A Review on Harnessing Renewable Energy Synergies for Achieving Urban Net-Zero Energy Buildings: Technologies, Performance Evaluation, Policies, Challenges, and Future Direction

Round 1

Reviewer 1 Report

A review on harnessing renewable energy synergies to achieve net-zero energy urban buildings: Technologies, performance assessment, policies, challenges and future direction.
First of all, I would like to thank the editor for having me to review this paper.
The text is a review on renewable energies in net-zero energy buildings. I find the article interesting, well structured, but I have some comments for the authors:
Special care should be taken when using the terms energy demand and energy consumption. E.g. in line 186. A microturbine system does not reduce energy demand, but provides on-site renewable energy, and reduces the consumption of energy provided by the system. But the energy generated by the turbine is consumed, so it is not possible to speak of a reduction in demand. This appears in a few other places (the author himself explains it implicitly around line 365). This error appears again in line 456.

The authors talk about amortization periods from an economic point of view at several points. In my opinion this is correct, but it should always be supplemented from an amortization in CO2 reduction, provided the data is available. Amortization periods are currently very complicated to calculate with any accuracy, firstly because of the changing energy prices, and secondly because of the increasing tax rate in the form of CO2 emission taxes. After all, the ultimate goal of reducing energy demand and consumption is to reduce environmental impacts, specifically greenhouse gas emissions. While it is true that the economic return seems to be a very important way to promote the energy transition, it is not the only one.

As a comment, the Passivhaus standard is not a standard of sustainability or environmental certification, but, unlike VERDE, LEED, etc.. only limits the demand for buildings.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Amid growing concerns about rising energy prices, energy independence, and the impact of climate change, statistics show buildings to be the primary energy consumer. This fact underscores the importance of targeting building energy use as a key to decreasing the nation's energy consumption. The building sector can significantly reduce energy use by incorporating energy-efficient strategies into the design, construction, and operation of new buildings and undertaking retrofits to improve the efficiency of existing buildings. It can further reduce dependence on fossil fuel derived energy by increasing use of on-site and off-site renewable energy (RE) sources. The concept of a Net Zero Energy Building (NZEB), one which produces as much energy as it uses over the course of a year, recently has been evolving from research to reality.  As such, this study aims to explore the role of RE synergies in the context of urban NZEBs including discussions on definition and development of NZEBs, RE-synergies for achieving NZEBs, sustainable trends and cluster of NZEBs, climate change impacts on NZEBs, its performance evaluation, policy and regulatory frameworks, and challenges and possible solutions related to NZEBs. The results show that the assessment of climate change effects and NZEB practices should involve evaluating building energy equilibrium, occupant comfort, and interactions with the energy grid. 

I think this study is a progress by deepening and expanding studies focused on technologies, performance evaluation, policies, challenges, and future direction of Net Zero Energy Buildings. I have one question for the study: it's better to add country or regional area analysis in '8. Challenges and possible solutions'. As you mentioned 'Every country or regional area may need to adapt the NZEB definition to its own specific conditions', it is interesting to compare challenges and possible solutions for different countries or regional areas, maybe in a table.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

I have reviewed your paper and I commend your comprehensive approach. However, I have a few suggestions that could enhance the clarity and depth of your work.

1) Your paper covers a broad range of topics related to NZEBs. While this is commendable, it might be beneficial to narrow the scope or highlight a specific aspect of NZEBs for a more in-depth analysis. This would not only make your paper more focused but also allow for a more detailed discussion. Furthermore, it would be beneficial to emphasize the novelty of your paper’s contribution to the existing body of research. This will help readers understand the unique value of your work.

2) Since your paper is a literature review, it would be helpful to explicitly state the methods used for searching and selecting relevant studies. This will provide readers with a clear understanding of how you arrived at your conclusions and will also allow others to replicate your study if they wish.

3) The discussion section can be strengthened by providing a deeper analysis of the challenges and solutions presented. I encourage you to go beyond summarizing references and delve into critical evaluation and insights. Consider incorporating opposing viewpoints or discussing the limitations of existing research. This will add depth to your analysis and make your paper more robust.

4) The conclusion could be strengthened by briefly restating the paper’s main findings and emphasizing their significance. This will help readers remember the key points of your paper. Additionally, concluding with clear future research directions or recommendations for policymakers and practitioners will give your paper a strong ending and potentially inspire future work in this area.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

The authors presented the work titled "A review on harnessing renewable energy synergies for achieving urban net-zero energy buildings: Technologies, performance evaluation, policies, challenges, and future direction" is a good effort. However, there are some suggestions which needs to be addressed before final publication.

1- Please add some latest research in the literature review.

2- Add these works also for comparison.

a- BUKHARI, Syed Muhammad Salman, et al. Federated transfer learning with orchard-optimized Conv-SGRU: A novel approach to secure and accurate photovoltaic power forecasting. Renewable Energy Focus, 2024, 48: 100520.

b- KHAN, Muhammad Kamran, et al. Enhancing efficient solar energy harvesting: A process-in-loop investigation of MPPT control with a novel stochastic algorithm. Energy Conversion and Management: X, 2024, 21: 100509.

c- ABOU HOURAN, Mohamad, et al. COA-CNN-LSTM: Coati optimization algorithm-based hybrid deep learning model for PV/wind power forecasting in smart grid applications. Applied Energy, 2023, 349: 121638.

3- Please check the proper template of MDPI.

Author Response

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Author Response File: Author Response.pdf

Reviewer 5 Report

This study explores net-zero energy buildings in urban areas, aiming to balance energy consumption and production, mainly from renewable sources. It reviews the role of renewable energy in NZEBs, discussing their definition, development, sustainable trends, and challenges. 

The manuscript adds to the body of knowledge. However, the following concerns to be addressed to improve the clarity of the presentations:   

• 1-The manuscript uses too many acronyms, and some are defined multiple times, which can be confusing for readers. It's better to avoid excessive use of acronyms for clarity. 

• 2- The authors should compare their work with existing review articles to highlight the unique contributions of their study. This comparison can be presented in a table format, showing what aspects are covered in the current survey that are not addressed in previous works. 

• 3- Tables in the manuscript should be concise, providing only essential information. Excessive descriptions, like in Table 3, can be trimmed to focus on key points, with additional details provided in the text. The authors can refer to some of the published survey articles to improve the presentation of the work, for example, see the following (https://doi.org/10.3390/electronics10091043) . 

• 4- The section on Challenges and Solutions needs more in-depth discussions. It would be beneficial to discuss various perspectives on addressing these challenges and to provide a comparison table or taxonomy to offer a comprehensive review. 

• 5- Including charts and figures throughout the manuscript can help illustrate key points and make the argument more accessible to readers. Additional visual aids can enhance understanding of the topic.

1-The manuscript uses too many acronyms, and some are defined multiple times, which can be confusing for readers. It's better to avoid excessive use of acronyms for clarity.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 5 Report

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