Exergoenvironmental evaluation of kalina power generation system

Advanced exergy and exergo-economic analyses of a novel combined power system using the cold energy of liquefied natural gas

Advanced exergy and exergoeconomic analysis for a polygeneration plant operating in geothermal cascade

In this paper, the supercritical carbon dioxide power cycle used to recover the waste heat of gas turbine is investigated by means of conventional exergy analysis and advanced exergy analysis. Firstly, the thermodynamic parameters of carbon dioxide cycle in design stage are determined by single-objective optimization with net power output as objective function. Then, conventional exergy analysis is carried out on the partial heating cycle under real, unavoidable and ideal conditions. After that, advanced exergy analysis, in which the exergy destruction is divided into endogenous / exogenous part and avoidable / unavoidable part is adopted to reveal the improvement potential of the system and illustrate the interaction among the components. According to the calculation results, a total amount of 3.55MW (47.33%) exergy destruction could be reduced by the improvement of component efficiency. Endogenous exergy destruction is higher than exogenous exergy destruction in all components. Based on the results of conventional exergy analysis, the high-temperature heater should be paid attention in order to reduce exergy destruction. However, according to the results of advanced exergy analysis, the technical improvement of turbine should be emphasized due to its high endogenous-avoidable exergy destruction. Meanwhile, for the components with high unavoidable exergy destruction, external systems should be employed to exploit the underutilized energy and enhance the system performance.

Hot dry rock is an abundant, stable and low-carbon geothermal resource, which has a promising prospect for power generation in China. In this paper, a hot dry rock power generation system model based on conventional organic Rankine cycle was established. The performance of the system was evaluated by thermodynamic analysis, as well as energy and exergy analyses. Four types of organic working fluids were selected to investigate their effects on system energy efficiency. R114 had much higher energy efficiency (17.50%~ 19.00%) than other three organic working fluids (R245fa, R245ca and R601) when water flow rate ranged from 80 t/h to 260 t/h. When R245fa was used as working fluid and power output was set at 4 MW, energy and exergy efficiency of the system were 15.27% and 50.42%, respectively. According to the energy flow analysis, the major energy losses (15.67 MW) in the system were attributed to the discharge temperature of turbine exhaust. However, exergy flow analysis indicated that the energy loss from turbine exhausts was not as serious as expected, since the work potential of that energy was limited. The exergy destruction of each component in the system was calculated, and the results showed that heat exchanger and the vapor separator were the weakness components in the system, and they respectively contributed to 44.8% and 29.8% of the total exergy destruction. The results obtained in this study provide possible strategies to improve the overall performance of the hot dry rock power generation system based on conventional organic Rankine cycle.

Conventional exergy analysis identifies component exergy destruction, however, does not give clear picture whether occurs because of component itself or due to remaining components and then the advanced exergy analysis is emphasized. The main purpose of this study is to apply advanced exergy analysis to the transcritical CO2 vapor compression heat pump system for simultaneous water cooling and heating, along with the conventional exergy analysis. The novelty of the present study is the advanced exergy analysis (with modified methodology) of transcritical superheat cycle based on experimental data. Endogenous, exogenous, avoidable and unavoidable exergy destructions are determined for each component of this system. Results show that compressor is having highest exergy destruction among the CO2 system components and also its major part is avoidable endogenous exergy destruction. According to conventional exergy analysis, the sequence for improvement seems to be compressor, gas cooler, expansion valve and evaporator; however, the in-depth analysis (advanced exergy analysis) shows compressor is the first component followed by evaporator, gas cooler and expansion valve to be considered for improvisation. Thus it is concluded that compressor provides highest opportunity for improvement and new design of the same will improve overall transcritical CO2 system performance.

The purpose of this research is in-depth understanding of the internal causes of exergy destruction in various parts of the system and to identify potential improvements for the components. The focus is on a combined cycle power generation system that utilizes the organic Rankine cycle (ORC) and direct expansion cycle (DEC). To investigate the primary sources of exergy destruction in each component, advanced exergy analysis (AEA) is utilized. The result demonstrates that the net out power of the proposed system can reach 106.64 kW with energy efficiency of 11.22%, and exergy efficiency of 21.40%. The heat exchanger is identified as the primary contributor to exergy destruction, constituting 81.70% of the total ratio. Specifically, the condenser exhibits the highest exergy destruction ratio at 59.82%, indicating a need for prioritized optimization efforts. The findings of AEA reveal that the primary source of component irreversibility stems from the endogenous part. This shows that, while most exergy destruction is unavoidable, there remains room for system improvement. Regarding the turbine, its exergy destruction is primarily attributed to inefficiencies, leading to irreversibility. Nevertheless, there is exergy destruction that may be avoidable and can be reduced by 25.93 kW, which is 2.5 times greater than that of the heat exchanger. This finding underscores the high potential for improvement in ORC and DEC turbines, making them a priority for optimization efforts.

Process development and exergy cost sensitivity analysis of a novel hydrogen liquefaction process

The thermal efficiency of the high‐temperature solid oxide electrolysis cell system for steam electrolysis has drawn extensive concern in the energy conversion field. This work presents a thermodynamic investigation of a high‐temperature steam electrolysis system by conventional and advanced exergy analyses. A steady‐state simulation of a 20 kW high‐temperature steam electrolysis system is performed for system performance analysis. The thermal inefficiency of each component in the system is revealed by conventional exergy analysis. The predictions show the system exergy efficiency is 49.98%, H2‐compressor has the largest exergy destruction (6773.6 W, 39.16% of the total exergy destruction). Through advanced exergy analysis, the impacts of the interactions among components and the technical limitation with each component are considered. The results indicate the H2‐compressor has the highest exergy saving potential owing to the largest avoidable exergy destruction (1935 W), followed by the stack and vapor generator. Thus, the solid oxide electrolysis cell stack, H2‐compressor, and vapor generator have tremendous potential in energy conservation. Advanced exergy analysis also indicates the interactions among components have less influence on the exergy destruction which means most measures toward improving high‐temperature steam electrolysis systems should be taken to improving each component itself rather than interconnections among components.

Geothermal power generation improvement of organic Rankine flash cycle using exergy, advanced exergy and exergoeconomic analyses

Assessment of a waste energy recovery (WER) unit for power and refrigeration generation: Advanced thermodynamic examination

Application of advanced exergy analysis for optimizing the design of carbon dioxide pressurization system

Exergy analysis provides useful information about the system optimization. An exergy analysis identifies the sources of thermodynamic inefficiencies by evaluating the exergy destruction within each system component. Splitting the exergy destruction into endogenous/exogenous parts represents a new development in the exergy analysis of energy conversion systems. The present work is an attempt to investigate the combustion process in a simple gas turbine and a cogeneration power plant based on the general concept of endogenous and exogenous exergy destruction. Therefore, using a graphical approach, the advanced exergy analysis is applied to both cycles with different fuels such as methane and diesel. Also, dual-fueling of combustion chamber is investigated based on the aforementioned approach in which 90% substitution of methane fuel for diesel one is considered. It is found that, in both cycles the combustion chamber has the largest value of the endogenous exergy destruction. The exergetic efficiency of combustion chamber increases when methane fuel is substituted for diesel fuel. Therefore, cycles efficiencies have been enhanced when fuel is substituted for diesel one. The results obtained here may provide some useful information for the optimal design and performance improvement of these cycles.

Energy, exergy and advanced exergy analysis of a milk processing factory

Ambitious targets on reduction of greenhouse-gas emissions have motivated further studies to improve energy efficiency in offshore gas and oil production. Identifying the causes of inefficiencies and the improvement potentials within these processes is crucial. The oil and gas processing plant on a North Sea platform is evaluated by advanced exergy analysis for a real production day. The study focuses on components and sub-systems with high exergy destruction through conventional exergy analysis in previous research. Splitting the exergy destruction into endogenous and exogenous parts provides information about mutual interdependencies among the system components. The results show that the inefficiencies of compressors are attributed to their inherent irreversibility, while the exergy destruction within the coolers could particularly be reduced by improving the remaining system components. Further, the total exergy destruction avoidable by improving each single component determines the importance of the components. The results indicate that the compressors have relatively large exergy saving potential (14% of total power consumption), while it is relatively low for coolers. Advanced exergy analysis suggests an optimization sequence different from the conventional exergy analysis. The findings indicate that the improvement efforts should be focused essentially on the compressors, especially for the recompression compressors with anti-surge operations.

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.