Hybrid CHP/Geothermal Borehole System for Multi-Family Building in Heating Dominated Climates

Round 1

Reviewer 1 Report

The article presents results of CHP system simulations. In reviewers opinion article has serious flaws regarding methodology and results as listed below.

-authors do not present the values used in the article for CHP efficiency 

- the used symbols are not unified eg. ?_??ℎ and ℎ?_??ℎ

-ref 14  is not working,

-line 146 "Data on heating and cooling requirements for Winnipeg are constructed from data on the Ohio heating and cooling requirements by scaling the Ohio data by the ratio of degree-day values (Canada to Ohio)." Oversimplification  - the resulting graph shows that the heating load starts in the same time which isn't the case.

-Columbus and Ohio are used in the text , in reviewers opinion this is misleading

-How does starting point in fig 9 and 10 differ? It implies that authors are comparing two very different cases.

- introduction section needs to be enhanced with better literature review

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper presents a study describing a co-optimization of combined heat and power, electrochemical battery storage, and ground-source heat pump systems. The authors describe a number of interesting points and technical issues that warrant further study for a hybrid system such as the one described in the paper. In general, the paper is interesting and a relevant topic.

Review comments and suggestions:

1. The wording in parts of the introduction is nearly unintelligible at times. I had to go to the source reference [1] to even understand the first two sentences, which is not a great start for a reviewer… Please have a native English speaker review and edit the introduction for clarity and intent.
2. It’s clear that the introduction was written by one person, and the rest of the paper was written by another person. The “voice” of the paper needs to be melded together so this is not so obvious.
3. Lines 130-132: how were the electrical, hot water, and heating loads determined? Provide details of the building energy models, building codes, statistical methods, etc. used to determine these loads.
4. Lines 189-190: you are assuming the CHP waste heat is sufficient to meet the domestic hot water loads. Why is this? Please explain. There must be some sort of thermal efficiency assumption from the CHP built into your model.
5. Line 324-ish: need some details regarding your heat pump model. Fixed COP model? Energy input ratio as a function of temperature model? One data point pulled from an MFR cut sheet?
6. Figure 9: with negative fluid temperatures, you likely had to assume some sort of antifreeze mixture. Provide these details.
7. Table 2: please add assumed ground heat exchanger pipe size and type.
8. Table 2: units of GPM. Convert to LPS as the primary unit. Add in-text somewhere if you considered whether the flow rate is sufficient to maintain turbulent flow.
9. Table 2: please add assumed ground heat exchanger pipe size and type.
10. In-text symbols need to be typeset in math mode. See lines, 223, 234, 236, 247, 249.
11. Table 3, rows 1 and 3: it seems very unlikely that these prices are equal for both locations. Please check and add clarification if correct.
12. I suggest you add in the text that battery degradation, battery replacement costs, non-ideal battery efficiency, O&M costs, and thermal losses are not considered and what effects these could have on the results if considered.
13. Right-top header: page 8-end goes out of sync with the document.

The paper can be accepted after revision.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

In this paper, the authors present the design of a hybrid CHP/GCHP system for a multi-family building. I found this article interesting and I consider that the manuscript has real potential to be published in sustainability. The text is written in a good and comprehensive English. Approximately 56% of this document consists of text more or less similar to the content of 61 sources considered most relevant. The largest section with similarities contains 224 words and has a similarity index of 82% with its main source. The similarity index presented above does not in any way indicate the proven presence of plagiarism. Indeed, the only source comes from the dissertation presented to The School of Engineering of the University of Dayton by Saeed A. Alqaed with a view to obtaining the degree of Doctor of Philosophy https://etd.ohiolink.edu/!etd.send_file?accession=dayton1484060080437186&disposition=inline

However, modifications may be made like :

Line 61: ... domestic ventures [8].

Line 220: Table 1. Variables used for calculating annual system cost.

Line 247: ... 〖B〗_cap.

Line 258: Use (7)-(12) to evaluate ...

Line 306: You can delete: Table 2: Summary of design parameters for Ohio.

Author Response

Please see the attachment

Author Response File: Author Response.pdf