. In order to address sustainability, the relationship between efficiency and environmental
impact is also investigated. The results show that solar based hydrogen production options (photocatalysis,
photoelectrolysis, and photoelectrochemical methods) provide near zero global warming potentials and air pollutants, while
coal gasification has the highest ones. In regards to the exergy efficiencies, biomass gasification gives the highest exergy
efficiency, while photoelectrochemical method ends up with the lowest one.

- by Canan Acar
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- Renewable Energy, Hydrogen, Energy, Energy and Environment

... Various criteria in optimization of a geothermal air conditioning system with a horizontal ground heat exchanger Hoseyn Sayyaadi Ć,y and Emad Hadaddi Amlashi Faculty of Mechanical EngineeringEnergy Division, KN Toosi University of... more

... Ahmet Koca a , Hakan F. Oztop b , Tansel Koyun c and Yasin Varol a , Corresponding Author Contact Information , E-mail The Corresponding Author. ... from 1.22 to 2.63 kW, whereas the rate of heat stored in the LHS unit were 111.2 and... more

- by Yasin Varol
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- Mechanical Engineering, Chemistry, Renewable Energy, Heat Transfer
- by George Tsatsaronis
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- Mechanical Engineering, Exergy