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Peer-Review Record

Implementing Cool Roof and Bio-PCM in Portable Cabins to Create Low-Energy Buildings Suitable for Different Climates

Sustainability 2023, 15(20), 14700; https://doi.org/10.3390/su152014700

by Ahmad Sedaghat^1,*

, Arash Mahdizadeh², Ramadas Narayanan³

, Hayder Salem¹

, Wisam K. Hussam¹, Mohamad Iyad Al-Khiami⁴

, Mahdi Ashtian Malayer⁵, Sayed M. Soleimani⁶, Mohammad Sabati^7,8, Mohammad Rasul³ and Mohammad Masud Kamal Khan³

Reviewer 1: Anonymous

Reviewer 2: Anonymous

Reviewer 3:

Ratchagaraja Dhairiyasamy

Reviewer 4:

Rahul Kumar

Sustainability 2023, 15(20), 14700; https://doi.org/10.3390/su152014700

Submission received: 12 September 2023 / Revised: 2 October 2023 / Accepted: 9 October 2023 / Published: 10 October 2023

(This article belongs to the Special Issue Advances in Thermal Performance and Energy Efficiency of Buildings in Various Regions)

Round 1

Reviewer 1 Report

1. The "Importance and Outline of the study" can be removed. It is suggested to write the significance of the study separately and include the outline of the study in the methodology;

2. Please avoid to too many "In this study..." "In this work..", "In our previous work...". Please cite past works in the same as the related literature;

3. always choose the third-person stance when writing scientific articles ;

4. Introduce at the start of the paper the chosen locations of the study, including the reasons for the selection;

5. Use the proper citation of references and registered trademarks.

1. It is suggested to check the grammar and composition of the entire manuscript thoroughly;

2. The paper was written more of a project report than a scientific article

Author Response

Reviewer 1

Comments and Suggestions for Authors

The "Importance and Outline of the study" can be removed. It is suggested to write the significance of the study separately and include the outline of the study in the methodology;

Response: Thank you for this comment. We removed the subtitle "Importance and Outline of the study" however, we cannot include outline of the study in the methodology. This is required in the Introduction section.

Please avoid to too many "In this study..." "In this work..", "In our previous work...". Please cite past works in the same as the related literature;

Response: Thank you for this comment. We removed these in the manuscript.

always choose the third-person stance when writing scientific articles ;

Response: Thank you for this comment. We used third person in the manuscript and removed “we’ first person words.

Introduce at the start of the paper the chosen locations of the study, including the reasons for the selection;

Response: Thank you for this comment. We modified the last paragraph in the Introduction to address this comment as follows:

This paper models two cabins with 12 Bio-PCM in TRNSYS for the desert climate of Kuwait and six different climates in Australia, including Equatorial (Darwin), Tropical (Normanton), Subtropical (Rockhampton), Desert (Meekatharra), Grassland (Alice Springs), and Temperate (Sydney). These locations provide major climates in Kuwait and Australia and the impact of the climate on the studied energy savings can be analysed.

Use the proper citation of references and registered trademarks.

Response: Thank you for this comment. We corrected all references according to MDPI style.

Comments on the Quality of English Language

It is suggested to check the grammar and composition of the entire manuscript thoroughly;

Response: The English language was checked by a native English-speaking colleague.

The paper was written more of a project report than a scientific article

Response: We did our best to change style. We reduced diving sections by subsections to avoid interpretation of the paper as a report.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is very interesting but several changes are needed to left it ready for publication. My indications are:

1. The novelty must be show at the abstract section;

2. The criterion of the city selection should be explained;

3. A flowchart of the methodology applied should be explain;

4. The validation section is very poor, the authors must be showed the comparison adding figures and table. Also, they need to explain how the comparison was conducted;

Author Response

Reviewer 2

Comments and Suggestions for Authors

The manuscript is very interesting but several changes are needed to left it ready for publication. My indications are:

Response: Many thanks for expressing your positive views.

The novelty must be show at the abstract section;

Response: Thank you for this comment. We used the word novel and new few times to emphasis what is different in this work. To emphasis this point we added in the Abstract:

To the best of our knowledge, no existing studies have been conducted in the literature regarding the energy-saving aspects of portable cabins made from sandwich panels.

The criterion of the city selection should be explained;

Response: Thank you for this comment. We modified the last paragraph in Introduction to address this comment as follows:

A flowchart of the methodology applied should be explain;

Response: Thank you for this comment. The following changes applied:

The flowchart in Figure 3a illustrates the overall methodology employed in the study. The left cabin serves as the base case, with continuous measurements of indoor air and AC power recorded and stored in an internet cloud. The right cabin is designated as the testing cabin, where two cool roofs are implemented, and similar measurements are conducted. Additionally, computational simulations are utilized to assess the effects of Bio-PCMs on the right cabin.

The validation section is very poor, the authors must be showed the comparison adding figures and table. Also, they need to explain how the comparison was conducted;

Response: Thank you for this comment. The following changes applied:

To analyze energy saving of various Bio-PCM in different climates for the portable cabins, the TRNSYS models are developed here. For evaluating the accuracy of these models, TRNSYS simulation results must be validated against experimental data. TRNSYS uses the available weather data (the year 2020) for the site at Kuwait International Airport. The measurements of the energy consumption of the AC systems in the portable cabins were discontinuously conducted at the Australian University of Kuwait in October 2022. As shown in Figure 6, measurements were carried out during 4-15 October 2022 and also during 23-31 October 2022. The AC cooling power measurement with an average of 314.6W was 4.8% higher than the simulation results with a value of 299.5W (see Figure 6a). In late October, as shown in Figure 6b, the AC cooling measurement with an average of 163W was -8.2% lower than the simulation prediction of 176W. Considering the cumulative readings, a total of 475.7W was simulated from the two measured intervals, while a total of 477.4W was measured. This gives merely a 0.37% cumulative error. Hence, the overall accuracy of TRNSYS simulation is exceptionally well for the cooling power measured here.

(a) Power consumption during October 4-15, 2022.

(b) Power consumption during October 23-31, 2022

Figure 6. Comparison between AC power measurements and TRNSYS simulation in October 2022 for the portable cabin in Kuwait.

Reviewer 3 Report

This manuscript makes a valuable contribution in experimentally and computationally assessing the energy savings potential of cool roofs and PCMs in portable cabins across different climate zones. The work appears original, the methods are sound, and the findings are appropriately interpreted. The paper is well-written and structured. I recommend publication after any minor revisions suggested in my comments are addressed. The work provides useful insights to inform low-energy building design in diverse climates.

Ø Include more background on previous studies applying PCMs specifically in portable cabins/prefab structures rather than just buildings in general.

Ø Summarize prior work investigating building energy performance across different climate zones.

Ø Add more context on using TRNSYS for modeling PCMs and its relation to other simulation tools.

Ø Describe the calibration/accuracy of the sensors used in the cabins.

Ø Explain how factors like occupancy, equipment loads, and ventilation rates were controlled between the cabins.

Ø Specify insulation levels in the cabin walls/roof construction.

Ø Perform uncertainty analysis to quantify error bars on the simulation results.

Ø Provide statistical testing between energy savings for different PCM types and configurations.

Ø Include more quantitative indicators of PCM stability issues observed.

Ø Compare simulation predictions to any available real-world portable cabin/PCM data.

Ø Discuss broader implications - how well would the results extrapolate to full-sized buildings?

Ø Highlight the optimal PCM type and location for different climate zones.

Ø Summarize key practical takeaways for engineers/designers wanting to implement PCMs.

Ø Discuss future work such as long-term PCM performance studies and techno-economic analysis.

Ø Comment on the potential for novel PCMs explicitly engineered for portable cabins.

Author Response

Reviewer 3

Comments and Suggestions for Authors

Response: Many thanks for expressing your positive views.

Ø Include more background on previous studies applying PCMs specifically in portable cabins/prefab structures rather than just buildings in general.

Response: Thank you for this comment. As added to the Abstract: To the best of our knowledge, no existing studies have been conducted in the literature regarding the energy-saving aspects of portable cabins made from sandwich panels.

Ø Summarize prior work investigating building energy performance across different climate zones.

Response: Thank you for this comment. The manuscript has a long Introduction (3 Pages and 61 references). Since we could not find any articles investigating the same (portable cabins in different climate), we would trust that this manuscript will add an interesting contribution for future works of this type.

Ø Add more context on using TRNSYS for modeling PCMs and its relation to other simulation tools.

Response: Thank you for this comment. We have quizzed the manuscript and cut much information from our KFAS First and Second reports yet the submitted paper is 28 pages and lengthy to add more. In our previous and most recent publication below, we address some of these points requested.

Sedaghat, A., Salem, H., Hussam, W.K., Mahdizadeh, A., Al-Khiami, M.I., Malayer, M.A., Soleimani, S.M., Sabati, M., Narayanan, R., Rasul, M. and Khan, M.M.K., 2023. Exploring energy-efficient building solutions in hot regions: A study on bio-phase change materials and cool roof coatings. Journal of Building Engineering, 76, p.107258.

Ø Describe the calibration/accuracy of the sensors used in the cabins.

Response: Thank you for this comment. The accuracy of devices are enlisted in Tables 1 and 2. We also extended validation part by:

(a) Power consumption during October 4-15, 2022.

(b) Power consumption during October 23-31, 2022

Figure 6. Comparison between AC power measurements and TRNSYS simulation in October 2022 for the portable cabin in Kuwait.

Ø Explain how factors like occupancy, equipment loads, and ventilation rates were controlled between the cabins.

Response: Thank you for this comment. Each cabin is equipped with a split AC unit with preset temperature of 22 C. No occupancy, no equipment, and no air ventilation was used to contribute to the loads in the Portable Cabins. In the text we modified as follows:

An 18000BTU split unit is installed for air-conditioning in each cabin. Both split units were preset at 22°C for indoor temperature while the air conditioning system was on. No occupancy, equipment or air ventilation rates were applied throughout the tests.

Ø Specify insulation levels in the cabin walls/roof construction.

Response: Thank you for this comment. Here details (within text):

Two identical portable cabins are manufactured from sandwich panels with measuring 2m × 2m ×3m as shown in Fig. 3. The internal dimensions are 2m × 2m wall to wall and 2.8m ground to the false ceiling. The frame structure of the cabins is made from 120mm I-beams, 40mm × 40mm square hollow sections at the bottom, and purlins at the roof from 50mm × 50mm × 2mm (thickness) hollow sections to support the frame. Columns are made from 50mm × 50mm × 2mm (thickness) hollow sections with angles, and Leg height is 300mm from the ground. PVC skirting 100mm height and 3mm thickness is used. The walls and the roof are made from 75mm Polyurethane sandwich panel consisting of 74mm insulation material, and 1mm galvanized steel sheets. The slope roof is covered with a gypsum ceiling to provide an internal height of 2.8m everywhere. An 18mm thick plywood finished with a Vinyl sheet is used for flooring. One aluminium external door and one aluminium window are used. The door is a single leaf of size 2m × 1m with a heavy-duty shutter. The window is a double leaf of size 1m ×1m with weatherproofed glass located 60 cm below the roof and in the middle of the wall.

Also in simulation part:

The thermal properties of wall materials, roof, and ground floor of the portable cabins made from 75mm sandwich panel are listed in Table 3. Plywood is a massless layer with the thermal resistance of 0.04335 hm²K/kJ [61]. The 18mm plywood and an airgap were used for the floor in TRNSYS simulation. For the sandwich roof, 10mm gypsum board [62], airgap, and 75mm sandwich panel are considered. For the walls here just a 75mm sandwich panel is used and later, a Bio-PCM layer was added to the inside face of the walls, the outside face of the walls, and in the middle of the walls (see Table 3).

Ø Perform uncertainty analysis to quantify error bars on the simulation results.

Response: Thank you for this comment. There are many results for experimental work (figures 8-9) and simulations results (figures 10-17). We are unclear what specific graph the reviewer interested in to add error bars. However, please refer to the validation of experimental results versus simulation of power.

Ø Provide statistical testing between energy savings for different PCM types and configurations.

Response: Thank you for this comment. This is out of the scope of the present study.

Ø Include more quantitative indicators of PCM stability issues observed.

Response: Thank you for this comment. We have submitted a paper titled by: Practical Aspects for Selecting and Implementing Phase Change Materials in Kuwaiti Buildings: A Data-Driven Approach. We have provided more details in that paper. There are no room to add all such information in one paper.

Ø Compare simulation predictions to any available real-world portable cabin/PCM data.

Response: Thank you for this comment. We are in process of obtaining PCM and will be the first to do the same once experimental data available. There are no previous literature of this type.

Ø Discuss broader implications - how well would the results extrapolate to full-sized buildings?

Response: Thank you for this comment. We studied different wall materials in [59] to assess real buildings’ materials. The overall application to a full-sized building is concluded in the conclusion by:

This study highlights the importance of using insulation materials for the development of low-energy buildings in Kuwait, despite current government regulations prohibiting their use for fire safety reasons.

Ø Highlight the optimal PCM type and location for different climate zones.

Response: Thank you for this comment. The results presented from Figure 11 to Figure 17 are optimal PCMs located at the exterior side of walls and roofs for all the climates studied. This is highlighted in text by, e.g.:

Figure 11. The overall performance of the portable cabin in the State of Kuwait with the optimal Bio-PCM at the optimal location (outside surfaces of walls and roof).

Ø Summarize key practical takeaways for engineers/designers wanting to implement PCMs.

Ø Discuss future work such as long-term PCM performance studies and techno-economic analysis.

Response: Thank you for this comment. We have added in conclusions:

The future work includes using solar reflective paints on the roof and walls and applying cool roof paints for the finned metal roof. Long-term experimental work on PCM performance studies and techno-economic analysis will be conducted in the continuation of the present work. Additionally, TRNSYS models may be extended to simulate portable cabins with cool roofs and different PCM models.

Ø Comment on the potential for novel PCMs explicitly engineered for portable cabins.

Response: Thank you for this comment. Due to customs clearance restrictions in Kuwait, PCM stabilized forms in solid form will be purchased. The installation of these PCMs inside the portable cabin will occur in two phases. Initially, they will be hung in the middle of the cabins to analyze the sensible heat storage capacity and energy-saving potential of the PCMs. Subsequently, the PCMs will be installed on wall surfaces and ceilings to assess the combined contribution of sensible and latent heat storage, considering the possibility of phase change occurring as wall temperatures exceed the selected PCMs' melting point. However, installing stabilised solid shape PCMs on the outside walls may not be feasible as they can undergo significant shape changes and may alter their properties under extreme temperatures. Computational investigations can be conducted on the interior wall of sandwich panels. The energy-saving performance of the cabins will be compared with Type1270 and Type399 in TRNSYS, and if necessary, Design Builder can also be employed for further analysis.

Reviewer 4 Report

The manuscript serves as an introduction to a research project focused on addressing the rising energy consumption in the building sector due to climate change by developing low-energy buildings. Here is a review of the introductory paragraph:

Does the title accurately reflect the content of the paper?
Is the abstract concise and informative, summarizing the purpose, methods, key findings, and implications of the study?
Does the introduction provide adequate background and context for the research?
The paragraph effectively sets the stage by emphasizing the significance of the issue: the increasing energy consumption in the building sector due to climate change. This is a critical and relevant problem to address.
Mentioning that the project is a joint effort between Kuwait and Australia highlights international collaboration, potentially bringing diverse perspectives and resources to the research.
Describing the construction of two portable cabins with specific dimensions and materials provides essential context for the subsequent experiments. This clarity is appreciated.
The inclusion of indoor air quality sensors and a power monitoring system demonstrates a commitment to thorough data collection, which is crucial for credible research.
The paragraph outlines a logical progression of research phases, from investigating cool roof techniques to simulating the cabins in TRNSYS and exploring the use of Bio-PCM materials. This structure is well-presented.
Are the results presented in a clear and organized manner, using tables, figures, or graphs when necessary?
The mention of EPI as a metric for assessing heating, cooling, and total energy demands indicates a quantitative approach to evaluating the cabins' performance.

Author Response

Reviewer 4

Response: Many thanks for expressing your positive views.

Does the title accurately reflect the content of the paper?

Response: Yes.

Is the abstract concise and informative, summarizing the purpose, methods, key findings, and implications of the study?

Response: Yes

Does the introduction provide adequate background and context for the research?

Response: Yes

The paragraph effectively sets the stage by emphasizing the significance of the issue: the increasing energy consumption in the building sector due to climate change. This is a critical and relevant problem to address.

Response: Thank you for this comment. We highlighted this in the first sentence of the Abstract:

The building sector's energy consumption has significantly increased due to climate change, emphasizing the need to develop low-energy buildings using experimental and computational tools.

Mentioning that the project is a joint effort between Kuwait and Australia highlights international collaboration, potentially bringing diverse perspectives and resources to the research.