Research on Passive Design Strategies for Low-Carbon Substations in Different Climate Zones

Round 1

Reviewer 1 Report

Dear Authors,

Research about energy saving is a crucial element in sustainability.  The introduction is very well written, with many articles cited. However, more papers are needed to be cited, and the following research articles are recommended, which are explained the thermal comfort of the personnel in the building:

1) https://doi.org/10.1038/s41598-023-34542-9

2) https://doi.org/10.1016/j.jobe.2023.106344 

 

Page 3: Five climate zone were listed in the paper. But it is not clear, so numbering is needed as "... selected typical cities in five climate zones: (i) cold, (ii) hot, (iii) mild and (iv)others ..."

Page 4: Figure 1 is not the correct road map in optimization. All the initial parameters, control parameters, and constraints should be given. Arrow connections are not correct. 

Page 4: It is hard to understand Figure 2. All arrows need a caption and explanation. Components in substation should be detailed and explained with more labels and annotations  (figure 2). 

Page 5: "... if cooling is required, the symbol is “-“, ...", where "-" minus sign is not needed as heat transfer depends on coil temperature and indoor temperature and automatically satisfies plus or minus sign. 

Page 5. Figure 3. Where is the Tin? The building envelope should be marked. Also, variables from Equation (3) and Equation (4) should be shown in Figure 3. 

Page 5. Equation (4) is not correct.  Heat transfers through the building envelope by conductive heat transfer. 

Page 5. Some formulas are missing before "??? denotes the sum of all heat gains from thermal conductivity of the outer surface of the outer envelope, W/m2". Also, heat cannot be gained from thermal conductivity as heat conductivity is a parameter. Heat can be gained from conduction heat transfer or conduction.

Page 5. Small q is heat flux (or heat transfer per unit area) as it is W/m2. Heat is Q, and its unit is W.

Page 6. Many formulas are missing in the following sentences "??? denotes the sum of all heat gain from thermal conductivity of the inner surface of the outer envelope, W/m2; ???denotes the sum of all solar radiation heat gain on the inner surface of the outer envelope, W/m2; ??? denotes the sum of all radiation heat transfer on the inner surface of the outer envelope, W/m2; ??? denotes the sum of all convection heat transfer on the inner surface of the outer envelope, W/m2." and "???denotes the thickness of this outer envelope, m." And many similar typos. 

Page 7. Figure 4 needs more explanations. All arrows need annotations. Components in the substation should be detailed and explained with more labels (figure 4). 

Link to the website of software "DeST-c" needed.

 

Figure 5. A horizontal axis title is needed for all five cities. They can be marked as a,b,c,d,e.

In "Nomenclature," some formulas are missing.

Technical writing in English should be checked. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Please, find the attached file.

Comments for author File: Comments.pdf

Minor editing of English language required.

Please, revise the manuscript. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This review of options for improving substations the authors have taken a classic approach and made a number of assumptions some of which need testing.  The paper is rather brief on the specific requirements for environmental conditions needed for electrical switching equipment in substations and how they differ from those of staff working in the building.

 

The figures showing the example substation building would be helped with some dimensions.  Substation buildings in other regions of the world tend to have much higher ceilings in the equipment rooms than are shown in the figure. Glazing seems to be evenly distributed around the facade.  In other regions equipment rooms would tend to have much smaller areas of glazing - typically strips of glazing high on the walls and perhaps skylights because the rooms will have infrequent occupancy.  The same with pump rooms they are rarely occupied so why so much glass? A single metric of window to wall ratio seems not appropriate for this building type.

 

In other regions substation buildings will take many different plan forms and have considerably different sizes. Some will  only be occupied for a few hours each month and will be controlled strictly for equipment requirements.  The study does not seem to have dealt with this special case. It would greatly improve the paper if a discussion was included.

 

Although there will be some requirement for new substations there will be hundreds, if not thousands of existing buildings which will need upgrading.  It would be good to have further paragraphs discuss retrofit advise.

 

There is no mention of the radiant component of heat emissions from equipment - does the analysis assume a purely convective heat output?

 

There seems to be little mention of the movement of air within substations and as infiltration. Please discuss. Older substations might be quite leaky and this would complicate the task of maintaining control. Some weather patterns might allow for periods where mechanical ventilation or even natural ventilation could be used instead of HVAC. Please discuss.

 

The list of internal heat gains seems to be incomplete - pump rooms will have substantial internal gains. Table 3 is slightly confusing the colour needs to be explained better. For rooms with brief occupied periods the lighting I was expecting a lot more variation.

 

It would be useful to state the temperature set points for the different room types.  Given that there will be different temperature regimes within the building it would be useful to discuss heat transfer between the equipment rooms and the adjacent occupied spaces.  The table of constructions does not discuss the composition in internal partitions.

 

The paper includes sections on basic heat transfer through building facades which seems unnecessary as a numerical simulation tool is being used to assess performance.  We have seen these equations many many times so there is no need to repeat.

 

Table 5 shows heat transfer coefficients - so the authors are imposing fixed values rather than using time-varying heat transfer that takes into account changes in boundary conditions.  This is so 1980s.  We can do so much better than that. Please justify this simplification.

 

Given the different environmental conditions required in a substation it might make sense to adapt the levels of insulation and the qualify of the glazing to fit the room type - for example invest in higher performance for the offices.

There are a few typos.  A few strange wordings. A light editing needed.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

1. The three elements proposed by the authors in the energy saving design of substations: the building envelope thermal parameters, window to wall ratio and shape factor, are the most basic and common inflencing factors for buildings. There is no specific need to run such a simulation again to prove the conclusion. The novelty needs to be clearly addressed.

2. There is even not any specific result, such as how much energy is saved, in the abstract.

3. The literature reivew fails to illustrate the research gaps and that is why I have the first comment about novelty.

4. Since Dest is used, why the authors spend so much time and space on the theorectical model? Those equation sets are very basic and are not necessary to repeat again.

5. The substation model is just a simple building model. It did not consider the complexity of the substation itself, such as the connection with tunnel or trains, impact of underground wind etc. 

6. The overall paper is more like a master thesis, which lacks novelty in both concept and research method. The case studies are not well defined in terms of boundary conditions. So I must regret to suggestion a rejection to this paper.

The english is fine to read.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors,

All the comments and suggestions are considered. I have no any other suggestions.

 

Thanks,

Regards,

Reviewer

 

Author Response

Thank you very much for your comments.

Reviewer 3 Report

I made a number of recommendations to improve the value of the paper. Very few of these have been addressed:

Dimensions missing on Figures 4 & 5. No comments added about the distribution of glazing. No comments about why un-occupied rooms have so much glazing. 

No discussion about how differences between new-build substations and retrofit of existing buildings.

No discussion of the radiant component of heat emissions from equipment.

No mention of air movement (infiltration or use of limited mechanical ventilation). 

Table 3 missing composition of internal partitions.

No explanation for the colour used in figures 6-9

No discussion of the authors choice of fixed heat transfer coefficient rather than based on wind speed and direction.

No discussion of strategies for basing insulation thickness levels on the type of room.

How the plan of the building was altered to get different shape factors is not described.

Only a few phrases could use some editing.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

The authors have addressed well of my comments. 

Please double check the grammar.

Author Response

Thank you very much for your comments. We double-checked the grammar of the full text.

Round 3

Reviewer 3 Report

Comments on the ‘Authors response’:

 

The paper is improved. I find some of the authors choices continue to limit the value of the paper.

 

Thanks for response 2 - it is clearer.  The use of a constant WWR for all room types limits the degree to which cost-effective improvements can be implemented.

 

Response 4 - this is clearer.

 

Response 5 - By limiting your choices to those in ‘Design of Industrial Buildings’ you miss out on many possible options which numerical methods would allow you to explore.  This is regrettable.

We ‘don’t use mechanical ventilation response because it is pre-design’ is not convincing.  MV can sometimes save lots more energy vs HVAC and act as a useful backup when there is little wind.  

It is possible to calculate air flows in buildings and you choose not to. You choose to use a standard value - again this is a 1980s approach to physics.  At least you could explore what would happen if the building were able to be much tighter (say 0.3 each) or if natural ventilation was enhanced during warm periods (say 0.7 ach) to see what impact that might have.

 

Response 6  ‘since there is no temperature difference’ is NOT a true statement UNLESS you are conditioning the pump room and battery room to the same environmental conditions as the office.  And if all rooms are the same temperature then you are missing out on a massive possible savings. Who would believe that any operations manager would use such a primitive control strategy?

 

Response 8 - energy saving codes fix heat transfer coefficients so that buildings can be compared NOT because they represent actual heat transfer.    You mistake the purpose of energy saving codes. Different regions in China will have big differences in wind speeds. And you choose not to take this into account.  Please state this assumption in your paper.

 

Response 9 - a designer serious about saving energy at the least cost would consider making each portion of the facade fit-for-purpose.  Could you at least do one case where room by room optimisation is considered?  This would allow readers to see whether there is scope beyond general recommendations.

 

Response 10 - you change your model shape factor only by changing the ceiling height?  An office with a 5m ceiling? If I told a client that is how I tested design variants they would cancel my contract.  You can be much more clever than that!

Mostly ok. 

Author Response

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Author Response File: Author Response.pdf