Optimizing a Green and Sustainable Off-Grid Energy-System Design: A Real Case
Round 1
Reviewer 1 Report
Comments on “Optimizing a Green and Sustainable Off-grid Energy System Design Enhancing with a Real Case”.
Dear Authors,
The paper must be significantly improved. Please consider the following remarks:
Major comments:
(1) Please improve abstract part. Please answer the questions:
a) What problem did you study and why is it important?
b) What methods did you use?
c) What were your main results? “The best-obtained results by the proposed PSO offered 160 PVs, 5 WGs, and 350 batteries, respectively, while the best solution found by the simulation method was using 384 PVs, 5 WGs, and 189 batteries for the considered off-grid system.” Please add units for device capacity.
d) What conclusions can you draw from your results?
(2) Please add units to an abbreviations and nomenclature part
(3) Line 54-55: “According to the presented information in Table 1, the PSO method is one of the most practical and successful techniques” Please explain this sentence.
(4) Figure 2: Please explain accuracy of results. Simulation or real, mean median?
(5) Line 210-211: please add resolution, time, where
(6) Figure 4-6 Please change into heat map: vertical axis: hour a day, horizontal axis: day of year. Please explain which year and which place
Minor comments:
(1) Line 64: Please avoid of using “we”
(2) Page 4. Please explain the source of solar and wind speed data
(3) Table 2. Please explain description of column. Please also add unit.
(4) Table 4.: please explain the first column
(5) Line 235-236: please use euro or USD: not SEK, kr, Mkr
(6) Table 5, 6. Please add unit
(7) Line 298: what does “salvage price” mean?
(8) Please improve reference part in line with journal template
Author Response
Response to Reviewer #1
We appreciate the opportunity to improve the quality of our manuscript. The manuscript has been carefully revised in response to the suggestions and comments raised. Please find enclosed a revised version of the manuscript for further consideration for publication. We were pleased by the constructive comments from the reviewer and have revised the paper in response to all the suggestions. A full response to each comment is provided below, while key changes are also highlighted in green within the text. We hope that the respected reviewer will find the paper suitable for publication in the highly ranked Journal of Sustainability.
Comments and Responses
Dear Authors,
The paper must be significantly improved. Please consider the following remarks:
Major comments:
(1) Please improve abstract part. Please answer the questions:
- a) What problem did you study and why is it important?
- b) What methods did you use?
- c) What were your main results? "The best-obtained results by the proposed PSO offered 160 PVs, 5 WGs, and 350 batteries, respectively, while the best solution found by the simulation method was using 384 PVs, 5 WGs, and 189 batteries for the considered off-grid system." Please add units for device capacity.
- d) What conclusions can you draw from your results?
The authors appreciate the reviewer's constructive comments. The abstract section was completely revised, considering all the above-mentioned points and suggestions.
(2) Please add units to an abbreviations and nomenclature part
Following the respected reviewer's comment, the unit of each parameter has been added to the Nomenclature list.
(3) Line 54-55: "According to the presented information in Table 1, the PSO method is one of the most practical and successful techniques" Please explain this sentence.
The authors appreciate the precise hint from the respected reviewer. The content of Table 1 was concluded in a better sentence, and was linked to why PSO and HOMER methods have been considered in this study.
(4) Figure 2: Please explain accuracy of results. Simulation or real, mean median?
Thanks to the respected reviewer for this comment. According to the obtained data, the characteristics and details of the information have been added to the explanations of the figure in the text.
(5) Line 210-211: please add resolution, time, where
Following the respected reviewer's concern, the necessary information was added to the manuscript.
(6) Figure 4-6 Please change into heat map: vertical axis: hour a day, horizontal axis: day of year. Please explain which year and which place
The authors thank to the respected reviewer for this comment. The authors have decided to eliminated those figures and use reference for the respected potential readers. In addition, all the data might be available according to the request of the readers. Moreover, some other related and more appropriate figures have been added to the text.
Minor comments:
(1) Line 64: Please avoid of using "we"
It has been eliminated from the text and the sentence has been rewritten without using it.
(2) Page 4. Please explain the source of solar and wind speed data
The sources for obtaining the data have been mentioned and explained in the text.
(3) Table 2. Please explain description of column. Please also add unit.
Following the respected reviewer's suggestion, the content of Table 2 has been rewritten as functions and equations, and each of them has been completely explained with a mention of the unit for each.
(4) Table 4.: please explain the first column
A paragraph has been added to the text containing explanations about the content of Table 4.
(5) Line 235-236: please use euro or USD: not SEK, kr, Mkr
Thanks to the respected reviewer for this comment. The costs in Tables 4 and 5 and their explanations have been changed to dollars instead of krona.
(6) Table 5, 6. Please add unit
All the units have been explained in the text below each table.
(7) Line 298: what does "salvage price" mean?
It means the value an asset is estimated to be worth at the end of its useful life. This is a common parameter in engineering when deciding between more than one project. The definition has been added to the text.
(8) Please improve reference part in line with journal template
With appreciation to the respected reviewer for all the constructive comments, all the references have been rechecked and modified according to the reference types in the journal template.
Reviewer 2 Report
Figure 3 is blurred.
Equations 8-9 have not been written properly.
PSO parameters have been listed for the scenario simulated and presented in this paper. I would strongly recommend to compare the PSO parameters in context of efficiency, optimization of the off-grid energy system with those already done in the literature using PSO algorithm.
Please justify. What is that special PSO used in this study bringing more optimal results then the PSO used in the other studies in the literature?
Author Response
Response to Reviewer #2
We appreciate the opportunity to improve the quality of our manuscript. The manuscript has been carefully revised in response to the suggestions and comments raised. Please find enclosed a revised version of the manuscript for further consideration for publication. We were pleased by the constructive comments from the reviewer and have revised the paper in response to all the suggestions. A full response to each comment is provided below, while key changes are also highlighted in green within the text. We hope that the respected reviewer will find the paper suitable for publication in the highly ranked Journal of Sustainability.
Comments and Responses
Figure 3 is blurred.
Following the respected reviewer’s comment, Figure 3 was replaced with a higher-resolution one.
Equations 8-9 have not been written properly.
The authors thank the respected reviewer for such a precise comment. Following this hint, both equations were rewritten. Because of some changes in the equation numbers, the numbers of these equations are (16) and (17) in the revised version of the manuscript.
PSO parameters have been listed for the scenario simulated and presented in this paper. I would strongly recommend to compare the PSO parameters in context of efficiency, optimization of the off-grid energy system with those already done in the literature using PSO algorithm.
Thanks to the respected reviewer for this precise recommendation. Four of the references used in this study have been considered for parameter settings and efficiency indexes. The data from these references has been compared with what has been done in the present study. Please see Section 5.1.
- Maleki, A., Khajeh, M. G., & Rosen, M. A. Two heuristic approaches for the optimization of grid-connected hybrid solar–hydrogen systems to supply residential thermal and electrical loads. Sustainable cities and society 2017, 34, 278-292.
- Maleki, A., & Rosen, M. A. Design of a cost-effective on-grid hybrid wind–hydrogen based CHP system using a modified heuristic approach. International Journal of Hydrogen Energy 2017, 42(25), 15973-15989.
- Diaf, S., Diaf, D., Belhamel, M., Haddadi, M., & Louche, A. A methodology for optimal sizing of autonomous hybrid PV/wind system. Energy policy 2007,35(11), 5708-5718.
- Kaviani, A. K., Riahy, G. H., & Kouhsari, S. M. Optimal design of a reliable hydrogen-based stand-alone wind/PV generating system, considering component outages. Renewable energy 2009, 34(11), 2380-2390.
Please justify. What is that special PSO used in this study bringing more optimal results then the PSO used in the other studies in the literature?
The authors thank the respected reviewer for this comment. In using the PSO method in this study, the parameter setting is where, and are equal to 1, 0.7, 2.5, and 1.5, respectively, while and gradually change to 1.5 and 2.5, respectively. Such a parameter setting gives the method the advantage of covering any number and combination, and that should be between 1.5 and 2.5. In some studies, like Maleki et al. [14], the setting of the values was like 1, 1, 2, and 2, respectively, which does not give any flexibility to the parameter during solving the problem. Moreover, to design and optimize the proposed system, a 20-year life span has been considered, and a very small annual shortage, less than 0.1% unmet demand, has been considered. All the above-mentioned explanations have been mentioned in different parts of the text.
Reviewer 3 Report
It seems to this reviewer that there are two more constraints of importance for a real-world situation: 1) does the supermarket roof area have to be horizontal and is it sufficient to accommodate the required number of panels? If not where would the additional panels be placed and how does it affect the cost estimate?
2) Are there constraints on the noise output of the selected wind turbines in case the supermarket is located in an urban area? Therefore, are there constraints on the placement of the wind turbines in the vicinity of the supermarket?
Reviewer suggests to comment on these questions.
Author Response
Response to Reviewer #3
We appreciate the opportunity to improve the quality of our manuscript. The manuscript has been carefully revised in response to the suggestions and comments raised. Please find enclosed a revised version of the manuscript for further consideration for publication. We were pleased by the constructive comments from the reviewer and have revised the paper in response to all the suggestions. A full response to each comment is provided below, while key changes are also highlighted in green within the text. We hope that the respected reviewer will find the paper suitable for publication in the highly ranked Journal of Sustainability.
Comments and Responses
It seems to this reviewer that there are two more constraints of importance for a real-world situation:
1) does the supermarket roof area have to be horizontal and is it sufficient to accommodate the required number of panels? If not where would the additional panels be placed and how does it affect the cost estimate?
The authors thank the respected reviewer for such precise comments and agree with the reviewer about such concerns. The case study in this research is related to an off-grid system that is located far from the city. In this case, there was no limitation on the facility's location. In addition, interestingly, the two different solution methods, simulation and PSO, have obtained different numbers of facilities at similar costs. The PSO suggests using 160 PV arrays with 350 batteries, and the simulation method obtained 384 PVs and 189 batteries. It is also suggested that in the case of not having enough space, the latter answer with more PVs might be used, where they can be installed on the roof, in the parking area that also makes shelters for the cars, etc.
2) Are there constraints on the noise output of the selected wind turbines in case the supermarket is located in an urban area? Therefore, are there constraints on the placement of the wind turbines in the vicinity of the supermarket?
Thanks to the respected reviewer for this comment. In this study, the monthly average wind speed data for a whole year has been used. In addition, according to the assumptions, the number of necessary facilities has been measured in such a way that there should be almost no unmet electricity demand during the year. Therefore, the batteries are most of the time fully charged, and in the event of noise from wind turbine outputs, solar panels and batteries can cover the electricity production and demand. For the placement constraints of the wind turbines, as has been mentioned in the previous comment, it is considered that there is enough space in the rural area for five wind turbines, and there is no feasibility study for facility placement in this research.
Reviewer 4 Report
The authors have attempted to model an off-grid energy system for a supermarket. The methodology of the paper, especially the system configuration, is discussed in great detail. The authors need also to discuss if there are any limitations to the two approaches they have undertaken (PSO and HOMER pro software). Also, they need to specify how and where they have obtained the demand data for the considered supermarket.
In addition, the authors need to discuss the results of their simulations and the implications of such a study.
In regards to the equations - for Equation (2), authors need to also include equal to sign for V greater than or equal to Vcutout.
Author Response
Response to Reviewer #4
We appreciate the opportunity to improve the quality of our manuscript. The manuscript has been carefully revised in response to the suggestions and comments raised. Please find enclosed a revised version of the manuscript for further consideration for publication. We were pleased by the constructive comments from the reviewer and have revised the paper in response to all the suggestions. A full response to each comment is provided below, while key changes are also highlighted in green within the text. We hope that the respected reviewer will find the paper suitable for publication in the highly ranked Journal of Sustainability.
Comments and Responses
The authors have attempted to model an off-grid energy system for a supermarket. The methodology of the paper, especially the system configuration, is discussed in great detail. The authors need also to discuss if there are any limitations to the two approaches they have undertaken (PSO and HOMER pro software). Also, they need to specify how and where they have obtained the demand data for the considered supermarket.
The authors thank the respected reviewer for these comments and recommendations. The HOMER and PSO methods, like any of the other software and applications, have their own limitations. The limitations of these methods have been mentioned in the revised version of the manuscript.
Moreover, the collection of demand data for temperature, wind speed, etc. has been mentioned in subsection 4.2, including the related references.
In addition, the authors need to discuss the results of their simulations and the implications of such a study.
The authors appreciate the respected reviewer's constructive comment. The results and discussion section have been significantly extended in the revised version of the manuscript.
In regards to the equations - for Equation (2), authors need to also include equal to sign for V greater than or equal to Vcutout.
Thanks to the respected reviewer for this precise comment. The equal sign was added to the function in the revised version of the manuscript.
Reviewer 5 Report
Congratulations on the great article.
Interesting approach through a simple solution with satisfactory results.
Two suggestions for improvement:
1. Present a table with all equipment initial costs and mainly O&M costs and the expected periodicity in terms of preventive and corrective maintenance.
2. Present simulation results considering variation in equipment initial costs, O&M and occupied area.
Bear in mind that a storage system of almost 8MWh is an expensive asset with high installation and O&M costs.
Author Response
Response to Reviewer #5
We appreciate the opportunity to improve the quality of our manuscript. The manuscript has been carefully revised in response to the suggestions and comments raised. Please find enclosed a revised version of the manuscript for further consideration for publication. We were pleased by the constructive comments from the reviewer and have revised the paper in response to all the suggestions. A full response to each comment is provided below, while key changes are also highlighted in green within the text. We hope that the respected reviewer will find the paper suitable for publication in the highly ranked Journal of Sustainability.
Comments and Responses
Interesting approach through a simple solution with satisfactory results.
Two suggestions for improvement:
- Present a table with all equipment initial costs and mainly O&M costs and the expected periodicity in terms of preventive and corrective maintenance.
The authors thank the respected reviewer for this comment. A table has been added to the revised version of the manuscript containing the operating costs.
- Present simulation results considering variation in equipment initial costs, O&M and occupied area.
Bear in mind that a storage system of almost 8MWh is an expensive asset with high installation and O&M costs.
Following the respected reviewer’s comment, a table and a figure have been added to the results and discussion section of the revised version of the manuscript.
Round 2
Reviewer 1 Report
Figure 4. Please improve. Please add heat map: horizontal: days, vertical: hours
Table 5. Please add unit
Figure 3 Please improve the quality
Author Response
Response to Reviewer #1
The authors appreciate the respected reviewer for the comments. The manuscript has been carefully revised in response to the suggestions and comments raised. A full response to the comments is provided below while key changes are also highlighted in green within the text. The authors hope that the respected reviewer will find the paper suitable for publication in the high-ranked Journal of Sustainability.
Comments and Responses
Figure 4. Please improve. Please add heat map: horizontal: days, vertical: hours
Table 5. Please add unit
Figure 3. Please improve the quality
Thanks to the respected reviewer for these comments. The quality of the figures were improves as much as possible. The heat maps for solar irradiations, wind speed, and temperature were added to the text. Finally, the units for tables 4 and 5 were added.
Reviewer 2 Report
Thanks for addressing the comments positively.
Author Response
Response to Reviewer #2
Thanks for addressing the comments positively.
The authors appreciate the positive opinion of the respected reviewer on this manuscript.
