Over the last decade, the volume of cellular subscribers has grown quickly because of the requirement for ubiquitous connection [1
]. The significant rise in the number of mobile users and the demand for high speed data require mobile network providers to deploy more base stations (BSs) throughout the world [3
]. Base stations are the main consumers of energy in the cellular industry that consume 57% of total energy [4
]. The telecommunication industry’s annual worldwide energy usage was 219 TWh in 2007 that amounted to 354 TWh in 2012 [4
]. It is expected that the worldwide use of energy is may upsurge by around 27 percent within 2017 to 2040, corresponding to 3.743 million tons of oil [6
]. Moreover, this energy consumption growth is envisioned to negatively affect the environment due to the increase of carbon emissions. In fact, carbon dioxide (CO
) emissions are also anticipated to proliferate by a growth of 6% every year through 2021 [8
]. The information and communications technology (ICT) industry is predicted to account for 2–4 percent of the global carbon footprint, and the exponential rise of mobile traffic is projected to increase every year. The urgent need is thus to develop an alternative energy source and to decrease the carbon footprints of communication network systems [9
Because of the above facts, telecommunication network operators are always striving to discover alternative, environmentally compatible, and economical energy sources. More specifically, the generation of renewable energy (RE) is a dire need for facilitating sustainable development and ensuring a more green future for every country [10
]. The collection of energy from locally available RE sources for example solar, wind, biomass, etc. has therefore been one of the main concerns for academia and researchers [13
]. Renewable energy is reusable and readily available from various areas across the world. In addition, an enormous amount of energy may be gathered with the aid of contemporary technologies from renewable energy sources by reducing costs. Based on the expected advantages of renewable sources, cellular BSs powered by locally accessible RE sources are being gradually installed by telecommunications providers. Despite the potential benefits, harvesting power from renewable sources is not viable because of their stochastic tempo-spatial behaviors in a wide ranging operation. As a result, the more diverse option with an appropriate power storage facility is therefore required to strengthen the system’s reliability. Moreover, the techniques and constraints of batteries, hydro pumped, mechanical, and other conventional energy storage technologies have their limitations and challenges [17
]. These restrictions underline the necessity for a new energy storage device with a large capacity and longer duration of discharge. The integration of the hydrogen (H) and fuel cell (FC) with renewable energy sources through an intelligent control system is seen as a compelling solution to fulfill the huge power demand. This can also ensure the required sustainability, reliability, and safety. Due to the energy carrier, hydrogen introduces hydrogen power to electricity (P2H2P) technology, which is capable, transportable, and usable to store surplus power into renewable energy storage systems (RESS) [17
]. This innovative P2H2P concept provides sufficient opportunity for the storage and reducing carbon footprints of renewable energy [17
]. Renewable hydrogen is linked to modern energy supply, transportation, industry, and the export of RE.
The production and storage of hydrogen are some of the key technologies for storing the extra energy produced from renewable sources [19
]. As major components, the electrolyzer, the hydrogen tank, and the fuel cell system assigned with specific tasks are included in this scheme. The surplus renewable source (i.e., solar) is used in an electrolyzer that generates hydrogen and oxygen by electrolyzing water. The fuel cell uses this hydrogen and creates electricity (typically by absorbing atmospheric oxygen). This hydrogen is stored in the tank and provides backup power when renewable sources fail to fulfill the BS energy demand. Energy storage using hydrogen provides excellent energy performance and is suited to satisfy (seasonal) long term energy storage needs. In contrast, due to the particular geographical requirements and potential environmental consequences, the pumped hydroelectric storage system has a limited possibility for further development in long term storage applications [20
]. Besides, due to the uncertain lifespan and rapid degradation (i.e., by loading cycles), environmental sensitivity (e.g., temperature), self discharge, and limited storage capacity (per unit volume and mass), batteries cannot be considered as perfect candidates for long term energy storage solutions [19
]. So, the development of solar photovoltaic (PV) systems along with hydrogen and fuel cell system can diminish the problems addressed earlier.
This study is mainly aimed at integrating the solar PV system along with hydrogen and fuel cell system for powering the cellular macro network in Bangladesh, taking into consideration the dynamic profile of traffic and renewable energy sources. A detailed hybrid optimization model for electric rnewables (HOMER) simulation was carried out over 20 years to evaluate the techno-economic feasibility of hydrogen-based renewable energy systems for the storage of surplus energy. In addition, the performance of the wireless network has been assessed using Monte-Carlo simulation. The chosen field of this research is Patenga, which is part of Bangladesh under the division of Chittagong and it’s located between 221514 North, and 914821 East. To the best knowledge of the authors, for the intended green wireless networks, we are the first to do a techno-economic analysis that integrates the hydrogen and fuel cell with the solar PV system. The most significant contributions are summed up as follow:
To propose an energy sustainable hybrid-powered (integration of hydrogen and fuel cell with the solar PV system) cellular networks emphasizing long-term reliability through green engineering solutions.
To find out the optimum solution of the proposed framework with the help of HOMER optimizer software focusing on the techno-economic feasibility of using hydrogen as an energy storage medium.
To investigate the system performance in terms of surplus electricity, carbon footprints, energy storage system, and cost of electricity varying system bandwidth. Additionally, we examine the performance of the wireless network with reference to energy efficiency, and throughput using MATLAB-based Monte-Carlo simulations considering the dynamic traffic profile.
Finally, a comprehensive comparison of system performance will be carried out with that of other power supply solutions and with the previously published research work to validate the effectiveness of the suggested system.
The arrangement of the rest of the article is described below: Section 2
discusses a review of relevant works. The discussion on the solar power model, the energy storage unit, the hydrogen production, and the fuel cell electrical system is presented in Section 3
. The same part also presents a load dependent BS power model, the mathematical reliability model, and the method of energy collaboration. In Section 4
, cost modeling and optimization problems are presented. Section 5
provides a comprehensive overview of the results and discussion on the proposed system. Section 6
compares the energy, economic, and cleanliness concerns of the proposed system to existing systems to support the validity of the network. This part also discusses the breakeven point for the hybrid supply system to determine economic stability. Finally, Section 7
finishes this study by analyzing the key results and gives the the directions for further research. Symbols and notations used in the following sections are summarized in Table 1
2. Previous Work
Many research works were carried out to establish an energy efficient, reliable, and sustainable supply system that uses local renewable energy sources. Some of the academics advocate the mixing of multiple renewable or non-renewable energies with renewable sources, whereas others advise the incorporation of electricity grids with renewable or single renewable energies with sufficient storage facilities [13
]. For instant, the authors in [23
] propose a single solar photovoltaic energy based cellular network with an appropriate battery bank addressing important elements of the system. Different performance metrics such as optimal sizing, energy issues, economic issues, and environmental factors, have been rigorously evaluated in these studies including the dynamic nature of solar intensity. The references [25
] studied the optimum system design and technical criteria set by the HOMER platform for the installation of hybrid solar-PV/diesel generator powered off-grid BSs across the world. The development of a solar PV/wind turbine (WT) powered isolated base station is studied in references [6
]. A solar PV and biomass gasifier-focused energy supply was introduced in the references [28
]. In the report [30
], the optimization of the hybrid (Solar & Hydro) and diesel generator (DG) powered system for a distant BS was explored. These works offer exclusive methods to harvest energy from renewable energy sources with specific limitations. Firstly, the single RE technique may cause energy deficiency/outage. Secondly, wind power generation needs enough wind speed, which may normally be achieved in coastal locations and offshore islands. Finally, the establishment of the DG leads to the emission of enormous quantities of carbon footprints while biomass generators demand a big quantity of biomass, land, and water generally unavailable in all parts of the globe.
Recently, several investigations were carried out using the hydrogen energy storages system to obtain a better degree of dependability in the renewables system. Significant work has been done on the power to hydrogen to the power system (P2H2P) by concentrating on the technical obstacles to pick adaptive energy storage systems such as charge/discharge time, size, cost, safety & management, and life cycle problems [17
]. In order to optimize the RE’s utility and to reduce investment costs, reference [32
] evaluated the best schedule of RESS components. These investigations have revealed that an energy management strategy is important for the efficient use and optimization of P2H2P systems. Reference [35
] proposed a smart management method for the efficient management of renewable energy resources microgrids by analyzing the various energy storage technologies including hydrogen. The development of a 100% renewable energy standalone microgrid system in West Australia (WA) has received a comprehensive evaluation of the hydrogen battery storage technology for renewable energy [17
]. Reference [31
] introduces a hybrid battery-hydrogen system for the South Australian (SA) grid, to produce a long-term sustainable renewable-energy storage system. After an in-depth evaluation of the technical criteria and the economic feasibility of the system using the “HOMER-Pro” optimized software, the present article states that the energy storage system based on hydrogen is cheap compared with the solely battery based energy storage system. Australia has already created a hub of power to hydrogen (P2H) to store renewable energy as a zero carbon energy carrier, inspired by the potential benefits of a hydrogen energy storage system [36
]. Reference [38
] has suggested two approaches for efficient integration of renewable into the hydrogen energy system, addressing future problems and potentials of the hydrogen energy system. Authors in [18
] have examined the importance of the hydrogen carrier and the pathway of hydrogen generation to support a statement of energy and industry globally. The articles [21
] examined the key problems and technology criteria of P2H2P to maximize renewable energy profitability and decrease investment costs. These research investigations have revealed that the energy management approach is based on the most efficient use of P2H2P systems and the greatest RESS performance. The effective design of the supply scheme and the development of contemporary control algorithms is thus essential to integrate the hydrogen in renewable energy sources and provide it to the load/grid.
Despite extensive literature study about the technical, economic, and greenhouse gas (GHG) assessment of the hybrid P2H2P, there is no research available to identify the potentials of the renewable energy-powered cellular base station using hybrid as energy storage. The purpose of this research work is to analyze the techno-economic feasibility and environmental impacts of a 100% RE-based cellular network with hybrid energy storage devices for off-grid areas in Bangladesh. The results of this study will be beneficial for the telecom industry, the authorities in the power sector, and government bodies in the installation of a power supply unit with hydrogen energy storage to supply power to the off-grid base stations and community.
6. Payback Period, Limitation Analysis, and Feasibility Comparison
In this section, the breakeven point of the integrated solar PV/H/FC system is estimated for justifying economic feasibility. In addition, the results of this system are compared with the other supply schemes with a view to guaranteeing the network sustainability, taking into account the technical criteria, economic analysis, energy yield analytics, and greenhouse gas emissions. Finally, the performance parameters of the introduced system are compared with the previously published research work.
6.1. Breakeven Point Calculation
The breakeven point (BP) is the period in which the capital cost of the project is expected to get back by selling the generated energy. The breakeven point is also known as the sample payback period (SPP) and can be calculated as follows [48
is the total investment ($
) for the hybrid supply system and
is the annual return ($
) by selling the generated green energy. The annual return of the system is calculated by subtracting the annual operational cost from the annual income. In this work, we have estimated the breakeven point considering the consumption of generated energy at a rate of $
0.39/kWh, which is higher than the generation cost. The detailed calculations of the payback period under 10 MHz system bandwidth are shown below:
Total investment = $20,570
Production rate of energy = $0.38/kWh
Selling rate of energy = $0.39/kWh
Sold energy = 8844 kWh/Year
Operation and maintenance cost = $306/Year
Replacement cost = $627/Year
Thus, annual return = ($0.39/kWh × $8844/Year) − $306 − $627 = $2516.16
According to Equation (24
), the breakeven point of the solar PV/H/FC is 8.17 years. Moreover, the increase in the energy rate from $
0.39 to $
0.41/kWh, increases the return and decreases the breakeven period from 8.17 years to 7.63 years as summarized in Table 9
. Table 9
also represents that a higher value of the energy selling rate steps down the breakeven point leading to enhancement in economic feasibility. This implies that the sample payback period is dependent predominantly on the energy selling rate.
6.2. Limitation Analysis
The green cellular network powered by a hybrid solar PV/H/FC system offers many potential benefits, but it is difficult to deploy it. The following list recaps the major difficulties and possible solutions associated with the hybrid solar PV/H/FC powered cellular networks:
6.3. Feasibility Comparison
It is found that, while the standalone PV and the hybrid PV/WT systems offer better off-grid performance, the first system is not so reliable due to its dependence on a single renewable energy source and the latter solution is not workable because of its poor wind profile at the chosen location.
As we had expected, the stand-alone DG and hybrid PV/DG are inadequate, as enormous volumes of fossil fuel and significant transportation costs in remote locations are needed. The hybrid solar PV/H/FC system is an appealing alternative for the distant off-grid locations in Bangladesh because of the enormous potential of solar PV energy, despite the emission of very little carbon content. In addition, by using hydrogenbased renewable energy storage technology, the proposal indirectly decreases GHG emissions and pressure on the public utility grid. Table 10
highlights the major references to similar projects in other countries, to compare the essential parameter of the proposed system. The renewable-energy based supply system has recently attracted different stakeholders’ attention as a viable approach to build a green cellular network. As a consequence, telecom operators and researchers have intensively examined the collection of energy from locally available renewable energy sources. Inspired by the above possible advantages, Nokia Siemens has already built a green cellular BS in rural parts of Germany using a hybrid solar PV and wind turbine [51
]. In addition, Ericsson has deployed off-grid wind power BS for grid energy reduction [52
The Huawei technology already established a hybrid solar PV/DG system in distant parts of Africa and the Middle East [60
]. Most of the author’s nevertheless considered the major issues involved in developing a green cell network utilizing solar photovoltaic and wind turbines together with backup systems (such as battery banks and DG). With the aid of HOMER, they investigated the techno-economic viability by disregarding the dynamic behavior of traffic intensity. To the best of our knowledge, we are the first to establish the techno-economic analysis for green networks which integrate hydrogen fuel cells with solar PV.