Realistic Energy, Exergy, and Exergoeconomic (3E) Characterization of a Steam Power Plant: Multi-Criteria Optimization Case Study of Mashhad Tous Power Plant

Round 1

Reviewer 1 Report

The manuscript presented a techno-economic analysis of a steam power plant. Also, the authors developed an optimization method to optimize the system under real conditions. The topic is interesting and also is appropriate for the Water Journal. The manuscript could be published after good addressing the following comments:

1. The optimal data of the article should be brought at the end of the introduction section.

2. The authors should be presented the novelty of their work clearly.

3. Please bring some relevant articles from the Water journal and cite them in the manuscript.    

4. Please rewrite the Conclusion section and use the findings of this review article. In addition, it would be positive to get some future research suggestions on this topic.

Please check again the English level of the manuscript to avoid any typos and grammar mistakes

Author Response

Firstly, the authors would like to thank the reviewer for his helpful comments and also for the time spent on reviewing process. The detailed response to the comments is as follows:

• The optimal data of the article should be brought at the end of the introduction section.

@Answer:

• According to the reviewer's comment, optimization results have been given in the abstract section.

Abstract: This paper investigates the performance of Mashhad Tous power plant, a natural gas-fueled steam cycle with an output power of 4150 MW in Iran. The analyses include energy, exergy, and exergoeconomic. A robust code is developed to simulate the thermodynamic topology of the power plant. The simulation is validated using realistic site conditions. Three distinct decision variables: boiler water mass flow rate, turbine inlet pressure from, and ambient temperature ranging from 90  to 150 , 12 MPa to 19 MPa, and 10  to 40 , respectively. Three different heat loads, including 423 MW, 311 MW, and 214 MW, are used to analyze the performance of the power plant. A Pareto-based multi-criteria optimization intertwined with the technique for order of preference by similarity to ideal solution (TOPSIS) is used to find the optimum conditions in terms of having the highest work output and exergy efficiency while simultaneously reducing the plant’s total cost. The optimization results demonstrate a 4.28% increase in output at full load (423 MW). Additionally, a 1.52% increase is observed at partial load (311 MW), and there is a notable 16% increase in output at low load (214 MW). These improvements have also positively impacted energy efficiency. Specifically, there is a 4% improvement at full load, a 0.9% enhancement at partial load, and a remarkable 5.4% increase in energy efficiency at low load. In terms of costs, substantial reductions of 37% at full load, 31% at partial load, and an impressive 72% at low load are evident.

• The authors should be presented the novelty of their work clearly.

@Answer:

• Thanks for the valuable reviewer’s comment, some important novelties have been added in new version of manuscript as follow:

Considering the importance of exergy analysis in the reviewed literature above, this investigation evaluates the thermodynamic performance of a potential and strategic power plant in Iran, Mashhad Tous power plant. The thermodynamic analyses consist of energy, exergy, and exergoeconomic, which is the amalgamation of exergo into economic notions. Regardless of the most literature mimicking the power plant system through simulation, this work peruses the thermodynamic efficiencies completely with the experimental and data log from the site condition. Three distinct parameters: mass flowrate water inlet to the boiler, turbine steam pressure inlet, and ambient temperature are considered the power plant's input variables. The optimum working condition to maximize the network output and exergetic performance while simultaneously curbing the system’s cost is applied using Pareto-based multi-criteria. Some important novelties of the present study are as follows:

• Utilizing energy, exergy, and eco-exergy equations for the Tous power plant.
•   Optimizing effective parameters through a multi-objective optimization method.
• Best ambient temperature has been selected based on exergy efficiency, work, and capital cost in various load.
• Employing experimental results for validation and modeling of a power plant.

• Please bring some relevant articles from the Water journal and cite them in the manuscript.

@Answer:

• Thanks for your valuable feedback. Some relevant paper, which were published in Water journal, have been added to the new version of manuscript.

• Chen, TC. Kumar, NK. Dwijendra, A. Majdi, AR. Asary, AH. Iswanto, I. Khan, DØ. Madsen, R. Alayi.., "Energy and Exergy Analysis of the Impact of Renewable Energy with Combined Solid Oxide Fuel Cell and Micro-Gas Turbine on Poly-Generation Smart-Grids," Water, vol. 15, no. 6, p. 1069, 2023.

• Hao, L. Qiao, L. Han, and C. Tian, "Experimental study on the effect of heat-retaining and diversion facilities on thermal discharge from a power plant," Water, vol. 12, no. 8, p. 2267, 2020.
• Please rewrite the Conclusion section and use the findings of this review article. In addition, it would be positive to get some future research suggestions on this topic.

@Answer:

• Thanks for your comment, the conclusion has been rewritten as follow:

4. Conclusion

The thermodynamic performance of the Tous power plant, acknowledged as a significant energy source in northeastern Iran, has been thoroughly investigated and analyzed. This analysis, which focuses on energy, exergy, and exergoeconomic aspects. This study involved the multi-objective optimization of influential parameters through the employment of the TOPSIS method. To achieve this, the power plant was examined under three conditions: low load ( = 214), intermediate load ( = 311), and high load ( = 423). In each of these scenarios, optimization was carried out for ambient temperature and inlet pressure into the high-pressure turbine. The most significant findings of this study are as follows:

• Ambient temperature has a greater impact on intermediate and low loads compared to high load.
• In the optimal conditions, the highest exergy efficiency of 42.15% occurs at the intermediate heat load.
• The power plant's output at a high thermal load stands at 145 MW and after optimization, this value escalates to 151 megawatts.
• The most improvement in power plant output is 16.37% for low thermal loads.
• The lowest cost reduction is related to the intermediate thermal load.

Reviewer 2 Report

Journal: Water

Paper: water-2552389

Title: Realistic energy, exergy, and exergoeconomic (3E) characterization of a steam power plant: Multi-criteria optimization, case study: Mashhad Tous Power Plant

Description: The paper deals with important problem of  the performance of Mashhad Tous power plant, a natural gas fueled steam cycle  Abstract reflects the content of the problem, method, results, and summarizes the results. Conclusion summarizes well the results of the paper. 

Strength of the paper:

1. The subject is relevant and important for industrial applications.

2. The technique is appropriate.

3. The amount of work done is more than adequate.

4. The results are well presented and illustrate the points to be made.

5- The figures are clear and self-explanatory.

6. The conclusions are adequate.

7. The article is well-written. 

8. The references are relevant and adequate.

Recommendation: I recommend the publication of this paper, with following minor revision:

1- The author needs to define and explain the flow chatrt in Figure 1 and 2.

2- Authors should accurately explain how the data is collected, as well as the type of bearings under table 6 and 7 Data collection and features extraction'.

3- Authors should more accurately explain in Figure 9-11.

4- Authors should indicate the variation of total cost and exergy efficiency with HP turbine inlet pressure and  ambient temperature.

5- The language throughout the manuscript must be checked.

Journal: Water

Paper: water-2552389

Title: Realistic energy, exergy, and exergoeconomic (3E) characterization of a steam power plant: Multi-criteria optimization, case study: Mashhad Tous Power Plant

Description: The paper deals with important problem of  the performance of Mashhad Tous power plant, a natural gas fueled steam cycle  Abstract reflects the content of the problem, method, results, and summarizes the results. Conclusion summarizes well the results of the paper. 

Strength of the paper:

1. The subject is relevant and important for industrial applications.

2. The technique is appropriate.

3. The amount of work done is more than adequate.

4. The results are well presented and illustrate the points to be made.

5- The figures are clear and self-explanatory.

6. The conclusions are adequate.

7. The article is well-written. 

8. The references are relevant and adequate.

Recommendation: I recommend the publication of this paper, with following minor revision:

1- The author needs to define and explain the flow chatrt in Figure 1 and 2.

2- Authors should accurately explain how the data is collected, as well as the type of bearings under table 6 and 7 Data collection and features extraction'.

3- Authors should more accurately explain in Figure 9-11.

4- Authors should indicate the variation of total cost and exergy efficiency with HP turbine inlet pressure and  ambient temperature.

5- The language throughout the manuscript must be checked.

Author Response

First of all, the authors would like to thank the reviewer for his/her thoughtful comments and also for the time spent on reviewing process. The detailed response to the comments is as follows:

• The author needs to define and explain the flow chart in Figure 1 and 2..

@Answer:

• Thanks to the reviewer's comment, explanations related to Figures 1 and 2 have been given before the Figures as follow:

Steam Rankine cycle is employed for the Tous power plant with natural gas as the main fuel. Figure 1 shows the thermodynamic cycle of the power plant. Point 1 is the place where water enters the boiler with a temperature of 243  and pressure of 13.684 . Superheated steam leaves the boiler at point 2 with a temperature of 538  and pressure of 12.919 . After the shaft power generation in the high-pressure turbine, the steam’s temperature and pressure are reduced to 355  and 3.633 . Prior to entering the intermediate pressure turbine, the steam is reheated by exploiting the boiler’s heat shown at point 5. The reheated steam leaves the boiler at 538  and 3.239 . The steam enters the intermediate pressure turbine at point 6, and before entering the condenser, the steam releases its enthalpy by expansion in a low-pressure turbine.

The condensation process in the Tous power plant is air-cooled type. The low-pressure steam enters the condenser at point 12, and the condensate goes to the tank at point 13. The leaving water from the condensate tank has a temperature of about 45 . The condensate pump increases the water pressure up to 1.358 . The pressurized waters go through low-pressure heaters, leading to have a temperature of 132  at point 22. Then by receiving heat energy in the deaerator, the temperature meets 170 . The boiler feed pump at point 24 soars the pressure up to 17.732 . Two high-pressure heaters are aimed to intensify the temperature of the steam, where it reaches 243  at point 1. The energy required to increase the temperature of water in the two phases, water, and steam, is obtained through the steam removals from the turbines in different points, including 3, 4, 5, 6, 7, 8, and 9. Table 2 provides the thermodynamic details of the cycle: temperature, pressure, mass flow rate, enthalpy, entropy, and specific exergy from the site measurements. The fundamental thermodynamic analyses, including energy and exergy, are explained in the following section.

Figure 1. Topology of the power plant

In the current study, the thermodynamic cycle of the Mashhad Tous power plant is simulated and validated with the experimental data log gathered from the site condition. A robust exergy and exergoeconomic code are developed to analyze the performance of the power plant; three distinct input parameters are chosen, including the ambient temperature, mass flow rate to the boiler, and HP turbine inlet pressure, as a case study. The results are explained in detail, and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method [38] is employed to reveal the most optimum conditions for each investigated case study to have the highest exergy efficiency and work output in the lowest total cost. The flowchart of the current study is shown in Figure 2.

Figure 2. Flowchart of finding the optimum conditions for Mashhad Tous power plant.

• Authors should accurately explain how the data is collected, as well as the type of bearings under table 6 and 7 Data collection and features extraction.

@Answer:

• Thanks to the respected reviewer's comment, the power plant's output power has been extracted from its data sheets. More explanation has been added in new version of manuscript.

3.1 Validation

The simulation of the power plant cycle is validated actual work in Table 7. The power plant's output power has been extracted from its data sheets, and these values have been compared with the calculated power. Table 7 depicts the actual work versus the calculated power output for different heat loads:  = 214 MW,  = 311 MW, and  = 423 MW at 28  and 12.76 MPa.

  Table 7. Validation of Mashhad Tous power plant simulation

• Authors should more accurately explain in Figure 9-11.

@Answer:

• Thanks for your comment, further explanation has been added for Figure 9-11 as follows:

This section focuses on conducting a multi-criteria optimization considering ambient temperature and the inlet pressure of the HP turbine. Figure 9 depicts an optimal point demonstrating the highest exergy and work output coupled with the lowest overall system cost achieved based on ambient temperature. For the highest heat load,  = 423 MW the optimal point for exergy efficiency, work output, and total cost is 38.9%, 151 MW, 18.79  , respectively. Ambient temperature has a greater impact on intermediate and low loads compared to high load. Among the optimal points, the highest exergy efficiency of 42.15% occurs at the intermediate heat load)=311 MW(, the lowest total cost of 4.844 dollars per hour occurs at the low heat load)=214 MW(, and the highest work output of 155.21 MW occurs at the high heat load)=423 MW(.

Figure 10 displays the optimal points for all heat loads based on the turbine Hp inlet pressure within the range of 12 MPa to 19 MPa. Among the optimal points, the minimum total system cost for the heat load of =214 MW is 1.668 .As the heat load increased to the next level, =311 MW, the power plant cost escalated fivefold, reaching 8.362  under optimal conditions. Subsequently, this pattern is accompanied by a tenfold increase in cost, approximately 17.85  spanning from the lowest to the highest heat load. The highest exergy efficiency by 42.23% can be obtained at =311 MW and 18 MPa. Decreasing the heat load by half, from  = 423 MW to  = 214 MW, leads to an almost 50% work output reduction from 150.77 MW to 74.17 MW at 18 MPa and 17 MPa in respect for the optimum situation.

 Figure 9. Multi-criteria optimization profile for different ambient temperature.

Figure 10. Multi-criteria optimization profile for different turbine inlet pressure.

The performance of the power plant, including work output, exergy efficiency, and total cost for the three distinct heat loads before and after optimization, is shown in Figure 11. Under optimal conditions, the work output increases by 16.37% at a heat load of  = 214 MW. Following optimization, the exergy efficiency in the 423 MW heat load rises from 28% to 29.5%, and additionally, there is a  7.516  difference in the total system cost between conventional and optimized conditions for this heat load.

Figure 11. Work output, exergy efficiency, and cost analysis for different heat loads before and after optimization.

• Authors should indicate the variation of total cost and exergy efficiency with HP turbine inlet pressure and  ambient temperature.

@Answer:

• Thanks for your comment, variations of total cost and exergy efficiency with HP turbine inlet pressure and ambient temperature have been illustrated in Figures 7 and 8.

Figure 7. Variation of total cost and exergy efficiency with HP turbine inlet pressure.

Figure 8. Variation of total cost and exergy efficiency with ambient temperature.

• The language throughout the manuscript must be checked.

@Answer:

• Thanks for your comment, the manuscript's language has been reviewed and errors have been corrected.

Author Response File: Author Response.docx

Reviewer 3 Report

Comment No. 1: The Abstract should contain answers to the following questions: What problem was studied and why is it important? What methods were used? What are the important results? What conclusions can be drawn from the results? What is the novelty of the work and where does it go beyond previous efforts in the literature? Please include specific and quantitative results in your Abstract, while ensuring that it is suitable for a broad audience. References, figures, tables, equations and abbreviations should be avoided.

Comment No. 2: The originality of the paper needs to be stated clearly. It is of importance to have sufficient results to justify the novelty of a high-quality journal paper. The Introduction should make a compelling case for why the study is useful along with a clear statement of its novelty or originality by providing relevant information and providing answers to basic questions such as: What is already known in the open literature? What is missing (i.e., research gaps)? What needs to be done, why and how? Clear statements of the novelty of the work should also appear briefly in the Abstract and Conclusions sections.

Comment No. 3: An updated and complete literature review should be conducted and should appear as part of the Introduction, while bearing in mind the work's relevance to this Journal and taking into account the scope and readership of the journal. The results and findings should be compared to and discussed in the context of earlier work in the literature.

Comment No. 4: You should double check the mathematical formulations.

Comment No. 1: The Abstract should contain answers to the following questions: What problem was studied and why is it important? What methods were used? What are the important results? What conclusions can be drawn from the results? What is the novelty of the work and where does it go beyond previous efforts in the literature? Please include specific and quantitative results in your Abstract, while ensuring that it is suitable for a broad audience. References, figures, tables, equations and abbreviations should be avoided.

Comment No. 2: The originality of the paper needs to be stated clearly. It is of importance to have sufficient results to justify the novelty of a high-quality journal paper. The Introduction should make a compelling case for why the study is useful along with a clear statement of its novelty or originality by providing relevant information and providing answers to basic questions such as: What is already known in the open literature? What is missing (i.e., research gaps)? What needs to be done, why and how? Clear statements of the novelty of the work should also appear briefly in the Abstract and Conclusions sections.

Comment No. 3: An updated and complete literature review should be conducted and should appear as part of the Introduction, while bearing in mind the work's relevance to this Journal and taking into account the scope and readership of the journal. The results and findings should be compared to and discussed in the context of earlier work in the literature.

Comment No. 4: You should double check the mathematical formulations.

Author Response

First of all, the authors would like to thank the reviewer for his/her thoughtful comments and also for the time spent on reviewing process. The detailed response to the comments is as follows:

• The Abstract should contain answers to the following questions: What problem was studied and why is it important? What methods were used? What are the important results? What conclusions can be drawn from the results? What is the novelty of the work and where does it go beyond previous efforts in the literature? Please include specific and quantitative results in your Abstract, while ensuring that it is suitable for a broad audience. References, figures, tables, equations and abbreviations should be avoided.

@Answer:

• Thanks for your useful comment, the items mentioned in your comment have been incorporated into the abstract and introduction sections of the new version of the manuscript.

• The originality of the paper needs to be stated clearly. It is of importance to have sufficient results to justify the novelty of a high-quality journal paper. The Introduction should make a compelling case for why the study is useful along with a clear statement of its novelty or originality by providing relevant information and providing answers to basic questions such as: What is already known in the open literature? What is missing (i.e., research gaps)? What needs to be done, why and how? Clear statements of the novelty of the work should also appear briefly in the Abstract and Conclusions sections.

@Answer:

• Thanks to the reviewer's comment, a significant portion of the world's power requirements is fulfilled through the utilization of fossil fuels. Hence, there is a need to investigate and improve the efficiency of these power plants. Previous researches have extensively explored various aspects of power generation cycles, as discussed in the literature review section. In this study, we evaluated a realistic power plant in terms of energy, exergy, and eco-exergy. Additionally, we employed a multi-objective optimization approach to enhance the performance of the power plant under three different load conditions. Parameters such as ambient temperature and inlet pressure of the high-pressure turbine were optimized as part of this approach. This explanation has been incorporated into the introduction section.

• An updated and complete literature review should be conducted and should appear as part of the Introduction, while bearing in mind the work's relevance to this Journal and taking into account the scope and readership of the journal. The results and findings should be compared to and discussed in the context of earlier work in the literature.

@Answer:

• Thanks for your comment, more relevant literature has been added in introduction sections as follow:
• Chen, TC. Kumar, NK. Dwijendra, A. Majdi, AR. Asary, AH. Iswanto, I. Khan, DØ. Madsen, R. Alayi.., "Energy and Exergy Analysis of the Impact of Renewable Energy with Combined Solid Oxide Fuel Cell and Micro-Gas Turbine on Poly-Generation Smart-Grids," Water, vol. 15, no. 6, p. 1069, 2023.

• Hao, L. Qiao, L. Han, and C. Tian, "Experimental study on the effect of heat-retaining and diversion facilities on thermal discharge from a power plant," Water, vol. 12, no. 8, p. 2267, 2020.

Author Response File: Author Response.docx