Breaking-Down and Parameterising Wave Energy Converter Costs Using the CapEx and Similitude Methods
Round 1
Reviewer 1 Report
This paper introduces the CapEx method to the wave renewable energy field. The CapEx method can provide comprehensive approach for WEC and WEF cost parameterisation, which can be useful for future calculations of large datasets of WEC, WEF, and site characteristics to select optimised pairs of WEC/WEF configuration and site. This method distinguishes WEC and WEF elements and sub-elements, an element and sub-elements being a system, module, component, piece, or task, in the calculations. Then, tasks such as manufacturing and assembling, are assigned to the different parts. For each element and sub-element, a base cost, a margin, and one or more factors are estimated. In its simplest form, the CapEx method appears as an ordinary cost estimation leading to an overall sum of costs with margins. In the alternative approach, the factors enable the encapsulation of several phenomena concerning site characteristics, and WEC and WEF configurations. In its advanced form, more abstract elements can be included such as economies of scale and weather and wave climate influence on the costs of the element and sub-elements of the WEC and WEF, through the factors leading to the complex parameterised CapEx calculation.The manuscript is well written and seems to be acceptable for the journal energies mainly for the case studies adopted to study the cost perameterisation. However, there are some difficulties in appreciating the results from the comparisons to show the better performance of some improved numerical technologies. In fact the basis on which these comparisons are adopted are perhaps not justified. Some of them can be found in many places in the comments.
1 In order to justify the results, it is better to give an extra example which can do the comparison with corresponding results.
2.To show the whole process of cost calculation, a flow chat should be given at the end of Part 3.
3. It is better to show the location of the wave renewable energy field, it is helpful for readers to know the cost calculations.
Hence there are some moderate works and revisions required before the manuscript should finally be accepted for energies.
Author Response
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Reviewer 2 Report
The paper presents a reasonable and straightforward investment cost estimation method, which is relevant to the readership of Energies. The principles presented are not novel as such, but their application in the case of wave energy is interesting. The article is clearly written and well-structured. However, some readers might be confused by the differences between capital expenditure and overnight cost. For example, at NREL CAPEX calculation involves interest during construction (this is crucial for larger projects that take more than one year), see the spreadsheet for more details: https://atb.nrel.gov/electricity/2020/files/2020-ATB-Data.xlsm
Therefore, the authors are advised to choose from the following options: highlighting their focus on overnight cost; extending the methodology and article by including all CAPEX elements; clearly stating their definition of CAPEX and why interest during construction is not relevant in this particular case.
Author Response
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Reviewer 3 Report
This work investigates the integration of WEC, WEF, and site characteristics directly in the cost calculations. The authors mention that this calculation method will eventually improve WEC configuration-location pairing and selection. The paper is very interesting and it states an important and actual topic of research regarding renewable generation from marine sources. In my general optinion, some minor changes are required previous to a possible publication. 1. The usage of commas and dots in numbers are not clear. These are for decimals or thousands? 2. How was defined the coefficient in the margin component of Equations (1) and (2) equal to 0.01? 3. It is important to mention in the conclusions section, which aspects could be improved in the proposed method. Uncertainties, element costs variations, information availability? In my opinion, the next step with this research is to develop a software that includes all the main calculation components of the CapEx method proposed, since this can help to interested companies to know how they can explote marine energy in promissory regions with reliable tools.Author Response
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Reviewer 4 Report
The topic presented in this work is really interesting. However several challenges are strictly required to make acceptable the manuscript.
Going through some major comments:
1. Abstract has inappropriate structure. I suggest to answer the following aspects: - general context - novelty of the work - methodology used - main results
2. Introduction presents interesting information, but could be improved. In general terms,I would suggest the authors to add at least a paragraph where introducing the need for energy transitions (in which also wave energy is paramount) looking at the role of public (e.g. policy maker) and private actors (e.g. financial sector).
Some reference to start with:
"When democracy meets energy transitions: A typology of social power and energy system scale" where the potential energy future perspectives are discussed.
"Circular bio-economy via energy transition supported by Fuzzy Cognitive Map modeling towards sustainable low-carbon environment" where impacts of biowaste-based energy transition are examined.
"Instrument mix for energy transition: A method for policy formulation" where the most effective instrument mix for energy transition in biofuel industry is provided.
"Enabling investment for the transition to a low carbon economy: government policy to finance early stage green innovation" where the green finance gap for the transition is introduced
"Analysing stakeholders’ perspectives towards a socio-technical change: The energy transition journey in Gela Municipality" where the perspectives of involved stakeholders in supporting a sustainable energy transitions are investigated3.
2. Material and methods are clear. However, they should be better linked to the existing literature. what is the potential? its limit?
4. Results are not always linked to the methodology. Please define the relationship and relate your finding with the relevant literature.
4. Conclusion are succinct. Please provide limitation and future research need. Is there space for financial implications for wave energy development?
Author Response
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Reviewer 5 Report
General comments
The paper deals with the cost calculation for wave energy converter and wave energy farm. In particular, this paper proposes a parameterised cost calculation for the Capital Expenditure CapEx.
The topic is of interest considering the growing interest in sea wave energy and the lack of information and studies on costs and economic feasibility of the projects.
Overall the paper is well structured but it is hard to follow. I have the following suggestions and comments.
The Introduction section should be more concise as it is too extensive. In the revierwer's opinion, it would be more useful to summarize some concepts and dwell more on the methodology.
Similarly, the Method Section is too extensive and complexly organized; this makes difficult to understand the proposed method. I suggest to simplify this section in order to better explain the proposed CapEX method by highlighting the focus of the methodology. I also suggest eliminating some redundant concept or sentence.
As regards the method, it is not very clear how the weights of the parameters must be defined. It would be useful to provide more comments in relation to the feasibility/complexity aspects of this approach with respect to parameterization, definition of weights, etc.
In the reviewer’s opinion, it would be interesting to provide some further comments in relation to the OpEx cost and its calculation for an LCOE analysis (will OpEx be considered as a percentage of CapEx or is it planned to use a similar method to the one proposed?)
Minor comments
Please to verify the definition on LCOE in the Introduction Section
Authors state that other studies, despite providing detailed costs, did not offer clear methodologies for calculating costs. Since in some studies the cost estimation methodologies have been described, in the reviewer’s opinion, it would be useful to better clarify this statement.
I suggest to review the numbering of the references in the text (reference 25 follows number 17)
line 221: delete the semicolon
Author Response
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Round 2
Reviewer 2 Report
The authors sucessfully addressed reviewer's concerns.
Reviewer 4 Report
All comments have been properly addressed.
Reviewer 5 Report
Accept in its present form
