“Canalvoltaico” in Emilia-Romagna, Italy: Assessing Technical, Economic, and Environmental Feasibility of Suspended Photovoltaic Panels over Water Canals

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Brief summary:

The study showcases photovoltaic systems that when installed over open canals, lower water evaporation and enhance water quality while providing a long-term solution to problems with land use and occupation.

The study which was conducted in Emilia-Romagna, Italy is one of the canal-top solar plants found in the world. The authors focused on identifying the associated costs, benefits, and criticalities. However, they do not provide a direct comparison between this project and the those from other countries, i.e., India and United States.

Construction: According to their research, two main structures are used: steel truss structures (with beams) and tensile structures, often known as suspension cable structures. The estimates show that the guyed and cable constructions enable a 15–20% reduction in structure expenses.

Some challenges relate to nature conservation aspects such as potential for conflicts with other water uses. Then investment at present could be seen by enterprises and consortia unfeasible to invest in Canal-Top solar systems due to their expensive installation and maintenance expenses.

Broad comments:

Article:

Introduction

The authors adequately educate the reader about Canal-Top Solar PV. The research information gathered literature sources provided a good study on the application of the technology in the Italian context.

Methodology

The technical calculations were from environmental loads and optimal panel orientation angles to calculate forces acting on support structures. A cost analysis was performed through sources from market data and publicly available catalogues. Visentini equations were used to estimate water savings through evaporation reduction.

Results

The results were well presented—some specific comments about the inconsistent use /design of the table were noticed.

Conclusion

The conclusion section of the article was well presented. It is concluded and recommended to invest in a similar pilot research project, possibly in the Emilia-Romagna region or in Italy.

Overall, it is a good and exciting study, showing the capabilities and advantages of making canals to address land shortage for PV plants.

Please refer to some comments in the manuscripts.

Specific comments:

The references were mostly from recent years and are well cited and referenced.

Some questions:

What are ecological effects of placing PVs over canals?

Can flooding of the canals due to natural disasters or upstream overflow affect the structure?

Comments for author File: Comments.pdf

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files

1. What are ecological effects of placing PVs over canals?

As suggested we have added a section (Other Ecological Aspects) where we discussed in greater detail land consumption, water quality, and impact on fauna. The information provided is solely qualitative (modification ID 13 in the reviewed text).

2. In result section inconsistent use /design of the table were noticed.

As suggested, we have removed the two tables containing the final estimated costs of the two configurations. They contained limited information, and their use was inconsistent.

3. Can flooding of the canals due to natural disasters or upstream overflow affect the structure?

About flooding, a structure raised above the maximum level of the canal is planned precisely to avoid flood damage. As suggested, it was also specified further in the construction hypotheses (modification ID 3).

As mentioned in the section on evaporative effects, the application of the panels over the canals would reduce evaporation losses and thus mitigate the risk of drought. As suggested we have added more references about drought risk in Emilia Romagna (modification ID 13).

4. Figure references and copyright as indicated in the reviewer attached report.

We have added references for all the figures used. We are asking for copyright.

Please see attached reviewed article. The changes have been highlighted and marked with the ID XX.

Author Response File: Author Response.pdf

Reviewer 2 Report

Authors have studied various canal-top solar panels across the world and the feasibility of installation of canal-top solar panels in the Italian region “Emilia-Romagna”. The study is very interesting and has a serious interest in terms of practical applications. However, authors did not mention any details on the materials and mechanism of the existing canal-top solar panels in United States. Further, authors did not comment on the manufacturing cost details of canal-top solar panels in India and United States. These two facts can be incorporated in the manuscript. Further, more references should be added.

English language is fine. Minor editing is required.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

1. Authors did not mention any details on the materials and mechanism of the existing canal-top solar panels in United States.

2. Authors did not comment on the manufacturing cost details of canal-top solar panels in India and United States

The installations in the United States have not yet actually been realized, so the available information is limited. As suggested more data has ben added (modification ID 4) about studies conducted in the US and Indian plants. However, there are no publicly available cost data, apart from those made available for the CAP (Central Arizona Project), which are reported the article.

We have included the reported costs for the facilities implemented in India, New Sama, even though they are not comprehensive (modification ID 5).

3. More references should be added

We have worked on the initial version delivered to the summer school, incorporating numerous citations and references to similar articles, as kindly suggested. Additional references have been introduced to provide greater structure and significance to the paper, as per your advice. We used Zotero app to avoid formatting errors.

Please see attached reviewed article. The changes have been highlighted and the changes marked with ID XX).

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments for author File: Comments.pdf

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

1.Regional specificity. .Justify why the Emilia-Romagna region was chosen for the case study and how its characteristics compare to other potential locations in Italy. Explain the relevance of this region to the broader context.

As suggested, a pagagraph has been added in the section 2 (Materials and Methods, modification ID 8) describing the regional specifity of Emilia-Romagna region.

2. No net present value (NPV) analysis

NPV calculation was added (modification ID 7), thank you for the suggestion. Initially, we had not considered including an NPV as we were unable to quantitatively determine the additional maintenance costs, which could have a significant impact on the outcome. NPV does not contain mantainance cost, it could be improved with implementing a pilot plant or with further research work.

3. Limited data

We have worked on the initial version delivered to the summer school, incorporating numerous citations and references to similar articles, as kindly suggested. Additional references have been introduced to provide greater structure and significance to the paper, as per your advice.

Please see attached reviewed article. The changes have been highlighted and the changes marked ID XX.

Author Response File: Author Response.pdf

Reviewer 4 Report

The paper explores the feasibility, economic aspects, and environmental benefits of canal-top solar plant installations, focusing on the Emilia-Romagna region in Italy. Canal-top solar systems involve placing solar panels on the surface of water canals, leveraging the benefits of solar energy generation and efficient land and water resource utilization. The article begins by providing a global overview of existing canal-top solar plants, highlighting their features and technological aspects. It emphasizes the lack of detailed cost analyses for such installations and addresses this gap through a preliminary feasibility study specific to the Emilia-Romagna region. The study includes a case study with load analysis, economic cost estimations, and assessments of water evaporation reduction, maintenance impacts, and safety risks.

My Comments and Suggestions:

1) The title could be more concise and specific. 

2) Consider streamlining the introduction section to highlight the research objectives, particularly focusing on the lack of cost analyses for canal-top installations.

3) Clearly state the primary research objectives early in the paper to engage the reader and set expectations for the study.

4) Specify the sources of market data and publicly available catalogs used for cost estimations. Transparency in data sources enhances the credibility of the cost analysis.

5) Discuss the environmental benefits, such as reduced water evaporation and improved water quality, in greater detail. Quantify the potential environmental gains of canal-top solar installations.

6) Justify why the Emilia-Romagna region was chosen for the case study and how its characteristics compare to other potential locations in Italy. Explain the relevance of this region to the broader context.

7) The conclusion suggests that canal-top photovoltaics are currently not cost-effective, but it also hints at future possibilities. Provide more explicit recommendations for future research and what conditions might make these installations more viable.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

1. Regional specificity .Justify why the Emilia-Romagna region was chosen for the case study and how its characteristics compare to other potential locations in Italy. Explain the relevance of this region to the broader context.

As suggested, a pagagraph has been added in the section 2 (Materials and Methods, modification ID 8) describing the regional specifity of Emilia-Romagna region.

2. The title could be more concise and specific

As suggested, we changed the title and now it is more concise (modification ID 9).

3. Consider streamlining the introduction section to highlight the research objectives, particularly focusing on the lack of cost analyses for canal-top installations. Clearly state the primary research objectives early in the paper to engage the reader and set expectations for the study.

We have revised the abstract and introduction in accordance with the provided suggestions, placing greater emphasis on the primary objective of the analysis (modification ID 11). The introduction has been further streamlined by omitting the section that delineates the contributions of individual paragraphs. In accordance with the recommendations, we have underscored the dearth of literature and practical instances in Europe, with a specific focus on Italy (modification ID 10).

4. Specify the sources of market data and publicly available catalogs used for cost estimations. Transparency in data sources enhances the credibility of the cost analysis.

The costs of the photovoltaic system (excluding structure) were provided by a local photovoltaic installer, while the costs of the structure were estimated through contacts with two local builders. Unfortunately, public catalogues and price lists are not available for the Emilia-Romagna commercial area. We asked for request quotes via phone or email.

5. The conclusion suggests that canal-top photovoltaics are currently not cost-effective, but it also hints at future possibilities. Provide more explicit recommendations for future research and what conditions might make these installations more viable.

As suggested, we have added suggestions for new research, placing particular emphasis on the development of a pilot plant. In our view, only by attempting to implement a real-scale plant can costs be accurately calculated and all associated positive and negative impacts quantified. We have also added that to make the technology more economically competitive, a reduction in the cost of photovoltaic equipment (such as panels) is needed primarily. Additionally, efforts should be directed towards optimizing the design of structures, possibly creating economies of scale (modification ID 14).

6. Discuss the environmental benefits, such as reduced water evaporation and improved water quality, in greater detail. Quantify the potential environmental gains of canal-top solar installations.

We have added a section (Other Ecological Aspects) where we discussed in greater detail land consumption, water quality, and impact on fauna. The information provided is solely qualitative (modification ID 13).

In addition, we have worked on the initial version delivered to the summer school, incorporating numerous citations and references to similar articles, as kindly suggested. Additional references have been introduced to provide greater structure and significance to the paper.

Please see attached reviewed article. The changes have been highlighted and marked ID XX.

Author Response File: Author Response.pdf

Reviewer 5 Report

The article explores various canal-top solar projects over the world, then a feasible application in the Italian region “Emilia-Romagna” is discussed, evaluating specialized designs, installation and maintenance costs, water evaporation reduction and the potential for conflicts with other water uses. The study reports technical and economic evaluations regarding the use of two different panel anchoring methods. Two types of structures will be assumed: i) scheme 1: suspension cable; ii) scheme 2: steel truss.

The manuscript could be improvement in some issues:

-          Tables and figure figures without references

-          Text without bibliographic references

-          The references are not correct.

-          Review of similar studies (e.g. Baradei, S. E., & Sadeq, M. A. (2020). Effect of solar canals on evaporation, water quality, and power production: An optimization study. Water, 12(8), 2103.)

-          Explain better the conflict with other water uses.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

1. Tables and figure figures without references. Text without bibliographic references.

Following your suggestions, we have included citations in all the images, incorporating them into the captions. We are in the final stages of verifying the copyright for two images. Captions have been added to each table.

We have worked on the initial version delivered to the summer school, incorporating numerous citations and references to similar articles, as kindly suggested. Additional references have been introduced to provide greater structure and significance to the paper, as per your advice.

2. The references are not correct.

We have reviewed all the citations, using Zotero app in IEEE format, aiming to avoid any formatting errors.

3. Explain better the conflict with other water users.

We have created a new dedicated paragraph (modification ID 19). Furthermore, we added a section dedicated to ecological aspects, beyond water conservation (modification ID 13).

4. With the existing climate changes, increase in the water level in the canals or drought was not predicted.

As suggested, we have incorporated additional information on extreme events caused by climate change. Concerning the risk of drought, Emilia-Romagna is a region at high risk, and this risk is expected to increase further (modification ID 8). Water savings due to reduced evaporation could become an increasingly important factor. Regarding the risk of flooding, we have further specified the necessity for the system to be above the riverbank level. We have also indicated that it would be advisable not to position the system in areas at higher risk of overflowing (modification ID 3)

Please see attached reviewed article. The changes have been highlighted and marked ID XX.

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report

Accept in present form.

Reviewer 5 Report