Review Reports - Environmental Comparison of Energy Solutions for Heating and Cooling

Round 1

Reviewer 1 Report

Comments:

Abstract:

Keywords needs to be re-written. For example: “bidirectional low temperature…” is not mentioned in abstract but it is in keywords and in the other hand, “Geothermal energy” is in the abstract as one compared solution but it is not mentioned in the abstract. Also, “Ectogrid” needs to be mentioned after smart energy system.

Introduction:

Lines 29 to 30: it is better to write the sentence as below:

Therefore, it is of paramount importance to reduce the use of electricity and heat and in the same time increase the share of renewable energy.

Line 31: instead of “will be” it is better to use “may be” or “can be”

Line 33: “Climate” mostly used for outdoor and I suggest to use “indoor-air condition”

Line 36: instead of “answers” use “approaches”

Lines 36 to 43: if “ectogrid” is based on an existing technology, please add the reference to this paragraph.

Line 41: “move energy”? it is better to use “transfer the energy”

Lines 44 to 48: it is better to move this paragraph before previous paragraph (Lines 36 to 43). Because this is more general.

Lines 49 to 56: You used “The purpose” three times in this paragraph which is not professional in English writing. I suggest you to use “the aim” for one, and “the reason” for another one or some other words with the same meaning of purpose.

Line 57: it is better to say: “The following aspects are covered in this study:”

General comment: Introduction is written well but just few points that I mentioned. Only the referencing is not done well. Please reference any sentence which is not your own work on this paper.

Heating and Cooling Buildings

Lines 64 to 66: There is a non-acceptable and basic mistake here. Heat transfer from higher temperature area to lower, but the statement in the paper is revers which is wrong. Please fix this.

Line 66 to 68: These two sentences needs to be re-written.

Line 90 to 91: “Geothermal heat comes from pressure and nuclear reactions at the earth's core.” This statement in the paper is completely wrong. Also, I checked the reference 7 as pointed in the paper. In Ref.7 the statement is this: “Geothermal heat comes from pressure and nuclear reactions at the earth's core.”

To let the author know, the geothermal energy is one of the renewables which is not related to Sun at all.

These two major mistakes are not acceptable for a paper. You must to redo the literature review and understand the facts.

Author Response

Dear Reviewer 1,

Thank you very much for your comments. We think that they are very good comments and we have updated the paper with all of them. Please find below the answers to each of the comments.

Abstract:

Answer: This is a good point. “Bidirectional low temperature” has therefore been taken away from the keywords. “Geothermal energy” has been added, and “smart energy systems” has been moved so that it is mentioned before “ectogrid”.

Introduction:

Lines 29 to 30: it is better to write the sentence as below:

Therefore, it is of paramount importance to reduce the use of electricity and heat and in the same time increase the share of renewable energy.

Answer: Thank you for the comment. The sentence has been changed according to the recommendation.

Line 31: instead of “will be” it is better to use “may be” or “can be”

Answer: The sentence has been changed according to the recommendation. The expression “can be” is used instead of “will be”. Thank you for the comment.

Line 33: “Climate” mostly used for outdoor and I suggest to use “indoor-air condition”

Answer: Yes, that is a better alternative. The sentence has been changed according to the recommendation.

Line 36: instead of “answers” use “approaches”

Answer: Yes, that is a better word to use. The sentence has been changed according to your recommendation.

Lines 36 to 43: if “ectogrid” is based on an existing technology, please add the reference to this paragraph.

Answer: We agree that there should be references of ectogrid in this part of the paper. In this section three references have been added. One of them is a reference that originally was used later in the paper, and the other two are new references added to the paper.

Line 41: “move energy”? it is better to use “transfer the energy”

Answer: Yes, that is right. The sentence has been changed according to the recommendation.

Lines 44 to 48: it is better to move this paragraph before previous paragraph (Lines 36 to 43). Because this is more general.

Answer: This is a good point. The paragraph “lines 44 to 48” has been moved before the paragraph “lines 36 to 43”.

Answer: That is right. Now “The purpose” is only used once in the paragraph. The other two have been replaced with “The aim” and “The objectives”.

Line 57: it is better to say: “The following aspects are covered in this study:”

Answer: Thanks, that is better. The sentence has been changed according to the recommendation.

General comment: Introduction is written well but just few points that I mentioned. Only the referencing is not done well. Please reference any sentence which is not your own work on this paper.

Answer: Thank you for this comment. Another 6 sentences now have references in the introduction chapter. Since there are some new references that have been added, and some of the original references that have changed order, the reference list has also been updated.

Heating and Cooling Buildings

Lines 64 to 66: There is a non-acceptable and basic mistake here. Heat transfer from higher temperature area to lower, but the statement in the paper is revers which is wrong. Please fix this.

Line 66 to 68: These two sentences needs to be re-written.

Answer: We agree that the paragraph needs to be changed. We have clarified that there is a need of adding work to the process to be able to transfer energy from a lower to a higher temperature. The text is now changed to: “The principle for both heat pumps and cooling machines is the same. By using additional work to the process in the form of electricity, heat can be transferred from an environment of lower temperature to an environment of higher temperature [9].”

Answer: Thanks for noticing this. The sentence has now been changed to “Geothermal heat, which is stored in the bedrock, originates from pressure and nuclear reactions at the core of the earth [13]”.

Best Regards,

Maria Andersson

Reviewer 2 Report

In Figure 1, there is a building that is equipped with both a heat pump and a cooling machine. Is that necessary to have that cooling machine, since the heat pump is able to do both of the cooling and heating jobs? On page 7, line 257, why the pump power is estimated to be 1% and 1.5% for case 2 and 3? Why not 2% or 5%? On page 7, line 280, is the “hourly values of the heat demand” a known value? Simulated or measured? On page 8, line 315, “In the model the heat and cooling demand for Medicon Village during 2015….”. How are you able to know the heating and cooling demands? Is this a new project or an existing project (it said “ectogrid is implemented for the first time in Medicon Village as a pilot project, and is expected to be finalized during 2020”)? We need more information about this project. A big concern for this paper is if the author is able to verify the energy usage result shown in Figure 3. This result is the basis of the paper, which was used to estimate the environmental impact. It is not clear if a well-known or well-developed energy modeling environment (such as some commercial energy simulation software) is used. The models used for the three cases seem too simple with many assumptions, and I did not see any model validation or calibration. So the result obtained from these models is questionable. Please provide more information and descriptions about the simulation model and how these numbers representing the energy usage of these three cases were calculated. In this case, readers would have more confidence to use your results in their studies.

Author Response

Dear Reviewer 2,

Thank you very much for taking time to read and comment on our paper. We think that the comments have helped us to improve the paper. Please find our answers below.

Thank you for this comment. Figure 1 is just an example of a possible combination. Which components that are necessary depends on the heating and cooling needs and the local conditions. In Figure 1, the building in the top right manages to satisfy both heating and cooling needs using only a heat pump, while the building in the bottom to the left has a different heating and cooling demand and needs both a heat pump and a cooling machine.

The presentation of Figure 1 has been changed to the following: “Figure 1. An example of a possible combination of demands and components in ectogrid^TM.”

On page 7, line 257, why the pump power is estimated to be 1% and 1.5% for case 2 and 3 Why not 2% or 5%?

Answer: Thank you for this comment. The reason why we choose these figures is that we have got them from a person that is an expert in the field and also for the environment of Medicon Village. Reference [28] refers to this conversation. This is the best estimation that we can do for this case.

We have changed a bit in the paragraph to clarify the reason for choosing the figures for the area of Medicon Village.

“Only the pumps that will distribute energy between the energy source and the buildings are included in the calculations. In Case 1 and this particular network the energy supplied to the pump is assumed to be 1.5 % of the total energy use [28]. In that case the pumps are used to deliver the district heating and cooling from the production place. In Case 2 and Case 3 the energy supplied to the pump is estimated to be 1.0 % of the total energy use [28]. There are several reasons why the supplied energy to the pump is estimated to be lower in Case 2 and Case 3. In Case 1, a higher pressure and more energy are needed to ensure a desired flow to all the customers in the network. In Case 2 and Case 3 the energy source is closer to Medicon Village. The pumps are situated in connection with the components in the system and use only the amount of energy needed to deliver the desired flow. All pumps are assumed to work all the year with the same load.”

On page 7, line 280, is the “hourly values of the heat demand” a known value? Simulated or measured?

Answer: Thank you for this comment. The hourly values of the heat demand are known values based on measurements from meters in the buildings for 2015. We have clarified this in the first paragraph of chapter 3, which now also includes a new reference [25]. This reference indicates the order of magnitude of the energy use of the conventional system and the energy use of ectogridTM. This could be seen as a verification of our results, including a verification of the relative difference between the energy use of Case 1 and Case 2.

On page 8, line 315, “In the model the heat and cooling demand for Medicon Village during 2015….”. How are you able to know the heating and cooling demands? Is this a new project or an existing project (it said “ectogrid is implemented for the first time in Medicon Village as a pilot project, and is expected to be finalized during 2020”)? We need more information about this project.

Answer: Thank you for this comment. We agree this needs to be more explained in the paper. Medicon Village consists of an existing group of buildings, containing laboratories and offices. Until the installation of ectogrid, the energy solution has been district heating and cooling. The heating and cooling demands (10 GWh and 4 GWh respectively) are known based on hourly metering of district heating and cooling in the buildings. The heating and cooling demand of Medicon Village is also mentioned in a reference that has been added to the paper:

EON is building the world’s first ectogridTM at Medicon Village. Available online: http://ectogrid.com/use-cases/medicon-village/ (accessed on 22 November 2019).

To give further information about the existing ectogrid project, two more references have been added to the paper. These are:

EON The ectogrid^TM technology. Avaliable online: http://ectogrid.com/business-customer/ (accessed on 21 November 2019). Game changing technology connects Medicon Village buildings. Available online: https://www.mediconvillage.se/sv/game-changing-technology-connects-medicon-village-buildings (accessed on 21 November 2019).

A big concern for this paper is if the author is able to verify the energy usage result shown in Figure 3. This result is the basis of the paper, which was used to estimate the environmental impact. It is not clear if a well-known or well-developed energy modeling environment (such as some commercial energy simulation software) is used. The models used for the three cases seem too simple with many assumptions, and I did not see any model validation or calibration. So the result obtained from these models is questionable. Please provide more information and descriptions about the simulation model and how these numbers representing the energy usage of these three cases were calculated. In this case, readers would have more confidence to use your results in their studies.

Answer: Thank you for this comment. That is true, this needs to be more clarified. The results of Figure 3 can be verified against reference [25], which indicates similar results for Case 1 and Case 2. Moreover, there has been a close cooperation with experts in the field for both the conventional solution with district heating and cooling and ectogrid, both for the area of Medicon Village. Case 3 has been designed in close cooperation with experts on geothermal energy. The results of the work have been presented to E.ON who were satisfied with the results. We have provided more information in different parts of the paper to answer this comment. Please find these parts below:

Section 4, 4.1: The calculations are made hourly and divided into district heating use and electricity use for each of the three cases. The aim of the calculations is to obtain the sufficient amount of energy needed to meet the heating demand of 10 GWh and the cooling demand of 4 GWh [25]. The method considers the different components of the different energy solutions including their energy losses. The calculations are performed with a method based on Microsoft Excel [27].

Section 4.1.1: In Case 1 the use of electricity and heat connected to the district heating and cooling in Medicon Village has been calculated. The aim of the calculations is to find the amount of energy that can meet the heating and cooling demand of 10 GWh and 4 GWh respectively.

Section 4.1.2: In Case 2 the use of electricity and heat for the ectogrid™ system in Medicon Village is calculated. As in Case 1, the aim of the calculations is to meet the heating and cooling demand of 10 GWh and 4 GWh respectively.

Section 4.1.3: In Case 3 the electricity use connected to a geothermal energy solution in Medicon Village is calculated, with the aim of meeting the heating and cooling demand of 10 GWh and 4 GWh respectively.

Section 5.1: Figure 3 shows the annual energy use for Case 1, Case 2 and Case 3. The energy use has been calculated according to the procedures described in section 4 including 4.1.1, 4.1.2 and 4.1.3. The calculations show that the energy use of Case 1 amounts to 12 250 MWh, which is the highest of the three cases. The electricity use for Case 1 is however the lowest. The energy use of Case 2 is considerably lower and represents a reduction of 61 % compared to Case 1. The energy use for Case 3 is reduced further and represents a reduction of 70 %. The results for Case 1 and Case 2 can be verified by [25] where approximately the same energy amounts are obtained for the conventional district heating and cooling system and ectogridTM, and also a similar relative difference in energy use between the two cases.

and

Figure 4 shows the climate impact quantified in number of CO2 equivalents for a year. The procedure for the calculations is explained in 4.2, and the emission factors for the electricity and district heating are shown in Table 2.

We have also added in the discussion chapter a section 6.1 where we discuss the data and some of their uncertainties.

We hope that this can improve the description of the procedure and the results.

Best Regards,

Maria Andersson

Round 2

Reviewer 2 Report

Interesting idea and project. Thanks!