scholarly journals Dynamic Extended Exergy Analysis of Photon Enhanced Thermionic Emitter Based Electricity Generation

2021 ◽  
Author(s):  
Canberk Unal ◽  
Emin Acikkalp ◽  
David Borge-Diez
Keyword(s):  
Environmental Impact ◽  
Electricity Generation ◽  
Exergy Analysis ◽  
Energy Analysis ◽  
Energy Systems ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Related System ◽  
Social Data ◽  
Energy Flows

Exergy is the very useful tool to evaluate energy systems besides energy analysis based on the first law of the thermodynamics. In contrast to energy, exergy is not conserved and always decreases. There are many types of exergy analysis involving exergoeconomic, exergoenvironmental, advanced exergy-based analyses, extended exergy analysis etc. In this study, an application of the extended exergy analysis is performed. In extended exergy analysis, not only energy related system is considered but also all materials and energy flows’ exergy, non-energetic and immaterial fluxes (capital, labor and environmental impact) are turned into exergy equivalent values and utilized in the analysis, which are calculating for local econometric and social data. These methods can be applied to societies or energy based or non-energy-based system. In this study, dynamic exergy analysis and extended exergy application of electricity generation from photon enhanced thermionic emitter is conducted. According to results, some important values can be listed as; extended exergy destruction, conventional based exergy destruction, extended exergy efficiency, conventional exergy efficiency, extended sustainability ratio, conventional sustainability ratio, extended exergy-based depletion ratio and conventional exergy-based depletion ratio are 542106006 MJ, 542084601 MJ, 0.01094, 0.01094, 1.011, 1.011, 0.978 and 0.989 respectively.

scholarly journals Performance Optimizations of the Transcritical CO2 Two-Stage Compression Refrigeration System and Influences of the Auxiliary Gas Cooler

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5578
Author(s):  
Yuyao Sun ◽  
Jinfeng Wang ◽  
Jing Xie
Keyword(s):  
Exergy Analysis ◽  
Energy Analysis ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
System Operation ◽  
Two Stage ◽  
Intermediate Pressure ◽  
Discharge Temperature ◽  
Performance Optimizations

To optimize the performance of the transcritical CO2 two-stage compression refrigeration system, the energy analysis and the exergy analysis are conducted. It is found that higher COP, lower compression power, and less exergy destruction can be achieved when the auxiliary gas cooler is applied. Moreover, the discharge temperature of the compound compressor (HPS) can be reduced by decreasing the temperature at the outlet of the auxiliary gas cooler (Tagc,out). When the Tagc,out is reduced from 30 to 12 ℃, the discharge temperature of the compound compressor (HPS) can be decreased by 13.83 ℃. Furthermore, the COP and the exergy efficiency can be raised by enhancing the intermediate pressure. Based on these results, the optimizations of system design and system operation are put forward. The application of the auxiliary gas cooler can improve the performance of the transcritical CO2 two-stage compression refrigeration system. Operators can decrease the discharge temperature of the compound compressor (HPS) by reducing the Tagc,out, and increase the COP and the exergy efficiency by enhancing the intermediate pressure.

Exergy Analysis of a Combined Power and Refrigeration Thermodynamic Cycle Driven by a Solar Heat Source

2003 ◽  
Vol 125 (1) ◽  
pp. 55-60 ◽  
Author(s):  
Afif Akel Hasan ◽  
D. Y. Goswami
Keyword(s):  
Heat Source ◽  
Exergy Analysis ◽  
Thermodynamic Cycle ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Water Mixture ◽  
Exergy Destruction ◽  
Ammonia Water ◽  
Solar Heat

Exergy thermodynamics is employed to analyze a binary ammonia water mixture thermodynamic cycle that produces both power and refrigeration. The analysis includes exergy destruction for each component in the cycle as well as the first law and exergy efficiencies of the cycle. The optimum operating conditions are established by maximizing the cycle exergy efficiency for the case of a solar heat source. Performance of the cycle over a range of heat source temperatures of 320–460°K was investigated. It is found that increasing the heat source temperature does not necessarily produce higher exergy efficiency, as is the case for first law efficiency. The largest exergy destruction occurs in the absorber, while little exergy destruction takes place in the boiler.

Teaching Power Cycles by Comparative First- and Second-Law Analysis of Their Evolution

1997 ◽  
Vol 25 (1) ◽  
pp. 13-31 ◽  
Author(s):  
William R. Dunbar ◽  
Noam Lior
Keyword(s):  
Power Plants ◽  
Exergy Analysis ◽  
Energy Analysis ◽  
Energy Systems ◽  
Thermal Engineering ◽  
Second Law ◽  
Intellectual Curiosity ◽  
Educational Approach ◽  
Power Cycles ◽  
Second Law Analysis

The teaching of power cycles in courses of thermodynamics or thermal engineering was traditionally based on first-law analysis. Second-law analysis was typically taught later, and not integrated with it. This approach leaves the student ignorant of the effect of operating parameters and cycle modifications on the accompanying exergy (availability) magnitudes and component irreversibilities, which are necessary for evaluating the potential for further system improvements. It also leaves many of the students with an ambiguous understanding of the exergy concept and its use. Consonant with the gradual changes in this educational approach, which increasingly attempt to integrate first- and second-law analysis, this paper recommends a strategy which integrates exergy analysis into the introduction and teaching of energy systems, demonstrated and made didactically appealing by an examination of the historical evolution of power plants, emphasizing the objectives for improvements, accomplishments, constraints, and consequently the remaining opportunities. Important conclusions from exergy analysis, not obtainable from the conventional energy analysis, were emphasized. It was found that this approach evoked the intellectual curiosity of students and increased their interest in the course.

scholarly journals Probabilistic Exergoeconomic Analysis of Transcorp Power Plant Ughelli

2016 ◽  
Author(s):  
Otujevwe P. Ogbe ◽  
Nnamdi B. Anosike ◽  
Ugochukwu C. Okonkwo
Keyword(s):  
Combustion Chamber ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Design Point ◽  
Destruction Efficiency ◽  
Plant Operations ◽  
Full Load Operation ◽  
Exergoeconomic Analysis ◽  
Industrial Gas Turbine

In this study, the probabilistic exergoeconomic analysis was performed for four industrial gas turbine (GT) units comprising of two   (GT16 and GT19) units of 100MW GE engine and two (GT8 and GT12) units of 25MW Hitachi engine at Transcorp Power Limited, Ughelli. These four industrial GT engine units were modelled and simulated using natural gas as fuel. The design point (DP) simulation results of the modelled GT engines were validated with the available DP thermodynamic data from original equipment manufacturer (OEM). This was done before the off-design point (ODP) simulation was carried out which represents the plant operations. The results obtained from exergy analysis at full load operation show that the turbine has the highest exergy efficiency followed by compressor and combustion having the least. For turbines these were 96.13% for GT8 unit, 98.02% for GT12 unit, 96.26% for GT16 unit, and 96.30% for GT19 unit. Moreover, the combustion chamber has the highest exergy destruction efficiency of 55.16% GT8 unit, 56.58% GT12 unit, 43.90% GT16 unit, and 43.30% GT19 unit respectively. The exergy analysis results obtained from the four units show that the combustion chamber (CC) is the most significant exergy destruction with lowest exergy efficiency and highest exergy destruction efficiency of plant components. The exergoeconomic analysis results from four units showed combustion chamber energy destruction cost of 531.08 $/h GT8 unit, 584.53 $/h GT12 unit, 2351.81$/h GT16, and 2315.93$/h GT19 unit. The probabilistic results analysis based on the input parameters distributions evaluated and discussed.

scholarly journals Exergy Analysis of Kalina and Kalina Flash Cycles Driven by Renewable Energy

2020 ◽  
Vol 10 (5) ◽  
pp. 1813
Author(s):  
Kyoung Hoon Kim ◽  
Hyung Jong Ko ◽  
Chul Ho Han
Keyword(s):  
Exergy Analysis ◽  
Power Production ◽  
Ammonia Concentration ◽  
Exergy Efficiency ◽  
Low Grade ◽  
Heat Sources ◽  
Exergy Destruction ◽  
Kalina Cycle ◽  
Low Grade Heat ◽  
Exergy Performance

The Kalina cycle (KC) has been recognized as one of the most efficient conversion systems of low-grade heat sources. The Kalina flash cycle (KFC) is a recently proposed novel cycle which is equipped with an additional flash process to the KC. In this study, the exergy performance of KC and KFC driven by a low-grade heat source are investigated comparatively. The dependence of the exergy destruction at each component as well as the system’s exergy efficiency on ammonia concentration, separator pressure and, additionally, flash pressure for KFC, are systematically investigated. Results showed that KFC can be optimized with respect to flash pressure on the base of exergy efficiency, and the component where largest exergy destruction occurs varies for different separator pressure and ammonia fraction in both systems. It is also shown that the maxima of net power production and exergy efficiency in KFC with optimal flash pressure are superior to those in KC.

scholarly journals Exergy Efficiency Optimization for Gas Turbine Based Cogeneration Systems

2013 ◽  
Author(s):  
Ana C. Ferreira ◽  
Senhorinha F. Teixeira ◽  
José C. Teixeira ◽  
Manuel L. Nunes ◽  
Luís B. Martins
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Plant Performance ◽  
System Component ◽  
Inlet Temperature ◽  
Exergy Destruction ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

Energy degradation can be calculated by the quantification of entropy and loss of work and is a common approach in power plant performance analysis. Information about the location, amount and sources of system deficiencies are determined by the exergy analysis, which quantifies the exergy destruction. Micro-gas turbines are prime movers that are ideally suited for cogeneration applications due to their flexibility in providing stable and reliable power. This paper presents an exergy analysis by means of a numerical simulation of a regenerative micro-gas turbine for cogeneration applications. The main objective is to study the best configuration of each system component, considering the minimization of the system irreversibilities. Each component of the system was evaluated considering the quantitative exergy balance. Subsequently the optimization procedure was applied to the mathematical model that describes the full system. The rate of irreversibility, efficiency and flaws are highlighted for each system component and for the whole system. The effect of turbine inlet temperature change on plant exergy destruction was also evaluated. The results disclose that considerable exergy destruction occurs in the combustion chamber. Also, it was revealed that the exergy efficiency is expressively dependent on the changes of the turbine inlet temperature and increases with the latter.

Exergy and energy analysis of the Spirulina microalgae blends in a direct injection engine at variable engine loads

2021 ◽  
pp. 1-18
Author(s):  
Nguyen Chi Thanh Thanh ◽  
Ahmad El Askary Askary ◽  
Ashraf Elfasakhany Elfasakhany ◽  
S Nithya
Keyword(s):  
Diesel Engine ◽  
Exergy Analysis ◽  
Fossil Fuel ◽  
Energy Analysis ◽  
Direct Injection ◽  
Experimental Tests ◽  
Exergy Destruction ◽  
Fuel Blends ◽  
Brake Power ◽  
Overall Efficiency

Abstract This paper explores the exergy analysis of the diesel engine with the selected Spirulina Microalgae biooil (SMBO) biodiesel. The adaptability of the biofuels as an efficient replacement to the fossil fuel has to be tested and proved. To estimate the overall efficiency of the engine with the biofuel blends, it is essential to find out the energy conversion capability of the engine. Different fuel blends were taken as B0 (100% diesel), B10 (10% SMBO+90% diesel), B20 (20% SMBO+80% diesel) and B30 (30% SMBOO+70% diesel). All experimental tests were conducted in a naturally aspirated DI engine. The brake power (BP), heat release rate (HRR), exergy destruction, ideal efficiency, actual efficiency, exergy rate and energy rate of the fuel as well as exhaust were measured for all fuel blends. All tests were conducted at different rpm from 0 to 3000 rpm with 500 rpm interval and also at different loads such as 0%, 25%, 50%, 75% and 100% load. The loss of exergy of fuel and thermal was on the rise and noticed in B0, B10, B20 and B30 while the HRR and loss of exergy rate were found in exhaust as more decreasing one in B10, B20 and B30 fuel blends than B0 (pure diesel).

Exergy, Exergoeconomic and Exergoenvironomic Analyses of Selected Gas Turbine Power Plants in Nigeria

2014 ◽  
Author(s):  
Richard Olayiwola Fagbenle ◽  
Sunday Sam Adefila ◽  
Sunday Oyedepo ◽  
Moradeyo Odunfa
Keyword(s):  
Environmental Impact ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Co2 Emissions ◽  
Thermodynamic Analysis ◽  
Power Plants ◽  
Energy Systems ◽  
Energy Utilization ◽  
Inlet Temperature ◽  
Exergy Destruction

Energy supply trends as well as environmental regulations and climate change issues have made it necessary to closely scrutinize the way energy is utilized. Efficient energy utilization thus requires paying more attention to accurate and advanced thermodynamic analysis of thermal systems. Hence, methods aimed at evaluating the performances of energy systems take into account the Energy, Environment and Economics. Therefore, the first and second law of thermodynamics combined with economics and environmental impact represents a very powerful tool for the systematic study and optimization of energy systems. In this study, a thermodynamic analysis of eleven selected gas turbine power plants in Nigeria was carried out using the first and second laws of thermodynamics, economic and environmental impact concepts. Exergetic, exergo-economic and exergo-environmental analyses were conducted using operating data obtained from the power plants to determine the exergy destruction and exergy efficiency of each major component of the gas turbine in each power plant. The exergy analysis confirmed that the combustion chamber is the most exergy destructive component compared to other cycle components as expected. The percentage exergy destruction in combustion chamber varied between 86.05 and 94.6%. Increasing the gas turbine inlet temperature (GTIT), the exergy destruction of this component can be reduced. Exergo-economic analysis showed that the cost of exergy destruction is high in the combustion chamber and by increasing the GTIT effectively decreases this cost. The exergy costing analysis revealed that the unit cost of electricity produced in the plants ranged from cents 1.88/kWh (₦2.99/kWh) to cents 5.65/kWh (₦8.98/kWh). Exergo-environmental analysis showed that the CO2 emissions varied between 100.18 to 408.78 kgCO2/MWh while cost rate of environmental impact varied from 40.18 $/h (N6, 388.62/h) to 276.97 $/h (N44, 038.23/h). The results further showed that CO2 emissions and cost of environmental impact decrease with increasing GTIT.

scholarly journals Exergy Analysis of 1 x 135 MW Jeneponto Steam Power Plant

2021 ◽  
Vol 7 (2) ◽  
pp. 150
Author(s):  
Nur Hamzah ◽  
A.M Shiddiq Yunus ◽  
Waqva Enno Al Fadiyah
Keyword(s):  
Power Plant ◽  
Ambient Temperature ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Second Law ◽  
Exergy Destruction ◽  
Steam Power ◽  
Total Destruction ◽  
Destruction Efficiency ◽  
Mass Flowrate

Exergy analysis is application of the second law thermodynamics which provides information about large exergy, exergy efficiency, destruction, and destruction efficiency in each component of PLTU so can be reference for improvement and optimization in an effort to reduce losses and increase efficiency. The exergy value obtained from calculating mass flowrate, enthalpy, ambient temperature, and entropy. The destruction value is obtained from difference between input exergy value and exergy output. The destruction exergy value from comparison between output exergy value to input exergy value, and destruction efficiency value from comparison of destruction value to total destruction value of PLTU components. The results showed that the largest exergy occurred in boilers, namely 778.225 MW in 2018, 788.824 MW in 2019, and 796.824 MW in 2020, lowest exergy value in CP was 0.160 MW in 2018, 0.176 MW in 2019, and 0.160 MW in 2020. The largest destruction occurred in boilers, namely 163.970 MW with destruction efficiency 79.242% in 2018, 179.450 MW with destruction efficiency 82.111% in 2019, and 199.637 MW with destruction efficiency 83.448% in 2020, lowest exergy destruction value at CP, namely 0.056 MW with destruction efficiency 0.027% in 2018, 0.059 MW with destruction efficiency 0.027% in 2019, and 0.056 MW with destruction efficiency 0.023% in 2020. The exergy efficiency occurred in HPH 2, amounting to 94.750% in 2018, 95.187 % in 2019, and 94.728% in 2020, while lowest of exergy efficiency was in LPH 1, namely 43.637 MW in 2018, 33.512 MW in 2019, and 38.764 MW in 2020.

scholarly journals An exergy analysis for overall hidden losses of energy in solar water heater

2020 ◽  
pp. 343-343
Author(s):  
Sathyakala Ponnusamy ◽  
Sundara Sai Gangadharan ◽  
Balaji Kalaiarasu
Keyword(s):  
Entropy Generation ◽  
Exergy Analysis ◽  
Glass Plate ◽  
Exergy Efficiency ◽  
Solar Water Heater ◽  
Exergy Destruction ◽  
Water Pipe ◽  
Water Heater ◽  
Collector Plate ◽  
Solar Water

This study investigates the hidden thermal losses of glass plate, collector plate, water pipe and storage tank of solar water heater in the process of energy conversion. The present non-conventional energy methods are insufficient, whereas the exergy analysis provides a remarkable solution. Thus, employing the exergy analysis, entropy generation, exergy destruction and exergy efficiency of each subsystem of solar water heater are computed. The obtained results showed that the entropy generation and exergy destruction are high during the heat transfer in each subsystem. Henceforth, the existing solar water heater design is modified placing hexagonal honeycomb structure between the glass plate and the collector plate and also water pipe is insulated to trap huge amount of solar energy. The proposed design exhibits improved exergy efficiency when compared with the existing model, which enhances the performance of the system.

Sign in / Sign up

Export Citation Format

Share Document