Review Reports

Round 1

Reviewer 1 Report

The topic is very interesting and points in the future. Authors presented the green line and tried to find the way of cost reduction. They used proper literature sources and cited them well. The methods used in the article allow you to fully explore, introduce the topic. Those figures and tables which they presented in the text were clear and helped to understand the research work. I agree and appreciated their conclusions which would be useful at different sectors in the near future.

Author Response

Thank you for your review and feedback, we very much appreciate you taking the time to review this paper.

Reviewer 2 Report

In the manuscript, the authors investigated the early-state cost requirement to achieve the SET-Plan for LCOE target for three types of emerging renewable energy technologies using a methodology termed ‘reversed LCOE’. This method accounts for the learning rate of different components and activities of a system for different levels of maturity of technologies. Cases studies were conducted for three types of renewable energy technologies: offshore wind, tidal stream, and wave energy. The authors present detailed analyses and comparisons of the early-stage and commercial-stage cost for three technologies. The potential requirements for innovation are identified by comparing the cost with that of existing devices.

 

Overall, the manuscript is well-structured and presentation of technical details is clear and concise. The methodology used in the manuscript and conclusions could be potentially useful in the industry. Therefore, I recommend publication with minor revision.

 

Typo: Page 16, paragraph 3, “Figure 8” should be “Figure 11”.

Author Response

Thank you for your review and for bringing our attention to this typo. The authors realised that the final figure was mislabelled, so both the figure caption and the reference have been corrected in the resubmitted version of the manuscript.

Reviewer 3 Report

Economic assessments are paramount for any commercial viability and scaling up of the technology. Though there are some independent evaluation of marine based energy production technology, the moment they are ambitioned to become mainstream a techno-economic analysis becomes warranted. Without backing and consolidation of such data, these technology remain grounded. In that connection, the manuscript address a timely challenge grappling the developed world.

The objective of the paper is to use a reversed LCOE together with a component specific learning rates for attacking the future LCOE from incumbent perspective. However the different sections are missing a glue and are found superficially standing, failing to connect with each other.

Some specific comments along the sections:

1. What is ORE technology? I googled to find this out and must be expanded by the authors.
2. Visual depictions always transfer better messages than a lot of associated text. In this connection, it might be worthwhile to draw different curves corresponding to different technology (CHP, waste-to-electricity, marine-energy, coal-based,  offshore wind, etc.) in one graph that implies different learning rates, as a depiction of straight line of different slopes, exponential or parabolic curve representing the learning rate, presented, maybe against effort or time in X-axis- just a suggestion.
3. The assessment of Table 4, 6 and 8 demands further explanation as it seems to have derived the cost breakups from relevant references. Whether they are adjusted from 2014 and 2015, considering the material and technology advancement that has gone through, is subjective. However, the maturity level of each of the category seems to be the current authors’ evaluation and the authors must shed some more light on how they arrived on the respective assessments and how they arrived on the % of CAPEX consideration on this, considering the technology gap between the references [22] and [25] and present time. To me, Section 3 has many loose ends that needs addressal before the authors can extrapolate and procrastinate the future LCOE based on this, considering the technology maturity level is an element of constant improvement that would readjust the CAPEX percentage, even the base technology remains unchanged.
4. I am not entirely convinced about the CAPEX breakdrown based on subsystem represented in Figure 4, primarily because the discussions are for different technology and hatching them together little bit dilutes the objective and I am not sure what kind of advantage we gain, from such a combined view of the subsystems? Since the hatched portions are different mix in different technology, they don’t offer a great advantage of comparison.
5. How was the numbers arrived for different subcomponents in Section 4.1, 4.2 and 4.3? please elaborate!
6. Regarding the comparison of the projected costs against a baseline presented by BVGA (Table 11), I personally feel negative changes may not be so much of a problem, as long as the cost centers are not way off from the central LR scenario. The hint of the differences (say above 10% in either side)- could it be a reflection of some inappropriate assumptions in the cost center categories? In order to verify, this the authors might have further classification of this percentage of Table 11, that they would like to present or at least substantiate their thoughts on this.
7. While the authors acknowledge the limitation of the paper, in considering a limited device data for their cost breakdowns, this also warrants mention of what flexibility Table 11, for instance will bring in, had there been a deviation from the selected devices. Such reflections in the discussion section, would elevate the merit and unbiasedness of the paper.

Not withstanding the above comments, the paper certainly triggers further discussion on comparing different cost centers across ORE technology and giving a sense of LCOE for future implementation considerations.

Author Response

Thank you for your review and feedback. We have addressed your comments in the attached response.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

The authors' responses are adequate and convincing. It might be considered accepted with the present changes.