Renewables and Advanced Storage in Power Systems: The Iberian Case
Round 1
Reviewer 1 Report
Review for
applsci-1621291
Renewables and Advanced Storage in Power Systems. The Iberian Case
This work is focusing on the analysis of energy storage in the Iberian peninsula, which is significant and innovative. I would like to recommend it for publication. I think, nonetheless, that the manuscript could be improved if the authors could address the comments and recommendations I listed below.
If possible, describe some current storage techniques in the Intro part.
Line 96-99: the description of the Li+ battery needs a reference.
Line 117: Sentence without full stop(.).
Line 121: Tow full stop(.) at the end of this sentence.
Line 197: The table needs the data source citation. Additionally, the significant digits in the table should consistent.
Many tables without citations. Please add.
If possible, I recommend you add some figures to represent your calculation results, which could be more friendly to the reader.
Appendix: Make sure you have the copyright to copy those equations.
Overall, this article is in good shape, but several points need to be addressed or revised.
Author Response
Thank you for your comments. They have been used to improve the paper and they are answered below
If possible, describe some current storage techniques in the Intro part.
The following paragraph has been added in lines 33-39 "Storage in power systems include technologies that have been used for many years, like pumping hydro power plants or batteries, and others that are in an experimental or precompetitive stage, like compressed air, flywheels, hydrogen, or supercapacitors. Their applications can be classified into those that can handle large amounts of energy (energy arbitrage, seasonal storage, congestion management or operational reserves) and others aimed at power quality issues or providing short term reserves. Each technology has its own niche, although some compete among them for the same use [5].", and the technical explanation of storage in section 2 has been enlarged
Line 96-99: the description of the Li+ battery needs a reference.
Line 117: Sentence without full stop(.).
Line 121: Tow full stop(.) at the end of this sentence.
Line 197: The table needs the data source citation. Additionally, the significant digits in the table should consistent.
Many tables without citations. Please add.
All these queries have been corrected in the text. Thank your for your accurate reading.
If possible, I recommend you add some figures to represent your calculation results, which could be more friendly to the reader.
Three figures have been added in order to clarify the overall process, and to illustrate the results. I hope that the reader may follow the main findings of the paper more easily.
Appendix: Make sure you have the copyright to copy those equations.
I am grateful to this hint. I have contacted the ieee to arrange the copyright issues when needed.
Reviewer 2 Report
The authors assessed the profitability requirements of advanced storage systems for an optimal Iberian power system using an optimization method. In the discussion part, the authors can add the comparisons to other optimization methods. The authors can also add sensitivity test to see how their result change with different parameters.
Author Response
Thank you for the comments. Regarding the comparison with other optimization methods, it is not clear to me if it is about the optimization method itself or to other studies. As for other optimization method, the problem is linear and the linear solver of matlab has been used. It is not the aim of the paper to propose a novel, time saving optimization algorithm, so the matlab solver seemed good enough.
As for other studies, it is difficult to compare because other studies have different geographical scopes, assumptions or renewables targets. It has been compared with the Iberian National Energy Plans, but the comparison is just informative. A paragraph have been aded to underline this difficulty (lines 342-345): "Comparisons to other simulations studies like [12-15] are difficult because the assumptions, considered technologies and geographical scope are widely different. All of them, however, remark the importance of storage in an intermittent renewable-dominated power system."
About sensitivity studies, they cannot be missing in an assessment study as this. This is why the paper includes two sensitivity studies, with respect to storage cost and carbon price. To remark the importance of the sensitivity studies, this expression has been added to various places in the paper, to make clear that a sensitivity study is being performed.
Reviewer 3 Report
The topic is interesting, and the developed method is useful for the study of power systems. The obtained results are important in the field and would justify publication. The manuscript quality is high and no revision is required. The manuscript is appropriate for publication in Applied Sciences under its present form.
Author Response
Thank you for your positive review.
Reviewer 4 Report
It was a great article about the profitability requirements of future storage systems (batteries). Please consider the following suggestions:
L22: Please fix the referencing “[1], [2] or [3]” should be [1-3]; L30: “[5], [6]” should be [5,6]
P96-99: Please add the reference.
L42: “European power system planning is the subject of references” please mention the Authors (year) instead of references
L46: Likewise “The Spanish system is studied in reference [15]” please indicate “by the author (year)” instead of “in the reference”.
Author Response
Thank you for your comments. All your suggestions have followed.
Reviewer 5 Report
The only method of minimization of emission related to the production of energy comes from fossil fuel is increasing the share of renewable energy sources. In the case of PV and wind turbine farms the production is strongly dependant on the weather conditions. In that respect the usage of energy storage system seems to be necessary. It should store the energy overproduced by PV and Wind turbines farms and supply it to the grid when its production is unsufficient. The managment of the energies comes from the so many different kinds of energy sources is crucial for the proper operation of energetic system, both on the technical and economic aspects.
In the paper Authors focusing on the second one aspect. Based on the prediction of expected share of renewable energy sources in energy production for Iberian Penisula Authors optimize the capacity of energy storage system and based on obtained results and assumend expected prices in 2030 predicts the cost of storage and the revenues. Moreover Authors extendts this calculations for the different costs of CO2 emission.
From technical point of view, in my opinion, a certain surprise is so low capacity of energy storage system in the scenario where the share of PV and Wind energy increase almost 2 times. It is probaly related to the assumend incresing of energy consumption in 2030 what information is not included or I didn't notice it.
In Table 3 the fixed cost unit is not clear for me also. I think that directly below or above of mentioned table should be a few sentence of explanation what this cost include.
Author Response
Thank you for your comments. In fact, the relatively small amount of storage capacity compared to the demanded energy is a result that has been obtained in other performed studies. Reference [30] includes more information and a study for different share levels of renewables in the energy mix. Comments and a new reference [42] has been added to support this conclusion. This new references includes an extensive review of many previous references. The demanded energy for 2030 increases with respect to the present one according to the expectations of the Iberian National Energy Plans.
The explanation of the meaning of the fixed cost units have been enlarged in lines 272-274. It represents the money per MW of the installed capacity that must be recovered each year to pay up the investment and fixed O&M costs over the lifetime of the facility with a given discount rate.
Reviewer 6 Report
- Since the study focused on making a profitable business model, it is required to clarify the stakeholders.
- Please clearly mention the paper contribution and put the short brief description of each section in the introduction section.
- Please provide an algorithm to show the steps, input, and output of deployed optimization.
- Please provide some graphs to provide the results more understandable and attractive for readers.
- Please improve the conclusion based on numerical results.
Author Response
Thank you for your constructive comments. Please find the answers to them below.
1. Since the study focused on making a profitable business model, it is required to clarify the stakeholders.
This is an interesting point, since it allows to comment on the EU regulation about this issue. The following paragraph has been added. "Stakeholders of storage are companies willing to invest in storage facilities, either existing generating companies, consumers, or dedicated companies. European regulation [4] gives a special role to storage facilities, but excludes, with some exceptions, transmission and distribution companies from the property or management of storage facilities. Of course, this might be an obstacle for optimal sizing and management of system storage."
2. Please clearly mention the paper contribution and put the short brief description of each section in the introduction section.
The following paragraph has been added in lines 99-104: "The intended contributions of this paper are the assessment of uncertainty of storage costs in generation planning with low computational cost as well as the conditions under which the arbitrage in electricity markets may cover the investment costs of storage. Another contribution is to consider the storage capacity as an optimization variable to check if the envisaged progress of storage technologies would cover power system needs."
3. Please provide an algorithm to show the steps, input, and output of deployed optimization.
Figure 1 has been added to clarify the outline of the followed method.
4. Please provide some graphs to provide the results more understandable and attractive for readers.
Three figures, the one mentioned before, and two more illustrating the results have been added.
4. Please improve the conclusion based on numerical results.
Numerical results have been added in the conclusion section to support the main findings of the paper.
Reviewer 7 Report
This paper presents Iberian power system as a case study to analyze the profitability requirements of incorporating advanced storage systems in the power system through an optimization model.
Below are my comments:
Abstract
Suggest including some of main findings/results in the abstract.
- Introduction
Suggest rewriting and stressing on the importance and motivation of this paper and how it is different from previous literature studies.
“The uncertainty in storage costs has been considered by means of the two-point estimate method to study the effect of storage cost uncertainty on the optimal deployment of renewables.” This sentence is confusing. Consider rewrite. Split into two sentences might be easier to understand.
- Storage and its applications
Consider rewrite and clarify why choosing the two storage methods (batteries, and hydro pumping storage methods)?
- Power system planning under Uncertainty. The Point Estimate Method
- Optimization problem and basic assumptions
Suggest including the detailed mathematical model in this section.
- Uncertainty assessment method
Page 4, line 154: pay attention to format.
Equation 6a, 6b, 6c, pay attention to format.
- Study case. The Iberian system in 2030 according to the National Energy and Climate Plans (NECPs)
- Results and Discussion
- Conclusion
Consider rewrite this section. It is useful to include the outlook of this study.
Page 11, line 361 is not necessary.
- Appendix
Pay attention to the format. Suggest including the appendix in the main body.
Table
Pay attention to format, be consistent with all tables.
Author Response
Thank you for the comments. I think that they will help to improve the paper. They are answered below.
Abstract
Suggest including some of main findings/results in the abstract.
The abstract has been enlarged to include the main findings of the paper.
- Introduction
Suggest rewriting and stressing on the importance and motivation of this paper and how it is different from previous literature studies.
The following paragraph has been added in lines 99-104 to underline the intended contributions of the paper: "The intended contributions of this paper are the assessment of uncertainty of storage costs in generation planning with low computational cost as well as the conditions under which the arbitrage in electricity markets may cover the investment costs of storage. Another contribution is to consider the storage capacity as an optimization variable to check if the envisaged progress of storage technologies would cover power system needs."
“The uncertainty in storage costs has been considered by means of the two-point estimate method to study the effect of storage cost uncertainty on the optimal deployment of renewables.” This sentence is confusing. Consider rewrite. Split into two sentences might be easier to understand.
The sentence has been split as follows. "The uncertainty in storage costs has been considered using the two-point estimate method. In this way the effect of storage cost uncertainty on the optimal deployment of renewables can be easily assessed. "
- Storage and its applications
Consider rewrite and clarify why choosing the two storage methods (batteries, and hydro pumping storage methods)?
The following explanation has been added in lines 183-187: "The reason for this choice is that this is the most promising and economical technology for most applications according to [6]. New pumping hydro facilities must also consider the available places to build them and environmental issues, so the results obtained by an optimization problem would not be realistic."
- Power system planning under Uncertainty. The Point Estimate Method
- Optimization problem and basic assumptions
Suggest including the detailed mathematical model in this section.
Since the paper is focused on the storage and its need in a mostly decarbonized energy mix more than in the optimization process itself, the equations are more for information, and this is why they are in an appendix. By the moment, the equations are left in the Appendix. I hope I have convinced the reviewer.
- Uncertainty assessment method
Page 4, line 154: pay attention to format.
Equation 6a, 6b, 6c, pay attention to format.
Format has been corrected
- Study case. The Iberian system in 2030 according to the National Energy and Climate Plans (NECPs)
- Results and Discussion
- Conclusion
Consider rewrite this section. It is useful to include the outlook of this study.
The outlook of the paper has been included at the beginning of the Conclusions section.
Page 11, line 361 is not necessary.
The line has been removed
- Appendix
Pay attention to the format. Suggest including the appendix in the main body.
The format has been corrected
Table
Pay attention to format, be consistent with all tables.
Captions have been added to the tables, to give them the same format as the other tables in the paper.
Round 2
Reviewer 6 Report
The authors appropriately modified the paper based on the comments.
Reviewer 7 Report
no further comment
