Evaluation of Thermal Comfort and Energy Consumption of Water Flow Glazing as a Radiant Heating and Cooling System: A Case Study of an Office Space
, Benito Lauret Aguirregabiria 1 and Juan A. Hernandez Ramos 3
Round 1
Reviewer 1 Report
The authors present a careful study of the performance of a WFG internal wall installation. Overall, the paper is well-written.
In the materials and methods section, it would be desirable to learn some more details on some of the design choices like the use of individual heat-exchangers for each transparent unit; also it would be interesting to learn whether any static measures had to be taken to deal with the considerably higher weight of the walls compared to standard dry wall constructions. Furthermore, it would be interesting to understand what advantages the translucent nature of the walls between the offices brings with respect to light management (and how user feedback with respect to visual comfort of these walls is).
In the results ssection, most figures beginning from figure 5 are presented split between pages. This should be changed in the final version.
In order to help the reader to understand the operation of the system, it would furthermore be desirable to provide information which of the operation days were working days and which ones during weekends.
Furthermore there are some interesting features in the figures which are not explained in the legends or in the text: For example, the oscillation of the inlet temperature in fig 5 a is much faster than in fig 5b despite the larger energy flows handled in the scenario of figure 5b.
Last but not least, it would be helpful to see colours and sequence of the data sets in figures 5 to 9 better matched between the figures - figure 8 seems to be different from the others in the present form.
In the discussion or conclusion sections, it would be desirable to have at least some reference data for typical energy consuption in a conventional office space at a similar location to better be able to judge the performance of the WFG system with respect to energy efficiency.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper covers an interesting study which can be useful in many countries. The increasing use of airconditioning is creating a GHG effect, which is not suitable for our environment, and there is a strong need to adopt other solutions for the improvement of comfort.
The authors have made a good effort, yet there are serious issues in the experiment and study methods which should be addressed properly. Since such type of study is not supported by BES, it is important to take great care at the experiment and monitoring level. The paper can not be accepted in its current format. However, the authors are encouraged to improve it and resubmit after clarifying the issues. Additional experiment and monitoring may be needed. You can find my comments and suggestion below:
Keywords: you can add 2-3 more keywords.
Authors should discuss the feasibility, initial cost and energy saving using WFG system.
Line 92: add space and change ISO77726 to ISO 7726.
I wonder if the indoor temperature was also monitored before using WFG. If yes, it will be added value to include it in this study.
It is not clear which type of pyranometer was used in this study? Brand, model? Was it of class A, B, C? Does the used pyranometer satisfy the conditions mentioned in ISO 9060 standard? Add limitations and validation of the device?
Figure 3: It is not clear from the figure if the selected room is used as an office or just a meeting room which not always in use.
Figure 4: mark/ specify (a), and (b).
Line 188: DS18B20 is a digital thermometer rather than a sensor. What are the error margin (accuracy level) and the measurement range of this thermometer? Please include it. Can you please include any reference of published work using this thermometer.
What was the reason for the selection of this building? Except the authors found it available and convenient to perform this study? Figure 2 and 3 doesn't show a large glazed area? What is the WWR in the selected offices? The WFG system would have more influence on comfort if authors would have chosen a better representative office.
It is not clear if any other heating/ cooling system(s) was also in use during the monitored dates/ time?
Kindly include the thermophysical and construction material details of the said office building/ rooms.
Line 229: It would be better to use indoor and outdoor temp rather than interior and exterior temp.
Why selected four days in summer, three days in winter and two days in Spring?
Since this is an office building? What is the reason for selecting the weekend days in summer? 13-14 July 2019.
Spring days, 21-22 Feb 2020: Friday and Saturday. Any logic behind the selection of these days?
Figure 14: The selected sitting and visual angles are based on the real use of the room? I think no. It would be interesting to include how people use this office and include their sitting position and visual angles.
Please clarify how MRT was measured?
Line 456: Sure, there is a strong need for further research in this area. However, from this study, it is not clear that the methods and devices used are validated, and calibrated according to the standards.
Figures 5-17: Change the date format to date, month, year.
It would be better if authors add tables to represent their results of kWh and temperatures rather than just adding too many figures.
Since it is not possible to calibrate the data based on the monitored dates and predict the results for a whole year. Longitudinal data at least a week in all seasons. Comfort monitoring with and without WFG in the selected period and energy savings should be added.
The study is mainly based on experiment and monitoring. However, research is missing experimental control, the reasoning for the selection of base-case building, office, monitoring devices, selection of dates etc. Longitudinal monitoring is required for better understanding.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
This study conducted filed experiments to investigate the energy consumption and thermal comfort of Water Flow Glazing as a radiant heating and cooling system in office space. Results showed that office environments and energy consumption in cooling and heating. It’s an interesting paper, but I would like to clearly show your results (ex. tabulates the case). So, the following should be clarified before the consideration of the publication.
- Section 1. Introduction: 3rd paragraph, what you want to say here. Is the radiant panel efficient system or would you like to talk about how to measure efficiency?
- Your system is controlled by an indoor temperature, but set-point (heating&cooling) is not indicated in this paper.
- Section 2.1. Description of the facility: Is the ‘Air heat exchanger’ used only for precooling (night cooling)?
- Line168: In Figure 3, is the (b) radiant panel on the interior wall unaffected by solar radiation?
- In Figure 4: how the actual water flows? In each case of cooling/heating, the movement of buoyancy varies depending on the cold/hot water. Is the temperature evenly distributed due to the flow of water in the wide panel? And in which part of the panel is the surface temperature used in your MRT calculation?
- In Table 1: T_ext_doorD or T_ext_doorDW(in figure 2)? kWh_heatpumpà kWh_AHX?
- Section 3. Results: The results are too difficult to see. At the beginning, organize or tabulate what you want to say (cases). It is difficult to see the resolution of the graph is poor.(also legend, axis). The same graph with different scales is included. (figure7, figure11)
- Section 3.1. Analysis of the facility. Summer conditions. à1. Analysis in Summer conditions. right?
- Line 244-246: Figure 7 shows the tank temperatures' curves (T_tank_top, T_tank_middle, T_tank_bottom) when the energy management system is operating (on 2019/07/10 and 2019/07/11) and when the flow is stopped (on 2019/07/10 or 13? and 2019/07/11 or 14?).’
- In Figure 7, the outside air temperature is higher than the water tank, Why heat exchange in the air heat exchanger? Is control wrong?
- Line 267: On 09/01/2020,à2020/01/09/
- Line 273: In the graph in Figure 9, the temperature of the water entering is higher than the temperature of the water coming out. Your sentence wrote that you removed heat from the interior (line273). confusing.. And, what is the meaning of ‘without the WFG’(line 274)? it means ordinary glass window Or does it mean that the WFG system is not running?
- In Figure 10, is the variation of ‘T_tank_middle’ in (a) due to heat-pump?
- Section 4.1 Validation of energy management system: There is no mention of COP for cooling. Why?
- In Table 3. >0.2m/s 0.6 to 1.0 m/s?
- Line 387: Is the ventilation system not considered in this experiment?
- In your reference (introduction), the office building has a lot of internal heat gain. (PC, lighting…). However, in your experiment, it seems that internal heat gain is not considered. The increase in load can show a change in actual efficiency of system. I would like to briefly state the reason for not considering internal heating.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
The paper presents an interesting concept of water flow glazing elements that can be used as space heating and cooling elements in building HVAC installations. The authors have developed two different types of transparent and translucent prototypes that have been installed in an office space. The system and operating conditions were monitored in order to collect experimental data and evaluate the performance of the installations. Overall the paper presents an interesting and practical concept. However, the analysis and discussion is limited. The number of figures is excessive while the critical analysis of the performance data is very limited and must be significantly improved. The authors must also discuss the limitations of the proposed concept. The technical specifications of the installation and the operating controls must be better documented.
Interest to the readers of SUSTAINABILITY is low. As a note for consideration: the contents of the paper will better match the subject areas of other MDPI Journals like ENERGIES. The "sustainability" term is not even used in the paper. The editor in consultation with the authors may wish to reconsider the publication Journal.
To facilitate the review of the revised document, please provide a version of the paper with track changes along with a clean one.
Specific comments are outlined below.
INTRODUCTION – The entire section MUST BE REWRITTEN. Currently, most of the sentences are very abrupt and incoherent with each other. The concepts and the ideas they are addressing are appropriate but the order and placement in the text must be improved.
Edit the text so that sentences flow in a more logical manner
For example,
L49-L51 It is evident that you are trying to link the contribution and importance of electricity demand to meeting the EU goals and objectives in the coming
L58-60 "Energy Consumption Guide (ECG) shows patterns ... buildings." Is this referring to a specific guide? Then provide a reference. If this is a general desirable outcome of this work, rephrase accordingly.
L74-76 "The steady growth" of what ? "leads to an additional generating capacity" power generating capacity? or cooling generating capacity? Is either one having a positive or negative impact?
"and more effective management of summer peak loads" ? peak loads of what ? Is this positive or negative ?
In either cases, the authors should provide some numerical values to support their statements instead of wordy sentences.
L76-78 "Split systems ...majority of AC units per type [27]. Air-to-water and water-to-water heat ..." This is another example of incoherent sentences. Their content is ok, but the way they are presented is not.
L79-80 "FCUs are factory-made assemblies ... air flowing to spaces [28, 29]." This is trivial, no need to make this statement since it is not even relevant o this work and rather confuses the reader. No need to include two references [28, 29].
L80 onward "Radiant panels ..." This must start a new paragraph and a provide more information since this is the main element of this work and should familiarize the reader.
L81-83 "Occupants in an area heated or cooled by radiant panels ... in summer." Another example of abrupt sentences. This is a true observation but the reader needs to understand why. Must elaborate and substantiate.
L83 "The energy performance of AC systems ..." Then the discussion returns to the equipment performance that confuses the reader. The paragraph started with a discussion of the market, the types of HPs, the emission equipment (FCUs and radiant panels, although WFG was mentioned in the previous paragraph, along with solar heat gains!) and then returns back to the equipment performance
L83-87 is there a reason that the discussion focuses solely on cooling? Should also relate to heating season
L88-94 Is it necessary to use 5 references to simply relate to the assessment of indoor thermal comfort conditions? Try to be more selective
L98-114 is so confusing, with sentences jumping from one topic/theme to another, that the reader can not follow. UNACCEPTABLE must rewrite
L130 "panels were southwest oriented and belonged to an interior corridor" What does this mean ?
L130 -132 Apparently the description of the building construction and the "main glazed facade" installation is not clear. The WFG panels are internal? The description of the building and the installation should be improved. The picture from Fig 3 should be moved here.
L132-133 and L138-139 are practically repeating the same. Combine in one and provide some technical specifications of the equipment (e.g. HP capacity, SEER, water flow rates etc) OR include them in Figure 1.
Keep consistent with the terms, e.g. "air-to-water heat exchanger", "plate heat exchanger", "air heat exchanger"
In addition, where is the fresh air supply coming from? Is there a mechanical ventilation system? Is the supply air conditioned ? at what conditions How does the air supply interact and influence the system's performance or the measurements and the system's monitoring.
It is not clear whether the AWG surface was sized to cover the cooling and heating loads or they were practically sized for convenience.
Similarly for the HP.
L144-145 "the buffer tank was cooled down by the air heat exchanger as a free cooling device" How does free cooling work?
L152 "The translucent interior partitions were connected to a different circulation device"? What does this mean ? Why is this relevant? What is the other circulation device? Are they related to the WFG and the translucent elements that are described next ? The authors must present the installation, the primary and secondary circuits etc in a more logical manner.
L174 "the position of the pyranometer" It is not clear where the pyranometer is located? There is one to measure global and one to measure diffuse ? Fig 4 is showing only one
L180 Fig 4 "pyranometer circulating device" What is this ?
L182 "tiny solar pump" Must present and explain better.
L196-197 "The heating system assured comfort during working hours by minimizing energy consumption." This may be an objective as stated in L193-195 but there is no basis (at this stage of the paper) to support the claim. There has been no data to support that thermal comfort conditions were achieved nor any data on energy consumption. The sentence should be deleted.
L205-206 "This free cooling strategy"? The authors must reveal what is the free cooling strategy to support their claim.
Table 1:
T_tank_... Whys is it so important to measure the stratification in the tank (bottom, middle, top)? There is no relevant discussion in the text
What is the "lower part of the corridor" and the "upper part of the corridor" ? Why is this information relevant?
Twall At what height was it measured ?
TWFG same
TWFG_TP same
What is the difference between "Sun_rad" and "Sun_energy"?
KWh_heatpump Is this supplied or consumed?
KWh_heatpump is used for both "heating/cooling energy by the heat pump" and then also for the "cooling energy by the air heat exchangers" Is this right ?
RH is this indoor or outdoor ? If outdoor, why is it relevant? How can one regulate indoor thermal comfort conditions in an office building without regulating humidity?
Section 3.1
Fig 5 It is not clear whether the system is always on or the period of operation. There is no discussion about the indoor temperature variation. Is it considered satisfactory temperature regulation ?
What does the temperature increase (during the night hours) mean ?
For the clear day 11/7 the indoor temperature is around 28oC and reaches reaches 30oC?
Fig 5 Why are the corridor temps T_ext_doorUP and D during the partly cloudy day (10/7) higher than the clear day (11/7)?
L235 During the "free floating regime" is there any water flow in the WFG panels or are the elements simply filled with water so that they act as thermal water storage? or are they empty? Most likely the HP is not in operation.
Section 3.2
Fig 8 During the days with the system in operation, there is an overheating with the indoor temperature exceeding 23oC.
Is this a good indoor temperature regulation?
L267 "steady comfort temperature at noon" There is nothing "constant" at noon or any other period
Since there is no shading the indoor space suffers from direct solar heat gains. The authors should comment
L271-273 "maintained comfort conditions" The indoor temperature is always above the desirable temp; more than anything else this is a definition of "overheating". The authors should rephrase this sentence.
Again, does the "free-floating" mean that there is no water circulation in the WFG or that the HP is not operating, or both?
Some information is presented in section 4 but this is too late since there are results presented in this section that must be interpreted.
L273 "The WFG removed heat from the interior temperatures at the corridor 273 (T_ext_doorD, T_ext_doorUP), without the WFG, " What does this mean ?
L298 "The translucent interior partitions operated during the night" this was not clearly presented in section 3. Overall, there is a confusion of what and how the systems components and elements operate and when. It may be a good idea to tabulate all the system components and indicate their operating status ? At least at the beginning of each subsection 3 the operating conditions and status of the system components must be clearly explained.
L310-311 May be interesting to know how the theoretical cop related to the actual value
Section 4 When and how did the "free cooling" aspect of the installation performed ?
What were the high "internal heating loads"? They have been referenced in the text a few times but it is not evident whether the space was occupied, by how many people, equipment, lights etc. It would be useful to quantify them and provide a value early in the text
Equation 2 & 3, check units Tmr in oC and TN in oR?
Equation 4 simplifies eqn 3, but then L345-346 refers back to eqn 3 to provide the margin error. What was finally used in the calculations?
Equation 5: define a, b, c and relate to Fig 14?
L358-360 Did you measure the surface temperatures to support this assumption? A thermal image could have provided some evidence.
L365 "air velocity" "relative air speed" what are they referring to ? natural or mechanical ventilation?
Eqn 6 and Table 3 What is the air speed referring to ? Natural indoor air flow or mechanical ventilation? What is the relevant air speed at the office space?
What are the HP operating periods ?
What are the control rules for the system operation?
Fig 15:
The RH is relatively low and stable. How is it controlled?
Fig 15 for 10/7 Tfloor and Tceiling have about the same temperature up to noon, then their T and their difference increases. The following day 11/7 they converge again which is logical and then at 10:30 they start a similar behavior. For 12/7 there is a large 5oC drop in the morning. Any comments?
Fig 15 for 10/7 The TWFG temperature cycles between 16-19oC three times per hour. What is the interpretation for this behavior? Is this due to poor control/operation of the HP?
There is a 9oC sudden temperature drop of TWFG over a 2hour period in the morning of 15/7. Any comments?
The TWFG_TP is consistently higher than TWFG. Any comments?
L388 "the air velocity can be controlled and depends on ventilation needs" This is the first time there is a reference to a ventilation system and needs. IS there a mechanical ventilation system in the room?
L383-390 For practically all figures, as in this example for Figure 16, the supporting text is limited to observations. The focus should be on the discussion of important variations and performance analysis that reveal the positive aspects or possible operational problems.
Fig 16 Is it logical and expected that the T_int for 11/7 is constantly increasing resulting to a 5oC ? Even during the morning hours 7-12pm it is not possible to maintain the indoor temperature around 25oC as it does during the other days.
L417-420 What do the PMV results mean? Once again, please make some more in-depth analysis and discussion. Do the results document satisfactory control and operational behavior?
L426 "A simple logic energy management system" This has not been properly documented in the previous text.
How would the system handle and control the indoor humidity ?
L431-434 This conclusion was not evident from the previous discussion. Should strengthen the analysis in the previous sections so that one can naturally draw these conclusions.
L440-442 What is the meaning and claim of this ?
The authors must identify and discuss any possible and limitations of the proposed installation, along with future work.
The authors should include some financial analysis and provide some relevant information and cost data for the WFG, circulators, hydraulics, installation etc, even as an approximation, since the WFG were probably prototypes.
EDITORIAL
Define all abbreviations
L40 HVAC (although this is a very commonly used abbreviation, it should be spelled out)
L41 PCs (may even better to simply spell it out)
L43 IT
Etc
On the other hand, abbreviations are only defined once and then used in the text thereafter. Correct text accordingly. For example,
L43 "The European air-conditioning (AC) market ..."
L74 "The Air Conditioning (AC) market in Europe ..."
L40-41 Include "energy" - Office buildings have a high "energy" use of ...
L115-120 Very poorly written
L122-126 Very poorly written
L137 "25,35m2" The decimal point should be with a "." not ","
L204 "In summer, the low exterior temperature" This is a paradox !
L205 "allowed refrigerating" ? does this mean "cooling"?
L224 "central hours"
L225 "total solar energy (Sun_energy), obtained from the integral of the irradiance" Improve language
L226 and several others…"KWh" lower k "kWh" throughout the text
L226 "4 kWh" This is 3.8 kWh and 3.9 kWh
L249 "the electric energy ranged"
Equation 1 include units for all parameters
Equation 6 should use the same symbol for MRT as the one used previously
Include units for all parameters
L427 "It actuated on the heating"
L446-448 This sentence is not necessary
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 4 Report
The authors have considered and addressed most of the initial review comments in their revised paper and as a result there has been significant improvement and the effort is appreciated. However, as a result of the new material inserted in the revised paper, there are some additional comments that the authors should consider along with some pending ones from round one.
The main concern is with regard to the mechanical ventilation that serves the office space. Now that the authors have revealed its existence, there is a need to clearly substantiate how it operates and most important how it was taken into account while assessing the WFG system's performance. Clearly there is an interaction with the indoor conditions but this is currently not addressed in the calculations and the results.
Please clearly mark all edits in the revised paper using track changes.
L73 "increasing price of energy" ? what form of energy is this referring to? electricity? oil? nat gas? Is this referring to an average in the EU? or the USA ? For consistency with the previous text this should refer to the EU
Provide a suitable reference for "17% from 2008 to 2019".
L95 "the poor quality of windows" ? poor quality in construction ? poor quality in terms of thermal performance ? Must clarify
L115-116 Is the goal to prepare a WFG model? perform simulations and then validate them?
L116-121 The new text is not suitable for a scientific paper. Delete and rephrase with more generic introductory statements. This is not a project report. Credit to the research project is properly given in the acknowledgment section.
L136-138 The new text now mentions that there is a "mechanical ventilation" system. Apparently this system supplies conditioned outdoor air and controls indoor humidity. How is the WFG system performance evaluated if the mechanical ventilation system covers part of the heating/cooling loads?
UNLESS the mechanical ventilation system supplies unconditioned outdoor air? This is very unlikely, since it is stated that the system controls indoor humidity.
Furthermore, in the authors' response it was also stated that "The mechanical ventilation system does not affect the heating or cooling loads, it only affects the air speed and relative humidity" This is NOT possible. The ventilation system will influence the latent and sensible loads and the indoor conditions of the space.
Accordingly, the authors must provide a more persuasive explanation of how they have accounted for the mech vent role in the overall system performance assessment.
L162-163 "Radiant walls are the only elements that provide the studied offices with heating and cooling needs." As previously noted this statement remains unclear until the mechanical ventilation issue is clarified.
L169-170 "Although more surface area of WFG radiant panels seemed to be required" This appears to be in response to the previous comment "It is not clear whether the WFG surface was sized to cover the cooling and heating loads or they were practically sized for convenience." Apparently WFG area was less than required. First, need to specify (quantify) the deviation for heating and/or cooling. Second, explain how despite this deviation it was possible to achieve comfort conditions. Was it a simple overestimation of the cooling/heating loads ?
Table 2 indicates a 2 kW heating load and 3.2 kW cooling load. The selected heat pump is 7.6 kW. Any comments?
L178-179 What do the heat pump characteristics mean? "8/1 Power A7/W35 = Power A35/W18"? Would help the reader to put them in simple words along with the rated SEER etc
Section 2.2 As indicated in the authors' response letter, all temperatures are measured 150 cm above the floor level. This information should be included in section 2.2 or Table 1
L214 The pyranometer measures global (total) solar irradiance. Avoid referring to direct and diffuse that may confuse the reader. Delete "...measuring the beam and diffuse solar radiation. The measured irradiance is the sum of the direct irradiance of the sun and the diffuse irradiance."
Specify whether the pyranometer was placed on the vertical façade
Table 1 Apparently the electricity consumption of the heat pump was not measured. Why ?
Table 1 Include "indoor" for RH
In the response to the previous comment on how indoor humidity is controlled, it was indicated that "There is a renovation system that controls the RH in comfort levels" This is not clear.
In another response, it was mentioned that the mechanical ventilation system was used to control humidity. This is not clear.
Once again, how was indoor humidity controlled?
L271 Include "Over the weekend, the mass flow rate was 0 and the HP was not in operation." as it was stated in the response letter.
L273-274 "an extra cooling power was needed in the morning, " What does this mean? What system provided the "extra cooling power"?
L280-282 "the heat pump worked at three cycles per hour", "fixed to meet the manufacturer's requirement for minimum cycle times", "the minimum time between starts was, at least, forty minutes" These statements must be better explained and discussed. It is evident that the HP cycles and possibly controls are problematic. Maybe not. In either case the HP's operation and control must be clearly presented. If there were problems or other issues they should be recognized and advise on how they may be handled in the future.
Figure 7 Over the weekend the indoor temperature remains below 20oC although the corridor temp is about 29.5oC
Fig 8a After 10am there is an overheating with the indoor temperature well over 20oC. Is this a good indoor temperature regulation? Something is not properly operating?
L314-315 "The indoor air temperature continued to rise to 22°C because the corridor air temperature reached a peak of 30°C." This is not a satisfactory explanation.
Also in Figure 7 Over the weekend that the system is not in operation, the indoor temperature remains below 20oC although the corridor temp is about 29.5oC.
Apparently, the corridor temperature does not appear (and should not be) the determinant factor. Please discuss the control issues. Can the system maintain a stable indoor temperature or not? Is the overheating an operational issue. Can it be handled in the future? What can be done to improve operation?
L326 "free-floating" In the authors' response, there is an appropriate clarification that should be also included in the document, i.e. "The WFG circuit is never empty. During the "free floating regime" the mass flow rate is 0 and the HP is not in operation."
Figure 10 The Indoor temperature during winter reached 25oC. The peak may occur at 5pm but throughout the day (after 9am) it is over 20oC. Once again, is this overheating appropriate ? Are the operating controls appropriate?
L346 "the transparent WFG circuit was stopped to allow solar radiation to enter the office space" What does this sentence imply?
L353 "On 20/02/2020, the system was working in cooling mode." Where is this coming from? Even if the corridor high temp was creating this problem, what is the difference of 20/02 compared with 19/02 (as shown in Fig 10)
It is not clear why the corridor space is reaching this high temperature since there is an independent air-conditioning system that serves the space.
Table 6 the major differences in the system operating mode and performance must be discussed for 09/01 and 20/02. The prevailing conditions from figures 8 and 10 do not justify these distinctively different system operating conditions. The conditions in the corridor and the solar radiation are very similar. How can this ve explained?
L441 The authors should provide some calculations for the system's annual energy performance? It would be useful to include some basic indicators like the energy consumption per m2
There is no cost analysis. A basic payback analysis should be performed.
Fig 14 As it was also noted in the first review, the indoor RH remains low 30-40%. In the authors' response it was mentioned that "There is a mechanical ventilation system to keep RH within those values." The mechanical ventilation system then becomes a mandatory component of the proposed system/concept. Is this accurate? However, there is no relevant information presented in the paper. Accordingly, some relevant discussion must be included in the paper. How does the mechanical ventilation system condition the air? At what conditions? For example, dehumidifying the indoor air reduces the latent cooling load, improves the indoor conditions that impact thermal comfort, PMV etc and of course the energy use. How were all these taken into account in the calculations for the assessment of the WFG system?
Fig 14 As it was also noted in the first review, for 10/7 Tfloor and Tceiling have about the same temperature up to noon, then their T and their difference increases. The following day 11/7 they converge again which is logical and then at 10:30 they start a similar behavior. For 12/7 there is a large 5oC drop in the morning. Any comments? Some relevant discussion must be included in the paper to explain this and other similar variations.
Fig 14 As it was also noted in the first review, for 10/7, the TWFG temperature cycles between 16-19oC three times per hour. What is the interpretation for this behavior? Is this due to poor control/operation of the HP? Some relevant discussion must be included in the paper to recognize that this was not a desirable HP operation and advise on how to handle this limitation.
L519 "indoor air temperature, from 25.2 °C to 27.4°C. " Looking at Fig 15 T_int reaches up to about 30oC.
Fig 15 What is the shaded green area ? Discuss/Explain in the text
Section 4.4 Include some results from winter ?
Section 5 Conclusions The section must be reorganized, move some text to other parts of the paper and enrich with appropriate general concluding remarks, and the discussion on limitations and future work. There is no need to number paragraphs as bullets
L550-555 This paragraph is NOT appropriate for the conclusions section. This is a perfect example of the discussion that should complement the corresponding figures.
L556-559 L564-566 Similar comment
L560-563 Good comments, but no concluding remark.
L572-574 There are no results from the operation in winter?
L577-579 A single sentence is not sufficient discussion of the limitations.
L579-580 A single sentence is not sufficient discussion of the future work.
EDITORIAL
L41 "heating, cooling, air conditioning (HVAC)..." must include "V"entilation (not "C"ooling)
L42 "Office buildings have a high energy use of computers and monitors..." Office buildings have a high number of energy use ...
L43 "energy consumption in lighting ..." change to "for lighting"
The abbreviation "Air Conditioning (AC)" is mentioned 3 times in the text (e.g. L45, L71, L80. Once is enough for the first time and then use AC
L162-163 the radiant walls cover the heating and cooling needs OR provide heating and cooling
L215-216 "and the World Meteorological Organization (WMO) had to be placed outdoors"
L287 "it seemed too high" …. L287 "the comfort conditions had to be discussed"
INSTEAD use the sentence provided in the author's response "Although the temperatures might seem too high, due to the effect of radiating panels and a low mean radiant temperature, there is thermal comfort in the space, as it is shown in the discussion section."
L356 "The energy delivered by the heat pump was 0.6" Include units
Table 10 title "ener3gy"
L421-423 Correct and differentiate the "outlet temperature" and "outdoor temperature" with different symbols than "To"
L513 "was taken from figure 16 " there is no figure 16. Do you mean the temps presented in Figure 15?
Author Response
Please, see the attachment.
Author Response File: Author Response.pdf
Round 3
Reviewer 4 Report
The authors have considered and addressed practically all 1st-2nd review comments in their revised paper and as a result there has been significant improvement and the effort is appreciated.
Following are some minor comments that must be addressed preparing the final version of the paper.
L166-167 and new L170-171 Both statements can not be accurate. Did you need more WFG surface or not ? Was the delivered cooling capacity sufficient or not?
L179-181 As noted in the previous comment and recognized by the authors, the HP is oversized. This fact must not be hidden or overlooked. For whatever reasons, the authors must include a justification statement for the selection/installation. This is a straight forward weakness of the installation and should be recognized as such. Furthermore, it does not properly serve the main features of the installation and oversized units will also consume more energy.
For the record, the response to the comment in the 2nd review on the fact that "Apparently the electricity consumption of the heat pump was not measured" was very "simplistic" since there are ways for in-situ measurements, without any interaction with the building's electric system. The authors need to be direct and state in the text that it was (unfortunately) not considered. In any event, the issue is to be clear in the text and not let the reader wonder about these issues. At least include a simple and fair statement in the set up of the monitoring system, in the estimated energy consumption indicators and as a recommendation in the future work. In the era of nearly zero energy buildings there is a need to clearly monitor and document energy consumption of any concepts
L196-202 The authors have now confirmed that the mechanical ventilation system supplies conditioned air and have inserted some new text. The key-term "conditioned air" is still not stated. Accordingly, the corresponding text must be edited and linked to the desirable indoor conditions.
However, the main issue is that the energy consumption for conditioning the ventilation air is not accounted in the system's energy performance. This is misleading and must be corrected.
L475-483 & Table 12 It must be clearly noted that this final energy analysis and data related to the installation's energy performance is in addition to the energy consumption for the ventilation system that must be also taken into account. How much is this ventilation component? You can at least make an estimate knowing the air flow rates and out/indoor conditions.
L475-483 & Table 12 It must be clearly noted that this final energy analysis and data related to the installation's energy performance is in addition to the energy consumption for the ventilation system that must be also taken into account. How much is this ventilation component? You can at least make an estimate knowing the air flow rates and out/indoor conditions.
EDITORIAL
L200 "liters/second person" edit the units not to be misread as "second person"
L201 you can either have a VAV or a CAV; replace "without a variable air volume" to "as a constant air volume"
L282 Delete the double quote at the end of the sentence
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
