Performance Evaluation and Integration Strategies for Solar Façades in Diverse Climates: A State-of-the-Art Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Review Comments

1. On page 2, in the "1. Introduction" chapter, lines 59-74, I suggest expanding the discussion of national goals and development trends by exploring the policy measures that different countries have implemented to promote photovoltaic facade technology and its impact on the construction industry. For example, how do certain European countries encourage the adoption of building-integrated photovoltaic technology through subsidy policies or green building certification standards?

2. On page 2, in the "1. Introduction" chapter, lines 64-65, the sentence currently reads, "with solar and wind significantly contributing to new capacity [10], which reached 136 GW in 2020 alone [11]." I suggest updating this to include the latest available data, such as figures from 2023, as solar and wind power installed capacity has seen significant growth following China’s announcement of its dual carbon targets.

3. On page 2, in the "1. Introduction" chapter, lines 86-88, the sentence currently reads, "Facade-mounted photovoltaics (PVs) have the potential to deliver substantial energy generation and demonstrate economic viability, particularly in highly urbanized areas [24]." However, the article lacks a realistic cost-benefit analysis when discussing the economic potential of photovoltaic facades. For instance, how do the economics of photovoltaic facades in high-density urban areas compare to those of rooftop photovoltaic systems? I suggest incorporating a relevant analysis to address this comparison.

4. On pages 3-4, in the "2. Materials and Methods" chapter, although the article lists 16 relevant review articles and briefly describes their contributions, the analysis of each document lacks sufficient depth. For example, it would be helpful to highlight which research conclusions are highly consistent, and which are contradictory or lack sufficient evidence. I suggest expanding the discussion and providing a more detailed summary of these points.

5. On pages 3-4, in the "2. Materials and Methods" chapter, lines 119-120, the sentence currently reads, "excluding from the selection ones with keywords ('photovoltaic-thermal', 'hybrid solar systems', 'PVT')." I suggest specifying the reasons for excluding these documents to provide greater clarity.

6. On pages 3-4, in the "2. Materials and Methods" chapter, line 121, the sentence currently reads, "The time frame used was 2020-2024." It could be improved to "Study period: 2020-2024." Additionally, while the study focuses on literature from 2020 to 2024, this may be too narrow. I suggest that including some earlier key studies would provide a more comprehensive overview.

7. On page 5, in the "3. Literature Review" chapter, lines 215-216, the sentence currently reads, "Figure 2. The main research keywords (compiled from selected article keywords with a free online word cloud generator)." While Figure 2 presents a keyword cloud map, it lacks a specific explanation or analysis of the keywords. For example, which keywords appear most frequently in the research, and are there any emerging technologies or methods that are central to current research trends? Although the keyword cloud map is visually informative, I suggest supplementing it with relevant articles to explain its significance.

8. On page 6, in the "3. Literature Review" chapter, lines 244-246, under the category of "climate adaptation and optimization," the article mentions the optimization design of photovoltaic systems in different climate zones. However, there are few specific case studies and data to support these discussions. It would be beneficial to include a more detailed analysis of specific climate regions, highlighting studies that have proposed practical optimization strategies for BIPV systems under particular climate conditions. For example, what are the differences in BIPV optimization design between tropical and cold climates?

9. On page 6, in the "3. Literature Review" chapter, lines 247-252, the article mentions major research areas such as "Building Integration and Design Strategies" and "Material and Technological Innovations." However, it does not delve deeply into the evolving trends within these research areas. For example, have there been any recent breakthroughs in the innovation of BIPV technology and materials? Which regions are leading the application of these technologies?

10. On page 6, in the "3. Literature Review" chapter, lines 255-257, the article mentions major research on "Economic Feasibility and Social Acceptance." I suggest incorporating more economic feasibility analysis of BIPV systems, particularly through case studies from different regions, to evaluate how factors such as policy support, market acceptance, and installation costs impact the promotion of BIPV.

11. On pages 7-15, in the "3. Literature Review" chapter, for Table 1, although the article mentions that the literature is classified by topic and a table (Table 1) is provided, there is a lack of quantitative analysis for these categories. For example, the percentage of literature in each category and the geographical distribution of the research are not included. I suggest adding a quantitative analysis to more clearly illustrate the distribution of research across different categories and their focus areas. Additionally, a summary of these findings would enhance the clarity of the analysis.

12. On page 15, in the "4. Discussion: Key Barriers to the Widespread Adoption of BIPV Systems" chapter, although the article references multiple studies and cases, it lacks supporting charts and data, particularly in areas such as economic feasibility, thermal performance, and social acceptance. I suggest adding relevant data charts, such as a comparison of the economic returns between BIPV and rooftop photovoltaic systems, and a comparison of heat loss under different climate conditions. Using data and charts would significantly enhance the persuasiveness and intuitiveness of the paper.

13. On page 15, in the "4. Discussion: Key Barriers to the Widespread Adoption of BIPV Systems" chapter, in the discussion of "Barrier 1" (lines 293-309), the article mentions that the payback period of BIPV systems is long and compares it with rooftop photovoltaic systems. However, it does not analyze in detail the specific factors that influence the payback period, such as initial costs, maintenance costs, and energy price fluctuations. Additionally, while the article notes that "BIPV panel installation in cold climate regions has additional advantages," it lacks specific data support and case analysis. I suggest incorporating case studies of BIPV systems in relevant cold and temperate climate regions to provide a more comprehensive evaluation of their economic feasibility.

14. On page 18, line 427, "5. Conclusions" should be corrected to "6. Conclusions."

15. On page 18, in the "5. Conclusions" chapter, in the discussion of "Economic Viability" (lines 429-434), the article mentions that "the shortest payback period for rooftop PV systems is 6.16 years," while "BIPV systems usually require a payback period of 13-18 years." However, it lacks specific case data or further statistical analysis. I suggest including specific project cases or comparative studies in the conclusion section. Additionally, it would be valuable to analyze in detail why this difference exists and explore whether costs can be reduced through technological innovation, policy support, or production scale effects.

16. On page 18, in the "5. Conclusions" chapter, in the discussion of "Technological Innovations" (lines 461-462), the sentence reads, "Emerging technologies like perovskite and tandem solar cells offer significant potential for BIPV applications." While the article mentions the potential of perovskite photovoltaics and tandem photovoltaic materials, it does not explore in detail their technical maturity, market prospects, and possible challenges, such as stability and production costs.

Comments for author File: Comments.pdf

Author Response

Comments 1: On page 2, in the "1. Introduction" chapter, lines 59-74, I suggest expanding the discussion of national goals and development trends by exploring the policy measures that different countries have implemented to promote photovoltaic facade technology and its impact on the construction industry. For example, how do certain European countries encourage the adoption of building-integrated photovoltaic technology through subsidy policies or green building certification standards?

Response 1: We have expanded the discussion in the lines 59-104, by including a detailed analysis of national goals and development trends related to photovoltaic facade technology. We have specifically addressed the policy measures implemented by different countries, highlighting examples of how European nations promote the adoption of building-integrated photovoltaic (BIPV) technology. This includes mechanisms such as green tradable certificates, feed-in tariffs, capital subsidies, tax credits, and net-metering.

 

Comments 2: On page 2, in the "1. Introduction" chapter, lines 64-65, the sentence currently reads, "with solar and wind significantly contributing to new capacity [10], which reached 136 GW in 2020 alone [11]." I suggest updating this to include the latest available data, such as figures from 2023, as solar and wind power installed capacity has seen significant growth following China’s announcement of its dual carbon targets.

Response 2: The Solar PV capacity data for the year 2023 was added (line 83 in revised document).

Comments 3: On page 2, in the "1. Introduction" chapter, lines 86-88, the sentence currently reads, "Facade-mounted photovoltaics (PVs) have the potential to deliver substantial energy generation and demonstrate economic viability, particularly in highly urbanized areas [24]." However, the article lacks a realistic cost-benefit analysis when discussing the economic potential of photovoltaic facades. For instance, how do the economics of photovoltaic facades in high-density urban areas compare to those of rooftop photovoltaic systems? I suggest incorporating a relevant analysis to address this comparison.

Response 3: Some analysis is added using the reference no. 60 from Switzerland (lines 118-125). More detailed analysis was not found in recent studies.

Comments 4: On pages 3-4, in the "2. Materials and Methods" chapter, although the article lists 16 relevant review articles and briefly describes their contributions, the analysis of each document lacks sufficient depth. For example, it would be helpful to highlight which research conclusions are highly consistent, and which are contradictory or lack sufficient evidence. I suggest expanding the discussion and providing a more detailed summary of these points.

Response 4: The reviews were described in a more detail highlighting the main findings and deficiencies (see lines 167-281).

Comments 5: On pages 3-4, in the "2. Materials and Methods" chapter, lines 119-120, the sentence currently reads, "excluding from the selection ones with keywords ('photovoltaic-thermal', 'hybrid solar systems', 'PVT')." I suggest specifying the reasons for excluding these documents to provide greater clarity.

Response 5: The reason was specified (line 159 in reviewed document)

Comments 6: On pages 3-4, in the "2. Materials and Methods" chapter, line 121, the sentence currently reads, "The time frame used was 2020-2024." It could be improved to "Study period: 2020-2024." Additionally, while the study focuses on literature from 2020 to 2024, this may be too narrow. I suggest that including some earlier key studies would provide a more comprehensive overview.

Response 6: The study period was left as it is in order to ensure distinctiveness and avoid duplication with prior reviews. The explanation was added in lines 159-161.

Comments 7: On page 5, in the "3. Literature Review" chapter, lines 215-216, the sentence currently reads, "Figure 2. The main research keywords (compiled from selected article keywords with a free online word cloud generator)." While Figure 2 presents a keyword cloud map, it lacks a specific explanation or analysis of the keywords. For example, which keywords appear most frequently in the research, and are there any emerging technologies or methods that are central to current research trends? Although the keyword cloud map is visually informative, I suggest supplementing it with relevant articles to explain its significance.

Response 7: Thank you for your valuable suggestion. We have revised the manuscript accordingly by adding an explanation of the keyword cloud map to clarify its significance. In lines 319-323, we provided an analysis of the most frequently appearing keywords, this should provide a clearer connection between the visual representation in Figure 2 and its context in the research literature.

Comments 8: On page 6, in the "3. Literature Review" chapter, lines 244-246, under the category of "climate adaptation and optimization," the article mentions the optimization design of photovoltaic systems in different climate zones. However, there are few specific case studies and data to support these discussions. It would be beneficial to include a more detailed analysis of specific climate regions, highlighting studies that have proposed practical optimization strategies for BIPV systems under particular climate conditions. For example, what are the differences in BIPV optimization design between tropical and cold climates?

Response 8: These findings are usually very general; for example, studies often highlight that in tropical climates, shading and ventilation are critical for mitigating overheating and ensuring system efficiency, whereas in cold climates, insulation and maximizing solar gain during shorter daylight hours are prioritized. However, detailed case studies focusing on specific regions remain limited.

To address this, we have expanded the discussion by incorporating additional examples and analyses of BIPV optimization strategies tailored to distinct climate conditions. For instance, we included studies that emphasize the use of ventilated double-glazed BIPV systems in tropical climates to enhance thermal performance, as well as research highlighting vacuum-insulated BIPV technologies as a promising solution for cold climates due to their superior thermal insulation properties. These examples provide a clearer understanding of the practical application of BIPV systems across varying climate zones.

Comments 9: On page 6, in the "3. Literature Review" chapter, lines 247-252, the article mentions major research areas such as "Building Integration and Design Strategies" and "Material and Technological Innovations." However, it does not delve deeply into the evolving trends within these research areas. For example, have there been any recent breakthroughs in the innovation of BIPV technology and materials? Which regions are leading the application of these technologies?

Response 9: The great breakthroughs happened a little earlier that the studied period, we have added the summary for this to the ending chapters. Also we have mentioned the leading regions for BIPV innovations (lines 472-494 in revised document)

Comments 10: On page 6, in the "3. Literature Review" chapter, lines 255-257, the article mentions major research on "Economic Feasibility and Social Acceptance." I suggest incorporating more economic feasibility analysis of BIPV systems, particularly through case studies from different regions, to evaluate how factors such as policy support, market acceptance, and installation costs impact the promotion of BIPV.

Response 10: We appreciate your valuable suggestion to incorporate a more comprehensive economic feasibility analysis of BIPV systems, including case studies from different regions. In response, we have added references to five additional research papers ( references 149-155) that discuss various aspects of economic feasibility, policy support, market acceptance, and installation costs related to BIPV systems. These papers provide insights into economic challenges and opportunities in promoting BIPV adoption.

However, due to the limited revision timeframe provided for this article, we were unable to fully address this recommendation by conducting an in-depth analysis or including detailed case studies. Additionally, the initial focus of our review was not specifically centered on economic issues, but rather on the technological, environmental, and performance aspects of BIPV systems.

We acknowledge the importance of this topic and suggest that future studies should explore the economic dimensions of BIPV systems in greater detail, as this is a critical factor for their broader adoption. Thank you again for highlighting this area, which will form our future research endeavors.

Comments 11: On pages 7-15, in the "3. Literature Review" chapter, for Table 1, although the article mentions that the literature is classified by topic and a table (Table 1) is provided, there is a lack of quantitative analysis for these categories. For example, the percentage of literature in each category and the geographical distribution of the research are not included. I suggest adding a quantitative analysis to more clearly illustrate the distribution of research across different categories and their focus areas. Additionally, a summary of these findings would enhance the clarity of the analysis.

Response 11: The geographical distribution was added according to this suggestion. The number of studies in each category is also given in parentheses in lines 381-386 just before the Table 1.

 

Comments 12: On page 15, in the "4. Discussion: Key Barriers to the Widespread Adoption of BIPV Systems" chapter, although the article references multiple studies and cases, it lacks supporting charts and data, particularly in areas such as economic feasibility, thermal performance, and social acceptance. I suggest adding relevant data charts, such as a comparison of the economic returns between BIPV and rooftop photovoltaic systems, and a comparison of heat loss under different climate conditions. Using data and charts would significantly enhance the persuasiveness and intuitiveness of the paper.

Response 12: We acknowledge the importance of including supporting charts and data to enhance the persuasiveness and clarity of the paper. However, obtaining consistent and reliable data from existing studies for economic feasibility, thermal performance, and social acceptance has proven to be challenging. The available data is often contradictory, largely due to variations in measurement technologies, methodologies, and regional factors.

For example, differences in tools used to assess heat loss, variations in local economic conditions influencing return on investment, and differing societal attitudes towards BIPV systems contribute to a lack of standardized and comparable datasets. Additionally, much of the reported data lacks uniformity in how parameters are measured and interpreted, leading to discrepancies across studies.

While it was not feasible to address this fully within the limited revision period, we have acknowledged this challenge in the manuscript and emphasized the need for standardized methodologies in future research. We also suggest that future studies include systematic data collection and comprehensive case studies to address these gaps.

 

Comments 13: On page 15, in the "4. Discussion: Key Barriers to the Widespread Adoption of BIPV Systems" chapter, in the discussion of "Barrier 1" (lines 293-309), the article mentions that the payback period of BIPV systems is long and compares it with rooftop photovoltaic systems. However, it does not analyze in detail the specific factors that influence the payback period, such as initial costs, maintenance costs, and energy price fluctuations. Additionally, while the article notes that "BIPV panel installation in cold climate regions has additional advantages," it lacks specific data support and case analysis. I suggest incorporating case studies of BIPV systems in relevant cold and temperate climate regions to provide a more comprehensive evaluation of their economic feasibility.

Response 13: We appreciate the suggestion to include a detailed analysis of factors influencing the payback period of BIPV systems and to provide specific case studies from cold and temperate climate regions. However, obtaining such detailed data from existing studies is challenging, as the factors impacting payback periods—such as initial costs, maintenance requirements, and energy price fluctuations—are highly variable and depend on regional policies, technological configurations, and market conditions. Furthermore, the available data on BIPV installations in cold climates is often inconsistent, with case studies employing different methodologies and assumptions, leading to contradictory findings.

While we acknowledge the importance of these analyses, incorporating detailed case studies and comprehensive evaluations was not feasible within the limited revision timeframe. Additionally, the primary focus of this paper was not on the economic aspects, which are often secondary to the technological and integration challenges discussed in the study. We suggest that future research should aim to consolidate standardized case studies and provide a more in-depth examination of these economic factors across varying climatic contexts.

 

Comments 14: On page 18, line 427, "5. Conclusions" should be corrected to "6. Conclusions."

Response 14: corrected

Comments 15: On page 18, in the "5. Conclusions" chapter, in the discussion of "Economic Viability" (lines 429-434), the article mentions that "the shortest payback period for rooftop PV systems is 6.16 years," while "BIPV systems usually require a payback period of 13-18 years." However, it lacks specific case data or further statistical analysis. I suggest including specific project cases or comparative studies in the conclusion section. Additionally, it would be valuable to analyze in detail why this difference exists and explore whether costs can be reduced through technological innovation, policy support, or production scale effects.

Response 15: Some new references were added to support these arguments, and it also changed the shortest payback period for rooftop mounted PV (lines 568-571).

Comments 16: On page 18, in the "5. Conclusions" chapter, in the discussion of "Technological Innovations" (lines 461-462), the sentence reads, "Emerging technologies like perovskite and tandem solar cells offer significant potential for BIPV applications." While the article mentions the potential of perovskite photovoltaics and tandem photovoltaic materials, it does not explore in detail their technical maturity, market prospects, and possible challenges, such as stability and production costs.

Response 16: In response to the referee's comment, we have added a more detailed discussion of the technical maturity, market prospects, and challenges of emerging technologies like perovskite and tandem solar cells. This includes the ongoing challenges related to stability, ecology, and production costs.

Reviewer 2 Report

Comments and Suggestions for Authors

For Barrier 3 (lines 324-328), some examples (citations) might be more clarifying, but it is not mandatory

Comments for author File: Comments.pdf

Author Response

Comments 1: 

For Barrier 3 (lines 324-328), some examples (citations) might be more clarifying, but it is not mandatory

Response 1:

Thank you for your suggestion. We appreciate your feedback and have revised the text to provide greater clarity regarding Barrier 3. While specific examples or citations might enhance the discussion further, we have clarified the content to the best of our ability within the scope of the current revision. Please refer to lines 444–455 of the revised document for the updated text.

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript titled “Performance Evaluation and Integration Strategies for Solar Facades in Diverse Climates: State-of-the-Art Review” presents a comprehensive review of the literature devoted to different aspects of the performance of bifacial photovoltaic modules under variety of external climatic conditions. The submitted manuscript is a systematic study which clearly presents current data based on 148 references from recent years. Table 1 contains short summaries of publication from years 2023-2025 which are divided into a few categories. In “Discussion” section there are 5 barriers to the widespread application of BIPV identified basing on the literature review. However in the part “Findings” there are some general well know statements (lines 357-398) and in the opinion of Referee this fragment should be enriched with synthetic analysis of cited literature taking into account various climates as the title of the manuscript suggests.

 

Minor remarks:

l. 105 – “Despite this theme’s importance” should be replaced with “Due to the theme importance”

l. 364 – inverter is not a part of solar panel

Author Response

Comments 1:

The manuscript titled “Performance Evaluation and Integration Strategies for Solar Facades in Diverse Climates: State-of-the-Art Review” presents a comprehensive review of the literature devoted to different aspects of the performance of bifacial photovoltaic modules under variety of external climatic conditions. The submitted manuscript is a systematic study which clearly presents current data based on 148 references from recent years. Table 1 contains short summaries of publication from years 2023-2025 which are divided into a few categories. In “Discussion” section there are 5 barriers to the widespread application of BIPV identified basing on the literature review. However in the part “Findings” there are some general well know statements (lines 357-398) and in the opinion of Referee this fragment should be enriched with synthetic analysis of cited literature taking into account various climates as the title of the manuscript suggests.

 

Response 1:

Thank you for your detailed feedback and suggestion. We appreciate the importance of enriching the findings section with a more synthetic analysis of the cited literature, particularly in relation to various climates, as aligned with the manuscript's title. In response, we have made every effort to improve the section by analyzing the available data and incorporating additional insights where possible. However, we acknowledge that the data from existing studies is somewhat limited, especially regarding comparative analyses across diverse climates. Many studies do not provide sufficiently detailed or consistent data, making it challenging to perform a more comprehensive synthesis.

Despite these limitations, we have revised the “Findings” and “Conclusions” sections to the best of our ability based on the data available, and we believe it now offers a clearer and more nuanced discussion. We agree that further detailed studies are necessary to address these gaps, and we have highlighted this need in our conclusions.

 

 

Comments 2:

1. 105 – “Despite this theme’s importance” should be replaced with “Due to the theme importance”

Response 2:

fixed (line 143 in revised document)

Comments 3:

364 – inverter is not a part of solar panel

Response 3:

text was corrected, line 516 in revised document.

Reviewer 4 Report

Comments and Suggestions for Authors

Appreciation and recommendations:

·    The paper ” Performance Evaluation and Integration Strategies for Solar Façades in Diverse Climates: State-of-the-Art Review” addresses a particularly important and topical problem in the context of the energy crisis, of global drought and environmental pollution. Solar energy is a real alternative to classical sources.

·    This paper presents a literature review and an overview of the main findings regarding building-integrated photovoltaic (BIPV) systems, focusing on their performance, environmental impact, and technological developments.

·    The paper provides a holistic perspective on the performance and integration strategies of photovoltaic façades. Additionally, it inspires new research and technological developments, serving as a starting point for optimizing BIPV solutions in various regions and climatic conditions.

·    The paper does not clearly outline the expertise and experience of the authors in the BIPV field; thus, it would be beneficial to include this information.

·    To enhance the research methodology and its credibility, a detailed presentation of concrete case studies demonstrating the performance of BIPV systems in Diverse Climates is necessary.

·    Section 5 is numbered twice, appearing under both "Findings" and "Conclusions."

·    The conclusions respond to the topic addressed but are presented in a general manner. Many of them are already known. The concrete elements of the conducted study should be highlighted.

·    References are appropriate to the addressed research.

·    Figures and tables are clear and concise.

Author Response

Comments 1:

• The paper does not clearly outline the expertise and experience of the authors in the BIPV field; thus, it would be beneficial to include this information.

Response 1:

We appreciate your thoughtful feedback. Regarding the comment on outlining the authors' expertise in the BIPV field, we would like to clarify the following:

Both authors are affiliated with Vilnius Gediminas Technical University, a well-established institution recognized for its contributions to building construction and engineering research. Additionally, the authors work as a professional construction expert and architect, providing hands-on experience in the design, evaluation, and implementation of innovative building technologies, including BIPV systems.

We intentionally chose not to include references to our own research papers in the manuscript to avoid potential concerns regarding self-citation, as such practices are often discouraged in scholarly publishing. Furthermore, we believe that describing the authors' expertise is not essential to the objectives of this review article, which aims to provide an impartial synthesis of the existing knowledge in the BIPV field.

We hope this clarifies our approach and rationale, and we remain open to further addressing any specific concerns you might have.·    To enhance the research methodology and its credibility, a detailed presentation of concrete case studies demonstrating the performance of BIPV systems in Diverse Climates is necessary.

Comments 2:

• Section 5 is numbered twice, appearing under both "Findings" and "Conclusions."

Thank you for noticing, it was fixed.

• The conclusions respond to the topic addressed but are presented in a general manner. Many of them are already known. The concrete elements of the conducted study should be highlighted.

Response 2:

We appreciate your comment regarding the general nature of the conclusions. Based on your feedback, we have updated the conclusions to include more specific information drawn from the case studies analyzed in our review. However, it is important to note that many case studies in the reviewed literature also present general findings, which limits the extent of detailed, context-specific conclusions that can be derived.

Our intention was to provide a comprehensive synthesis of the field, highlighting both general trends and specific insights where available. We hope the revised conclusions better address your concerns while remaining true to the scope and nature of the reviewed research.