Small Cogeneration Unit with Heat and Electricity Storage
Round 1
Reviewer 1 Report
The paper presents a case study on the use of CNG engine for operation as a micro-CHP unit for a house. It is within the current trends for implementation of dispersed power sector. The proposed solution operates in the island mode, in which the heat storage tank containing water is charged as well as battery. There is required operation of the engine only for 2 hours per day to cover the demand of the studied dwellings. Generally the paper is well written, however it does not bring into the knowledge any significant progress. It would be interesting to have a more detailed economic analysis, as in the present case the investment cost are not showing the economy of the system in use. That is a major drawback of the study, which I would be glad to see elaborated in a greater detail.
Author Response
We appreciate the reviewer’s careful reading of our manuscript and his/her comments. The comments have substantially helped us to improve the quality of the manuscript.
While the great part of firstly developed EVs is starting to reach their batteries end of life cycle with approximately 80% of their initial accumulation capacity the possibility of using these packs in residential applications is a great relieve for recycle factories while no such an efficient recycle technology is being yet developed. The vision of implementation aged battery packs in specialised centres as a backup accumulation storages is now starting to developed, and approximately 10-15 years the second life can be the way of how to deal with it and is suggested in this article.
Rough economic analysis of using such proposed system is discussed and compared to the price of OEM.
Reviewer 2 Report
The Figure 1 resolution must be changed. In its current form it looks like a print screen.
In Table 5, decimal points should be used for distance values. Commas are used in current form.
If possible, enter more information about the type of Lithium-ion batteries. If a battery management system must also be used. To supervise both, charging and discharging of the batteries.
Author Response
We appreciate the reviewer’s careful reading of our manuscript and his/her comments. The comments have substantially helped us to improve the quality of the manuscript.
We address the reviewer’s questions/comments below:
- The quality of Figure 1 was improved.
- Based on the article template commas were used to distinct the thousands. As recommended decimal points were used in case of decimals. In our opinion the use of decimal/commas is right. Nevertheless the commas were added in the text in case of thousands.
- In the real design, it is necessary to use a current regulator for optimal battery operation and also a phase converter, so that it is possible to take 230V AC at the output. More advanced controllers can be further programmed and thus speak of a battery control unit. These components are not included in the simple energy balance model, as they do not have a large influence on these calculations.
Reviewer 3 Report
The submission offers an original approach of using aged components such as CHP engine (gas based 1.0-L three-cylinder MPI engine) and vehicle battery as principal part of residential CHP distribution system. Proposed system is supposed to operate as autonomous AC/DC hybrid power systems. The potential of this non-standard solution is discussed.
Comments:
- No energy management system is discussed, i.e. how optimal load leveling problem will be solved on residential level? Pls discuss optimal storage usage.
- Discussion on storage system math models is necessary, pls review classic models incl. Tremblay, linear/nonlinear Volterra models and other.
Author Response
We appreciate the reviewer’s careful reading of our manuscript and his/her comments. The comments have substantially helped us to improve the quality of the manuscript.
We address the reviewer’s questions/comments below:
- The main idea is to utilize vast majority of energy from energy storages while the storages are oversized as mentioned in the article. With approximately 2 hours per day of CHP run the energy is sufficient for 24.3 kW of electric energy generated and up to 38.5 kW of thermal energy. The problem of charging and overcharging is not widely discussed in this study and is referenced to other paper.
- The used model in GT Suite was added to the article and the models are reviewed in enclosed reference
Round 2
Reviewer 3 Report
Most of the comments have been taken into account. As final remark, the referee would suggest authors to study mathematical integral models of dynamical systems including aging/hereditarity effects more in details in their future works.
