How Strategic Behavior of Natural Gas Exporters Can Affect the Sectors of Electricity, Heating, and Emission Trading during the European Energy Transition
Round 1
Reviewer 1 Report
The paper is well written and may be of interest to a wide range of readers of the journal, as this problem is relevant for many countries. I would like to know how the authors are going to take into account the issue of reliability of gas supplies from exporting countries, as well as possible changes (supply disruption, significant price increases, etc.) due to political and economic factors. The article contains many typos and formatting errors that need to be corrected. Conclusions should also be expanded.
Author Response
I thank the reviewer for her/his time and effort as well as the constructive comments. I made the following changes to address the points:
- The problem with cross-referencing and the errors ("Error! Reference source not found”) are all eliminated
- For the potential typos, A spell-check is conducted. Hardly readable sentences are rewritten
- Supplementary text added to the section “conclusion” (major change)
- A new section (section VI) is added where the sensitivities are discussed to support the results (page 13 line 24 to line 40)
- In the introduction, a new paragraph is added, discussing the issue and relevance of the security of European gas supply (page 2, line 17- 22) as well as in the section sensitivity (page 13 line 24 to line 40)
Also, these changes are done based on the comments from other reviewers
- The representation improved by:
- changing the text in various sections
- enlarging table 2 and moving it to the top of the page
- changing the figure 10 from bar to line for an exact identifying the points
- The enlargement of table 2 and putting it in the top
- Page 2 line 23-32, 5 more literature is reviewed
- Page 3 line 1-3 added, describes how the complex model construction add value to the existing literature in the field of sector coupling
- A new section H in page 7 ( the model) is added, which discusses the model construction and the issue of optimization
- The overall references increased by approx. 10
Note: all the changes are applied in the tracking modus. Changing the view between “simple markup” and “all markup” can cause the dislocation of the graphs. I recommend tracking the changes in the “all markup” modus and read the paper in “simple markup” modus
Author Response File: 
Author Response.docx
Reviewer 2 Report
I suggested (in the review comments) minor comments for improving the manuscript. To be more specific: 1) A number of references in the paper are missing (An "Error! Reference source not found" appears at several points in the paper). 2) The authors should include a Related Works Section and discuss thoroughly relevant studies. This part would be beneficial for the paper. 3) Table 2 should be enlarged and placed in the center of the page. To conclude, the paper is well-written and organized. The findings are very interesting and promising. In my opinion, the paper has the potential to contribute to the existing body of knowledge in the European energy sector.Author Response
I thank the reviewer for her/his time and effort as well as the specific comments. I made the following changes to address the points:
- The problem with cross-referencing and the errors ("Error! Reference source not found”) are all eliminated
- For the potential typos, A spell-check is conducted. Hardly readable sentences are rewritten
- Table 2 is enlarged and put it in the top
- I thank the reviewer for the interesting suggestion regarding adding a new section “Related Works”. Although having this section will be helpful to the readers and also the general representation of the paper, this will make the first section “introduction” look very short. Since it is also common within the scientific literature to review the related literature in the introduction section, I would recommend that we stay within the occurrent structure. A new paragraph (Page 2 line 23-32) is though added, to support the related works. The new paragraph reviews 5 more relevant literature.
Also, these changes are done based on the comments from other reviewers
- The representation improved by:
- changing the text in various sections
- changing the figure 10 from bar to line for an exact identifying the points
- Supplementary text added to the section “conclusion”
- A new section (section VI) is added where the sensitivities are discussed to support the results (page 13 line 24 to line 40)
- In the introduction, a new paragraph is added, discussing the issue and relevance of the security of European gas supply (page 2, line 17- 22)
- Page 3 line 1-3 added, describes how the complex model construction add value to the existing literature in the field of sector coupling
- A new section H in page 7 (the model) is added, which discusses the model construction and the issue of optimization
- The overall references increased by approx. 10
Note: all the changes are applied in the tracking modus. Changing the view between “simple markup” and “all markup” can cause the dislocation of the graphs. We recommend to trach the changes in the “all markup” and read the paper in “simple markup” modus
Author Response File: Author Response.docx
Reviewer 3 Report
#1 What is the difference between a complex model construction and other scholars' models? What reference value does this model construction have?
#2 How to estimate many parameters and variables? If the estimation deviation or estimation is facing high uncertainty, does the model's stability and consistency have reference value? It is recommended that the author should carefully handle the feasibility of the model to provide practical reference.
#3 The author did not explicitly address the issue of model optimization and lacked academic rigor. At the same time, it is recommended that the author should also explore sensitivity analysis to better judge the sensitivity of related variables.
#4 The general conclusion expression method is not recommended to be summarized by charts. At the same time, the author should cite more in the overall reference, in order to highlight the research importance and value of this topic.
Author Response
I thank the reviewer for her/his time and effort as well as the detailed comments.
#1 What is the difference between a complex model construction and other scholars' models? What reference value does this model construction have?
- I thank the reviewer for the constructive comment. Page 3 line 1-3 added, describes how the complex model construction add value to the existing literature in the field of sector coupling. Basically, this model construction is based on game theory, enabling to analyze the effect of market power in one sector on the other sectors. Most of the existing literature use the classical linear optimization, which is incapable to study this effect
#2 How to estimate many parameters and variables? If the estimation deviation or estimation is facing high uncertainty, does the model's stability and consistency have reference value? It is recommended that the author should carefully handle the feasibility of the model to provide practical reference.
- I thank the reviewer for the helpful comment. As the data part of the present study is very broad, publishing all the detailed data will prolong the study severely. Therefore, I tried to address the most sensitive parameters in the section “data assumption” . basically, A great part of the data used for the current study is gathered and published in “https://www.diw.de/de/diw_01.c.574115.de/publikationen/data_documentation/2017_0092/electricity__heat_and_gas_sector_data_for_modelling_the_german_system.html” which is also referenced in the work. I also orient myself to persisting literature and the magnitude of data they publish.
- Regarding the topic of uncertainties, we added a section “sensitivity” and discussed them
- Regarding the topic of feasibility, we added a section “the model” and discuss the optimization and convexity of the problem
#3 The author did not explicitly address the issue of model optimization and lacked academic rigor. At the same time, it is recommended that the author should also explore sensitivity analysis to better judge the sensitivity of related variables.
- I thank the reviewer for the constructive comment. A new section H in page 7 (the model) is added, which discusses the model construction and the issue of optimization
- A new section (section VI) is added where the sensitivities are discussed
#4 The general conclusion expression method is not recommended to be summarized by charts. At the same time, the author should cite more in the overall reference, in order to highlight the research importance and value of this topic.
- I thank the reviewer for the constructive comment. Figure 10 changed from bar to line for an exact identifying the points (we assume this was the concern of the kind reviewer)
- Page 2 line 23-32, 5 more literature is reviewed
- The overall references increased by approx. 10
Also, these changes are done based on the comments from other reviewers
- The problem with cross-referencing and the errors ("Error! Reference source not found”) are all eliminated
- For the potential typos, A spell-check is conducted. Hardly readable sentences are rewritten
- Table 2 is enlarged and put it in the middle
- Supplementary text added to the section “conclusion” ( major changes)
- In the introduction, a new paragraph is added, discussing the issue and relevance of the security of European gas supply (page 2, line 17- 22)
Note: all the changes are applied in the tracking modus. Changing the view between “simple markup” and “all markup” can cause the dislocation of the graphs. We recommend to trach the changes in the “all markup” and read the paper in “simple markup” modus
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
# Well done than the previous version from this revised version. However, the author still has not dealt with the complex variables and corresponding parameters.
# How can they be evaluated correctly and appropriately? If these variables and parameters cannot be measured correctly, the consistency and stability of the model will be decreased. Even the development of the model has no reference value, and the consideration of too narrow the scope of the hypothesis will lose its practical value.
Author Response
I especially thank the reviewer for his time and efforts and the constructive comment.
About the reference value of the model:
In the constructed model, the equations used in the power sector are similar to (https://www.sciencedirect.com/science/article/pii/S0140988310001118 and https://ieeexplore.ieee.org/document/6518221), in the natural gas sector the equations are similar to (https://www.sciencedirect.com/science/article/pii/S030142150800061X), for the combined heating and power sector (https://ieeexplore.ieee.org/document/8309280/). These articles are all referenced in the text. Therefore I would say that the model construction has a reference value.
It is notable to mention that, the result of the model in the scenario where there is no market power (the comp scenario) are equivalent to a similar linear programming model (here is the reason why https://ieeexplore.ieee.org/document/7981888).
Also, model outcomes in the power market (e.g.) are not far from what is being discussed currently and past studies. Outcomes such as increasing gas demand in the mid-term, investment in renewables etc. ( https://www.sciencedirect.com/science/article/pii/S0301421513010549 e.g. develops a LP model, yet the results are similar). Still, I avoided to compare the results with other studies as the aim of the present study is not to epic the future with different scenarios, but to focus on one- two aspects which are less considered.
About the stability of the model: I have run the model with different starting points (at least five different starting values) so that I do not end up in a local optima, the results were all the same. This can be considered a grid search method.
Regarding evaluating the variables and parameter:
I had a bit of a problem to understand the exact meaning. I went through multiple similar literature to find a section about “evaluating the variables and parameter”, so that I can orient myself to write a section about that. However I was unable to find it. Can the esteemed reviewer provide one reference, so I can understand exactly what it means?
E.g. when you have a parameter like efficiency of a thermal plant, which is based on current technologies and the future developments, how can this parameter be evaluated?
(In this case we used assumptions with references, listed in table 1 )
Best regards,
