Dynamic Simulation of a Pneumatic Transport Plant Powered by PV Panels and Equipped with Electro-Chemical Storage
Round 1
Reviewer 1 Report
The paper is evaluated as a valuable paper, with practical simulations. However, I would like to see additional consideration of the following points.
1. Can you mention originality as a simulation method? There is a variety of references that may have performed similar simulations.
2. Figure 1: It is easier to understand if there is numerical information that shows the size of the plant. For example, the size of the PV and batteries assumed in the simulation.
3. P10, 4.2. What is the rationale for setting up these cases?
4.3. With regard to the economic evaluation, it would be better to have a more detailed explanation. For example, how are electricity costs determined? I think it varies from country to country.
Figure 10, 11：The results suggest that storage batteries have little impact and PV capacity has a greater impact. It would be more meaningful results if the impact was considered a little more. Also, what are the reasons why the capacity of storage batteries has no impact?
Author Response
The paper is evaluated as a valuable paper, with practical simulations. However, I would like to see additional consideration of the following points.
- Can you mention originality as a simulation method? There is a variety of references that may have performed similar simulations.
To give examples of previous works envisaging a similar simulation approach, we have chosen the following papers which have been added in the references, and briefly exposed in the Introduction section.
- Sahin, M.E.; Blaabjerg, F. A Hybrid PV-Battery/Supercapacitor System and a Basic Active Power Control Proposal in MATLAB/Simulink. Electronics 2020, 9(1).
Matlab-Simulink model for simulating a combined PV panel – battery – supercapacitor system to smooth the electricity production peaks owing to unregulated energy demand and weather changes.
- Mirzapour, F.; Lakzaei, M.; Varamini, G.; Teimourian, M.; Ghadimi, N. A new prediction model of battery and wind-solar output in hybrid power system. Journal of Ambient Intelligence and Humanized Computing 2019, 10, pp. 77 – 87.
Hybrid wind-solar system production in combination with battery storage. The model envisages filter and hybrid forecast engine based on neural network and an intelligent evolutionary algorithm. Simulations showed the capacity of keeping batteries charge in a suitable range and decrease the on-off switching of panels and wind turbines.
- Olaszi, B. D.; Ladanyi, J. Comparison of different discharge strategies of grid-connected residential PV systems with energy storage in perspective of optimal battery energy storage system sizing. Renewable and Sustainable Energy Reviews 2017, 75, pp. 710 – 718.
Neural network based simulation model of domestic PV panel-battery systems aimed at assessing the battery sizing and the behavior with different control logics for managing the battery discharge methodologies.
- Ding, F; Li, P.; Huang, B.; Gao, F.; Ding, C.; Wang, C. Modeling and Simulation of Grid-connected Hybrid Photovoltaic/Battery Distributed Generation System, 2010 China International Conference on Electricity Distribution, Nanjing, Chin, September 13 – 16. ISBN:978-1-4577-0066-8.
Transient model of the connection of panel-battery hybrid generation system using Matlab-Simulink. Simulations, turned to assess the system interaction with the electric grid to stabilize output as varying environmental conditions.
- Figure 1: It is easier to understand if there is numerical information that shows the size of the plant. For example, the size of the PV and batteries assumed in the simulation.
Figure 1 has been changed according to the given suggestion.
- P10, 4.2. What is the rationale for setting up these cases?
The panel power and battery capacity set for the tests have been chosen in a way to match up with the features of the pneumatic plant compressor, which consumes 55 kW of electric power. We wanted to evaluate the results of two cases: one envisaging a PV panel sized with the same power of the compressor; the other one having a PV panel power half of that of the compressor. The battery capacity range was chosen according to the compressor operational cycle: a 50 kWh battery would be able to feed, alone, the compressor for circa 1 hour; in more, it would be totally charged by the full-power panel power in about 1 – 2 hours depending on the PV panel power.
This has been added in the article text.
4.3. With regard to the economic evaluation, it would be better to have a more detailed explanation. For example, how are electricity costs determined? I think it varies from country to country.
The electricity cost is dependent both on the country and on the type of contract stipulated with the supplier. In our paper, we decided to make an evaluation related to the Italian case: so the price of electricity was determined as the present average selling price in the Italian market. This is indicated in the paper.
The Current Discount Rate, assumed as 3.3%, was derived from EURIBOR.
The Re-Investment Rate, i.e. the percentage of saved money re-invested in other relevant profitable activities, assumed as 5.75%, was chosen prudentially low.
This has been added to the paper.
Figure 10, 11：The results suggest that storage batteries have little impact and PV capacity has a greater impact. It would be more meaningful results if the impact was considered a little more. Also, what are the reasons why the capacity of storage batteries has no impact?
Looking at Figure 9, which indicates the utilization diagrams of the batteries, it is possible to see that, even for the larger capacities (50 kWh and 75 kWh), the storage is full (thus unavailable) for about 50% of simulation time. This means that the energy flow in this component is small with respect to the energy flows of panel, grid and compressor. This might be the reason for which the economic impact of the different batteries on the system is not so important as expected, at least with the battery sizes range considered in this study.
The study of the economical impact of battery capacity and panel power would require a research of the components size optimized for the maximum economical income. This was not the initial purpose of this paper: at the beginning, we only wanted to provide a system able to store in battery the part of the solar power which was not used when the compressor was off, avoiding to overload the electric grid with an injection of power that might make it unstable.
Moreover, to economically optimize the system, there should be a deep study of the control logics that manage the power flows amongst the different system components. In this paper, we only tested the most rational control logics, which deliver all the possible power coming from the panel directly to the compressor when the latter is on, and stores the energy in battery when the compressor is off. If the battery is not available because already full, the panel power is finally delivered to the grid.
The above considerations have been added to the article.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Please present the conclusions part in more detail.Author Response
Please present the conclusions part in more detail.
Since the Reviewer does not specify which part or argument of the conclusions should be presented in more detail, we evaluated that the initial part of the section, explaining the plant configurations studied, the simulation model and the energetic results, are in our opinion rather explicative of the work done and can reasonably satisfy a reader’s comprehension.
Instead, we presented the conclusions adding more detail with regards to the economic assessment, which effectively, in the first draft, were presented in a rather synthetic manner. In particular, we added more observations on the trends of the actualized and cumulative costs for the various plant solutions.
Author Response File: Author Response.docx
Reviewer 3 Report
The paper presents a simulation of a transport plant powered by PV panels and equipped with a battery storage system. To the best of my knowledge, the paper is original and the presented application represents an interesting use case for a self-production system based on a PV field coupled with a storage system, used to contribute to feed a load consisting of a industrial process (less common, in my experience, than, for instance, the classical case of a "PV plus storage system" designed for residential applications)
The application can be interesting for researchers in the field and, in my opinion, the economic analysis, added to the Simulink simulation of the system, add value to the work.
Author Response
The paper presents a simulation of a transport plant powered by PV panels and equipped with a battery storage system. To the best of my knowledge, the paper is original and the presented application represents an interesting use case for a self-production system based on a PV field coupled with a storage system, used to contribute to feed a load consisting of a industrial process (less common, in my experience, than, for instance, the classical case of a "PV plus storage system" designed for residential applications)
The application can be interesting for researchers in the field and, in my opinion, the economic analysis, added to the Simulink simulation of the system, add value to the work.
We thanks the Reviewer for his appreciation in our work.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
It is assessed as being appropriately corrected.
