Exergy-based methods for computer-aided design of energy conversion systems

800x600 Normal 0 21 false false false DE X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman,serif;} Exergy-based methods (exergetic, exergoeconomic and exergoenvironmental analyses) are powerful tools for developing, evaluating and improving an energy conversion system. Until now, the exergoeconomic and the exergoenvironmental analysis have been conducted independently of each other. This paper presents a way for combining these analyses and for formulating common conclusions for further improvement of an energy conversion system by taking into account simultaneously the minimization of cost and of environmental impact. An academic example consisting of a simple air refrigeration machine, serves as an example for demonstrating the approach.

With the dimension of renewable energy and resources from the earth, solar power has come as a bundle of a package for energy production by using PV solar cells for residential applications. Extension of freshwater from the earth produces water near a city in different parts of the worldwide is the serious problem especially in North African countries and the Middle East. So, for the survival of humanity, desalination is a necessity for the living and with the use of natural energy i.e., plenty of sunshine coming from the sun. With recent advancements in technology in the field of solar power & improving the design of energy conversion systems operating on solar energy harvesting & converting it into electricity with the help of thermopiles. The major focus is on designing & designing parameters with the overall performance enhancement of the proposed energy conversion system. Nowadays, solar energy can also be employed independently or with fossil fuels to reduce CO2 emission & the Levelized cost of power generation. But with the advancement of the supercritical Brayton cycle also informs the prospects of lower Levelized cost for higher efficiency at accessible temperature.

Power-to-liquid hydrogen: Exergy-based evaluation of a large-scale system

Advanced exergy-based performance enhancement of heat pump space heating system

In addition to conventional exergy-based methods, advanced exergetic analyses consider the interactions among components of the energy-conversion system and the real potential for improving each system component. The paper demonstrates the results of application of a detailed advanced exergetic analysis to a wastewater source heat pump providing space heating in the built environment. In order to determine thermodynamic parameters of the refrigeration vapour compression cycle in different operating modes, the simulation model has been used. The analysis includes splitting the exergy destruction within each component of a heat pump into unavoidable, avoidable, endogenous and exogenous parts as well as detailed splitting of the avoidable exogenous exergy destruction. Besides, variabilities of heating demands of a building within both the chosen heating season and also from year to year are taken into account. Distribution of the split exergy destructions during different periods of time is also presented for the analysed cases of the heat pump and built environment. It is shown that in the investigated system only about 50% of the total annual destruction in components of the heat pump can be avoided. About 30…40% of this avoidable thermodynamic inefficiency is caused by interactions among components. Based on the applied advanced exergetic analysis it is possible to receive more precise and useful information for better understanding and improving the design and operation of the analysed energy-conversion system.

Exergoenvironmental analysis for evaluation of the environmental impact of energy conversion systems

Exergoenvironmental analysis of the integrated copper-chlorine cycle for hydrogen production

Exergo-environmental analysis of a reverse osmosis desalination plant in Gran Canaria

In this article, a new procedure was introduced for the optimal design of utility system in process industries. This method was based on the development of the R-curve concept and a new cogeneration targeting through estimating costs, environmental impacts, exergoeconomic, and exergoenvironmental analyses. In the exergoenvironmental analysis, the environmental impacts obtained by life cycle assessment are apportioned to the exergy streams pointing out the main system components with the highest environmental impact and possible improvements associated with these components. Moreover, exergoenvironmental variables are calculated, and an exergoenvironmental evaluation is carried out. In this regard, correlations for estimating the environmental impacts of cogeneration system have been introduced. In addition, the powerful and accurate cogeneration targeting method was applied. Also, the new graphic representations have been proposed. These curves are based on cost estimation, environmental impacts, and exergoenvironmental analysis. In addition, the optimal design of site utility was carried out in Iran LNG cogeneration plant, in which the usefulness of this method was clearly demonstrated.

Exergoenvironmental results of a eucalyptus biomass-fired power plant

Exergy and environmental impact assessment of solar photoreactors for catalytic hydrogen production

The basic needs of man are food, clothing, and shelter besides air and water. In providing these needs, power generation systems play a crucial role. Day by day, for various reasons such as explosion of population, the demand for power is increasing tremendously. Power generation systems need to generate more power. A novel power generation system suitable for recovering waste heat at a medium temperature range is examined in the present work. To assess the performance of a power generation system, energy and exergy measures are necessary. Energy measures provide enough details about the performance of the system. To know the systematic performance analysis, detailed exergy analysis alternatively profound as advanced exergy analysis and environmental impact are to be investigated. Exergoenvironmental analysis on the proposed Kalina power generation system has been carried out under hot sink conditions. Considering the proposed decision variables relative exergy destruction (ĖD/ĖP), relative environmental impact (Ẏ/ĖP), and relative investment cost (Ż/ĖP), the performance of the system has been assessed. The exergy destruction and the destruction cost rate of 29.23 kW and 0.478 $/hr at turbine inlet conditions of 185°C and 45 bar have been achieved. The exergoenvironmental factor fb and the relative difference rb have revealed that the components with high environmental impact have to be minimized. Turbine and HE4 are the components that contribute to higher total exergy and devise related impact on the environment.

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.

This study presents comprehensive thermoeconomic and thermoenvironomic modeling and analysis of selected gas turbine power plants in Nigeria using the first and second laws of thermodynamics (exergy) concept. Exergetic analysis was 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 results of the study showed that the combustion chamber (CC) is the most exergy destructive component compared to other cycle components. The percentage of exergy destruction in CC varies between 86.05% and 94.6%. By increasing the gas turbine inlet temperature (GTIT), the exergy destruction of this component can be reduced. The total exergy improvement potential of the selected plants varies from 54.04 to 159.88 MW. The component with the highest exergy improvement potential is the CC, which has the value that varies from 30.21 to 88.86 MW. Thermoeconomic analysis showed that the cost of exergy destruction is high in the CC, and an increase in the GTIT effectively decreases this cost. The exergy costing analysis revealed that the unit cost of electricity produced in the plants ranged from cents 1.99/kWh (N3.16/kWh) to cents 5.65 /kWh (N8.98/kWh). Thermoenvironomic analysis showed that the CO2 emissions varied between 100.18 and 408.78 kg CO2/MWh, while cost rate of environmental impact varied from 40.18 $/h (6, 388.62 N/h) to 276.97 $/h (44, 038. 23 N/h). The results further showed that CO2 emissions and cost of environmental impact decrease with increasing GTIT. The sustainability index increase with increasing GTIT. Finally, this study will assist efforts to understand the thermodynamic losses in the gas turbine cycle, and to improve efficiency as well as provide future recommendations for better performance, sustainability, and lessening environmental impact of power plant.

An exergoeconomic analysis identifies the location, magnitude and sources of thermodynamic inefficiencies and costs in an energy conversion system. This information is used for improving the thermodynamic and the economic performance and for comparing various systems. A conventional exergy-based analysis does not consider the interactions among the components of a system nor the real potential for improving the system. These shortcomings can be addressed and the quality of the conclusions obtained from an exergoeconomic evaluation is improved, when for each important system component the values of exergy destruction and costs are split into endogenous/exogenous and avoidable/unavoidable parts. We call the analyses resulting from such splittings advanced exergy-based analyses. The paper demonstrates how an advanced exergoeconomic analysis provides the user with information on the formation processes of thermodynamic inefficiencies and costs and with suggestions for their minimization. In the first part of the paper, the advanced exergy-based analyses are applied to an air refrigeration machine. In the second part of the paper, we demonstrate that the information obtained in the first part can be used to modify the values of the decision variables to reduce the cost of the final product (cold) of the overall system.