Optimal Design of a Hybrid Solar PV/BG-Powered Heterogeneous Network

Round 1

Reviewer 1 Report

The presented work can be accepted after undergoing several modifications.

 

1. I don't see clearly what is the novelty of this work? I have read a few other similar works. The authors need to cite similar work and justify what is the differences provided by this work.
2. What is the basis for the suggested constructed cost modeling?
3. Section 5.1: "This means that the proposed system can satisfy the energy demand of the BS". Please further explain this sentence and provide evidence.
4. Please reduce the self-citation in the reference section accordingly. 

Author Response

Reviewer#1

The presented work can be accepted after undergoing several modifications

Reviewer#1, Concern#1: I don't see clearly what is the novelty of this work? I have read a few other similar works. The authors need to cite similar work and justify what is the differences provided by this work.

Author response: Thank you for your insightful comments. To the best knowledge, we are the first to develop a techno-economic and energy efficiency analysis integrating solar PV/BG system with electrical grid system for the envisaged heterogeneous networks along with the sleep algorithm for IoT applications. We know that heterogeneous networks, offering a combination of a variety of wireless coverage zones, are cellular platforms addressing the fast-increasing traffic intensity.

As per your suggestion, we revised the article by comparing the proposed system and other systems in terms of energy, economic, and cleanliness issues to justify network validity

Author action: We have revised the manuscript as below:

Sub-section: 5.7: Feasibility Comparison

In order to ensure the effectiveness of the proposed approach, we compared it to some key approaches from the literature. The findings are summarized in Table 8.

From our literature review leading to the above comparison analysis, we noticed that most studies have focused on the key obstacles of establishing a green cellular network that included solar PV and wind turbines as well as a backup system. Furthermore, many of them didn't analyze the system for heterogeneous networks. To the best of our knowledge, we are the first to develop a techno-economic and energy efficiency analysis integrating solar PV/BG system with electrical grid system for heterogeneous networks, in addition to the proposed sleep algorithm for IoT applications. Additionally, the suggested system was found to have only have a net present cost of about $ 21, 445 and an energy-generating cost of $ 0.379/kWh for the macro base station. Furthermore, a steady decline in per-unit energy generation cost has been found in response to higher system bandwidth, resulting in lower carbon footprints.

References

56. Alsharif, M.H.; Kim, J.; Kim, J.H. Energy optimization strategies for Eco-friendly cellular base stations. Energies 2018, 11, doi:10.3390/en11061500.
57. Olatomiwa, L.; Mekhilef, S.; Huda, A.S.N.; Sanusi, K. Techno-economic analysis of hybrid PV–diesel–battery and PV–wind–diesel–battery power systems for mobile BTS: The way forward for rural development. Energy Sci. Eng. 2015, 3, 271–285, doi:10.1002/ese3.71.
58. Margaret Amutha, W.; Rajini, V. Techno-economic evaluation of various hybrid power systems for rural telecom. Renew. Sustain. Energy Rev. 2015, 43, 553–561, doi:https://doi.org/10.1016/j.rser.2014.10.103.
59. Asif, R.; Khanzada, F. Cellular Base Station Powered by Hybrid Energy Options. Int. J. Comput. Appl. 2015, 115, 35–39, doi:10.5120/20286-2842.
60. Alsharif, M.H.; Nordin, R.; Ismail, M. Green wireless network optimisation strategies within smart grid environments for Long Term Evolution (LTE) cellular networks in Malaysia. Renew. Energy 2016, 85, 157–170, doi:10.1016/j.renene.2015.06.044.
61. Hossain, M.S.; Rahman, M.F. Hybrid solar PV/Biomass powered energy efficient remote cellular base stations. Int. J. Renew. Energy Res. 2020, 10, 329–342.
62. Jahid, A.; Monju, M.K.H.; Hossain, M.E.; Hossain, M.F. Renewable Energy Assisted Cost Aware Sustainable Off-Grid Base Stations with Energy Cooperation. IEEE Access 2018, 6, 60900–60920, doi:10.1109/ACCESS.2018.2874131.

Reviewer#1, Concern#2: What is the basis for the suggested constructed cost modeling?

Author response: The foundation of the introduced cost modeling is to determine the net present cost (NPC) and per unit electricity generation cost (COE) of the hybrid supply system through the Hybrid Optimization Model for Electric Renewables (HOMER) optimization software under a wide range of network configurations. In HOMER, the net present cost (NPC) represents the present value of all the associated costs that occur over the project duration. The total NPC of the system includes a capital cost (CC), replacement cost (RC), cost of electricity (COE), operation and maintenance cost (OMC), fuel cost (FC), and salvage value (SV). The details of the suggested cost modeling can be found in [R1].

[R1] Alsharif, M.H.; Kim, J. Hybrid off-grid SPV/WTG power system for remote cellular base stations towards green and sustainable cellular networks in South Korea. Energies 2017, 10, doi:10.3390/en10010009.

Reviewer#1, Concern#3: Section 5.1: "This means that the proposed system can satisfy the energy demand of the BS". Please further explain this sentence and provide evidence.

Author response: As per your suggestion, we have added evidence and more explanation of the mentioned sentence. Table 2 provides the evidence of the mentioned statement. From Table 2 it is clearly seen that the optimal size of the BG, battery, and converter are in a smaller range and stay almost consistent for all system bandwidths.

Author action: We have revised the manuscript as below:

Sub-section 5.1: “As refer to Table 2, the optimal dimensions of the BG, battery, and converter are in a smaller range and stay almost consistent for all configurations. This indicates that the proposed system is technically feasible and can meet the BS's energy demand in a variety of bandwidth scenarios without requiring major changes to the system's components.”

Reviewer#1, Concern#4: Please reduce the self-citation in the reference section accordingly.

Author response: As per your suggestion, we have revised the article by reducing the percentage of self-citation. The revised has single-digit (around 8 %) self-citation.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is trying to propose a hybrid optimization model to determine the optimum system architecture economic and environmental analysis of a solar photovoltaic /biomass generator-powered HetNet in Bangladesh.

The topic addressed in the manuscript is potentially interesting, and the manuscript contains some practical meanings and interesting numerical results. However, there are some corrections, modifications, and unclear points to be considered and need to be addressed for further steps of publication:

1- The ABSTRACT has been written in a very complicated form! Too many abbreviations are used that make first readers confused and difficult to understand. Overall, the motivation, the model, and the outcomes are not clear for a reader. I recommend that the abstract should be overall revised and written in a more simple and clear form. For example, it should be clearly mentioned that: “This paper proposes a (hybrid) optimization model to determine the optimum system architecture, economic and environmental analysis of a potential (hybrid) solar photovoltaic (PV)/biomass generator (BG)-powered HetNet in Bangladesh.” The main objective (s) of the paper must be written in a more clear and more concise way at the abstract as well as the end of the introduction section (contribution).

2-   Avoid using abbreviations (or at least unnecessary ones)  in the abstract. The abbreviations should be introduced only for the first time they are used in the main text.

3- Provide a  Nomenclature section for all symbols. The abbreviations can also be reported in this section for readers’ convenience.

4-  Please add some quantitative data in the abstract section related to the main research outcomes. For instance: “the proposed hybrid system produces 9,902 kWh of total energy (66 % from 708 solar PV and 34 % from BG) and ….”.

5-  How have you evaluated/ verified your result? Any experimental data possible to be carried out by you or available in the literature to validate some results of your modes. It is worth reporting a validation even with some results of a simplified model.

6-  There are different options/technologies for utilizing solar energy (e.g., CSP and PV) and biomass (e.g., thermochemical (combustion and gasification) and biochemical (anaerobic digestion) and therefore different possible hybridization as well. Please indicate why you proposed/chose that combination (PV and bio?). Also, report what kind of biomass fuel/technology you targeted (combustion or gasification or…?). It is recommended to read the following recent article, which has reviewed the latest advances on hybrid solar–biomass power plants:

Latest advances on hybrid solar–biomass power plants

https://www.tandfonline.com/doi/full/10.1080/15567036.2021.1887974

7-  Based on the above paper, despite that several studies have been conducted in this field, there is currently only one operational hybrid solar-biomass power plant (Termosolar Borges). Hence, the literature part can mention this reference(s)/power plant and can be improved. Furthermore, the literature can also indicate the barriers and limitations of hybridization power plants.

8-  Get its English edited and typos very carefully.

Author Response

Reviewer#2

The manuscript is trying to propose a hybrid optimization model to determine the optimum system architecture economic and environmental analysis of a solar photovoltaic /biomass generator-powered HetNet in Bangladesh.

The topic addressed in the manuscript is potentially interesting, and the manuscript contains some practical meanings and interesting numerical results. However, there are some corrections, modifications, and unclear points to be considered and need to be addressed for further steps of publication:

Reviewer#2, Concern#1: The ABSTRACT has been written in a very complicated form! Too many abbreviations are used that make first readers confused and difficult to understand. Overall, the motivation, the model, and the outcomes are not clear for a reader. I recommend that the abstract should be overall revised and written in a more simple and clear form. For example, it should be clearly mentioned that: “This paper proposes a (hybrid) optimization model to determine the optimum system architecture, economic and environmental analysis of a potential (hybrid) solar photovoltaic (PV)/biomass generator (BG)-powered HetNet in Bangladesh.” The main objective (s) of the paper must be written in a more clear and more concise way at the abstract as well as the end of the introduction section (contribution).

Author response: Thank you very much for your valuable suggestion. As per your instruction, we have updated the abstract for presenting a clear view to the reader.

Author action: We have revised the manuscript as below:

Abstract: The increased penetration of renewable energy sources (RESs) along with the rise in demand for wireless communication had led to the need to deploy cellular base stations powered by locally accessible RESs. Moreover, networks powered by renewable energy sources have the ability to reduce the costs of generating electricity as well as greenhouse gas emissions, thus maintaining the quality of service (QoS). This paper examines the techno-economic feasibility of developing grid-tied solar photovoltaic (PV)/biomass generator (BG)-powered heterogeneous networks in Bangladesh, taking into account the dynamic characteristics of RESs and traffic. To guarantee QoS, each macro, and micro-base station is supplied through a hybrid solar PV/BG coupled with enough energy storage devices. In contrast, pico and femto BSs are powered through standalone solar PV units due to their smaller power rating. A hybrid optimization model for electric renewables (HOMER)-based optimization algorithm is considered to determine the optimum system architecture, economic and environmental analysis. MATLAB-based Monte-Carlo simulations are used to assess the system’s throughput and energy efficiency. A new weighted proportional-fair resource method is presented by trading power consumption and communication latency in non-real-time applications. Performance analysis of the proposed architecture confirmed its energy efficiency, economic soundness, reliability, and environmental friendliness. Additionally, the suggested method was shown to increase the battery life of the end devices.

Reviewer#2, Concern#2: Avoid using abbreviations (or at least unnecessary ones) in the abstract. The abbreviations should be introduced only for the first time they are used in the main text.

Author response: As per your suggestion, we have revised the abstract by removing the unnecessary abbreviations.

Reviewer#2, Concern#3: Provide a Nomenclature section for all symbols. The abbreviations can also be reported in this section for readers’ convenience.

Author response: As per your instruction, we have added an appendix at the end of the conclusion section identifying symbols and notations used in the manuscript.

Author action: We have revised the manuscript as below:

Appendix: Summary of the notations and symbols.

Notations/Symbols	Meaning
BG	Biomass generator
BS	Base station
BW	Bandwidth
COE	Cost of energy
DG	Diesel generator
DRX	Discontinuous reception
EE	Energy efficiency
GHG	Greenhouse gas
HetNet	Heterogeneous networks
IoT	Internet of Things
NPC	Net present cost
NRT	Non-real-time
PV	Photovoltaic
QoS	Quality of service
WT	Wind turbine
Nbatt	Number of batteries
	Traffic rate

Reviewer#2, Concern#4: Please add some quantitative data in the abstract section related to the main research outcomes. For instance: “the proposed hybrid system produces 9,902 kWh of total energy (66 % from 708 solar PV and 34 % from BG) and ….”.

Author response: Thank you for your valuable comment. As per your instruction, we have updated the abstract for presenting a clear view to the reader. But, we revised the manuscript by adding some quantitative data in the feasibility comparison subsection that are related to the research outcomes.

Sub-section: 5.7: Feasibility Comparison

Additionally, the suggested system was found to have only have a net present cost of about $ 21, 445 and an energy-generating cost of $ 0.379/kWh for the macro base station. Furthermore, a steady decline in per-unit energy generation cost has been found in response to higher system bandwidth, resulting in lower carbon footprints.

Reviewer#2, Concern#5: How have you evaluated/ verified your result? Any experimental data possible to be carried out by you or available in the literature to validate some results of your modes. It is worth reporting a validation even with some results of a simplified model.

Author response:  Thank you for the insightful query. We checked our results. The original manuscript had 28 pages. To make the paper concise, we didn’t present the comparison with the cases of some other published works. As per your suggestion, we revised the article by adding a feasible comparison sub-section.

Author action: We have revised the manuscript as below:

Sub-section: 5.7: Feasibility Comparison

In order to ensure the effectiveness of the proposed approach, we compared it to some key approaches from the literature. The findings are summarized in Table 8.

From our literature review leading to the above comparison analysis, we noticed that most studies have focused on the key obstacles of establishing a green cellular network that included solar PV and wind turbines as well as a backup system. Furthermore, many of them didn't analyze the system for heterogeneous networks. To the best of our knowledge, we are the first to develop a techno-economic and energy efficiency analysis integrating solar PV/BG system with electrical grid system for heterogeneous networks, in addition to the proposed sleep algorithm for IoT applications. Additionally, the suggested system was found to have only have a net present cost of about $ 21, 445 and an energy-generating cost of $ 0.379/kWh for the macro base station. Furthermore, a steady decline in per-unit energy generation cost has been found in response to higher system bandwidth, resulting in lower carbon footprints.

References

56. Alsharif, M.H.; Kim, J.; Kim, J.H. Energy optimization strategies for Eco-friendly cellular base stations. Energies 2018, 11, doi:10.3390/en11061500.
57. Olatomiwa, L.; Mekhilef, S.; Huda, A.S.N.; Sanusi, K. Techno-economic analysis of hybrid PV–diesel–battery and PV–wind–diesel–battery power systems for mobile BTS: The way forward for rural development. Energy Sci. Eng. 2015, 3, 271–285, doi:10.1002/ese3.71.
58. Margaret Amutha, W.; Rajini, V. Techno-economic evaluation of various hybrid power systems for rural telecom. Renew. Sustain. Energy Rev. 2015, 43, 553–561, doi:https://doi.org/10.1016/j.rser.2014.10.103.
59. Asif, R.; Khanzada, F. Cellular Base Station Powered by Hybrid Energy Options. Int. J. Comput. Appl. 2015, 115, 35–39, doi:10.5120/20286-2842.
60. Alsharif, M.H.; Nordin, R.; Ismail, M. Green wireless network optimisation strategies within smart grid environments for Long Term Evolution (LTE) cellular networks in Malaysia. Renew. Energy 2016, 85, 157–170, doi:10.1016/j.renene.2015.06.044.
61. Hossain, M.S.; Rahman, M.F. Hybrid solar PV/Biomass powered energy efficient remote cellular base stations. Int. J. Renew. Energy Res. 2020, 10, 329–342.
62. Jahid, A.; Monju, M.K.H.; Hossain, M.E.; Hossain, M.F. Renewable Energy Assisted Cost Aware Sustainable Off-Grid Base Stations with Energy Cooperation. IEEE Access 2018, 6, 60900–60920, doi:10.1109/ACCESS.2018.2874131.

Reviewer#2, Concern#6: There are different options/technologies for utilizing solar energy (e.g., CSP and PV) and biomass (e.g., thermochemical (combustion and gasification) and biochemical (anaerobic digestion) and therefore different possible hybridization as well. Please indicate why you proposed/chose that combination (PV and bio?). Also, report what kind of biomass fuel/technology you targeted (combustion or gasification or…?). It is recommended to read the following recent article, which has reviewed the latest advances on hybrid solar–biomass power plants:

Latest advances on hybrid solar–biomass power plants

https://www.tandfonline.com/doi/full/10.1080/15567036.2021.1887974

Author response: Bangladesh is a tropical country, whose geographical position is between 33º and 39º N latitude and between 124º and 130º E longitude. As a tropical country, Bangladesh has
enough potential to harvest renewable energy from the sunlight. As reported by [R2], [R3] the average sunlight intensity and clearness index are respectively 4.59 kWh/m²/day and 5.3; the highest solar intensity is 4 kWh/m²/day in May and the lowest solar intensity is 6.5 kWh/m²/day in June. With the help of this higher solar radiation profile and modern technology, Bangladesh has the capability of producing around 70 PWh electrical energy, which is 3000 times higher than the total electricity demand of the country [R3].

Bangladesh has enough potential for harvesting energy from biomass resources. The most available biomass sources of the country mainly include agriculture residue, animal
dung, poultry dropping, etc. As an agricultural country, agriculture residue is the main source of biomass, wherein rice husk plays a significant role. As mentioned by the ‘Rice
Mills Owners Association’ in Bangladesh, there are around 540 rice mills throughout the country, and the average capacity of the mills is 30 tons/day, which has the potential
of producing 171 MW per day [R4], [R5]. According to [11], Bangladesh had approximately 90.21 million tons of biomass available whose energy potential was 1,344.99 PJ equivalent
to 373.71 TWh of electrical energy in fiscal year (FY) 2012- 2013. Authors in [R5] studied that Bangladesh will be able to generate 7,682 GWh energy from the rice husk with a total capacity of 1,066 MW in 2030.

Being inspired by the above potential benefits, this work develop an energy-efficient hybrid supply system to power the green cellular network in Bangladesh, taking into account the locally available solar PV and biomass sources. In this paper, biomass combustion technology has been selected. Finally, we have added the mentioned article in the literature review section by addressing the barriers and limitations of the hybrid supply system.

[R2] NASA. Surface meteorology and solar energy: a renewable energy resource. Available online:
https://eosweb.larc.nasa.gov/sse/.

[R3] M. A. H. Mondal and A. K. M. S. Islam, ‘‘Potential and viability of grid-connected solar PV system in Bangladesh,’’ Renew. Energy, vol. 36, no. 6, pp. 1869–1874, Jun. 2011

[R4]A. S. N. Huda, S. Mekhilef and A. Ahsan, “Biomass energy in Bangladesh: current status and prospects,” Renew. and Sustainable Energy Reviews, vol. 30, no. 1, pp. 504-517, Feb. 2014.

[R5]M. Ahiduzzaman and A. Sadrul Islam, “Energy utilization and environmental aspects of rice processing industries in Bangladesh,” Energies, vol. 2, no. 1, pp.134–149, Mar. 2009.

Reviewer#2, Concern#7: Based on the above paper, despite that several studies have been conducted in this field, there is currently only one operational hybrid solar-biomass power plant (Termosolar Borges). Hence, the literature part can mention this reference(s)/power plant and can be improved. Furthermore, the literature can also indicate the barriers and limitations of hybridization power plants.

Author response: As per your instruction, we have added the mentioned article in the literature review section by addressing the barriers and limitations of the hybrid supply system.

Author action: We have revised the manuscript as below:

Literature Review: The integration of solar PV with biomass resources for establishing a long-term sustainable and reliable power station has been thoroughly investigated in reference [32]. In this work, the fundamental problems of developing a hybrid solar PV/biomass-focused power plant were investigated, and several significant solutions were proposed.

[32] Mohaghegh, M.R.; Heidari, M.; Tasnim, S.; Dutta, A.; Mahmud, S. Latest advances on hybrid solar–biomass power plants. Energy Sources, Part A Recover. Util. Environ. Eff. 2021, 00, 1–24, doi:10.1080/15567036.2021.1887974.

Reviewer#2, Concern#8: Get its English edited and typos very carefully.

Author response: As per your suggestion, we have revised the entire manuscript by improving the language and fixing typo errors.

Author Response File: Author Response.pdf

Reviewer 3 Report

introduction should be improved. Figure 8 and figure 9 cold be smaller. Author can compare with some of research in conclusion.

Author Response

Reviewer#3

Reviewer#3, Concern#1: Introduction should be improved. Figure 8 and figure 9 cold be smaller. Author can compare with some of research in conclusion.

Author response: As per your suggestion, we have revised the introduction section for presenting a clear view to the reader. Also, we updated the size of figures 8 and 9. Finally, Subsection 5.7 represents a comparison between the proposed system and other systems in terms of energy, economic, and cleanliness issues to justify network validity.

Author action: We have revised the manuscript as below:

Literature Review: The integration of solar PV with biomass resources for establishing a long-term sustainable and reliable power station has been thoroughly investigated in reference [32]. In this work, the fundamental problems of developing a hybrid solar PV/biomass-focused power plant were investigated, and several significant solutions were proposed.

 

Sub-section: 5.7: Feasibility Comparison

In order to ensure the effectiveness of the proposed approach, we compared it to some key approaches from the literature. The findings are summarized in Table 8.

From our literature review leading to the above comparison analysis, we noticed that most studies have focused on the key obstacles of establishing a green cellular network that included solar PV and wind turbines as well as a backup system. Furthermore, many of them didn't analyze the system for heterogeneous networks. To the best of our knowledge, we are the first to develop a techno-economic and energy efficiency analysis integrating solar PV/BG system with electrical grid system for heterogeneous networks, in addition to the proposed sleep algorithm for IoT applications. Additionally, the suggested system was found to have only have a net present cost of about $ 21, 445 and an energy-generating cost of $ 0.379/kWh for the macro base station. Furthermore, a steady decline in per-unit energy generation cost has been found in response to higher system bandwidth, resulting in lower carbon footprints.

References

56. Alsharif, M.H.; Kim, J.; Kim, J.H. Energy optimization strategies for Eco-friendly cellular base stations. Energies 2018, 11, doi:10.3390/en11061500.
57. Olatomiwa, L.; Mekhilef, S.; Huda, A.S.N.; Sanusi, K. Techno-economic analysis of hybrid PV–diesel–battery and PV–wind–diesel–battery power systems for mobile BTS: The way forward for rural development. Energy Sci. Eng. 2015, 3, 271–285, doi:10.1002/ese3.71.
58. Margaret Amutha, W.; Rajini, V. Techno-economic evaluation of various hybrid power systems for rural telecom. Renew. Sustain. Energy Rev. 2015, 43, 553–561, doi:https://doi.org/10.1016/j.rser.2014.10.103.
59. Asif, R.; Khanzada, F. Cellular Base Station Powered by Hybrid Energy Options. Int. J. Comput. Appl. 2015, 115, 35–39, doi:10.5120/20286-2842.
60. Alsharif, M.H.; Nordin, R.; Ismail, M. Green wireless network optimisation strategies within smart grid environments for Long Term Evolution (LTE) cellular networks in Malaysia. Renew. Energy 2016, 85, 157–170, doi:10.1016/j.renene.2015.06.044.
61. Hossain, M.S.; Rahman, M.F. Hybrid solar PV/Biomass powered energy efficient remote cellular base stations. Int. J. Renew. Energy Res. 2020, 10, 329–342.
62. Jahid, A.; Monju, M.K.H.; Hossain, M.E.; Hossain, M.F. Renewable Energy Assisted Cost Aware Sustainable Off-Grid Base Stations with Energy Cooperation. IEEE Access 2018, 6, 60900–60920, doi:10.1109/ACCESS.2018.2874131.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The submitted work can be accepted accordingly.

Author Response

As per your suggestion, we have revised the entire manuscript by improving the language and fixing typo errors.