Review Reports

Round 1

Reviewer 1 Report

The paper deals with the analysis of the long-term impact of on-grid storage systems on the development of renewables in Chile. It is an interesting work, the methodology and results of which may be used also in other similar contexts. Some parts are not completely clear, but I think that with minor integrations/adjustments may be suitable for publication on Energies:

1)      A linear growth of the energy demand is supposed (lines 182-186): the authors should explain, especially for a long-term analysis, how the probable diffusion of sustainable behaviors and energy savings is compatible with this linear behavior.

2)      Eq.(1), Figs. 6 and 9: are disposal costs not considered?

3)      Table 3 does not exist (and it is not cited in the text)

4)      Table 8 does not exist (it is cited in the text, probably it is Table 9 at Page 11

Author Response

We would like to thank the reviewer for the comments. We appreciate the effort and have used the comments to improve the submission. We modified the manuscript and the modifications are shown with track changes in the highlighted manuscript. We took all the comments provided by the reviewer into account and the detailed list of comments and associated changes are given below.

Reviewer 1: The paper deals with the analysis of the long-term impact of on-grid storage systems on the development of renewables in Chile. It is an interesting work, the methodology and results of which may be used also in other similar contexts. Some parts are not completely clear, but I think that with minor integrations/adjustments may be suitable for publication on Energies:

1)      A linear growth of the energy demand is supposed (lines 182-186): the authors should explain, especially for a long-term analysis, how the probable diffusion of sustainable behaviors and energy savings is compatible with this linear behavior.

Reply: The demand increase was wrongly described in line 184. We fit a linear model between the demand for 2016 and the projected demand for 2046 and use this model to calculate the demand for each year for the entire country. The demand growth projected by the Ministerio de Energia of Chile shows only slight variations from this linear model. We have updated the text accordingly.

Furthermore, we agree with the reviewer that the long-term prediction of electricity demand depends on a large number of assumptions such as population growth, increasing energy productivity and sustainable behaviour as well as increasing share of electric vehicles and electric heating. However, exact demand forecasts are beyond the scope of this population and we decided to use the official projection from the Chilean government. We have added the following sentence to highlight the different and competing factors.

Added: Like any projection, the demand forecast from the Ministerio de Energia of Chile is based on a large number of assumptions such as projections of population growth, energy productivity, sustainable behaviour as well as increasing share of electric vehicles and electric heating.

2)      Eq.(1), Figs. 6 and 9: are disposal costs not considered?

Reply: The reviewer is correct in assuming that the disposal and decommissioning costs are not included. While we agree with the reviewer that it would be interesting to add disposal and decommissioning costs, this was beyond the scope of this study because these costs are highly dependent on the location (e.g. future use of the site), market costs of recycled materials and regulatory framework. In addition, for fossil fuel and renewable generators these costs are estimated to be below 2% of the investment costs and thus would only have a small impact on the results presented in the manuscript. These costs have a much larger impact for nuclear power plants which are non existent in the Chilean energy system.

 

3)      Table 3 does not exist (and it is not cited in the text)

Reply: We have corrected this mistake and updated the table numbering of the subsequent tables.

 

4)      Table 8 does not exist (it is cited in the text, probably it is Table 9 at Page 11

Reply: We have corrected this mistake and updated the table numbering of the subsequent tables.

Reviewer 2 Report

Long term impact of grid level energy storage on renewable energy penetration and emissions in the Chilean electric system

The authors examine the Chilean power system's ability to increase renewable generation using a linear optimisation model and 4 nodes representation.

Consider putting the sentence in line 47 at the start as throughout the initial paragraph as it puts into context the values in the initial paragraph

line 45 - constrains should be constraints

Line 60 - check constrains is the correct usage here (and as above - would be worth checking constrains and constraints throughout)

the total in table 1 does not equal the total from line 49 - (SIC - 17,405 MW and SING - 5,360 MW) - this is worth checking and explaining

line 176 - Chile's Long Term Energy Plan

line 273 - references would help for the lifespan values

line 286 - reference for carbon price would help (it seems rather low for a carbon price)

Figure 3 (a) and (b) look exactly the same but with different values in the y-axis - check this and if ok then consider a dual axis Figure

line 316 'high decrease' - consider a rephrase here

Figure 7 - same comment as Figure 3 above

line 488 - perhaps a little further discussion of the level of carbon tax would help. what is Chile's ambition in its Nationally Determined Contribution? What if the level of this ambition was to be increased?

Author Response

We would like to thank the reviewer for the comments. We appreciate the effort and have used the comments to improve the submission. We modified the manuscript and the modifications are shown with track changes in the highlighted manuscript. We took all the comments provided by the reviewer into account and the detailed list of comments and associated changes (in italics) are given below.

Reviewer 2: Long term impact of grid level energy storage on renewable energy penetration and emissions in the Chilean electric system

The authors examine the Chilean power system's ability to increase renewable generation using a linear optimisation model and 4 nodes representation.

1.      Consider putting the sentence in line 47 at the start as throughout the initial paragraph as it puts into context the values in the initial paragraph

Reply: We have extended the first sentence to improve the context of the initial paragraph.

 

Added: Chile has significant potential for renewable energy but its long and narrow shape poses a challenge for the integration of renewable energy into the electricity system.

 

2.      line 45 - constrains should be constraints

Reply: We have changed the word accordingly.

 

3.      Line 60 - check constrains is the correct usage here (and as above - would be worth checking constrains and constraints throughout)

Reply: We have checked the use of constrain and constraint throughout the manuscript. We have changed a number of occurrences to ‘constraint’.

 

4.      the total in table 1 does not equal the total from line 49 - (SIC - 17,405 MW and SING - 5,360 MW) - this is worth checking and explaining

Reply: We thank the reviewer for highlighting this discrepancy. The values given in line 49 are for the year 2017 while the data in table 1 is for 2016. In addition, the installed wind and PV capacity given in line 36 are for 2018. We agree that this is confusing and have addressed it in the text. We have removed the capacities for 2017 given in line 49 and have added the year in line 36.

 

5.      line 176 - Chile's Long Term Energy Plan

Reply: We have changed the text accordingly.

 

6.      line 273 - references would help for the lifespan values

Reply: We have added a sentence and two references to explain our assumption of plant lifespans.

 

Modified text: The obsolescence of the existing power stations was considered, and the installed capacity was decreased in each period taking into account their initial year of operation and expected lifespans. While new plants are usually designed for a lifespan of 15 and 25 years for diesel and gas/coal, respectively, most plants have their lifespan extended by 5 to 15 years [33,34]. Here, lifespans of 25 years for diesel engines, 30 years for OCGT and CCGT, and 40 years for coal power plants are assumed.

 

7.      line 286 - reference for carbon price would help (it seems rather low for a carbon price)

Reply: Chile has introduced a carbon price of 5 $/tonCO2 in 2017 for heavy industry and the power sector. We have used the conversion of 1 $ = 1 €.

 

Modified text: Chile was the first country in South America to introduce a carbon tax of 5 US$/tonCO2 in 2017 [37]. Using the conversion of 1$=1€, a 5 €/tonCO2 fixed carbon tax is considered for all the modelled scenarios. This low carbon tax will have limited impact on the decarbonisation of the power sector and was introduced with the aim of implementing the regulatory framework, infrastructure and social acceptability [38].

 

8.      Figure 3 (a) and (b) look exactly the same but with different values in the y-axis - check this and if ok then consider a dual axis Figure

Reply: While we agree with the reviewer that the two figures look very similar, the energy values are growing slightly faster than the capacity values. However, the differences are very small and we would be happy to remove Figure 3 (b) if the reviewer thinks that this would improve the clarity of the manuscript.

 

9.      line 316 'high decrease' - consider a rephrase here

Reply: We have rephrased this to ‘large decrease’.

 

10.   Figure 7 - same comment as Figure 3 above

Reply: While we agree with the reviewer that the Figures 7 (a) and (b) look very similar, there are small differences for the later years. For example, scenario 4 shows a higher energy peak beyond 2040. However, the differences are very small and we would be happy to remove Figure 7 (b) if the reviewer thinks that this would improve the clarity of the manuscript.

 

11.   line 488 - perhaps a little further discussion of the level of carbon tax would help. what is Chile's ambition in its Nationally Determined Contribution? What if the level of this ambition was to be increased?

Reply: Chile introduced a low carbon tax with the view that “a lower tax

enables its implementation by: (i) facilitating the adaptation of regulated sectors; (ii)

increasing its social acceptability; and, (iii) allowing the implementation of the institutional

infrastructure to sustain it” [Chile’s green tax]. We have added a sentence in line 299 to clarify this (see also our reply to your comment 7).

 

While we agree with the reviewer that it would be interesting to evaluate the effect of carbon tax on the decarbonisation, this is beyond the scope of this study. We have added a sentence to the conclusion to suggest a potential future study.

 

Added: While there are currently no plans to increase the carbon tax in Chile, it would be worthwhile to evaluate the effect of different carbon tax scenarios in a future study.

Reviewer 3 Report

- Please expand the section 4. Conclusions - much more could be stated here

- Please meliorate the visibility of Figure 1

- Please further investigate/expand the part of the section 1.Introduction concerning barriers for a higher integration of renewables generation into the grid (line 57). Among others, please consider also:

https://www.mdpi.com/1996-1073/11/6/1460

https://www.sciencedirect.com/science/article/pii/S136403211730967X

https://www.oeko.de/oekodoc/1378/2012-012-en.pdf

Minor issues:

- Please fix the affiliation description - since all three authors have the same affiliation it can be mentioned also just once

- Please separate all keywords by semicolon

- Please check the unit utilized to indicate the irradiance. Usually it is indicated as kWh/m²/y

- Please check the way sources are indicated is correct (line 42)

- The section "Supplementary materials" is empty

- Please indicate the authors contribution at the end of the manuscript

Author Response

We would like to thank the reviewer for the comments. We appreciate the effort and have used the comments to improve the submission. We modified the manuscript and the modifications are shown with track changes in the highlighted manuscript. We took all the comments provided by the reviewer into account and the detailed list of comments and associated changes are given below.

Reviewer 2:

-        Please expand the section 4. Conclusions - much more could be stated here

Reply: We thank the reviewer for the encouraging remark and have significantly extended the conclusions as shown in the highlighted manuscript.

 

-        Please meliorate the visibility of Figure 1

Reply: We have added a higher resolution version of Figure 1.

 

-        Please further investigate/expand the part of the section 1.Introduction concerning barriers for a higher integration of renewables generation into the grid (line 57). Among others, please consider also:

o   https://www.mdpi.com/1996-1073/11/6/1460

o   https://www.sciencedirect.com/science/article/pii/S136403211730967X

o   https://www.oeko.de/oekodoc/1378/2012-012-en.pdf

Reply: We have add two sentences to the paragraph to highlight market and regulatory barriers for large scale integration of variable renewables and energy storage.

 

Added: However, to achieve the large scale integration of intermittent renewables and energy storage it is important to reform the market and regulatory framework which was designed for conventional and dispatchable electricity generation [8,9]. For example, energy storage systems can provide a number of services and roles, e.g. frequency response service and short term operating reserve, but most markets have limited mechanisms to enable this stacking of services [9].

 

Minor issues:

-        Please fix the affiliation description - since all three authors have the same affiliation it can be mentioned also just once

Reply: We have changed the affiliation accordingly.

 

-        Please separate all keywords by semicolon

Reply: We have changed the keywords accordingly.

 

-        Please check the unit utilized to indicate the irradiance. Usually it is indicated as kWh/m²/y

Reply: We have changed the unit accordingly.

 

-        Please check the way sources are indicated is correct (line 42)

Reply: We checked the sources for the references in line 42 and the sources are correct.

 

-        The section "Supplementary materials" is empty

Reply: We have removed this section.

 

-        Please indicate the authors contribution at the end of the manuscript

Reply: We added an Author Contribution section at the end of the manuscript.