Optimizing Energy Efficiency and Sustainability in Winter Climate Control: Innovative Use of Variable Refrigerant Flow (VRF) Systems in University Buildings

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Abstract

Include the full meaning of the acronym HVAC in the abstract.

Add a graphical abstract to summarise the study visually.

Introduction:

Make the introduction more concise by moving the literature review into a separate section

Line 47: Reword “final energy” to improve clarity for the reader.

Literature review

In the newly created literature review section, include a table summarising the selected papers.

Clearly state how this work differs from previous studies in the literature review.

Methodology

Incorporate the case study section into the methodology. State what is being done before introducing the case study.

Describe the location and rating of the university building first when describing the case study

Move line 333 to 335 to the methodology section

Add a limitation of the study in the methodology section (e.g the study is limited to only one location).

Label both columns in table 1 and table 2 for clarity.

Results and discussion

Section 4 should be labelled results.

Add a detailed discussion section to describe the significance of the results to the wider industry

Figure 6: Ensure all axes are labelled appropriately.

Author Response

Dear reviewer 1

I send you the revised manuscript entitled “Optimizing Energy Efficiency and Sustainability in Winter Climate Control: Innovative Use of Variable Refrigerant Flow (VRF) Systems in University Buildings”

First and foremost, I sincerely appreciate the reviewer’s meticulous analysis and insightful comments aimed at enhancing the quality of the paper. In this regard, all spelling errors have been corrected, and the manuscript has been reviewed by a certified translator to ensure linguistic accuracy. Regarding the remaining comments and suggestions, I will address each point individually in the following responses.

 

1.- Include the full meaning of the acronym HVAC in the abstract.

Thank you for your valuable feedback. The full meaning of the acronym HVAC (Heating, Ventilation, and Air Conditioning) has been explicitly introduced in the abstract. Additionally, it has been included in the manuscript’s acronym list to enhance clarity and ensure consistency throughout the text.

2.- Add a graphical abstract to summarise the study visually.

A new figure has been added to the manuscript that serves as a graphical summary and provides a clear visual summary of the study. This addition improves reader understanding by offering a concise and intuitive representation of the research approach

3.- Introduction: Make the introduction more concise by moving the literature review into a separate section

Thank you for your helpful suggestion. In response, we have revised the manuscript by making the Introduction more concise, as you recommended. The literature review has been reviewed, which allows the Introduction to focus more directly on the context and objectives of the study.

 

We believe this change improves the clarity and flow of the manuscript while providing a more organized presentation of the relevant background information in a dedicated section.

Line 47: Reword “final energy” to improve clarity for the reader.

Thank you for your suggestion. The term "final energy" has been replaced with "power consumption," which we believe enhances clarity and ensures a more precise understanding for the reader.

4.- Literature review

In the newly created literature review section, include a table summarising the selected papers.

Thank you for your insightful suggestion. In response, we have included a table in the newly added literature review section that succinctly summarizes the selected papers. This addition aims to provide a clearer and more organized overview, enhancing the reader's understanding of the key literature relevant to the study.

References
Politics and legislation	Energy Performance certificate	Software modelled building	Experimental analysis	Monitoring and other
1,2,3,4,5,9, 40,41,42,43 and 44	6,7,8,9,10,11,12,13,14 and 15	17,19,21, 22, 23, 25, 27, 29, 30 and 32	16,18,20, 25, 28, 33 and 35	26, 34, 36, 37 and 38

 

Clearly state how this work differs from previous studies in the literature review.

Thank you for your helpful suggestion. In response, a paragraph has been added to the literature review that explicitly highlights how this study differs from previous research. Specifically, we emphasize that the data used in this paper represent actual consumption over an entire heating period for buildings B1 and B2, offering a more comprehensive and realistic analysis compared to previous studies.

4.- Methodology

Incorporate the case study section into the methodology. State what is being done before introducing the case study.

Thank you for your thoughtful suggestion. To further clarify the process of obtaining the SCOP of the VRF system, we have included a figure and a detailed explanatory paragraph in the abstract, which we believe provides the reader with a clear understanding of the steps involved. Additionally, we have reorganized the case study description to begin with the location and energy rating of the university building, establishing a clear context before delving into the specifics of the study. We trust these revisions will enhance the clarity and coherence of the manuscript.

Move line 333 to 335 to the methodology section

Thank You very much for your suggestion. we have moved the content from lines 333 to 335 to the methodology section.

Add a limitation of the study in the methodology section (e.g the study is limited to only one location).

Thank you for your comment. We have included a limitation of the study in the methodology section, specifically noting that the study is limited to a single location. To further enhance clarity, we have also introduced the equivalent European climate zone and the assumptions regarding the building's electrical consumption in the description of the buildings. We believe these revisions address improve the manuscript.

Label both columns in table 1 and table 2 for clarity.

Thank you for your suggestion. We have labelled both columns in Table 1 and Table 2 to enhance clarity and ensure the data is more easily understood by the reader.

5.- Results and discussion

Section 4 should be labelled results.

Thank you. We have updated the title of Section 4 from "Analysis and Results" to "Results and Discussion," as per your recommendation, to better align with the standard structure and improve the clarity of the section.

Add a detailed discussion section to describe the significance of the results to the wider industry

We have expanded the discussion section to provide a more detailed analysis of the significance of the results, highlighting their implications for the wider industry.

Figure 6: Ensure all axes are labelled appropriately.

Thank you for your review. We have corrected the legends in Figure 6, addressing the error in one of the axes. All axes are now properly labelled to ensure clarity and accuracy in the figure.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript addresses the performance of Variable Refrigerant Flow systems compared to traditional Low-Temperature and Condensing Boiler systems in a university building during winter. It highlights significant improvements in energy efficiency and reductions in greenhouse gas emissions, presenting a topic of high relevance for energy-efficient and sustainable building design. However, the manuscript has several critical methodological, analytical, and presentation-related shortcomings that undermine the validity and clarity of the findings. Key issues include limited scope, insufficient statistical analysis, overgeneralized claims, and unclear data presentation. While the study's aims and findings are valuable, addressing these significant concerns is necessary to ensure the robustness and reliability of the conclusions. I recommend major revisions to address these issues.

Major concerns

1. The study focuses on only two university buildings (B1 and B2), limiting the generalizability of the findings. While the buildings are similar in design and operation, the results do not consider variability in building typologies, climates, or user behavior. These factors significantly impact the performance of HVAC systems. Additionally, the study does not explore whether VRF systems perform similarly in other regions or under different conditions. Expanding the study to include a wider range of buildings or explicitly addressing the limitations of the narrow scope is essential. If expansion is not feasible, the authors should provide a detailed discussion of how these findings apply specifically to the studied context.

2. The methodology for calculating the Correction Factor used to adjust SCOP for Reference Climate Zone conditions lacks sufficient justification and validation. The presented equation appears overly simplified and does not account for factors such as wind patterns, solar radiation, or local microclimate effects. Furthermore, there is no reference to prior research validating this approach or experimental data supporting its use. The authors should provide a detailed explanation of how the CF was derived, validate it using empirical or simulated data, and perform sensitivity analysis to determine its reliability.

3. The absence of statistical analysis undermines the reliability of the reported differences in energy efficiency and greenhouse gas emissions between the VRF and LTCB systems. Without statistical tests, such as t-tests or ANOVA, it is impossible to determine whether the observed differences are statistically significant. Additionally, the manuscript does not present confidence intervals, standard errors, or measures of variability for the reported values. Incorporating statistical tests and reporting error margins are necessary to substantiate the conclusions and improve the rigor of the study.

4. The calculation and reporting of renewable energy contributions by the VRF system are unclear. The manuscript claims that 83% of the energy demand is met by renewable energy but does not provide sufficient detail on how this figure was derived. It is unclear whether the authors define renewable energy based on grid electricity, system efficiencies, or specific renewable energy sources integrated into the system. A clearer explanation, supported by calculations and references to relevant standards (e.g., Directive 2018/2001), is required to ensure transparency and reproducibility.

5. The abstract and conclusions are overly broad and include generalized claims that are not fully supported by the results. For example, phrases like "groundbreaking insights" and "remarkable energy savings" lack evidence in the data presented. Furthermore, the conclusions do not adequately address the limitations of the study, such as the narrow scope, reliance on modeled data, and absence of broader comparisons to other HVAC systems. These sections should be revised to focus on specific, evidence-based outcomes while clearly acknowledging the study's limitations and proposing directions for future research.

6. The presentation of results in tables and figures is dense and difficult to interpret. For instance, Tables 12 and 13 include extensive numerical data without emphasizing key trends or takeaways, and figures lack annotations to guide the reader. Additionally, figure captions are too brief to provide sufficient context. Simplifying tables by summarizing trends, adding explanatory annotations to figures, and revising captions to be more descriptive would significantly enhance the clarity and readability of the manuscript.

Comments on the Quality of English Language

The quality of the English language in the manuscript is generally adequate for conveying the core ideas, but improvements are needed to enhance clarity, precision, and academic professionalism. Specific issues include:

1. Terms such as "groundbreaking" and "remarkable" in the abstract and conclusions are overly promotional and not well-supported by the data presented. Replacing these with more precise, evidence-based language would improve academic tone.

2. Certain phrases and ideas are repeated throughout the manuscript, particularly in the introduction and discussion. Streamlining the text would improve readability and reduce redundancy.

3. Several sentences are unnecessarily long and complex, which makes them difficult to follow. Breaking these into shorter, clearer sentences would aid comprehension.

4. Some descriptions, such as the methodology and renewable energy calculations, lack sufficient detail and clarity. This issue is partly linguistic and partly related to content gaps.

5. There are occasional grammatical errors, awkward phrasing, and inconsistent terminology (e.g., switching between "heating systems" and "climate control systems") that need to be addressed.

6. These are too brief and do not clearly explain the data presented. Expanding captions to provide context and key takeaways would enhance understanding.

In summary, while the manuscript is generally understandable, it would benefit significantly from professional proofreading and editing to ensure clarity, conciseness, and consistency in academic language.

Author Response

Dear reviewer 2

I send you the revised manuscript entitled “Optimizing Energy Efficiency and Sustainability in Winter Climate Control: Innovative Use of Variable Refrigerant Flow (VRF) Systems in University Buildings”

First and foremost, I sincerely appreciate the reviewer’s meticulous analysis and insightful comments aimed at enhancing the quality of the paper. In this regard, all spelling errors have been corrected, and the manuscript has been reviewed by a certified translator to ensure linguistic accuracy. Regarding the remaining comments and suggestions, I will address each point individually in the following responses.

1. The study focuses on only two university buildings (B1 and B2), limiting the generalizability of the findings. While the buildings are similar in design and operation, the results do not consider variability in building typologies, climates, or user behavior. These factors significantly impact the performance of HVAC systems. Additionally, the study does not explore whether VRF systems perform similarly in other regions or under different conditions. Expanding the study to include a wider range of buildings or explicitly addressing the limitations of the narrow scope is essential. If expansion is not feasible, the authors should provide a detailed discussion of how these findings apply specifically to the studied context.

Thank you for your constructive feedback. We understand the concern regarding the generalizability of the study's findings, and we appreciate the opportunity to address this.

Regarding the points raised:

1. Both buildings, B1 and B2, are situated on the same university campus and are separated only by a pedestrian path. As a result, they are subject to the same climatic conditions, ensuring consistency in environmental factors. Moreover, these buildings house two faculties with similar numbers of students and comparable schedules and occupancies. Given these similarities, we believe it is reasonable to use one building as a reference for the other in determining the base electrical energy consumption, making the findings relevant within this specific context.

 

1. We acknowledge that this study is based on real consumption data from specific buildings in a particular climatic zone, which inherently limits the ability to extrapolate the results to other building typologies or regions. However, we believe that sharing these results, even within the scope, contributes valuable insights to the field.

That being said, we have now included a detailed discussion in the manuscript to explicitly address these limitations and clarify how the results apply specifically to the studied context. We also emphasize that while our study focuses on these two buildings, the findings may still offer useful guidance for similar buildings under comparable conditions.

We trust that these clarifications will adequately address your concerns, and we are grateful for the opportunity to improve the manuscript

2. The methodology for calculating the Correction Factor used to adjust SCOP for Reference Climate Zone conditions lacks sufficient justification and validation. The presented equation appears overly simplified and does not account for factors such as wind patterns, solar radiation, or local microclimate effects. Furthermore, there is no reference to prior research validating this approach or experimental data supporting its use. The authors should provide a detailed explanation of how the CF was derived, validate it using empirical or simulated data, and perform sensitivity analysis to determine its reliability.

Thank you for your feedback. We fully acknowledge the importance of providing a more robust justification and validation for the Correction Factor (CF) used to adjust the SCOP for Reference Climate Zone conditions.

We would like to clarify that the methodology applied for calculating the CF is based on established principles outlined in Directive (EU) 2018/2001 of the European Parliament and of the Council (11 December 2018). Specifically, Annex IV of the directive emphasizes the need for a comprehensive understanding of the physical and operational principles of heat pumps, including the relationship between the low temperatures of the heat sink, high temperatures of the heat source, and the efficiency of the system. It also highlights the importance of determining key performance metrics such as the Coefficient of Performance (COP) and Seasonal Performance Factor (SPF). These guidelines were referenced to ensure that our approach aligns with recognized standards within the industry.

Moreover, Annex V provides specific formulas for calculating greenhouse gas impact and efficiency, which includes the Carnot efficiency, defined by the equation: ”
where T_h is the temperature of the heat source and T_O is the reference temperature. This formula underpins the theoretical basis for our correction factor, ensuring that it aligns with standard scientific and regulatory methods.

While the equation may appear simplified, it reflects the broad application of these principles in practice, particularly given that the study’s focus is on real-world energy consumption data, which inherently contains complex variables that cannot always be accounted for in a single equation. However, we recognize the importance of validating this approach further. To this end, we have now included additional references to prior research that support the methodology, and we plan to carry out a sensitivity analysis in future work to assess the reliability and robustness of the CF under different conditions, including variables like wind patterns, solar radiation, and local microclimate effects.

We hope that these clarifications will address your concerns regarding the justification and validation of the CF. We greatly appreciate your input and believe that this added context will enhance the rigor of the study.

3. The absence of statistical analysis undermines the reliability of the reported differences in energy efficiency and greenhouse gas emissions between the VRF and LTCB systems. Without statistical tests, such as t-tests or ANOVA, it is impossible to determine whether the observed differences are statistically significant. Additionally, the manuscript does not present confidence intervals, standard errors, or measures of variability for the reported values. Incorporating statistical tests and reporting error margins are necessary to substantiate the conclusions and improve the rigor of the study.

Thank you for your comment. We understand the concern regarding the lack of statistical analysis and its potential impact. We appreciate the opportunity to clarify our approach.

The energy consumption data used in the study is sourced directly from certified electric and natural gas meters installed in buildings B1 and B2, both of which are regularly calibrated according to industry standards. These real-world data provide a solid foundation for our analysis, ensuring high accuracy and reliability. However, as the data is based on actual consumption for a single year, rather than a controlled experimental setup, we did not perform statistical tests such as t-tests or ANOVA. The nature of the study, focused on real-world measurements from specific buildings, limited the possibility of applying these statistical methods.

We acknowledge that applying statistical tests, such as t-tests or ANOVA, would be a useful approach if the study were extended over multiple years or included additional buildings to allow for greater variability and more robust analysis. This would certainly enable us to determine whether the observed differences are statistically significant. We also recognize the value of reporting confidence intervals, standard errors, and measures of variability, particularly to strengthen the reliability of our findings. This could be addressed in future work, should the study be expanded to include a more extensive dataset over a longer period of time.

For the current study, we believe that the real-world data used, alongside the established parameters for primary energy conversion and emissions as determined by the Government of Spain (which are based on the national energy structure), provides a strong foundation for the conclusions drawn. However, we are open to the idea of incorporating statistical analysis in subsequent iterations of the research, should the scope of the study be broadened next researches.

We hope this explanation clarifies the methodology employed. We greatly value your feedback and will certainly consider it for future work to ensure the continued rigor and robustness of future studies

4. The calculation and reporting of renewable energy contributions by the VRF system are unclear. The manuscript claims that 83% of the energy demand is met by renewable energy but does not provide sufficient detail on how this figure was derived. It is unclear whether the authors define renewable energy based on grid electricity, system efficiencies, or specific renewable energy sources integrated into the system. A clearer explanation, supported by calculations and references to relevant standards (e.g., Directive 2018/2001), is required to ensure transparency and reproducibility.

Thank you for your comment.

The figure of 83% of energy demand being met by renewable energy is based on the SCOP (Seasonal Coefficient of Performance) concept, which represents the ratio of heat energy supplied by the heat pump (HP) to the electrical energy consumed. This figure is derived from the assumption that when the SCOP exceeds the conversion coefficient of primary energy to electrical energy—specific to each country and determined by the national energy structure—the excess energy can be classified as renewable.

In our study, the coefficient of primary energy conversion was defined using the energy structure of Spain, as determined by national guidelines. This conversion factor reflects the energy mix of the grid, which includes renewable sources such as wind, solar, and hydroelectric power. According to the Directive (EU) 2023/2413, which amends Directive (EU) 2018/2001, any excess energy from the system, when the SCOP surpasses the primary energy conversion factor, is considered renewable. This aligns with the legislative framework that governs the classification of renewable energy within the European Union.

We acknowledge that a more detailed explanation of the methodology behind this calculation is necessary for full transparency. Therefore, we have revised the manuscript to explicitly outline how this 83% figure was derived, providing clear references to the relevant standards, including Directive 2018/2001 and Directive 2023/2413, to ensure full reproducibility and clarity.

We greatly appreciate your input and are committed to refining the manuscript to better communicate our findings.

5. The abstract and conclusions are overly broad and include generalized claims that are not fully supported by the results. For example, phrases like "groundbreaking insights" and "remarkable energy savings" lack evidence in the data presented. Furthermore, the conclusions do not adequately address the limitations of the study, such as the narrow scope, reliance on modeled data, and absence of broader comparisons to other HVAC systems. These sections should be revised to focus on specific, evidence-based outcomes while clearly acknowledging the study's limitations and proposing directions for future research.

We have carefully reviewed the manuscript and made several revisions to address the points you raised.

Regarding the abstract and conclusions, we acknowledge your concern about the overly broad claims and have revised these sections to more accurately reflect the specific outcomes supported by the data. We have removed terms like "groundbreaking " and "remarkable," replacing them with more precise,  supported by our findings.

We have taken steps to better address the study's limitations. We now explicitly highlight the scope of the analysis, the reliance on modeled data, and the absence of direct comparisons to other HVAC systems. These limitations are discussed in detail, and we have proposed directions for future research to expand upon the current work and provide a more comprehensive understanding of the system's performance in broader contexts.

Once again, we greatly appreciate your constructive feedback, which has helped us improve the manuscript and ensure that the conclusions are both specific and well-supported by the data.

6. The presentation of results in tables and figures is dense and difficult to interpret. For instance, Tables 12 and 13 include extensive numerical data without emphasizing key trends or takeaways, and figures lack annotations to guide the reader. Additionally, figure captions are too brief to provide sufficient context. Simplifying tables by summarizing trends, adding explanatory annotations to figures, and revising captions to be more descriptive would significantly enhance the clarity and readability of the manuscript.

We have carefully reviewed your comments and made the necessary revisions to improve the presentation of the results.

 

Regarding Tables 12 and 13, we have provided a detailed explanation of what each column represents and clarified the methodology used to obtain the values. We believe that these additional details will help clarify the results and provide the necessary context for better interpretation.

 

Moreover, we have simplified the tables to highlight key trends and removed any unnecessary complexity, making the data more accessible to the reader. We have also enhanced the figure captions, making them more descriptive and providing adequate context to ensure clarity. In addition, we have included annotations in the figures to guide the reader through the main takeaways, facilitating a more intuitive understanding of the results.

 

Comments on the Quality of English Language

The quality of the English language in the manuscript is generally adequate for conveying the core ideas, but improvements are needed to enhance clarity, precision, and academic professionalism. Specific issues include:

1. Terms such as "groundbreaking" and "remarkable" in the abstract and conclusions are overly promotional and not well-supported by the data presented. Replacing these with more precise, evidence-based language would improve academic tone.
2. Certain phrases and ideas are repeated throughout the manuscript, particularly in the introduction and discussion. Streamlining the text would improve readability and reduce redundancy.
3. Several sentences are unnecessarily long and complex, which makes them difficult to follow. Breaking these into shorter, clearer sentences would aid comprehension.
4. Some descriptions, such as the methodology and renewable energy calculations, lack sufficient detail and clarity. This issue is partly linguistic and partly related to content gaps.
5. There are occasional grammatical errors, awkward phrasing, and inconsistent terminology (e.g., switching between "heating systems" and "climate control systems") that need to be addressed.
6. These are too brief and do not clearly explain the data presented. Expanding captions to provide context and key takeaways would enhance understanding.

In summary, while the manuscript is generally understandable, it would benefit significantly from professional proofreading and editing to ensure clarity, conciseness, and consistency in academic language.

Thank you very much for your detailed and constructive comments. We have carefully revisited the manuscript, taking into account each of your suggestions, and we believe these revisions have significantly improved the quality of the manuscript.

 

We have replaced terms such as "groundbreaking" and "remarkable" in the abstract and conclusions with more precise, evidence-based language that better reflects the data presented. This adjustment has enhanced the academic tone of the manuscript. Additionally, we have streamlined the text by eliminating repetitive phrases and ideas, particularly in the introduction and discussion sections, making the manuscript more concise and improving overall readability.

Several overly long and complex sentences have been revised into shorter, clearer ones to aid comprehension and improve the flow of the text. We also added more detailed explanations of the methodology and renewable energy calculations, addressing both the linguistic and content gaps to ensure greater clarity and transparency.

 

Furthermore, we have corrected grammatical errors, rephrased awkward sentences, and ensured consistent terminology throughout the manuscript, particularly in reference to "heating systems" and "climate control systems." In response to your comment regarding figure captions, we have expanded them to provide sufficient context and highlight key takeaways, thus enhancing the clarity and understanding of the data presented.

 

We believe that these revisions have helped significantly improve the manuscript’s clarity, conciseness, and academic professionalism. We appreciate your valuable feedback, which has played an essential role in refining the manuscript.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Here are some suggestions for revision:

1. At the end of the Introduction, it should be pointed out that the shortcomingsof the existing research, and the innovation of this paper should be further explained.
2. What is the role of the meteorological data of 2018 shown in table 4? The year 2018 does not seem to be mentioned in the previous text. In addition, the data of 2018 and 2022 appear several times in the paper. Is it for comparison? It’s suggested to clarify.
3. The numbering of the tables is incorrect. Table 3 appears after table 5 in the text.
4. There is no data in figures 3 and 4. How can the distribution of electricity consumption be demonstrated?

Author Response

Dear reviewer 3

I send you the revised manuscript entitled “Optimizing Energy Efficiency and Sustainability in Winter Climate Control: Innovative Use of Variable Refrigerant Flow (VRF) Systems in University Buildings”

First and foremost, I sincerely appreciate the reviewer’s meticulous analysis and insightful comments aimed at enhancing the quality of the paper. In this regard, all spelling errors have been corrected, and the manuscript has been reviewed by a certified translator to ensure linguistic accuracy. Regarding the remaining comments and suggestions, I will address each point individually in the following responses.

 

1.- At the end of the Introduction, it should be pointed out that the short comings of the existing research, and the innovation of this paper should be further explained.

 

Thank you for your thoughtful suggestion. We have revised the conclusion of the Introduction to more clearly highlight the shortcomings of existing research and emphasize the innovation of our study.

 

We have explicitly stated that previous research often relies on simulation models and software to estimate energy performance, which may not fully represent real-world conditions. Our methodology, in contrast, uses actual energy consumption data from two cloned buildings, B1 and B2, to calculate the SCOP of the VRF system in building B2 during the winter period. This approach does not involve any simulation models, providing a more accurate and practical insight into the system's performance.

 

2.- What is the role of the meteorological data of 2018 shown in table 4? The year 2018 does not seem to be mentioned in the previous text. In addition, the data of 2018 and 2022 appear several times in the paper. Is it for comparison? It’s suggested to clarify.

 

Thank you for your comment and for bringing up the role of the meteorological data in the manuscript.

 

To clarify, the meteorological data from 2018, as shown in Table 4, is specifically used to estimate the electrical consumption of the heat pumps (HP) that heat a small area of building B1. To obtain the base consumption of building B1, it is necessary to subtract the consumption of the pumping systems of the LTCB system, the difference in lighting systems between buildings B1 and B2, and the consumption associated with these heat pumps. The HP consumption is determined using the outside temperatures from 2018, as this is the only available set of temperature data we have for that year. While this data does not directly compare the buildings or the years, it is essential for accurately calculating the energy use of the specific area heated by the heat pumps.

 

Additionally, we have revised the manuscript to further clarify the role of the meteorological data and its application in the analysis. The data from 2018 and 2022 are indeed used for comparison in certain sections, and we have made this distinction clearer in the text. The 2018 data is used primarily for estimating energy consumption in building B1, while the 2022 data is used in comparisons of the performance of different systems.

 

We hope this explanation resolves any confusion and better clarifies the use of meteorological data in our methodology.

 

3.-  The numbering of the tables is incorrect. Table 3 appears after table 5 in the text.

 

Thank you for pointing out the issue with the table numbering. We have reviewed the manuscript and corrected the numbering of the tables accordingly. Table 3 now appears in the correct position before Table 5, ensuring consistency and clarity in the presentation of the content.

 

We appreciate your attention to detail.

 

4.- There is no data in figures 3 and 4.

 

Thank you for your comment regarding the missing data in Figures 3 and 4. We apologize for this oversight.

 

To clarify, the values that represent the distribution of electrical consumption and power for building B1, shown in Figure 3, are derived from the base electrical energy consumption of both buildings B1 and B2. This calculation is based on energy audits of both buildings, which include the installed power of the equipment, operating hours, and simultaneity coefficients.

 

By applying these parameters to the data presented in Tables 6, 7, and 8, we are able to determine the consumptions specific to building B1, which are not part of its base consumption.

 

Similarly, Figure 4 represents the distribution of electrical consumption and power for both buildings B1 and B2, with the corresponding results summarized in Table 10.

 

We ensure that the missing data in Figures 3 and 4 is properly included and that the figures are presented clearly in the revised manuscript. This will allow the reader to fully understand the distribution and comparison of electrical consumption and power for both buildings.

 

Thank you again for your valuable feedback.

 

5.- How can the distribution of electricity consumption be demonstrated?

The distribution of electricity consumption in building B1 is determined based on the specific electrical energy-consuming equipment that is not present in building B2. This is done by analyzing the installed power of the equipment, its operating hours, and the simultaneity of use.

We perform this calculation by first conducting an energy audit of both buildings, which provides detailed data on the equipment installed in each building, including power ratings and usage patterns. For building B1, we isolate the consumption that is specific to the equipment not present in building B2, thereby differentiating the consumption that contributes to the base energy usage from that which is uniquely attributed to building B1.

The distribution is then calculated by applying the parameters of installed power, operating hours, and simultaneity coefficients, as presented in Tables 6, 7, and 8. These factors allow us to determine the total electrical consumption attributable to the unique equipment in building B1.

We hope this explanation clarifies how the distribution of electricity consumption is demonstrated, and we appreciate your feedback in helping us ensure the methodology is clearly communicated.

 

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The undertaken work is interesting and supports the use of VRF systems for the heating of the buildings, as an alternative to condensing boilers, in the context of new decarbonization requirements for buildings.

However, there are several inconsistencies, which are required to be addressed by the authors:

Lines 286-287. It is not clear to what negligible heat transmission losses to the exterior you refer, from the indoor (conditioned) air inside the building to the outdoor air (which is related with the heat balance of the building envelope) or the losses of the indoor part of the HP equipment. If is the first case, it is unlikely to be negligible (would mean that you have passive building compliance). Please be more specific in this paragraph!

 

Lines 347-348. The alternative methodology for calculating the heat demand in buildings is erroneous. Thus, in Figure 5, in the proposed content, the calculation of the heat demand is performed starting from the final energy, to which the boiler losses are considered. However, from the building's heat demand (usually obtained through an energy balance) to energy consumption, there are losses at the emission level (considering the heating body types), at the distribution system level and at the generator level, along with the auxiliary electrical energy consumption.

On the one hand, through the proposed approach, you only consider the losses at the generator level, respectively separately the auxiliary electrical energy consumption. On the other hand, the considered generator losses are not introduced correctly in the model. Through the proposed formula (Specific Heating Demand 2022 (B1) in Figure 5), it results that the heat demand is higher than the final energy consumption (heat demand = final energy / measured boiler efficiency), which contradicts current practice and generally accepted models, including the European standards.

This error, in this point of the model, will influence your SCOP results (the SCOP will decrease after the correction of the Heating Demand calculation). However, I noticed that in Table 11 the Heating Demand is calculated correctly (heating demand = final energy * measured boiler efficiency). Please verify the SCOP calculations and the other subsequent calculations.

Also, the general presentation of the paper should be more synthetic and concise (currently being rather technical, than scientific).

Author Response

Dear Reviewer 4

I send you the revised manuscript entitled “Optimizing Energy Efficiency and Sustainability in Winter Climate Control: Innovative Use of Variable Refrigerant Flow (VRF) Systems in University Buildings”

First and foremost, I sincerely appreciate the reviewer’s meticulous analysis and insightful comments aimed at enhancing the quality of the paper. In this regard, all spelling errors have been corrected, and the manuscript has been reviewed by a certified translator to ensure linguistic accuracy. Regarding the remaining comments and suggestions, I will address each point individually in the following responses.

1.- The undertaken work is interesting and supports the use of VRF systems for the heating of the buildings, as an alternative to condensing boilers, in the context of new decarbonization requirements for buildings.

However, there are several inconsistencies, which are required to be addressed by the authors:

Thank you for your valuable feedback and the detailed observations you have provided. We have carefully reviewed the manuscript and made the necessary revisions to address the points you raised.

2.- Lines 286-287. It is not clear to what negligible heat transmission losses to the exterior you refer, from the indoor (conditioned) air inside the building to the outdoor air (which is related with the heat balance of the building envelope) or the losses of the indoor part of the HP equipment. If is the first case, it is unlikely to be negligible (would mean that you have passive building compliance). Please be more specific in this paragraph!

Regarding lines 286-287, we have clarified the reference to "negligible heat transmission losses." It was indeed referring to the losses from the indoor (conditioned) air to the outdoor environment, related to the heat balance of the building envelope. We have now specified this in the text to eliminate any ambiguity. We agree that such losses may not be negligible in most cases, and we have adjusted the language accordingly to reflect a more accurate and nuanced explanation.

 Lines 347-348. The alternative methodology for calculating the heat demand in buildings is erroneous. Thus, in Figure 5, in the proposed content, the calculation of the heat demand is performed starting from the final energy, to which the boiler losses are considered. However, from the building's heat demand (usually obtained through an energy balance) to energy consumption, there are losses at the emission level (considering the heating body types), at the distribution system level and at the generator level, along with the auxiliary electrical energy consumption.

On the one hand, through the proposed approach, you only consider the losses at the generator level, respectively separately the auxiliary electrical energy consumption. On the other hand, the considered generator losses are not introduced correctly in the model. Through the proposed formula (Specific Heating Demand 2022 (B1) in Figure 5), it results that the heat demand is higher than the final energy consumption (heat demand = final energy / measured boiler efficiency), which contradicts current practice and generally accepted models, including the European standards.

This error, in this point of the model, will influence your SCOP results (the SCOP will decrease after the correction of the Heating Demand calculation). However, I noticed that in Table 11 the Heating Demand is calculated correctly (heating demand = final energy * measured boiler efficiency). Please verify the SCOP calculations and the other subsequent calculations.

For lines 347-348, we have reviewed the methodology used for calculating the heat demand and identified the inconsistencies you pointed out. We have corrected the errors related to the calculation of heat demand in Figure 5. Specifically, we have addressed the issue of considering only the generator losses and auxiliary electrical energy consumption, without accounting for the losses at the emission level and distribution system level. We have revised the calculation of the heating demand to ensure consistency with standard practices (heating demand = final energy * measured boiler efficiency), and this correction has been applied to the SCOP calculations. We have also double-checked the subsequent calculations to ensure the accuracy of the results, including the SCOP, which has been updated accordingly.

Also, the general presentation of the paper should be more synthetic and concise (currently being rather technical, than scientific).

In response to your suggestion regarding the overall presentation of the paper, we have worked to make the manuscript more concise and focused, removing unnecessary technical details and improving clarity. We believe these revisions enhance the scientific rigor and readability of the paper.

Additionally, we have modified Figure 5 to improve its clarity, ensuring that the updated calculations and corrections are clearly represented. All errors and points of confusion have been addressed, and we hope that the changes made meet the manuscript’s quality to be published.

We greatly appreciate your insightful comments, which have contributed significantly to the improvement of the manuscript.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

No more comments.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have made substantial and satisfactory revisions following the initial peer review, addressing all major concerns and enhancing the manuscript’s overall quality. The study presents a well-structured, methodologically sound, and practically relevant analysis of Variable Refrigerant Flow systems' energy efficiency and sustainability in university buildings. The findings contribute significant insights into energy optimization strategies in building climate control systems, supporting broader sustainability and climate change mitigation objectives.

The revised manuscript is now clear, comprehensive, and well-positioned for publication.

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have responded satisfactorily to all my observations. I have no other observations.