Analysis of Challenges Due to Changes in Net Load Curve in South Korea by Integrating DERs

Round 1

Reviewer 1 Report

PRESENTATION COMMENTS:
Abstract
The abstract does not compare the key results with previously published work.
The abstract does not give the main conclusions or indicate any limitations.
Introduction
There is no review of previous work.
The introduction does not sufficiently review earlier findings.
The introduction does not clearly state what has been done that has not been done before.
The introduction does not indicate the comparators used to demonstrate relevance.
The manuscript discussed the need for the work carried out in Korea. However, a discussion of similar works is missing.
Manuscript Body
The clarity of the presentation can be improved. The title of graphs and figures need to be improved. Most of the graph axis is not properly labelled - the authors tend to use only units for the titles of the axis - mostly kW for the y-axis and hour/minutes for the x-axis
Conclusions
Important results and their consequences are missing.
Any reservations and/or limitations have not been indicated.
The paper does not have a conclusions section (but the last section is titled discussions). Kindly include a conclusions section that will:

(1) bring together the most important results and their consequences

(2) Talk about reservations and limitation
References

The existing references do not indicate alternative techniques which can be used to compare your work.

Formatting
Figure titles and labels need to be reviewed - particularly, the y-axis and x-axis labels for most figures are missing, the authors provide only the units.

TECHNICAL COMMENTS:

The paper is technically sound. However, it is not very clear what the contributions of the paper is/are. The contributions will become clearer if the authors can itemize them within the introduction.

 

A copy of the paper with some comments is attached.

Comments for author File: Comments.pdf

Author Response

[Authors’ Response]

We greatly appreciate the comments and suggestions from reviewer 1, by which, we think, this research paper is more logically reinforced.

 

1. Abstract

- The abstract does not compare the key results with previously published work.

- The abstract does not give the main conclusions or indicate any limitations.

☞ In order to address 2 problems that the reviewer pointed out, we have modified the related part of abstract to “And since ToU (Time-of-Use) tariff and Demand Response (DR) programs are very sensitive to changes in the net load curve, it is very essential to predeict the hourly net load pattern accurately for the modification of pricing and demand response programs in future. However, a long-term demand forecast in South Korea provides only the total amount of annual load (TWh) and the expected peak load level (GW) in summer and winter seasons until 2030.” to present the drawback of the previous national publication and to emphasize our contribution.

Please refer to lines 18 ~ 22 at page 1.

Thank you very sincerely for the good comments.

 

 

2. Introduction

- There is no review of previous work.

☞ As the reviewer pointed out, we have added some sentences and more references like “Previous studies address various problems in power systems such as ramping events, peak load time shifts due to duck curves and irregular generation depending on weather condition [12-13]. And the reference [14] says that the increasing PV penetration ratio and generation can cause a net load demand around the afternoon time to significantly decrease, resulting in an increase in the amount of attenuation of thermal power generators, which in turn leads to economic losses.” and “Other previous work such as 8th Basic Plan for Long-term Electricity Supply and Demand [16] mainly deal with overall negative impacts of the duck curve, and long-term power demand forecasting including the total amount of annual load (TWh) and the expected peak load level (GW) in summer and winter seasons until 2030. However, in order to accurately analyze the change of net load curve pattern, it is necessary to predict the hourly pure load curve and the hourly net load curve which includes the pure load level, demand response, renewable generation and other factors. Some studies introduced the hourly net load pattern with renewable energy resources, but they were based on only the current load level and mainly focused on the impact of variability of renewables [12, 17]. Now, we need for the hourly load pattern prediction considering the future change of energy circumstances until 2030.” to review previous studies and to emphasize our contribution in the introduction section.

Please refer to lines 60 ~ 65, and lines 73 ~ 82 at page 2.

Thank you very sincerely for the good comments.

 

 

- The introduction does not sufficiently review earlier findings.

☞ As the reviewer pointed out, we have modified the related part of introduction to “Figure 1 shows a difference of actual net load curves in South Korea on Nov. 20 and Nov. 21 in 2018. According to the Korea Meteorological Administration (KMA) information, it was clear on Nov. 20 and cloudy on Nov. 21 [15]. Total amounts of energy consumption were 1,525,173 GWh on Nov. 20 and 1,557,242 GWh on Nov. 21, which means that the difference of energy consumption was 32,069 GWh in just one day because of the change of weather condition. When we consider the additional EV charging effect, it will make the duck curve worse, especially after 8 PM when the need for EV charging is intensive, by making a large difference between the peak load and the off-peak load.” to provide more reviews of the Reference 14 as shown in Figure 1.

Please refer to lines 65 ~ 72 at page 2.

Thank you very sincerely for the good comments.

 

 

- The introduction does not clearly state what has been done that has not been done before.

☞ As the reviewer pointed out, we have added a paragraph of “However, in order to accurately analyze the change of net load curve pattern, it is necessary to predict the hourly pure load curve and the hourly net load curve which includes the pure load level, demand response, renewable generation and other factors. Some studies introduced the hourly net load pattern with renewable energy resources, but they were based on only the current load level and mainly focused on the impact of variability of renewables [12, 17]. Now, we need for the hourly load pattern prediction considering the future change of energy circumstances until 2030. Thus, we predict the hourly load curve and the hourly net load by taking into account PV installed capacity, PV generation, and the number of EVs based on the target of Korean policy until 2030.” to clarify what we do in our study.

Please refer to lines 76 ~ 84 at page 3.

Thank you very sincerely for the good comments.

 

 

- The introduction does not indicate the comparators used to demonstrate relevance.

☞ Our paper is written to analyze the changes of the future net load curve by predicting the hourly load curve considering the future PV and EV penetration changes until 2030, which has not been previously performed. We have tried to find other similar study cases in both Korea and international works. But we failed to find the related comparator for verification.

Thank you very sincerely for the good comments.

 

 

- The manuscript discussed the need for the work carried out in Korea. However, a discussion of similar works is missing.

☞ As the reviewer pointed out, we have added some paragraphs of “Previous studies address various problems in power systems such as ramping events, peak load time shifts due to duck curves and irregular generation depending on weather condition [12-13]. ~ When we consider the additional EV charging effect, it will make the duck curve worse, especially after 8 PM when the need for EV charging is intensive, by making a large difference between the peak load and the off-peak load.” and “Other previous work such as 8th Basic Plan for Long-term Electricity Supply and Demand [16] mainly deal with overall negative impacts of the duck curve, and long-term power demand forecasting including the total amount of annual load (TWh) and the expected peak load level (GW) in summer and winter seasons until 2030. ~ Thus, we predict the hourly load curve and the hourly net load by taking PV installed capacity into account, PV generation, and the number of EVs based on the target of Korean policy until 2030.” to discuss the similar works and the necessity of our study.

Please refer to lines 60 ~ 84 at page 2.

Thank you very sincerely for the good comments.

 

3. Manuscript Body

- The clarity of the presentation can be improved. The title of graphs and figures need to be improved. Most of the graph axis is not properly labelled - the authors tend to use only units for the titles of the axis - mostly kW for the y-axis and hour/minutes for the x-axis

☞ As the reviewer pointed out, we have modified the titles of the graphs and figures to match the MDPI format. Also, we have modified the titles of the axis appropriately.

Thank you very sincerely for the good comments.

 

 

4. Conclusions

Important results and their consequences are missing.

Any reservations and/or limitations have not been indicated.

The paper does not have a conclusions section (but the last section is titled discussions). Kindly include a conclusions section that will:

(1) bring together the most important results and their consequences

(2) Talk about reservations and limitation

☞ As the reviewer pointed out, we have modified the chapter 5. Conclusion as a whole, adding main contribution, limitation, application and future work.

Please refer to lines 366 ~ 390 in page 17.

Thank you very sincerely for the good comments.

 

 

5. References

- The existing references do not indicate alternative techniques which can be used to compare your work.

☞ As the reviewer pointed out, we have added more references in the paper to supplement the weakness and to compare with our work directly. We have tried to find other similar study cases in both Korea and international works. But we failed to find the related comparator, as we mentioned before.

Thank you very sincerely for the good comments.

 

6. Formatting

- Figure titles and labels need to be reviewed - particularly, the y-axis and x-axis labels for most figures are missing, the authors provide only the units.

 ☞ As the reviewer pointed out, we have modified the titles of the graphs and figures to match the MDPI format. Also, we have added y-axis and x-axis labels of figures

Thank you very sincerely for the good comments.

Author Response File: Author Response.pdf

Reviewer 2 Report

The PV generation and EV penetration are considered in this paper to predict the future net load curve in South Korea. It is concluded that the existing application of ToU tariff and DR operating time is no longer appropriate. The subject of high interesting for optimized energy use and supply.

However, it is lack of literature review on the subject and hard to assess the contribution or novelty of this paper. Please revise it to have previous works on the subject and make full discussion on methodologies used and results obtained in association with any progress made previously.

 

Some specific problems found:

• The keywords need to be reconfirmed. For example, the paper revolves around PV generation and EV penetration, therefore the keyword PV generation is even more important than SoC (State-of-Charge).
• In line 85, the ‘2030’ should be ‘2017’.
• In line 90, the ‘15:00’ should be ‘17:00’ according to the Table 2.
• In line 171, the additional ‘(1)’ should be removed.
• Some format errors in the manuscript such as Figure 5, Figure 6, Figure 7, and Figure 8 should be formatted carefully.

A large number of formatting problems are found in the titles of figures and tables and the line styles of tables such as Table 14, Table 18 and Table 19, all of the errors must be formatted and revised carefully according to the MDPI article template

Author Response

[Authors’ Response]

We greatly appreciate the comments and suggestions from reviewer 2, by which, we think, this research paper is more logically reinforced.

 

1. However, it is lack of literature review on the subject and hard to assess the contribution or novelty of this paper. Please revise it to have previous works on the subject and make full discussion on methodologies used and results obtained in association with any progress made previously.

☞ As the reviewer pointed out, we have added some paragraphs and more references of “Previous studies address various problems in power systems such as ramping events, peak load time shifts due to duck curves and irregular generation depending on weather condition [12-13]. And the reference [14] says that the increasing PV penetration ratio and generation can cause a net load demand around the afternoon time to significantly decrease, resulting in an increase in the amount of attenuation of thermal power generators, which in turn leads to economic losses.” and “Other previous work such as 8th Basic Plan for Long-term Electricity Supply and Demand [16] mainly deal with overall negative impacts of the duck curve, and long-term power demand forecasting including the total amount of annual load (TWh) and the expected peak load level (GW) in summer and winter seasons until 2030. However, in order to accurately analyze the change of net load curve pattern, it is necessary to predict the hourly pure load curve and the hourly net load curve which includes the pure load level, demand response, renewable generation and other factors. Some studies introduced the hourly net load pattern with renewable energy resources, but they were based on only the current load level and mainly focused on the impact of variability of renewables [12, 17]. Now, we need for the hourly load pattern prediction considering the future change of energy circumstances until 2030.” to introduce the previous studies and compare them with our study.

 Please refer to lines 60 ~ 65, and lines 73 ~ 82 at page 2.

Thank you very sincerely for the good comments.

2. The keywords need to be reconfirmed. For example, the paper revolves around PV generation and EV penetration, therefore the keyword PV generation is even more important than SoC (State-of-Charge).

☞ [Line 30] As the reviewer pointed out, we have removed SoC (State-of-Charging) and have added PV generation in keywords part.

Thank you very sincerely for the good comments.

 

 

3. In line 85, the ‘2030’ should be ‘2017’.

☞ As the reviewer pointed out, we have changed ‘2030’ into ‘2017’.

Thank you very sincerely for the good comments.

 

 

4. In line 90, the ‘15:00’ should be ‘17:00’ according to the Table 2.

☞ As the reviewer pointed out, we have changed the time format for ’17:00’ into ‘5 PM’. And all of the time has been changed into AM or PM form.

Thank you very sincerely for the good comments.

 

 

5. In line 171, the additional ‘(1)’ should be removed.

☞ As the reviewer pointed out, we have removed ‘(1)’ from the text.

Thank you very sincerely for the good comments.

 

 

6. Some format errors in the manuscript such as Figure 5, Figure 6, Figure 7, and Figure 8 should be formatted carefully.

☞ As the reviewer pointed out, we have modified the format of all the Figures in the paper according to the MDPI format.

Thank you very sincerely for the good comments.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

The topic of this work is interesting. Some extended works need to be done before the manuscript is accepted. Below are some detailed issues with this manuscript:

1. On page 2, the authors claimed that Figure 1 indicates an additional power generation of 32,069GWh was needed in just one day. How did the authors obtain this number? Some explanations are needed.
2. A reference is needed for Table 1 and Table 2.
3. The authors Figure 2 is based on the actual data obtained from KPX. A link or at least a reference is needed.
4. The authors wrote “However, the peak load time for the spring/fall changed from 11:00 in 2015 and 2016 to 15:00 in 2017, …” at the end of page 3. Table 2 indicates a different result. Is this a typo? Please check the whole manuscript. This kind of mistake affects the quality of the work. Also, it is not clear why the peak load time doesn’t shift in the summer and winter seasons.
5. In section 2.1, it is not clear which data is measured by the authors and which ones are from the references. Also, in this section, the authors mentioned three curves (load curve, net load curve, and PV generation curve), and the reviewer only saw the discussion of two figures. In addition, three years (2016, 2017, and 2018) were mentioned, which year’s data is known, and which year’s data needs to be predicted? Please make it clear.
6. The authors chose Monte Carlo simulation. Since there are so many other methods, why did the authors choose this method? Some explanations are needed.
7. This study focuses on the analysis of the net load curve in South Korea. Can the results of this study be applied to other countries around the world? A discussion is needed since this can be useful.

Author Response

[Authors’ Response]

We greatly appreciate the comments and suggestions from reviewer 3, by which, we think, this research paper is more logically reinforced.

 

1. On page 2, the authors claimed that Figure 1 indicates an additional power generation of 32,069GWh was needed in just one day. How did the authors obtain this number? Some explanations are needed.

☞ As the reviewer pointed out, we have added information on the power generation at 20/11/2018 and 21/11/2018 respectively, and the difference of power generation between 20/11/2018 and 21/11/2018 in Table 1.

Table 1. Net load difference between 20/11/2018 and 21/11/2018

	20/11/2018	21/11/2018
Net load (GWh)	1,525,173	1,557,242
Difference (GWh)	32,069

Thank you very sincerely for the good comments.

 

2. A reference is needed for Table 1 and Table 2.

☞ As the reviewer pointed out, we have added the reference [18] to Table 2 (Table 1 in the original version). And Table 3 (Table 2 in the original version) has no reference since it represents the contents of Figure 2.

Thank you very sincerely for the good comments.

 

3. The authors Figure 2 is based on the actual data obtained from KPX. A link or at least a reference is needed

☞ As the reviewer pointed out, we have added an internet link of KPX in the reference [20].

Thank you very sincerely for the good comments.

4. The authors wrote “However, the peak load time for the spring/fall changed from 11:00 in 2015 and 2016 to 15:00 in 2017, …” at the end of page 3. Table 2 indicates a different result. Is this a typo? Please check the whole manuscript. This kind of mistake affects the quality of the work. Also, it is not clear why the peak load time doesn’t shift in the summer and winter seasons.

☞ As the reviewer pointed out, we have checked all time forms and changed 15:00 to 5 PM, matching with Table values. Also, we have added a sentence of “This fact means that cooling and heating loads are not frequently used in spring and fall unlike summer and winter, so the peak load time due to increasing PV generation is shifted earlier than other seasons.”.

Please refer to lines 117 ~ 119 at page 4.

Thank you very sincerely for the good comments.

 

 

5. In section 2.1, it is not clear which data is measured by the authors and which ones are from the references. Also, in this section, the authors mentioned three curves (load curve, net load curve, and PV generation curve), and the reviewer only saw the discussion of two figures. In addition, three years (2016, 2017, and 2018) were mentioned, which year’s data is known, and which year’s data needs to be predicted? Please make it clear.

☞ As the reviewer pointed out, we have modified the part as a whole to minimize the reader’s confusion. Please check the chapter of 2.1.

Thank you very sincerely for the good comments.

 

6 The authors chose Monte Carlo simulation. Since there are so many other methods, why did the authors choose this method? Some explanations are needed.

☞ As the reviewer pointed out, we have added some sentences of “The data used to predict EV charging load is probability-based data based on surveys of actual EV users. Monte Carlo Simulation is the most suitable method to utilize probability-based data as a method of performing a simulation by repeating random selection of input variables from a probability distribution [23-24].” to explain why we used Monte Carlo simulation technique.

Please refer to lines 233 ~ 236 at page 10.

Thank you very sincerely for the good comments.

 

 

 

7. A large number of formatting problems are found in the titles of figures and tables and the line styles of tables such as Table 14, Table 18 and Table 19, all of the errors must be formatted and revised carefully according to the MDPI article template.

☞ As the reviewer pointed out, we have modified the format of all the Figures in the paper according to the MDPI format.

Thank you very sincerely for the good comments.

 

Reviewer 4 Report

This work discusses the concerns over the changes of the net load due to DER integration into the power system, which may lead to a negative impact on the existing operation of the power systems in South Korea.  The topic of the paper is interesting. However, the reviewer has some comments on this study, which need authors to address as follows,

1) Figure 1 shows the load curves over the two-day period. According to the diagrams, the authors point out that the discrepancy between the two days is due to the variation of the PV generation. However, there are neither obvious evidence nor references in the paper to support the authors’ comments.

2) The authors has drawn the conclusion (from lines 65 to 71) that both of the existing TOU and DR are improper to the situation caused by the changes of PV generation and EV consumption. However, there is no evidence or data to support the conclusion directly  from the beginning of the manuscript to the content there.

3)  Lines 89 and 90 present “…… the peak load time for the spring/fall changed from 11:00 in 2015 and 2016 to 15:00 in 2017……”. However, Table 2 presents the peak in Spring/Fall, 2017 at 17:00. Moreover, there are limited differences between the 11am, 5pm and 8pm in Spring/Fall, 2017 in Figure 2(a). The authors need to clarify where exactly is the peak in the authors’ view. The accurate data should be shown to support the conclusion drawn by the authors.

4) The author has cited the report “The 8th Basic Plan for Long-term Electricity Supply and Demand (2017 - 2031)” for the calculation as presented from lines 104 to 107. This report is made by Ministry of Trade, industry and Energy, South Korea and demonstrates the actual data for both accumulated consumption and peak demand in 2016 and 2017 (page 70). However, the data in this report (over 80GW) has relatively large discrepancy to the data in Figure 2 (below 70 GW) in the manuscript. The author need to explain where the data is adopted from. A reference is needed to further explain the issue.   

5) From line 101 to line 113, the authors uses 4 steps to predict the load curves. In the last step, the author uses the load curves in 2018 to minus the PV generation. However, Neither theoretical or practical methods, evidences or references to support correctness of this calculation. Convincing evidences are needed if the calculation is believed correct.

5) Table 3 provides a series of numbers in line with the load growth rates as stated by the author from Ref. 15. However, the numbers on page 74, ref. 15 shows apparently difference from the data in Table 3 in the manuscript. For instance, the rate in 2025 in the paper is 1.94% while being 0.6 on page 74 in Ref. 15. The author need to explain which parts of the data are cited from the reference or how the data in the table is received.

6) In lines 206-208, the authors state the numbers in Table 12 are derived on the basis of the principle of uniform distribution. However, these numbers are apparently incompatible to this principle. The authors need to explain how these data are derived. Or some references associated with the calculation methods should be added.

7)  Table 14 provides the accurate numbers to estimate the charging numbers for different EV users. The authors need to provide the evidence or calculation methods how the numbers are defined since there are no explanations on this issue.

8) The authors has drawn the conclusion that the ToU and DR scheme will be improper to operating the future power systems due to the load curves changed. However, there are lack of the necessary details to support the conclusions.

9) Both of the limitations and the future work are necessary in the conclusion or introduction.

10) Conclusions are needed to be improved.

 

Author Response

[Authors’ Response]

We greatly appreciate the comments and suggestions from reviewer 4, by which, we think, this research paper is more logically reinforced.

 

1. Figure 1 shows the load curves over the two-day period. According to the diagrams, the authors point out that the discrepancy between the two days is due to the variation of the PV generation. However, there are neither obvious evidence nor references in the paper to support the authors’ comments.

☞ 20/11/2018 is Tuesday and 21/11/2018 is Wednesday. Since the two days are weekdays, not holidays, they should have a similar hourly pattern of net load curve. However, the amount of power generation by PV has a large difference due to the weather conditions during daylight hours. The below table shows the actual cloud information of 20/11/2018 and 21/11/2018 obtained from Korea Meteorological Administration. In the table, the 0 to 5 levels mean clear, the 6 to 8 level mean cloudy, and the 9 to 10 levels mean heavily cloudy. As the reviewer pointed out, we have added a sentence of “According to the Korea Meteorological Administration (KMA) information, it was clear on Nov. 20 and cloudy on Nov. 21 [15].” and its reference.

Please refer to lines 66 ~ 67 at page 2.

Thank you very sincerely for the good comments.

Table. Weather conditions on 20/11/2018 and 21/11/2018 in South Korea.

Hour	20/11/2018	21/11/2018
7	0	10
8	0	10
9	0	10
10	0	10
11	0	10
12	0	10
13	0	10
14	0	10
15	0	10
16	0	10
17	1	10
18	2	10

 

2. The authors has drawn the conclusion (from lines 65 to 71) that both of the existing TOU and DR are improper to the situation caused by the changes of PV generation and EV consumption. However, there is no evidence or data to support the conclusion directly from the beginning of the manuscript to the content there.

☞ As the reviewer pointed out, we have modified the related part into “Table 2 shows the current seasonal time range for ToU tariff in Korea [18]. The peak load time will be shifted into other time ranges as shown in Figure 1. Additionally, DR is implemented from 9 AM to 8 PM (except 12 PM ~ 1 PM) to reduce electricity demand in South Korea [19]. Thus, as the number of EVs charging after 8 PM increases, it is necessary to change the DR operating time to manage new peak loads occurring after 8 PM due to EV charging load.” in the introduction and have added an additional explanation of “When considering only the penetration of PV, the currently operating systems are no longer suitable since the peak load time is expected to shift to 8 PM in spring/fall of 2018 and in summer of 2025. And when considering EV penetration further, the peak load time shifts to 8 PM in spring/fall of 2018, summer at 2023, and winter of 2027 in the expected case of Monte-Carlo Simulation. In the maximum case, the peak load time shifts to 8 PM in spring/fall of 2018, in summer of 2023. In particular, in the maximum case for winter season, the peak load time shifts to 8 PM in 2026, one year earlier than the expected case.” in the conclusion.

Please refer to lines 86 ~ 91 at page 3 and lines 376~382 at page 17.

Thank you very sincerely for the good comments.

 

 

3. Lines 89 and 90 present “…… the peak load time for the spring/fall changed from 11:00 in 2015 and 2016 to 15:00 in 2017……”. However, Table 2 presents the peak in Spring/Fall, 2017 at 17:00. Moreover, there are limited differences between the 11am, 5pm and 8pm in Spring/Fall, 2017 in Figure 2(a). The authors need to clarify where exactly is the peak in the authors’ view. The accurate data should be shown to support the conclusion drawn by the authors.

☞ As the reviewer pointed out, we have checked all time forms and changed 15:00 to 5 PM, matching with Table values. Please refer to line 115 at page 4.

The below table shows the data used to draw Figure 2. The seasonal peak load time for each year are indicated in yellow, and the results are shown in Table 2.

Thank you very sincerely for the good comments.

 

Table. The data used to make Figure 2

Hour	Spring/Fall (GWh)			Summer (GWh)			Winter (GWh)
	2015	2016	2017	2015	2016	2017	2015	2016	2017
1	50,000	50,965	51,760	48,354	50,092	51,560	57,123	57,767	59,640
2	48,681	49,565	50,360	47,268	48,476	50,039	55,676	56,036	57,801
3	48,281	49,313	50,147	46,944	48,138	49,641	55,123	55,556	57,280
4	48,240	49,274	50,160	46,757	48,018	49,456	54,869	55,475	57,199
5	48,572	49,573	50,608	46,846	48,095	49,539	55,165	55,823	57,683
6	49,119	50,302	51,606	47,093	48,389	50,097	55,694	56,515	58,661
7	50,248	51,715	53,178	48,188	49,778	52,029	56,499	57,658	60,260
8	51,838	53,498	54,859	50,196	52,256	54,759	57,829	59,351	62,160
9	54,753	56,349	57,183	54,215	56,447	58,435	61,565	62,910	65,802
10	56,297	57,804	58,291	57,253	59,816	61,458	63,209	64,455	67,357
11	56,571	58,124	58,500	58,689	61,430	62,998	63,287	64,618	67,431
12	56,332	57,845	58,156	59,314	62,118	63,587	62,646	63,948	66,612
13	53,623	55,122	55,789	57,251	60,154	61,608	59,265	60,520	63,131
14	55,519	56,958	57,481	59,463	62,427	63,877	60,681	61,967	64,390
15	56,339	57,791	58,319	60,427	63,383	64,861	61,126	62,408	64,875
16	56,158	57,672	58,292	60,121	63,107	64,632	60,765	62,158	64,739
17	56,390	57,972	58,746	60,036	63,071	64,630	61,151	62,675	65,423
18	56,122	57,682	58,565	59,072	62,053	63,678	61,349	62,949	65,679
19	56,344	57,823	58,722	57,949	60,860	62,544	61,543	62,953	65,554
20	56,526	57,893	58,722	57,801	60,553	62,193	60,465	61,792	64,284
21	55,713	56,930	57,704	57,370	59,947	61,432	59,293	60,450	62,801
22	54,557	55,619	56,348	55,375	57,758	59,216	58,369	59,329	61,479
23	53,848	54,779	55,412	53,019	55,216	56,621	58,792	59,574	61,507
24	53,091	54,262	55,035	51,414	53,527	54,967	59,852	60,738	62,695

 

 

4. The author has cited the report “The 8th Basic Plan for Long-term Electricity Supply and Demand (2017 - 2031)” for the calculation as presented from lines 104 to 107. This report is made by Ministry of Trade, industry and Energy, South Korea and demonstrates the actual data for both accumulated consumption and peak demand in 2016 and 2017 (page 70). However, the data in this report (over 80GW) has relatively large discrepancy to the data in Figure 2 (below 70 GW) in the manuscript. The author need to explain where the data is adopted from. A reference is needed to further explain the issue.

☞ Figure 2 shows the seasonal average net load curves in South Korea, not peak load curves. The below table shows the data including summer peak demand and winter peak demand for 2016 and 2017 used in Figure 2. Since the values mentioned at page 70 of “The 8th Long-Term Power Supply Basic Plan (2017-2031)” are the peak demand in 2016 and 2017, there is a difference between the two data.

As the reviewer pointed out, we have modified “Figure 2 is the net load curve for South Korea” with “Figure 2 is the seasonal average net load curve for South Korea” to minimize the reader’s confusion.

  Please refer to lines 103 ~ 104 at page 3.

Thank you very sincerely for the good comments.

Table. data including summer peak demand and winter peak demand for 2016 and 2017.

Hour	Sumer		Winter
	12/8/2016	21/7/2017	21/1/2016	12/12/2017
1	63,412.24	63,866.68	69,490.63	69,769.53
2	60,362.54	61,470.62	67,852.53	67,961.33
3	60,140.92	60,697.16	67,400.88	67,270.88
4	60,064.72	59,855.93	66,876.68	66,999.54
5	59,816.66	59,778.54	66,610.40	67,241.29
6	60,327.88	60,696.72	66,804.30	68,694.08
7	62,327.18	64,404.62	67,916.09	71,283.56
8	66,276.63	69,332.44	70,951.90	75,410.58
9	73,238.05	75,062.07	77,689.93	82,226.32
10	79,057.24	80,372.68	81,633.71	84,967.60
11	81,817.23	82,543.58	82,795.57	84,883.76
12	83,010.09	83,896.51	81,988.53	83,882.97
13	79,991.59	81,012.44	76,348.74	78,761.58
14	83,244.03	83,308.95	78,260.85	80,830.47
15	84,939.46	84,189.38	78,819.44	82,099.71
16	84,852.70	84,110.73	78,059.97	82,685.55
17	85,184.64	84,502.07	78,668.79	84,490.20
18	84,000.08	83,581.88	78,667.71	84,808.90
19	81,302.33	82,152.83	78,183.24	82,585.33
20	80,111.93	81,168.98	75,863.50	79,562.27
21	78,488.15	80,245.88	73,206.43	76,522.00
22	74,774.60	76,982.03	71,300.20	73,948.14
23	71,083.99	73,034.18	71,057.34	73,189.73
24	68,565.23	70,269.56	72,827.82	74,157.23

 

 

5. From line 101 to line 113, the authors uses 4 steps to predict the load curves. In the last step, the author uses the load curves in 2018 to minus the PV generation. However, Neither theoretical or practical methods, evidences or references to support correctness of this calculation. Convincing evidences are needed if the calculation is believed correct.

☞ As the reviewer pointed out, we have added a sentence and the reference like “A net load curve(or pattern) in a day is obtained by removing a PV generation curve from a load curve [21].” in line 195 and have modified the part as a whole to minimize the reader’s confusion.

Please check the chapter of 2.1.

Thank you very sincerely for the good comments.

 

6. Table 3 provides a series of numbers in line with the load growth rates as stated by the author from Ref. 15. However, the numbers on page 74, ref. 15 shows apparently difference from the data in Table 3 in the manuscript. For instance, the rate in 2025 in the paper is 1.94% while being 0.6 on page 74 in Ref. 15. The author need to explain which parts of the data are cited from the reference or how the data in the table is received.

☞ The numbers on page 74 of reference 16 (reference 15 in the original version) are the target demand growth rates, not the load growth rates. The definition of target demand is explained on page 31 of reference 16. In this paper, we used the load growth rates mentioned on page 70 of reference 16, not the target demand growth rates.

Thank you very sincerely for the good comments.

 

7. In lines 206-208, the authors state the numbers in Table 12 are derived on the basis of the principle of uniform distribution. However, these numbers are apparently incompatible to this principle. The authors need to explain how these data are derived. Or some references associated with the calculation methods should be added.

☞ As the reviewer pointed out, we have revised the part into “The SoC ranges from 20 % to 90 % with an interval of 10 % for each section, and the percentage of EV users starting charging for each section is also shown in Table 13. It is assumed that the detailed SoC values for the "Based on SoC" type of user, which are used in Monte Carlo simulation, are uniformly distributed in each SoC section.” to minimize the reader’s confusion.

  Please refer to lines 268 ~ 271 at page 12.

Thank you very sincerely for the good comments.

 

8. Table 14 provides the accurate numbers to estimate the charging numbers for different EV users. The authors need to provide the evidence or calculation methods how the numbers are defined since there are no explanations on this issue.

☞ As the reviewer pointed out, we have added the equation (1) and its explanation in details to show how the numbers are calculated.

Please refer to lines 277 ~ 288 at page 12.

Thank you very sincerely for the good comments.

 

9. The authors has drawn the conclusion that the ToU and DR scheme will be improper to operating the future power systems due to the load curves changed. However, there are lack of the necessary details to support the conclusions

☞ As the reviewer pointed out, we have revised the part of conclusion with “In this paper, the load curve and net load curve are predicted to confirm the change of the net load curve for each season by year considering high PV and EV penetrations until 2030. ~ In particular, in the maximum case for winter season, the peak load time shifts to 8 PM in 2026, one year earlier than the expected case.” to show why they are not suitable for the future seasonal load data.

Please refer to lines 367 ~ 382 at page 17.

Thank you very sincerely for the good comments.

 

10. Both of the limitations and the future work are necessary in the conclusion or introduction.

☞ As the reviewer pointed out, we have modified the chapter 5. Conclusion as a whole, adding main contribution, limitation, application and future work.

Please refer to lines 366 ~ 390 in page 17.

Thank you very sincerely for the good comments.

 

 

11. Conclusions are needed to be improved.

☞ As the reviewer pointed out, we have modified the chapter 5. Conclusion as a whole, adding main contribution, limitation, application and future work.

Please refer to lines 366 ~ 390 in page 17.

Thank you very sincerely for the good comments.

Author Response File: Author Response.pdf

Reviewer 5 Report

The article is well written and informative. The following suggestions are made:

1. The units followed by the values need a space throughout the article.
2. Fig 1: This is a load curve based on time and not the weather.
3. Graphs throughout the paper needs re-work in terms of labeling, font size, line width etc.
4. There are inconsistencies in font types in table 1.
5. The data are missing in table 11.
6. Where is Fig. 7?
7. Factors affecting the simulation results need to be discussed and listed.

Author Response

[Authors’ Response]

We greatly appreciate the comments and suggestions from reviewer 5, by which, we think, this research paper is more logically reinforced.

 

1. The units followed by the values need a space throughout the article.

☞ As the reviewer pointed out, we have added a space between number and unit throughout the paper.

Thank you very sincerely for the good comments.

 

2. Fig 1: This is a load curve based on time and not the weather.

☞ As the reviewer pointed out, we have changed the title of Figure 1 to "Net load curves for 20/11/2018 and 21/11/2018".

Thank you very sincerely for the good comments.

 

3. Graphs throughout the paper needs re-work in terms of labeling, font size, line width etc.

☞ As the reviewer pointed out, we have revised all graphs and tables throughout the paper.

Thank you very sincerely for the good comments.

 

4. There are inconsistencies in font types in table 1.

☞ As the reviewer pointed out, we have revised the font type of Table 1 and throughout the paper according to the MDPI format.

Thank you very sincerely for the good comments.

 

5. The data are missing in table 11.

☞ As the reviewer pointed out, we have revised the cell and the data of Table 12(Table 11 in the original version.

Please refer to line 219 at page 10.

Thank you very sincerely for the good comments.

 

6. Where is Fig. 7

☞ As the reviewer pointed out, we have edited Figure 7 again and rearranged it in page 9.

Please refer to line 214 at page 7.

Thank you very sincerely for the good comments.

 

7. Factors affecting the simulation results need to be discussed and listed

☞ As the reviewer pointed out, we have added a paragraph of “Each future seasonal curve drawn in this paper can be slightly changed due to variability in PV and EV penetration target values. In addition, used data such as load curve, net load curve, PV penetration, and EV penetration are only useful in South Korea. Therefore, the results of this paper are not suitable for application in other countries. However, the methodology is useful, so if using the same kind of data optimized for each country can get results that are suitable for that country.” in the conclusion to explain the factors affecting the simulation.

Please refer to lines 383 ~ 387 at page 17.

Thank you very sincerely for the good comments.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The revisions are acceptable.

Author Response

Thank you sincerely again for your good review comments.

Reviewer 3 Report

The reviewer is okay with the authors' responses. 

Author Response

Thank you sincerely again for your good review comments.

Reviewer 4 Report

The manuscript has been improved. However, there are some concerns left.
1) As Figure 1 shown, the authors point out that the discrepancy between the two days is due to the variation of the PV generation. However, why wind generation or other renewable resources have not been considered except PV in the discrepancy between the two days.
2) The last sentence between line 107 and 108 remains confusion since the authors state that Figure 2 shows the average value of these two years.
3) Grammar and punctuations should be checked throughout the revised manuscript.

Author Response

Thank you sincerely again for your good review comments.

Please check the attached response to reviewer's comments.

Author Response File: Author Response.pdf