Green wireless networks or energy-efficient wireless networks have gained popularity as a research topic due to the ecological and economic concerns of cellular operators. The specific power supply requirements for the cellular base station, such as cost-effectiveness, efficiency, sustainability, and reliability, can be met by utilizing the technological advances in renewable energy. There are numerous drivers for the deployment of renewable energy technologies and the transition towards green energy. Renewable energy is free, clean, and abundant in most locations throughout the year. Accordingly, this work proposes a novel framework for energy-efficient solar-powered base stations for the Oman site, specifically for off-grid locations where fuel transportation for diesel generator (DG) is a serious concern. To demonstrate the effectiveness of the proposed system for off-grid sites, the Hybrid Optimization Model for Electric Renewables optimization software is adapted by considering real-time conditions and its technical feasibility. Different cost factors such as capital cost, salvage cost, replacement cost, operational, and maintenance cost of PV panels, inverters, and batteries also undergo extensive analysis. From the observed results, the total net present cost (NPC) of the proposed system is $27,887, while the net NPC of the DG is estimated at $32,900. Remarkably, the proposed scheme can potentially achieve considerable savings in the operational expenditure at approximately 15.24%. Indeed, these outcomes can provide profound economic, technical, and ecological benefits to the cellular operators of Oman. It also ensures a sizeable reduction in greenhouse gas that supports sustainable green wireless network deployment in remote areas.

The energy consumption rate of information and communication technology (ICT) has seen a rapid increase over the last few decades due the excessive demand for multimedia services. Wireless networks are considered one
of the main sources of energy consumption in the ICT arena [

Researchers are focused on numerous distinctive approaches to reduce the energy consumption in wireless networks such as energy-efficient hardware components, selective operation of components, efficient use of radio
transmission process, deploying heterogeneous cells, and implementing renewable energy resources (RESs) [

Typically, the desired zone for PV-powered BSs is in the mid-latitude between 30

Considering all these inferences, researchers lack sufficient descriptions for the total OPEX savings due to RESs. Accordingly, this study examines the feasibility of using solar power solutions as the main power sources to supply the energy requirements of cellular LTE-BSs in Oman’s off-grid locations to determine the net OPEX savings. Oman is positioned at a latitude between 16^{2} in December to 6.52 kWh/m^{2} in May [

Implementing the PV system requires intensive study owing to its diverse design and the uncertainty of solar parameters, such as the dynamic rate of solar irradiation that adds to the difficulty due to its intermittent, seasonal, and uncertain nature. To overcome these issues, the HOMER model is used by creating the energy balance scheming every hour for 8,760
h per year. It also compares the actual hourly load demand with generated
energy. Additionally, it manages the charging and discharging features of
the batteries and computes the installation and operating cost for the complete lifespan of the project. Given all these advantages, the HOMER software is adapted in this work to achieve the techno-economic feasibility of the solar-driven LTE-BS. The contributions of this work are summarized
as follows:

To propose and determine the technical benchmarks of an optimal standalone PV system that guarantees energy autonomy.

To obtain a long-term energy balance for cellular networks based on the available solar irradiation in Oman that warrants sustainable green wireless networks.

To examine, analyze, and evaluate the viability of a standalone PV system for maximum energy yield and economic savings to guarantee both sustainability and cost-effectiveness.

The rest of this work is organized as follows. Section 2 presents the proposed system and mathematical modeling. Section 3 discusses the implementation of simulation configurations. Then, results and discussion are described in Section 4. Section 5 specifies the economic feasibility of the proposed scheme. Section 6 concludes the work.

The proposed system comprises three segments such as sources, converters, and loads as demonstrated in

The cellular BS consists of various pieces of equipment that can be used to communicate with mobile/cellular units. The backhaul network comprises the following sub-units: (i) multiple transceivers (TRXs), (ii) power
amplifier (PA), (iii) radio-frequency (RF), (iv) baseband (BB), (v) DC–DC Power supply, and (vi) cooling systems. The TRXs have a PA which amplifies the signal power coming from the BB unit. In addition, the BB is adapted for internal processing and coding. A detailed discussion of the BS components can be seen in [

A macro LTE-BS type subsystem has three sectors with two antennas based on the component level [

where _{TRX}

Elements | Parameters | Unit | Power consumption |
---|---|---|---|

PA | Watts | 102.6 | |

RF | Watts | 10.9 | |

BB | Watts | 14.8 | |

Loss factor ( |
% | 6.0 | |

Loss factor ( |
% | 10.0 | |

Watts | 151.65 | ||

No. of transceivers |
6 | ||

Total power of the BS |
Watts | 909.93 |

It consists of numerous solar cells that are connected in series and parallel to form a solar module or PV arrangement. It generates DC electric power through the absorption of shortwave irradiance. The total annual energy extraction from the PV arrangement (_{PV}

where _{PV}_{PV}

A solar power-driven macro LTE-BS consists of a battery bank that is allowed to charge during a sunny period with excess power generated by PV arrays. The BESS capacity of the BS merely depends on the depth of discharge (DOD) and requires evaluation before commissioning. It can be expressed as [

where _{min}

where the terms _{batt} and V_{nom} are the total number of battery units in the BESS and a nominal voltage of a single battery unit (V), respectively. The terms _{nom}

The lifetime of the battery plays a crucial role. It can be predicted on the basis of the operating conditions. More specifically, the DOD during each diurnal charge–discharge cycle displays a leading role in the battery lifetime and can be computed as [

where the term _{lifetime}_{thrpt}_{battf}

The total capacity of the inverter (_{inv}

where the term _{AC}

The configuration of a solar-powered base station is based on the following considerations: (i) the essential components that must be involved in the system design, (ii) the number of components that must be adopted,
and (iii) the size of each element. The HOMER Micro-power optimization tool aids in obtaining an optimal solar system with low net present cost (NPC). NPC contains all incurred expenses and incomes throughout the project lifetime. The total annualized cost (_{TAC}

The net present cost (_{NPC}

The term CRF denotes the recovery factor which converts a _{NPC}

The _{NPC}

where _{comp}_{rem}_{rep}

This study scrutinizes to minimize the total cost of the NPC for an optimal scheme of a stand-alone SPS based on various constraints. To attain
system optimization, the objective function of the NPC can be derived using

The above-derived objective function is subjected to the following constraints;

To warrant a power balance between actual demand and energy production, the power production of the sources (_{PV}_{Battery}_{BS}_{Losses}

The simulation consists of three major parts such as inputs, optimization, and outputs as given in

Components | Parameters | Range |
---|---|---|

Control factors | Interest rate-Annual (January 2021) | 1.0% |

Project lifespan | 10 years | |

PV | Sizes considered | 2, 2.5, 3, 4, 4.5, 5 kW |

Operational lifetime | 25 years | |

Efficiency | 85% | |

IC | $1/Watt | |

Replacement | $1/Watt | |

O&M price per year | $0.01/Watt | |

Inverter | Sizes considered | 0.1, 0.2, 0.3, 0.4 kW |

Efficiency | 95% | |

Operational lifespan | 15 years | |

IC | $0.4/Watt | |

Replacement | $0.4/Watt | |

O&M price per year | $0.01/Watt | |

Trojan L16P battery | Number of batteries | 24, 32, 40, 64,72 |

Round trip efficacy | 85% | |

Minimum operational lifespan | 5 years | |

IC | $300 | |

Replacement | $300 | |

O&M price per year | $10 |

Most economically, the total NPC cost is $27,887. It comprises 4.4 kW rated PV panels and 64 numbers of batteries connected in eight parallel strings along with a 0.1 kW inverter. The following subsections provide detailed discussions.

The optimal capacity of the PV is 4.5 kW. The yearly energy output of the PV is calculated using

The optimal capacity of the battery bank, as determined by the HOMER simulation for the system, is 64 units. The voltage rating of the Trojan L16P single battery is 6 _{dc}_{dc}

The net capacity of the inverter unit is 0.1 kW, and its efficiency is
annually computed between the input (837 kWh) and output energy (795 kWh)
and observed as 95%. The total operating hours are 8,759 h/year (24

The total NPC for the PV system is $27,887, i.e., $2,250 (_{PV}_{Battery}_{Inverter}

In remote areas, i.e., an off-grid station, the DG is typically used to power the cellular BSs. The rating of DG should be approximately 3.5 kW
that can be computed between the ratio of maximum macro LTE-BS and 30% DG

The IC is computed by multiplying the system size (3.5 kW) with its cost ($660/kW).

The O&M cost (annual) of the DG is approximately $2,366 (excluding fuel transportation cost). A breakdown of this cost is described as follows:

—The net maintenance cost of DG is $438/year, estimated using the product of DG maintenance cost of 0.05$/h with annual operating hours (8,760 h).

—The total fuel cost is computed using the product of diesel price ($0.54/L) with total diesel consumption (3,569 L/year) and found to be $1,928. It is calculated on the basis of specific fuel consumption

Every three years, a mobile operator must replace the DG, i.e., a minimum of three times during the lifespan of the project. Therefore, the net DG replacement cost is equal to $6,930, i.e.,

The net NPC of the solar system is approximately $27,887. Applying the proposed solar scheme, the total OPEX savings of 15.24% can be achieved compared with a conventional power source (DG).

This work proposed a framework for an energy-efficient RES-based cellular network for Oman off-grid sites using a PV module that acts as the main and standalone source for the base stations to minimize the OPEX. It also discussed the optimal system architecture, energy yield analysis, and economic analysis. The simulation results revealed that the proposed PV-based system can potentially meet the total demand for macro LTE-BS. Moreover, a battery bank can supply power to the macro LTE-BS load autonomy for 106 h. This figure is considered sufficient to fix the solar array in case of malfunctions. Regarding the economic aspect, the simulation results showed that the proposed solar system can achieve OPEX savings with a reliable energy supply. These results indicate that the PV-based power system is a good and effective choice for wireless network operators.

The authors wish to thank the editors of CMC and anonymous reviewers for their time in reviewing this manuscript.