A Solar Photovoltaic System Applied to Açaí Production and the Development of Riverside Communities in the Amazon

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript reports photovoltaic (PV) system that is used for Açaí production in the Amazon area. The work provides considerable insights to the field of PV research and application. For this reason, I am in favor of its publication in Sustainability. However, there are numerous issues that need to be properly addressed before it can be accepted for publication.

1.       Although authors have explicated the detailed systems (direct coupling system, PV system, etc.) that are to be set up in the riverside communities, these infrastructure and auxiliary seem to be widely applicable to all production settings. What are the specific characteristics of Açaí production and the corresponding requirements of PV power generation and inverter? Authors did not give adequate design and explanation into these matters.

2.       What are the advantages of PV system with respect to the generator in terms of Açaí production and community development? And what factors (mechanical- and system-wise) need to be improved/enhanced in order to bring PV system more substitutable to the conventional generators? These aspects are also lacking within the context.

3.       Also, within the solar PVs, I would also want to see some discussion regarding which generation of the PV technology (e.g. silicon PVs or perovskite PVs) that is most suitable to the weather and environment of Amazon, which seem to be at high temperature and high humidity constantly, and the solar irradiation may not be stable due to raining and tree blocking as compared to plains in other continent.

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

I appreciate the time and attention you have dedicated to evaluating the submitted research. Your contributions have been thoroughly analyzed and considered in all aspects. The responses to your questions are provided in more detail on this platform. In the article, they have been inserted in a more concise manner and in different sections, which I have highlighted in green for easy identification. Should you have any questions or pending issues, we are available to respond as soon as possible.

Sincerely,
Allan Pena

Comment 1:  "Although authors have explicated the detailed systems (direct coupling system, PV system, etc.) that are to be set up in the riverside communities, these infrastructure and auxiliary seem to be widely applicable to all production settings. What are the specific characteristics of Açaí production and the corresponding requirements of PV power generation and inverter? Authors did not give adequate design and explanation into these matters."
R: 

The first characteristic of açaí production concerns its socioeconomic importance: in addition to being the main source of income for riverside families (not only from Ilha das Cinzas but also from various communities in the region), açaí production is the staple food in family meals, both due to its abundance and its nutritional characteristics. The use of the PV system is justified by the region's energy potential (average solar irradiance ranges from 4.8 to 5.6 kWh/m²/day), competitive prices, established configurations, and lower maintenance and operation costs.

From a technical standpoint: the production of açaí, specifically the extraction of the fruit pulp, is carried out using a pulping machine - a metal tank with a movable shaft coupled to a motor, responsible for separating the pulp from the fruit seeds. Therefore, when deciding to use a PV system as the electricity source, it is essential to use an inverter to adapt the DC power generated to the AC power consumed by the pulping machine. The electrical power required to perform this task - extracting the açaí pulp, both for personal consumption and possible commercialization - is provided by a Three-Phase Induction Motor (TIM), which necessitates the use of a VSD to allow direct coupling of the driving load to the PV array.

 

Comment 2: What are the advantages of PV system with respect to the generator in terms of Açaí production and community development? And what factors (mechanical- and system-wise) need to be improved/enhanced in order to bring PV system more substitutable to the conventional generators? These aspects are also lacking within the context.

R: Dividing the response into two parts.

i) To understand the advantages of PV systems compared to conventional generators, we need to understand the region's reality regarding electricity supply. Brazil has almost all its states (except one, Roraima) connected to the National Interconnected System (SIN). However, in the Legal Amazon region, the SIN connects the capitals and most of the headquarters of other municipalities in the states. The remaining demands are met by Isolated Systems (SISOL), 98% of which consist of fuel generator groups: noisy polluting sources that emit greenhouse gases; they have high maintenance costs and fuel purchase and transportation costs to the place of use. With high fuel costs, the generator's usage period is extremely reduced, directly interfering with generation autonomy.

However, many communities are not served by SIN or SISOL. These are located in remote areas with populations dispersed over a large area, which are served by small decentralized generating sources, commonly diesel-powered.

Given this problem, the açaí production chain is reduced to fruit extraction in the region, without any processing or value addition. Regarding development, the community faces all the barriers that other communities face without access to conventional electricity: limitations in education, health, leisure, communication, information services, etc.

In this reality, photovoltaic systems are a prominent renewable technology: less frequent and cheaper maintenance and operation, individual generation autonomy, no pollution during generation, and different configurations that can be used for various applications: domestic and productive. Additionally, the region currently has a strong presence of Educational and Research Institutions that train professionals who can work in the maintenance and installation of these systems.

ii) One of the factors that increase the system's costs is the energy accumulators. Depending on the technology employed, the battery bank's lifespan will require a complete replacement within a few years, as is the case with lead-acid batteries. There are technologies with relatively long lifespans, but still with relatively high costs, such as lithium-ion batteries. In this sense, the proposal of the work is an example of how using a configuration suitable for the identified demands (domestic and productive) can be a way to make the PV system replaceable concerning a conventional generator, as it allows meeting the driving loads through a direct coupling configuration, dispensing with the use of a battery bank, a robust configuration that uses TIM, the same technology used in other applications powered by diesel generators.

 

Comment 3: Also, within the solar PVs, I would also want to see some discussion regarding which generation of the PV technology (e.g. silicon PVs or perovskite PVs) that is most suitable to the weather and environment of Amazon, which seem to be at high temperature and high humidity constantly, and the solar irradiation may not be stable due to raining and tree blocking as compared to plains in other continent.

R: Indeed, this was a discussion not conducted in the first version of the article. A text with the results of this discussion was inserted, but it is necessary to inform in advance that one of the factors in choosing the components and technologies used in the research was the logistics and local availability. Due to the geographical distance of the region from major commercial centers, many pieces of equipment are not available in the state, and the delivery rates for online purchases are high. This consideration has also been included in the text.

Reviewer 2 Report

Comments and Suggestions for Authors

1. Please add some more keywords. 2. Eq (1): subscripts, please, abbreviate, instead provide explanations in the text. 3. Table 1: Foreign words should be translated into English.

4. Table 1 “Top 5 – External Factors”: explain, please, presence of two identical columns «Opportunities».

5. Lines 261, 326, 377: please, correct the situation: «Error! Reference source not found». 6. In equations (2), (3), etc., please provide an explanation of the quantities and indicate units.

7. Eq (2): please explain the entry "1.090,98 𝑊𝑃". How to distinguish "decimals (point)" and "thousands (comma)"?

8. Eq. (3): the entry “1,104 𝑘𝑊 𝑥 85%+1,104%=2,04 𝑘𝑊” is incorrect, since different values (kW and %) can not be added. Keep, please, mathematical aesthetics.

9. Describe, please, the experimental installation, measuring equipment for experiments, its accuracy class and experimental error estimate. 10. Please add a "Discussion" item. In the "Discussion" item it can be indicated a regression analysis based on the results of the experiment, direction of the future research, etc. 11. The item “Conclusion” should be titled “Conclusions”, but not “Conclusion”. Phrases should be concise and in the form of numbered sentences. Please, shorten it.

 

12. Background is insufficient; 30 positions of the references are not enough. Please add at least 10-15 more positions. Please, replace the references dated before 2019 (within the last 5 years); positions: 2, 7, 9, 10, 11, 15, 16, 21, 26, 27, 29.

Author Response

Dear reviewer,

I appreciate the time and attention you have dedicated to evaluating the submitted research. Your contributions have been thoroughly analyzed and considered in all aspects. The responses to your questions are provided in more detail on this platform. In the article, they have been inserted in a more concise manner and in different sections, which I have highlighted in yellow for easy identification. Should you have any questions or pending issues, we are available to respond as soon as possible.

Sincerely,
Allan Pena

Comment 1: Please add some more keywords. 

R: Five additional keywords have been added.

Comment 2: Eq (1): subscripts, please, abbreviate, instead provide explanations in the text. 

R: The equation has been simplified, and the explanation in the text has been made more direct.

Comment 3: Table 1: Foreign words should be translated into English. 

R: Except for the word “açaí” and certain names of institutions and systems, I have translated all foreign words into English. I was unsure whether to include the original names, so I kept them as footnotes.

Comment 4: Table 1 “Top 5 – External Factors”: explain, please, presence of two identical columns «Opportunities».

 R: Dear reviewer, this was an error in the organization and transcription of the table. The second column actually represents “Threats,” which has been corrected.

Comment 5: Lines 261, 326, 377: please, correct the situation: «Error! Reference source not found». 

R: The corrections have been made.

Comment 6: In equations (2), (3), etc., please provide an explanation of the quantities and indicate units.

R: The corrections have been made.

Comment 7: Eq (2): please explain the entry "1.090,98 ??". How to distinguish "decimals (point)" and "thousands (comma)"?

R: Dear reviewer, this was an error during the transcription of the text. It has been corrected to use points as decimal separators and commas as thousand separators.

Comment 8: Eq. (3): the entry “1,104 ?? ? 85%+1,104%=2,04 ??” is incorrect, since different values (kW and %) can not be added. Keep, please, mathematical aesthetics.

R: The corrections have been made.

Comment 9: Describe, please, the experimental installation, measuring equipment for experiments, its accuracy class and experimental error estimate. 

R: Dear reviewer, there were no experimental installations before the system installations nor measurements for data collection. I would like to thank you for this inquiry, as I fear it was not clear that one of the research gaps is the lack of a monitoring system for subsequent analysis and comparison – something now highlighted in the text. Information about the model of the digital multimeter used during the installations for measuring current, voltage, and continuity tests has been included in the text.

Comment 10: Please add a "Discussion" item. In the "Discussion" item it can be indicated a regression analysis based on the results of the experiment, direction of the future research, etc. 

R: Dear reviewer, it was clarified that the “Results” section includes the discussion along with the presentation of the results, thus the title of the section was corrected to “Results and Discussions.” Adding a new “Discussion” section would alter the structure of the text and the complete way it was presented. Additionally, the authors believe that presenting the results followed by their discussion and analysis is an educational way to show what was obtained from the research. Regarding future research directions, I fear I did not address these contributions more explicitly. I sought to include a paragraph at the end of the “Results and Discussions” subsections commenting on possible gaps that could generate other works from this research.

Comment 11: The item “Conclusion” should be titled “Conclusions”, but not “Conclusion”. Phrases should be concise and in the form of numbered sentences. Please, shorten it.

 R: Dear reviewer, the corrections have been made, however, we sought to reconcile the idea of using numbered sentences in appropriate parts of the text.

12. Background is insufficient; 30 positions of the references are not enough. Please add at least 10-15 more positions. Please, replace the references dated before 2019 (within the last 5 years); positions: 2, 7, 9, 10, 11, 15, 16, 21, 26, 27, 29.
R: Dear reviewer, the corrections have been made. Except for reference 19 (11 in the first version of the article), which refers to a book with well-established important concepts such as the starting current in three-phase induction motors – a concept that could not be omitted from the discussion, all references have been replaced with more recent ones. Additionally, new references have been added to make the theoretical framework more robust.

Reviewer 3 Report

Comments and Suggestions for Authors

The design of a photovoltaic system as an integration mechanism for productive activities and better quality of life for riverside families in the Brazilian Amazon is presented in the paper. A SWOT analysis is used to define action plans to enhance the insertion of the photovoltaic system. The subject is worth investigating and the paper may be considered for publication after a revision addressing the following issues.

Line 71: “heated market” is not clear, please explain

Line 140: “(Error! Reference source not found.).” must be corrected

The quality of figure 1 must be improved in terms of readability.

Opportunities are included twice in Table 1 and the Threats are missing.

Line 258: “Heated photovoltaic solar energy market“is not clear, please explain

Line 261: “(Error! Reference source not found.).” must be corrected

Line 326: “(Error! Reference source not found.).” must be corrected

Line 340: “(Error! Reference source not found.).” must be corrected

Line 341: 3,59 kWh must be corrected to 3.59 kWh

Line 342: 4,875 hours must be corrected to 4.875 h

The mathematical model (Eq (2) - ) and the results obtained based on this model must be separately presented in the manuscript.

Equation (3) must be corrected.

Symbols must be used in Equations (4) and (5) instead of words.

Line 377: “(Error! Reference source not found.).” must be corrected

Line 410: “330 Wp photovoltaic modules” must be corrected

It seems that the Variable Speed-Drive presented in Fig.7 is actually an inverter. This should clearly mentioned in the paper and its full technical specifications provided.

Fig.11 is redundant and must be deleted. The functional schemes were already presented in Figs. 5 and 7.

Comments on the Quality of English Language

The English must be carefully checked for typos, grammar, spelling and syntax.

Author Response

Dear Reviewer,

I appreciate the time and attention you have dedicated to evaluating the submitted research. Your contributions have been thoroughly analyzed and considered in all aspects. The responses to your questions are provided in more detail on this platform. In the article, they have been inserted in a more concise manner and in different sections, which I have highlighted in blue for easy identification. Should you have any questions or pending issues, we are available to respond as soon as possible.

Sincerely,
Allan Pena

Comment 1: Line 71: “heated market” is not clear, please explain.

R: Dear reviewer, in recent decades, photovoltaic system technologies have gained more prominence and currently have a market that receives tax incentives and large investments, making the equipment more accessible with competitive prices compared to other generation technologies. The term “heated market” would be synonymous with “rising market,” which has been replaced.

Comment 2: Line 140: “(Error! Reference source not found.).” must be corrected

R: The corrections have been made.

Comment 3: The quality of figure 1 must be improved in terms of readability.

R: The corrections have been made. The figure is divided into three parts concerning Ilha das Cinzas, being: (a) the geographical location concerning the entire country; (b) the location within the Marajó archipelago; and (c) the map of the island with the location of the rivers that allow navigation through the community.

Comment 4: Opportunities are included twice in Table 1 and the Threats are missing.

R: The corrections have been made.

Comment 5: Line 258: “Heated photovoltaic solar energy market“is not clear, please explain.

R: Dear reviewer, in recent decades, photovoltaic system technologies have gained more prominence and currently have a market that receives tax incentives and large investments, making the equipment more accessible with competitive prices compared to other generation technologies. The term “heated market” would be synonymous with “rising market,” which has been replaced.

Comment 6: Line 261: “(Error! Reference source not found.).” must be corrected.

R: The corrections have been made.

Comment 7: Line 326: “(Error! Reference source not found.).” must be corrected.

R: The corrections have been made.

Comment 8: Line 340: “(Error! Reference source not found.).” must be corrected.

R: The corrections have been made.

Comment 9: Line 341: 3,59 kWh must be corrected to 3.59 kWh.

R: The corrections have been made.

Comment 10: Line 342: 4,875 hours must be corrected to 4.875 h.

R: The corrections have been made.

Comment 11: The mathematical model (Eq (2) - ) and the results obtained based on this model must be separately presented in the manuscript.

R: The corrections have been made.

Comment 12: Equation (3) must be corrected.

R: The corrections have been made.

Comment 13: Symbols must be used in Equations (4) and (5) instead of words.

R: The corrections have been made.

Comment 14: Line 377: “(Error! Reference source not found.).” must be corrected.

R: The corrections have been made.

Comment 15: Line 410: “330 Wp photovoltaic modules” must be corrected.

R: The corrections have been made.

Comment 16: It seems that the Variable Speed-Drive presented in Fig.7 is actually an inverter. This should clearly mentioned in the paper and its full technical specifications provided.

 R: Dear reviewer, the corrections have been made. Although it is commercially called a frequency inverter by the manufacturer, the device has the operational characteristics of a VSD. I have included a brief text explaining this information along with its technical specifications.

Comment 17: Fig.11 is redundant and must be deleted. The functional schemes were already presented in Figs. 5 and 7.

R: Dear reviewer, the authors understand that the reviewer considers Figure 11 redundant; however, it is interesting to keep it because, in the structure presented in the text, the details and descriptions of the two subsystems (DPS and DCPS) are made separately to, at the end of this stage, present the complete configuration as the system was installed in Ilha das Cinzas. I hope the reviewer can consider this point of view regarding the importance of Fig. 11 for the conclusion of the mixed configuration system description stage.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript was previously reviewed, and the authors have addressed all of my concerns and questions. It can therefore be accepted as is.