An Experimental and Numerical Case Study of Passive Building Cooling with Foundation Pile Heat Exchangers in Denmark
Round 1
Reviewer 1 Report
The paper investigates the evaluation of the passive cooling with foundation piles in Denmark. The Authors analyzed this option throughout 40 days when the building was closed, without people. They also evaluated the thermal comfort inside the building. The structure of the paper can be improved: there are several sub-sections. In addition, the English has to be improved: I suggest a revision by a native English speaker.
Specific comments:
Profiles in Figure 1 does not consider the effect of the solar radiation. Please add comments about that.
Equation (3): please add more details. What do you mean for instant steady-state heat conduction? The heat transfer in the energy pile is transient.
The Authors carried out simulation over 12 years: for 219 foundation piles this time is not sufficient.
Berkley >> Berkeley
Conclusions section is not a summary of the paper. Please, revise.
Please avoid commercial information in the text of the paper.
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
This paper reports a field study of a ground source heat pump for HVAC systems in Denmark. The temperatures and relative humidity were measured for conditioned and unconditioned rooms. Models are employed to compute the temperature of passive heat exchangers and energy pile, thermal comfort in terms of PMV and PPD and the building energy. Energy efficiency ratios and thermal comfort in terms of PMV are shown. The authors found that the passive cooling can meet the cooling demand in most of the time. The manuscript is easy to read and the English is good, although some details should be improved or corrected. I suggest to the authors performing a revision of the manuscript according to the following comments:
1. In the manuscript, there is no description about Figure 2b, although the caption shows it is about thermal conductivity and heat capacity. More details should be added to discuss Figure 2b.
2. The working principle of the GSHP is not very clear. More details and description of Figure 4 should be added.
3. In section 2.7 “Predicted Mean Vote and Predicted Percentage Dissatisfied (PMV/PPD) model of thermal comfort”, the clothing insulation at 0.155 is used. Can authors suggest why this value is used because 0.5 is used in summer assuming trousers and short-sleeved shirts? In addition, the mean radiant temperature is assumed to be the air temperature, does this assumption valid? Please clarify.
4. In section 2.8 “Building energy model”, can authors provide a schematic diagram of the building in the simulation? Is it the same to Figure 5? In Table 3, parameters of different room classes are shown, but it is not clear the quantity of each room. It is also important to understand the Energyplus model.
5. In section 3.1.1, the temperature shows in Figure 6 is day-average temperature, how about the hour-average temperature, because the temperature change within a day may be significant due the sunlight. The GSHP system can respond faster enough to the change of temperature.
6. Similar to the comment 4 above, in section 3.1.2, the hour average relative humidity and ventilation rate within a day are suggested to show for better understanding of the performance of the GSHP.
7. Page 3: Line 90, what is BHE? Please provide a full name for the first appearance.
8. Page 5: Line 151, superscript 2 of m2 and 3 of m3.
9. Page 10: Line 275, “while unconditioned rooms see temperatures” what does “see” mean here?
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
Although this is an interesting article on a relevant topic, it has several flaws that the authors need to address before this manuscript is acceptable for publication:
Please use subscripts in molecular formulas (CO2).
Abbreviations should be defined in parentheses the first time they appear in the abstract and main text (see for example pg. 1, ln. 18, pg. 3, ln. 90) or rather avoid abbreviations in the abstract.
Critical remark to the whole materials and methods section: please provide a more complete description to allow others to build on published results.
Fig. 2: Please change the caption to map or location of Rosborg Gymnasium… Please indicate the land mass. Which scale was used for Figure 2 (b)?
Critical remark to the whole Figures: figures should be described in a font not larger than the font size in the main text. I miss axes labels.
Fig. 5: The location of energy pile foundation should be indicated. It might be helpful to merge Fig. 3 and 5.
Pg. 6, ln. 150: Please use date format YYYY-MM-DD (ISO 8601).
Pg. 6, ln. 151: Please use superscripts for cubic meter and square meter.
Pg. 7, ln. 162. It may be useful to explain why room 6.03 and room 6.12 were used as reference. Both have two exterior walls facing south and west side (probably higher thermal conduction and solar radiation).
Pg. 7, ln 163: It may be useful to show the location of the temperature loggers. Was only one temperature sensor installed in each room? Does the temperature measured correspond to air temperature at normal shoulder level or rather to wall temperature? Please specify for example in Fig. 5 and provide the room height. I believe this is an important information especially for predicting the perceived comfort. Please address this in your discussion.
The test was performed with totally absence of people. However, occupancy is included in the building energy model. The inclusion of natural ventilation would be interesting. I believe that intermittent ventilation will occur through open doors and windows. Can you give an estimation of effects on the efficiency ratio? Please address this in your discussion.
Fig. 6 (a): Data recording started from 2018-06-30. Please include in the figures.
Fig. 8 (b): How did the EER come about? Did you simply take the EER as the ratio of cooling energy and electricity consumption of the circulation pump? However, electricity consumption of the circulation pump was recorded only at the beginning and the end of the test. Did you assume constant electricity consumption (pg. 12, ln 307)? The readability of the article would benefit if the materials and methods section would be reworked. Now this information is "hidden" in the rest of the text. Please explain and include an equation in the materials and methods section.
Pg. 12, ln. 309: It is not clear to me why the authors use COP here (again, abbreviations should be defined in parentheses the first time they appear in the text)? The COP is used for performance evaluation in heating mode. The EER is the ratio of cooling output to input electrical energy at a fixed outdoor temperature (steady state conditions). While what is recorded in this study is the cooling output for a typical cooling season and would correspond to the SEER. Is that correct?
Figure 9: The legend used in Figure 9(b) applies to both (a) and (b)? Please put the legend outside the graphic or insert in both. Again, axes titles would be helpful to understand the meaning of the bars (frequency? Normalized?). In (a) the authors use µ and σ for mean and standard deviation. In the abstract they use std. Please make it consistently.
Pg. 13, ln. 323: please change “0” to “zero”.
Critical remark to the whole conclusion: The passage ln. 375-385 is identical with ln 102-112 on pg. 4. The conclusion must be a déjà vu free zone. I believe that the manuscript would benefit if the conclusion was shortened to the important findings (ln. 395-406).
Pg. 17, ln. 426: Include reference for average ground temperature.
Reference Style: Translate topics of reference not written in English into English.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The Authors modified the paper according to the Reviewers comments
Reviewer 2 Report
The authors have well addressed the comments. This manuscript can be accepted.
Reviewer 3 Report
The authors addressed properly reviewers' comments in the revised manuscript.
