Exploring the Impact of a District Sharing Strategy on Application Capacity and Carbon Emissions for Heating and Cooling with GSHP Systems

Round 1

Reviewer 1 Report

Dear authors,

the paper explores some results, on three case studies, obtained by applying small district heating and cooling networks to GSHP system. The paper has the intention to support solving a very practical problem: not all the individual buildings have enough space in the courtyard to install the borehole heat exchangers for the GSHP.

 

The topic is interesting and deserves attention. Please find attached my review

Comments for author File: Comments.pdf

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

Thank you for the opportunity to review a good quality manuscript. I believe that it provides a useful academic contribution to a growing field of understanding how best to optimise use of ground source heat pumps with a district heat network.

I think the methods and results are sound, the major revisions I ask for are related to the introduction and discussion.

Firstly, I think the introduction needs to do more to place the current study in the context of previous work. I agree that this is an area which has had surprisingly little work done on it but I have identified the papers below which the authors have missed. Including more literature will help the authors better place their study amongst the growing body of work in this area.

De Carli, M., Galgaro, A., Pasqualetto, M. and Zarrella, A., 2014. Energetic and economic aspects of a heating and cooling district in a mild climate based on closed loop ground source heat pump. Applied thermal engineering, 71(2), pp.895-904.

Alavy, M., Dworkin, S.B. and Leong, W.H., 2014. A design methodology and analysis of combining multiple buildings onto a single district hybrid ground source heat pump system. Renewable energy, 66, pp.515-522.

Geng, Y., Sarkis, J., Wang, X., Zhao, H. and Zhong, Y., 2013. Regional application of ground source heat pump in China: a case of Shenyang. Renewable and Sustainable Energy Reviews, 18, pp.95-102.

I ask the authors, to explain in the introduction (with more reference to previous work) how specifically their work represents a step forward in our understanding and approach. At the moment the reader is left to work this out for themselves, so I think it would make a stronger paper if the authors were clearer about the novelty of their work.

Secondly, in the discussion I would like to see some clearer information about how industry can use the information presented in this study. Again, the text currently requires the reader to put several connections together. Simple statements would improve things by giving clear guidelines over when developers should consider one strategy compared with another.

I have included specific comments below, which I encourage the authors to address. The English is very readable, but does contain small errors. Some of which I’ve highlighted below.

Line 35: It reads quite odd to start off this study with a fact about the UK. It gives the impression that this study is only applicable to the UK. I suggest the authors set the international scene first, before explaining that they are using UK as a case study so that they can then explain the specific UK policy context in which that case study exists.

Line 26: change “both of strategies” to “both strategies”

Line 69: Could you explain more what C/D ratio means. Is that the capacity of the ground to meet the building demand? It is currently unclear what the “capacity” is referring to.

Line 98: I think we need a sentence explaining energy piles here. I assume you mean a hybrid between borehole heat exchanger and building foundation.

Line 99: BHE introduced but has not yet been explain what this means (Borehole Heat Exchangers).

Line 103: Does the thermal resistance of the in-pipe layer and surface of the pile really make a significant difference to the model? I would have thought they were negligible.

Line 118-119: Perhaps also include here that commercial building often have different heat demand timings compared with residential buildings. I.e. commercial buildings have demand in day, and residential early morning and evening.

Line 123: This is just a comment for the author’s general interest, but the different landlords issues is quite significant in Glasgow, where I’m based. Different land owners failing to agree has led to a lot of district heat projects not going ahead. Such a shame.

Line 136: I’m confused what (b) Individual System with Borehole Sharing means. Is it that the residential land is “rented” to the commercial building for heat exchange. Or that we use the ground for thermal exchange between the commercial and residential buildings? Perhaps, a few extra sentences explaining this in the paragraph above would be useful.

Line 231: I understand why the authors have used an official government report for the UK emissions factor which gives 0.533 kg CO2e/kWh. However, the UK grid is rapidly decarbonising and the official government reports are struggling to keep up. I refer the authors to this UK energy data collation website run by the University of Sheffield http://www.mygridgb.co.uk/historicaldata/. There the authors will find that 2019 saw a UK average grid intensity of 245 kg CO2e/kWh. The authors might also find this resource useful as it is run by the UK national grid operator. https://carbonintensity.org.uk/

Line 243: “50 x 50” should that be in metres?

Line 257: does the “1” in this line represent Scenario 1 in figure 5?

Line 363: I suggest changing “both of sharing strategies” to “both sharing strategies”.

Line 365: change “for both of scenarios” to “for both of the scenarios”.

Line 369: change “still in yellow range” to “still in the yellow range”.

Line 370; change “part of energy demand” to “part of the energy demand”.

Line 377: change “potential shows different” to “potential is different”

Line 385: change “shows less efficient” to “is less efficient”

Line 387: this is an interesting and useful finding. That different sharing strategies perform better depending on the mix of the energy profiles of the built environment.

Line 390: The conclusions present a summary of the work, but this is not needed as the abstract already provides an adequate summary of the work. I suggest the authors shorten the conclusions to only focus on the key findings from the study. 

Line 406: This paragraph starts with “Therefore, it can be concluded” which suggests that this paragraph contains the actual conclusions of the study. I suggests deleting the first paragraph from the conclusions. The second paragraph can be split in two on line 410. I think this will make it easier for readers to quickly see and understand the main conclusions of the study.

Author Response

Response to Reviewer
2 Comments
Dear Reviewer,
Many thanks for reviewing our paper. We sincerely appreciate you for all the suggestions and
comments. To the best of our ability, we have modified them and colored the changes in red in the
revised manuscript. The responses to comments are described in detail and listed below.
Point 1:
Firstly, I think the introduction needs to do more to place the current study in the context of
previous work. I agree that this is an area which has had surprisingly little work done on it but I have
identified the papers below which the authors have missed. Including more literature will help the
authors better place their study amongst the growing body of work in this area.
De Carli, M., Galgaro, A
., Pasqualetto, M. and Zarrella, A., 2014. Energetic and economic aspects of a
heating and cooling district in a mild climate based on closed loop ground source heat pump. Applied
thermal engineering, 71(2),pp.895 904.
Alavy, M., Dworkin, S.B. and Leong, W
.H., 2014. A design methodology and analysis of combining
multiple buildings onto a single district hybrid ground source heat pump system. Renewable energy,
66, pp.515 522.
Geng, Y., Sarkis, J., Wang, X., Zhao, H. and Zhong, Y., 2013. Regional
application of ground source
heat pump in China: a case of Shenyang. Renewable and Sustainable Energy Reviews, 18, pp.95 102.
I ask the authors, to explain in the introduction (with more reference to
previous work) how specifically
their work represents a step forward in our understanding and approach. At the moment the reader
is left to work this out for themselves, so I think it would make a stronger paper if the authors were
clearer about the novelty of their work.
Response 1:
Many thanks for the comment. W e have carefully read the papers and added to the
current literature part . In addition, we have provided more explanations on our motivation to do this
study. The revised part can be found from Line 71 to 114 in the manuscript as follows.
“
The utilization of shallow geothermal energy as energy source for district heating system is currently
more concentrated in the hybrid systems [14], which mean to integrate GSHP in heat network to
provide part of t he heating load. In Europe, over 50 successful schemes of this type have been running
for over a decade [5]. According to the regional application analysis of GSHP in Shenzhen of China[1],
it saw significant efforts to grow adoption to 59.41 million m2 fro m 780 projects and implemented
policies encouraged to plan GSHP technology at urban district and county level. The regional
application can contribute to an anticipated 4.18% of CO2 saving in Shenyang’s building sector. The
city scale analysis of GSHP appl ication in London showed that [15, 16] a high proportion (over 60%)
of buildings have a C/D ratio (the ratio of ground capacity to energy demand) of over 1.0, which
meant that a great many houses and buildings have enough space to install a GSHP and thus f ully
satisfy their own heating demands. In addition, it was found that the buildings demonstrated
significant spatial heterogeneity in C/D ratios due to variations in heating demand and available space.
significant spatial heterogeneity in C/D ratios due to variations in heating demand and available space. If spatial sharing strategy can be introduced, buildiIf spatial sharing strategy can be introduced, buildings with high C/D ratios will be able to share ngs with high C/D ratios will be able to share surplus capacity with their neighbors, to satisfy the heating and cooling demands of a greater number surplus capacity with their neighbors, to satisfy the heating and cooling demands of a greater number of buildings in the area. Alavy et al. [17] built a utility model of district hybrid GSHP system with of buildings in the area. Alavy et al. [17] built a utility model of district hybrid GSHP system with combicombining multiple commercial/industrial buildings to show that intelligent chosen combinations can ning multiple commercial/industrial buildings to show that intelligent chosen combinations can reduce the required ground loop length, and thus to diminish the drilling space. De Carli et al. [18] reduce the required ground loop length, and thus to diminish the drilling space. De Carli et al. [18] conducted study on a heating and cooling district in a mildconducted study on a heating and cooling district in a mild climate based GSHP and specifically climate based GSHP and specifically analyzed the influence of the district heating layanalyzed the influence of the district heating lay--outs and population density in the district on the outs and population density in the district on the most suitable solution. From both energetic and economical point of view, sharing can be a good most suitable solution. From both energetic and economical point of view, sharing can be a good way to bring benefitsway to bring benefits and, in some cases, splitting a district centralized system into two suband, in some cases, splitting a district centralized system into two sub--ones can ones can reduce more financial risks. Actually, in addition to the cost consideration, Soga et al.[19] simulated a reduce more financial risks. Actually, in addition to the cost consideration, Soga et al.[19] simulated a case study at city scale in London to investigate the influence of case study at city scale in London to investigate the influence of district size on GSHP application district size on GSHP application potential, which demonstrated that 50m×50m size can greatly improve the potential compared with potential, which demonstrated that 50m×50m size can greatly improve the potential compared with individual systems planning, but the improvement rate lowered down with the district sharing size individual systems planning, but the improvement rate lowered down with the district sharing size increased. According to the increased. According to the existing researches, it can be found that district sharing can benefit the existing researches, it can be found that district sharing can benefit the GSHP application and the sharing performance can be changed by building type and demand GSHP application and the sharing performance can be changed by building type and demand intensity. However, they mainly focus on utilization of the centralized GSHP system on specifintensity. However, they mainly focus on utilization of the centralized GSHP system on specific cases ic cases including certain building types but have no investigation on the systematical analysis to evaluate including certain building types but have no investigation on the systematical analysis to evaluate how the mix of typical building types can influence the district system performance. Moreover, GSHP how the mix of typical building types can influence the district system performance. Moreover, GSHP systems have their unique characteristics, so isystems have their unique characteristics, so it is worthwhile to compare more specific sharing t is worthwhile to compare more specific sharing strategies under different district scenarios to demonstrate their application capacity and carbon strategies under different district scenarios to demonstrate their application capacity and carbon saving ability. saving ability.
Accordingly, this study makes a number of contributions to the literature.
Accordingly, this study makes a number of contributions to the literature.
1. We develop t
1. We develop two district sharing models specific for GSHP system application. The two sharing wo district sharing models specific for GSHP system application. The two sharing strategies in models are: i) individual systems with borehole sharing, and ii) a district central system.strategies in models are: i) individual systems with borehole sharing, and ii) a district central system.
2. We performance the models on the three selected districts in Londo
2. We performance the models on the three selected districts in London. These districts are n. These districts are representative 50m×50m size and show the variety in the combination of typical building types. The representative 50m×50m size and show the variety in the combination of typical building types. The results demonstrate a good performance of models on the sharing potentials and, according to the results demonstrate a good performance of models on the sharing potentials and, according to the comparison analysis, the potentials acomparison analysis, the potentials are varied under different building type combinations.re varied under different building type combinations.
3. We evaluate carbon saving potential with the developed GSHP district systems, and the results
3. We evaluate carbon saving potential with the developed GSHP district systems, and the results show that the sharing strategies can cut significant carbon emissions compared individual systems, show that the sharing strategies can cut significant carbon emissions compared individual systems, which which is beneficial to achieving a low carbon city.is beneficial to achieving a low carbon city.””
Point
Point 22:: Secondly, in the discussion I would like to see some clearer information aboutSecondly, in the discussion I would like to see some clearer information about how industry how industry can use the information presented in this study. Again, the textcan use the information presented in this study. Again, the text currently requires the reader to put currently requires the reader to put several connections together. Simpleseveral connections together. Simple statements would improve things by giving clear guidelines over statements would improve things by giving clear guidelines over whenwhen developers should consider one strategy compared with another.developers should consider one strategy compared with another.
Response
Response 22:: Many thanks for the commentMany thanks for the comment. We have added . We have added related suggestions related suggestions on the strategy on the strategy selection to the section of discussionselection to the section of discussion from Line from Line 430 430 to Line to Line 436436 as followsas follows..
“
“Based on the findings from case studies, it can be suggested that combining more building types Based on the findings from case studies, it can be suggested that combining more building types
can increase the application potential of district GSHP sharing system and, particularly, residential
can increase the application potential of district GSHP sharing system and, particularly, residential building is a preferred type for combination with others abuilding is a preferred type for combination with others as it requires mainly heating. Regarding to s it requires mainly heating. Regarding to the strategy selection, for the district containing more building types, it is better to employ district the strategy selection, for the district containing more building types, it is better to employ district central system (CS, Sharing Strategy 2), while for the district with only single building type, individual central system (CS, Sharing Strategy 2), while for the district with only single building type, individual ssystem with borehole sharing (ISBS, Sharing Strategy 1) is considered to be a better choice. ystem with borehole sharing (ISBS, Sharing Strategy 1) is considered to be a better choice. ““
Point
Point 33:: Line 35: It reads quite odd to start off this study with a fact about the UK. ItLine 35: It reads quite odd to start off this study with a fact about the UK. It gives the gives the impression that this study is only applicable to the UK. I impression that this study is only applicable to the UK. I suggest thesuggest the authors set the international authors set the international scene first, before explaining that they are usingscene first, before explaining that they are using UK as a case study so that they can then explain the UK as a case study so that they can then explain the specific UK policy contextspecific UK policy context in which that case study exists.in which that case study exists.
Response
Response 33:: Many thanks for the commentMany thanks for the comment. . We We have added more information in fronthave added more information in front from Line 35 from Line 35 to 41 to 41 as follows.as follows.
“
“In response to global warming, sustainable energy technologies are encouraged worldwide to In response to global warming, sustainable energy technologies are encouraged worldwide to reduce carbon emission. The Chinese government has announced that China will reduce carbon reduce carbon emission. The Chinese government has announced that China will reduce carbon dioxide emissions per unit of GDP by 40dioxide emissions per unit of GDP by 40––45% in 2020 when compared to a 20045% in 2020 when compared to a 2005 baseline[1]. The EU 5 baseline[1]. The EU Energy Efficiency Directive (2012/27/EU) and the amending directive (2018/2002) announce a series Energy Efficiency Directive (2012/27/EU) and the amending directive (2018/2002) announce a series of binding measures to achieve its 20% energy efficiency target by 2020 [2].To reach these targets, of binding measures to achieve its 20% energy efficiency target by 2020 [2].To reach these targets, great efforts should be made for spgreat efforts should be made for space conditioning as building comfort consumes a large proportion ace conditioning as building comfort consumes a large proportion of energy, particularly around half in the EU [3].of energy, particularly around half in the EU [3].””
Point
Point 44:: Line 26: change “both of strategies” to “both strategies”Line 26: change “both of strategies” to “both strategies”
Response
Response 44:: Many thanks for the commentMany thanks for the comment. . We have changed We have changed to “both strategies”to “both strategies”
Point
Point 55:: Line 69: Could you explain more what C/D ratio means. Is that the capacity ofLine 69: Could you explain more what C/D ratio means. Is that the capacity of the ground to the ground to meet the building demand? It is currently unclear what themeet the building demand? It is currently unclear what the ““capacity” is referring to.capacity” is referring to.
Response
Response 55:: Many thanks Many thanks for the commentfor the comment. . We have added a clearer exWe have added a clearer explanation hereplanation here as “as “a C/D a C/D ratio (the ratio of ground capacity to energy demand)ratio (the ratio of ground capacity to energy demand)””..
Point
Point 66:: Line 98: I think we need a sentence explaining energy piles here. I assume youLine 98: I think we need a sentence explaining energy piles here. I assume you mean a hybrid mean a hybrid between borehole heat between borehole heat exchanger and building foundation.exchanger and building foundation.
Response
Response 66:: Many thanks for the commentMany thanks for the comment. . As As it is considered that it is considered that this this partpart has nohas not sot so strong strong relationship relationship toto the paperthe paper contentcontent, we have removed , we have removed this paragraphthis paragraph iin the revised manuscript version.n the revised manuscript version.
Point
Point 77:: Line 99: BHE Line 99: BHE introduced but has not yet been explain what this meansintroduced but has not yet been explain what this means (Borehole Heat (Borehole Heat Exchangers).Exchangers).
Response
Response 77:: Many thanks for the commentMany thanks for the comment. . As it is considered that this part has not so strong As it is considered that this part has not so strong
relationship to the paper
relationship to the paper contentcontent, we have removed this paragraph, we have removed this paragraph iin the n the revised manuscript version.revised manuscript version.
Point
Point 88:: Line 103: Does the thermal resistance of the inLine 103: Does the thermal resistance of the in--pipe layer and surface of the pilepipe layer and surface of the pile really make really make a significant difference to the model? I would have thought theya significant difference to the model? I would have thought they were negligible.were negligible.
Response
Response 88:: Many thanks for the Many thanks for the commentcomment. . As it is considered that this part has not so strong As it is considered that this part has not so strong relationship to the paperrelationship to the paper contentcontent, we have removed this paragraph, we have removed this paragraph iin the revised manuscript version.n the revised manuscript version.
Point
Point 99:: Line 118Line 118--119: Perhaps also include here that commercial building often have119: Perhaps also include here that commercial building often have different heat different heat demand timings compared with residential buildings. I.e.demand timings compared with residential buildings. I.e. commercial buildings have demand in day, commercial buildings have demand in day, and residential early morning andand residential early morning and evening.evening.
Response
Response 99:: Many Many thanks for the commentthanks for the comment. . We have We have added added this information from Line 141 to 143 as this information from Line 141 to 143 as followsfollows..
“
“As commercial buildings often have different heat demand timings compared with residential As commercial buildings often have different heat demand timings compared with residential buildings, the temporal heterogeneity can benefit energy use buildings, the temporal heterogeneity can benefit energy use efficiency with a shared system. With efficiency with a shared system. With respect of available space for borehole installationrespect of available space for borehole installation…”…”
Point
Point 1010:: Line 123: This is just a comment for the author’s general interest, but theLine 123: This is just a comment for the author’s general interest, but the different landlordsdifferent landlords issues is quite significant in Glasgow, where I’m based.issues is quite significant in Glasgow, where I’m based. Different land owners failing to agree has led Different land owners failing to agree has led to a lot of district heat projectsto a lot of district heat projects not going ahead. Such a shame.not going ahead. Such a shame.
Response
Response 1010:: Many thanks for the Many thanks for the informationinformation.. I think it is very I think it is very interesting to discuss about this, so interesting to discuss about this, so wwe have also e have also addedadded some discussionsome discussion here to here to this partthis part as follows.as follows.
“
“The landlords can make a contract to confirm a rental fee as a part of initial cost and run their own The landlords can make a contract to confirm a rental fee as a part of initial cost and run their own heat pump system separately to avoid heat pump system separately to avoid operation conflict. This way can reduce the negotiation on the operation conflict. This way can reduce the negotiation on the operation management arguments, which can be considered to enhance the feasibility of operation management arguments, which can be considered to enhance the feasibility of implementing the district system. However, as there is no limitation to install closedimplementing the district system. However, as there is no limitation to install closed--loop GSHP in the loop GSHP in the UK,UK, the subjective thought of landlords is always dominant reason to estimate if the district sharing the subjective thought of landlords is always dominant reason to estimate if the district sharing system can be built, which depends case by case.system can be built, which depends case by case.””
Point
Point 1111:: Line 136: I’m confused what (b) Individual System with Borehole SharingLine 136: I’m confused what (b) Individual System with Borehole Sharing means. Is it that means. Is it that the the residential land is “rented” to the commercial building forresidential land is “rented” to the commercial building for heat exchange. Or that we use the heat exchange. Or that we use the ground for thermal exchange between theground for thermal exchange between the commercial and residential buildings? Perhaps, a few extra commercial and residential buildings? Perhaps, a few extra sentencessentences explaining this in the paragraph above would be usefuexplaining this in the paragraph above would be useful.l.
Response
Response 1111:: Many thanks for the commentMany thanks for the comment. . Yes, the idea of this strategy is to encourage the Yes, the idea of this strategy is to encourage the residential land to be rented to the commercial building for heat exchange. We have added residential land to be rented to the commercial building for heat exchange. We have added more more explanations to this part explanations to this part at Line 163 at Line 163 as foas follows.llows.
“
“The building with surplus space for The building with surplus space for installation can rent their land to the building with short space.installation can rent their land to the building with short space.””
Point
Point 1212:: Line 231: I understand why the authors have used an official government reportLine 231: I understand why the authors have used an official government report for the UK for the UK emissions factor which gives 0.533 kg CO2e/kWh. However, the UKemissions factor which gives 0.533 kg CO2e/kWh. However, the UK grid is rapidly decarbonising and grid is rapidly decarbonising and the official government reports are strugglingthe official government reports are struggling to keep up. I refer the authors to this UK energy data to keep up. I refer the authors to this UK energy data collation website run bycollation website run by the University of Sheffield http://www.mygridgb.co.uk/historicaldata/. Therethe University of Sheffield http://www.mygridgb.co.uk/historicaldata/. There
the authors will f
the authors will find that 2019 saw a UK average grid intensity of 245 kgind that 2019 saw a UK average grid intensity of 245 kg CO2e/kWh. The authors CO2e/kWh. The authors might also find this resource useful as it is run by themight also find this resource useful as it is run by the UK national grid operator. UK national grid operator. https://carbonintensity.org.uk/https://carbonintensity.org.uk/
Response
Response 1212:: Many thanks for the commentMany thanks for the comment and valuable informationand valuable information.. We have added to the related We have added to the related information to Section 3.3 and information to Section 3.3 and provided more discussion on it from Line 274 to 279 as follows.provided more discussion on it from Line 274 to 279 as follows.
“
“One point should be addressed here that, due to rapid decarbonizing of the UK grid, the official One point should be addressed here that, due to rapid decarbonizing of the UK grid, the official government reports are struggling to keep up and the average carbon intensity of electricity has government reports are struggling to keep up and the average carbon intensity of electricity has continuously continuously decreaseddecreased. The exact numbers of every year can be. The exact numbers of every year can be looked up on the website of UK looked up on the website of UK national grid operator. However, as the carbon intensity of electricity is used in this study as a national grid operator. However, as the carbon intensity of electricity is used in this study as a reference value to compare different technologies, the trend of comparison results will not be reference value to compare different technologies, the trend of comparison results will not be influenced by selection of theinfluenced by selection of the intensity value.intensity value.””
Point
Point 1313:: Line 243: “50 x 50” should that be in metres?Line 243: “50 x 50” should that be in metres?
Response
Response 1313:: Many thanks for the commentMany thanks for the comment. . Yes ,they are in meters. We have already changed this Yes ,they are in meters. We have already changed this to to ““50m×50m50m×50m” at Line 285” at Line 285
Point
Point 1414:: LLine 257: does the “1” in this line ine 257: does the “1” in this line represent Scenario 1 in figure 5?represent Scenario 1 in figure 5?
Response
Response 1414:: Many thanks for the commentMany thanks for the comment. . Due to the figure arrangement, the figure is adjusted Due to the figure arrangement, the figure is adjusted as Figure 4 nowas Figure 4 now. Actually the “1”. Actually the “1” means means “Strategy 2“Strategy 2”. I am sorry for confus”. I am sorry for confusinging. . We have changed the We have changed the writing in this part writing in this part to make clear as follows.to make clear as follows.
“
“Two scenarios, Scenario 1(Boreholes Under Buildings) and Scenario 2 (Borehole Around Buildings), Two scenarios, Scenario 1(Boreholes Under Buildings) and Scenario 2 (Borehole Around Buildings), (Figure 4) were analyzed for comparison.(Figure 4) were analyzed for comparison.””
Point
Point 1515:: Line 363: I suggest changing “both of sharing strategies” to “both sharingLine 363: I suggest changing “both of sharing strategies” to “both sharing strategies”.strategies”.
Response
Response 1515:: Many thanks for the commentMany thanks for the comment. . We have changed to We have changed to ““both sharing strategies”both sharing strategies” at Line at Line 404404..
Point
Point 1616:: Line 365: change “for both of scenarios” to “for Line 365: change “for both of scenarios” to “for both of the scenarios”.both of the scenarios”.
Response
Response 1616:: Many thanks for the commentMany thanks for the comment. . We have changed to We have changed to ““for both of the scenarios”for both of the scenarios” at Line at Line 404066..
Point
Point 1177:: Line 369: change “still in yellow range” to “still in the yellow range”.Line 369: change “still in yellow range” to “still in the yellow range”.
Response
Response 1177:: Many thanks for the Many thanks for the commentcomment. . We have changed to We have changed to ““still in the yellow range”still in the yellow range” at Line at Line 410410..
Point
Point 1818:: Line 370; change “part of energy demand” to “part of the energy demandLine 370; change “part of energy demand” to “part of the energy demand””
Response
Response 1818:: Many thanks for the commentMany thanks for the comment. . We have changed to We have changed to ““part of the energy demand”part of the energy demand” at at Line 411Line 411..
Point
Point 1199:: Line 377: change “potential shows different” to “potential is different”Line 377: change “potential shows different” to “potential is different”
Response
Response 1199:: Many thanks for the commentMany thanks for the comment. . We have changed to We have changed to “potential is different”“potential is different” at Line 418.at Line 418.
Point
Point 2020:: Line 385: change “shows less Line 385: change “shows less efficient” to “is less efficient”efficient” to “is less efficient”
Response
Response 2020:: Many thanks for the commentMany thanks for the comment. . We have changed to We have changed to ““is less efficient”is less efficient” at Lineat Line 426.426.
Point
Point 2211:: Line 387: this is an interesting and useful finding. That different sharingLine 387: this is an interesting and useful finding. That different sharing strategies perform strategies perform better better depending on the mix of the energy profiles of thedepending on the mix of the energy profiles of the built environment.built environment.
Response
Response 2211:: Many thanks for the commentMany thanks for the comment. .
Point
Point 2222:: Line 390: The conclusions present a summary of the work, but this is notLine 390: The conclusions present a summary of the work, but this is not needed as the needed as the abstract already provides an abstract already provides an adequate summary of the work. Iadequate summary of the work. I suggest the authors shorten the suggest the authors shorten the conclusions to only focus on the key findingsconclusions to only focus on the key findings from the study.from the study.
Response
Response 2222:: Many thanks for the commentMany thanks for the comment. . We haveWe have shortenedshortened the conclusionsthe conclusions starting from Line starting from Line 444141 as follows.as follows.
“
“
It can be concluded from the case studies that a larger building type number and a higher variety in
It can be concluded from the case studies that a larger building type number and a higher variety in building type with greater differentiation in heating and cooling demands between these types can building type with greater differentiation in heating and cooling demands between these types can lead to a better district sharing performance on all the lead to a better district sharing performance on all the indicators including C/D ratio, required indicators including C/D ratio, required borehole number saving and carbon emissions, which means a greater GSHP system application borehole number saving and carbon emissions, which means a greater GSHP system application potential and a more significant environmental impacts. potential and a more significant environmental impacts.
In addition, district central system (CS, Sharing Strategy 2) has b
In addition, district central system (CS, Sharing Strategy 2) has better performance in higher sharing etter performance in higher sharing potential range, and individual system with borehole sharing (ISBS, Sharing Strategy 1) in lower range, potential range, and individual system with borehole sharing (ISBS, Sharing Strategy 1) in lower range, so the sharing strategies are applicable to different scope of districts. As for the strategy selection, for so the sharing strategies are applicable to different scope of districts. As for the strategy selection, for the disthe district containing more building types, it is better to employ district central system (CS, Sharing trict containing more building types, it is better to employ district central system (CS, Sharing Strategy 2), while for the district with only single building type, individual system with borehole sharing Strategy 2), while for the district with only single building type, individual system with borehole sharing (ISBS, Sharing Strategy 1) is considered to be bet(ISBS, Sharing Strategy 1) is considered to be better considering the application capacity and carbon ter considering the application capacity and carbon
emission saving. This study can support the decision making on the GSHP application planning for
emission saving. This study can support the decision making on the GSHP application planning for districts and provide reference for district division and sharing strategy utilization.districts and provide reference for district division and sharing strategy utilization.””
Point
Point 2233:: Line 406: This paragraph starts with “Therefore, it can be concluded” whichLine 406: This paragraph starts with “Therefore, it can be concluded” which suggests that suggests that this paragraph contains the actual conclusions of the study. Ithis paragraph contains the actual conclusions of the study. I suggests deleting the first paragraph suggests deleting the first paragraph from the conclusions. The secondfrom the conclusions. The second paragraph can be split in two onparagraph can be split in two on line 410. I think this will make it line 410. I think this will make it easier foreasier for readers to quickly see and understand the main conclusions of the study.readers to quickly see and understand the main conclusions of the study.
Response
Response 2233:: Many thanks for the commentMany thanks for the comment. . We have We have removed the first paragraph and split the rest removed the first paragraph and split the rest contentcontent from Line 438 as from Line 438 as follows.follows.
“
“This study developed two district sharing strategies specific for GSHP system application and This study developed two district sharing strategies specific for GSHP system application and compare their performances on C/D ratio, required borehole number and carbon emissions in three compare their performances on C/D ratio, required borehole number and carbon emissions in three selected districts in London. selected districts in London.
It can be concluded from
It can be concluded from the case studies that a larger building type number and a higher variety in the case studies that a larger building type number and a higher variety in building type with greater differentiation in heating and cooling demands between these types can building type with greater differentiation in heating and cooling demands between these types can lead to a better district sharing performance on all the indicators including C/D lead to a better district sharing performance on all the indicators including C/D ratio, required ratio, required borehole number saving and carbon emissions, which means a greater GSHP system application borehole number saving and carbon emissions, which means a greater GSHP system application potential and a more significant environmental impacts. potential and a more significant environmental impacts.
In addition, district central system (CS, Sharing Strategy 2) has better performance in high
In addition, district central system (CS, Sharing Strategy 2) has better performance in higher sharing er sharing potential range, and individual system with borehole sharing (ISBS, Sharing Strategy 1) in lower range, potential range, and individual system with borehole sharing (ISBS, Sharing Strategy 1) in lower range, so the sharing strategies are applicable to different scope of districts. As for the strategy selection, for so the sharing strategies are applicable to different scope of districts. As for the strategy selection, for the district containing more buithe district containing more building types, it is better to employ district central system (CS, Sharing lding types, it is better to employ district central system (CS, Sharing Strategy 2), while for the district with only single building type, individual system with borehole sharing Strategy 2), while for the district with only single building type, individual system with borehole sharing (ISBS, Sharing Strategy 1) is considered to be better considering the appli(ISBS, Sharing Strategy 1) is considered to be better considering the application capacity and carbon cation capacity and carbon emission saving. This study can support the decision making on the GSHP application planning for emission saving. This study can support the decision making on the GSHP application planning for districts and provide reference for district division and sharing strategy utilization.districts and provide reference for district division and sharing strategy utilization.””

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors,

 

You have properly addressed the main issues posed. Therefore, I recommend this paper for publication.

However, I encourage you to add further details in the discussion section about regulations for sharing land for GSHP-DHC purposes in different Countries. Moreover, you should emphasise and investigate more the topic of available spaces (green areas) in densely populated cities

Author Response

Response to Reviewer1 Comments
Dear Reviewer,
Many thanks for reviewing our paper. We sincerely appreciate you for all the suggestions and
comments. To the best of our ability, we have modified them and colored the changes in red in the
revised manuscript. The responses to comments are described in detail and listed below.
Point 1:
However, I encourage you to add further details in the discussion section about regulations
for sharing land for GSHP DHC purposes in different Countries . Moreover, you should emphasise and
investigate more the topic of available spaces (green areas) in densely populated cities
Response 1:
Many thanks for the comment. We have read more related references carefully and
added further details in the Section 4.3 of Discussion from Line 437 to 452, and we also discussed
more about the densely cities from Line 453 to 459 as follows:
“
Therefore, it can be seen that, in the UK, sharing application of GSHP systems can not on ly benefit
the application capacity and carbon saving, but also lead to a predictable economic improvement
potential due to their Renewable Heat Incentive (RHI). To the best knowledge of authors, the UK’s RHI
is quite advanced worldwide to encourage the di strict sharing of GSHP applications with detailed and
specific inventive categories. There are also other financial incentives dedicated to district sharing
support as well. For example, in France, for geothermal district heating, national funding grants a
bonus of € 250 per ton of CO2 emissions avoided and regional council provides a bonus of € 350 per
ton of CO2 avoided for connecting new dwellings to existing geother mal heating networks [26]. In
the USA, the qualified residential GSHP systems are eligibl e for a 30% credit of the installation cost
and the qualified commercial ones can have a 10%credit [27]. In Shandong Province of China, the
incentive is ￥ 20/m2 for GSHP, and in Henan Province, the incentive is ￥ 15/m2 for either heating or
cooling and ￥ 19.5/m 2 for both heating and cooling [27]. However, in some other areas and counties,
the small scale GSHP system seems to be the encouragement target. In Germany, in new bu ildings,
the support for GSHP is €10/m2 of used building area, up to €2000, and in refurbishment, the support
is €20/m2 of used building area, up to €3000 [26]. These maximum amounts (€2000 or €3000)
demonstrate apparently that this is a program for small homes primarily. In addition, according to the
C/D ratio distributions in the three case studies, the green color ( (≥100%) accounts for a large part.
The main reason for this is that in London the buildings are mainly in the low rise range, which makes
the comfort demand not too high compared with the available energy underground. However , in the
highly densely area, such as the mega city in China, the GSHP systems cannot afford to support energy
supply by themselves, so it is suggested to add the GSHP systems in the hybrid thermal network in
the district and the sharing strategies can sti ll benefit the energy efficiency in this situation.

Author Response File: Author Response.pdf