Review Reports

Round 1

Reviewer 1 Report

This paper describes the energy generation of Eskom (one of South Africa’s energy producers).

In the last years much more energy is produced by diesel generators. The authors argue that this is caused by weak maintenance of other (coal) plants. This caused in much higher operational costs.

Towards the end of the paper, they propose to replace these diesel generators by gas turbines.

The paper is well structured and written, but many readers will not be familiar with the South African energy market organization. This must be clarified.

In addition, the replacement of diesel generators by gas turbines demands large investments. These investment costs are not considered and could result in altered conclusions.

Other remarks can be found below.

 

Abstract

First half of the abstracts reads as a problem statement and introduction. The abstract should be a summarization of the paper.

What is Eskom? If I google it, it appears to be a company. Define it somewhere. According to Wikipedia, it is government owned. It represent SA in the Southern African  Power Pool. So is it also the transmission system operator? In addition is the largest producer of electricity in Africa; So it is at the same time a production unit. This is very confusing for me. It may be interesting to explain how the energy landscape is organized: who are the Transmission system operators? Who are the energy producers, etc.

What is OCGT? What is IPP? Try to avoid abbreviations in the abstract.

Introduction

Line 35: “various power station generating plants”. The plants do not generate power stations?

Line36: end-users

Line 38: approximately 45 117 MW => approximately 45 GW

Line 40: do they own only one single windfarm?

Line 56; point is missing at the end of sentence.

Line84: … to any system unforeseen events…: strange sentence. Please reformulate.

 

Question 1: is it the regulator of the diesel price that limits the volumes?

Question 2: how is the energy market organized in South Africa?

Question 3: if emergency, diesel-based, units are operational , this is reflected in the energy-market price? I assume that no other unit in the country can provide power at a lower marginal cost?

 

Methodology

Line 112: … will form THE basis for…

Line 120: you used historical gas prices from the period 2012-2016. Are these prices still representative for todays situation? Why not using gas prices for the last years (2019-2022)?

Table 1: is the natural gas price in the EU relevant for this study?

Line 153: from such minutes, hours up to seasons…

Line 159: what is the IRP?

Line 160: what is the IRP2019 and DMRE, 2019?

Line 164-165: ‘the high operational costs from diesel powered OCGT’s will put serious strain on Eskom’s finance’. Why is this? Are energy prices fixed in South Africa? See also question 2 and 3.

Line 198: the IPCC 2006 report is used. Are there more recent papers available ? I can imagine that gas turbines have become more efficient in the last 15 years.

 

Results and analysis

Open cycle gas turbine utilization and costs (write cost without s at the end)

Line 218: what is NERSA?

Lines 238-243 are difficult to read. What to conclude from figure 3?

Lines 247-251. Start with referring to table 2.

Lines 251-256: isn’t this the clue of the paper, so far: unplanned breakdowns resulted in more utilization of the diesel generators.

 

3.1.1 2018-2019OCGT’s utilization

No comments

 

3.1.2 2019-2020 OCGT’s utilization

No comments

 

3.1.3 2020-2021 OCGT’s utilization

Line 304: double spacing

 

3.2 OCGT’s impact on revenue and tariffs

Line 320: double spacing

Lines 353-361: this is a discussion and not a conclusion from the data.

 

3.3 OCGT’s long term sustainability and grid security

No comments

 

3.3.1 Fuel costs and savings- from diesel to natural gas

Table 7 and 8: put the numbers in billions of rand (BR)

Line 393: if natural gas prices increase, it is likely that diesel prices increases too. Both are correlated.

Question 4: did you take into account the investment cost if existing diesel generators are replaced by gas turbines?

 

Line 444: 3.3.2 instead of 3.8.2

3.3.2 Carbon Tax costs savings- from diesel to natural gas

General: Carbon dioxide: CO₂ (with 2 in subscript)

Table 9: use GWh

 

4 Conclusion and recommandations

No comments

 

 

Author Response

Authors Response 1

• The energy market of South Africa has been addressed accordingly in the introduction of the manuscript.
• The paper has justified the cost of using gas turbines, from both revenue and expenditure perspectives. Also, the paper has summarized the difference between the two-energy supply.
• The Abstract has been rejigged to appropriate standards, lacking the methodology used and demarcation of findings, and a lengthy problem statement.
• Eskom is an abbreviation that has been succinctly described in the introduction now to the extent needed for the nature of this paper.
• The OCGT has been factored in the title and the IPP in the introduction. However, the descriptions of both terms are explicit enough, as the paper is a technical paper for a target audience in energy sector, who uses these terms daily across the globe, thus aiding the sophistication of the paper and the Journal.
• All the lines 35, 36, 38, 40, 56 and 84 have been corrected and adjusted accordingly.
• Question 1: No, but the national energy regulation of South Africa as stated in the paper
• Question 2: The organization of energy market in South Africa is within the purview of Eskom and NERSA, which has been adequately mentioned in the paper, in accordance with the objectives and nature of the paper.
• Question 3: Yes Reviewer, your assumption are right.
• Line 112: the historical gas prices were used for consistency of prices and they were sourced from empirical literature of 2018. Also, the non – usage of 2019 – 2022 is due to the unique instability of prices occasioned by the covid – 19 pandemic and the Ukraine – Russia war.
• Line 120: the natural gas price comparison with EU is due to the market dynamics of gas in the European Union, evidenced in the fact that EU appears to be the worst hit in terms of gas prices by the Ukraine – Russia war.
• Line 153: the statement there is correct, as it has to with the sun and the revolving seasons of the earth.
• Line 198: The IPCC guidelines were used due to its international dimensions.
• Line 112, 120, 159, 160, 164, 165, and 198 have been adjusted accordingly.
• Line 218: NERSA has been described in the introduction as a regulatory organization.
• Line 238 – 243 explains the statistics of Figure 3, which are in millions of Rands.
• Line 247 – 251 have been adjusted accordingly
• Line 251 – 256 provides justification to the preceding estimated data.
• Line 353 – 361: Actually both.
• Table 7 & 8 have estimates in billions already and were not rounded up, hence, putting Billions of Rand will confuse the readers.
• Line 393: Not really, it depends on the forces of demand and supply.
• Question: Yes, it has been adjusted accordingly.

Author Response File: Author Response.docx

Reviewer 2 Report

I find this topic very interesting.

 

The paper has been correctly divided into relevant sections, and their content coincides with their titles.

The purpose of the article/research was specified

  

However, some parts of the article have to be strengthened:

·       The number of references is relatively sufficient. However, they should be numbered, and the text should include these numbers in the footnotes. Additionally, some references are written in two lines, while it was possible to write them in one line (Eskom for example); ·       You should work on the aesthetics of the work: for example in the table part. Tables "extend" beyond the line of text, not prepared according to the appropriate format, the font in the tables is too large, and there are tables with wide columns in which there is almost no text (e.g. table 7 and column 5 in this table). Also the charts are too large for the Sustainability template. Also text in some parts (for example page: 5 and 6);

·       no hypothesis was given;

·       in the introduction section, I cannot find out why the authors took up this topic. Not all those who read the first sentences will be clear what ESKOM is all about. The authors write as if their article was a continuation of another article that explains the whole phenomenon. Please complete the introduction section and explain more clearly why this topic is taken up ·       it is not clear to me on what basis (e.g. according to what formulas) the calculations were made? Did the authors make calculations themselves, the results of which are presented in tables, or did they only collect into tables calculations already made by someone else? ·       Why data from this period were analyzed? Why from this region? authors should deepen the justification of the topic

 

Author Response

All corrections stated have been adjusted accordingly and highlighted in yellow color.

Also, the referencing of the paper has been reformatted as suggested

Round 2

Reviewer 1 Report

The paper is adapted in accordance with most remarks made.

However, some shortcomings are still present

-        Why is the gas price for the period 2012-2016 used, while the paper handles the ESKOMs 2019-2022 period?

-        Why is a IPCC report from 2006 used, while newer reports are available?

-        The paper uses many abbreviations, which are often not defined. This makes reading the paper difficult, especially for people from other regions. Please define the abbriviations somewhere, eg in a table at the beginning of the paper.

-        The numbers in table 7 and 8 are difficult to interpret. Please change them to 24 675 MR.

Please consider these remarks.

Author Response

The natural gas price for 2012 - 2016 was used due to the market dynamics of the European Union, evidencing that it is the worst hit by the Ukraine - Russia war. Also, the 2018 - 2022 period used by Eskom's is due to the availability of data and the fact that the problem is currently being experienced.

The IPCC report of 2006 is currently being used due to its applicability of the report to South Africa's energy problem.

The abbreviation used has been listed before the introduction.

Table 7 and 8 are raw estimates which cannot be rounded up in order not to compromise the integrity of information passed to the readers.

Reviewer 2 Report

I'm sorry, but I don't see a large improvment. I don't see even the yellow colour you answered that all corrections have been adjusted. Maybe the wrong file was attached?

I have revised this file which is attached and I have some comments:

Comments regarding footnotes and references have been taken into account

 

·       The paper is much more aesthetic. But in some elements you should improve it: table 1 (too big letters, inconsistent with the template). General tables are not prepared according to template;

·      - still no hypothesis was given;

·       I don't see a significant change in terms of improving the introduction section. I still cannot find out why the authors took up this topic. Not all those who read the first sentences will be clear what ESKOM is all about. The authors write as if their article was a continuation of another article that explains the whole phenomenon. Please complete the introduction section and explain more clearly why this topic is taken up ·       This point was also not corrected: "it is not clear to me on what basis (e.g. according to what formulas) the calculations were made? Did the authors make calculations themselves, the results of which are presented in tables, or did they only collect into tables calculations already made by someone else?"

·       This point was also not explaind: "Why data from this period were analyzed? Why from this region? authors should deepen the justification of the topic"

Author Response

Sincere apologies for the certain mix-ups, all have been adjusted accordingly.

Table 1 has been adjusted accordingly.

The introduction has been adjusted accordingly, citing necessary justification.

The calculations used were based on audited Eskom financial reports and integrated reports.

Round 3

Reviewer 1 Report

Except for tables 7 and 8, all my remarks are taken into account.

IMO, the paper can be published.

Good luck!

Author Response

Thank you very much, distinguished reviewer. 

Tables 7 and 8 are good as we can't adjust the figures by rounding them up, which will alter the percentages as the figures were directly gotten from Eskom, thus justifying its authenticity. 

Reviewer 2 Report

Some of my last comments have been taken into account.

 

However, some parts of the article have to be strengthened:

·       But in some elements you should still improve the aesthetic: for example, the tables in the paper are not prepared with the Sustainability template. Additionally, the tables are illegible, e.g. table 9. The authors only corrected table 1, because in the previous review I wrote "e.g. table 1". But each of the tables needs to be corrected because it does not meet the standards. I also don't understand why so many free lines were left in the article

- still no hypothesis was given; ·       I don't see a significant change in terms of improving the introduction section. I still cannot find out why the authors took up this topic. Please complete the introduction section and explain more clearly why this topic is taken up

 

·       the authors added one paragraph at the beginning of the introduction part and cited two sources in it and instead of changing the order of the footnotes, so the first footnotes should be numbered 1 and 2, they gave them ending numbers 50 and 45. In general, the numbering of the footnotes does not coincide with the order their appearance in the text.

Author Response

All the tables have been adjusted accordingly and reformatted. 

The references in the introduction part were done in alphabetical order like other aspects of the references, for quick understanding. 

The free lines have been removed, which was due to the initial table format. 

The introduction was done accordingly in line with the objectives of the paper.