|Fig. 1: Percentage of mobile subscriptions by regional population as of Q2 2014. |
The number of mobile-cellular subscriptions is quickly approaching the number of people on our globe, expected to reach a penetration rate of 96% by the end of 2014.  At the time of this writing, 2014 second quarter reports have been released stating that there are around 6.8 billion mobile subscriptions (a 94% penetration rate). [2,3] However, the same report notes due to the existing trend of a single person holding multiple subscriptions, the actual number of unique subscribers remains far lower at around 4.6 billion people.  As statistics on these unique subscribers is harder to come by, Fig. 1 shows the percentage of mobile subscriptions by regional population, including the overall global percentage of subscriptions, as of the second quarter in 2014.  While the lower penetration rates in India, Africa and China can be attributed to various circumstances, one factor includes the simple lack of cellular coverage in these regions. For example, in Sub-Saharan Africa, an estimated 30% of the population remains outside the reach of all cellular networks. 
Often this lack in cellular coverage is accompanied by a lack of access to grid-based electrical infrastructure for rural inhabitants in these developing regions. In fact, about 600 million people in Sub-Saharan Africa, 325 million people in India, and another 300 million people in other parts of Asia live without access grid-based electrical systems.  Thus, as mobile network operators expand into these un-served regions, they are faced with the additional cost of rolling out power infrastructure in parallel with cellular network infrastructure. 
However, these regions also represent immense opportunities of further growth for mobile network providers. As of the end of 2013, mobile-cellular subscriptions had reached their slowest-ever growth rates, at 2.6% globally, suggesting that the market is approaching saturation.  However growth in developing regions has greatly outpaced that of developed. In the second quarter of 2014, alone, new mobile subscriptions in Africa and China reached about 20 million and 12 million respectively, while in North America and Western Europe the growth figures were only 2 million and 3 million respectively. 
A commonly cited report by Gartner in 2007 states that 2% of the human-driven CO2 footprint can be accredited to the information and communication technology (ICT) sector.  Less well known is that about 0.5% of the global energy supply is consumed by mobile communications infrastructure, alone, [6,7] Among the mobile communications infrastructure, cellular base-stations have the largest appetite, consuming around 80% of total power, in studies completed of 2G and 3G networks, and of 3G and 4G networks. [6,8]
The primary sources of power for these mobile base-station vary by region and can generally be categorized into 3 buckets:
As mentioned above, about 80% of Africa and 30% of developing Asia falls into the under-served electrification scenario that results in the bad-grid and no-grid power access to mobile base stations.  Table 1 shows the estimated total number off-grid and bad-grid base station tower sites at present and as predicted for 2020 based by region.  The table shows that bad-grid towers are predicted to increase by 13% while off-grid towers are predicted to increase by 22%. In the case of base stations situated in regions with bad-grid or off-grid power availability, the predominant source of power for the base stations is diesel generators. [4,6] Diesel generation is costly in both the procurement of fuel and travel required to maintain adequate fuel levels at the base stations. Often, the fuel expended to service a given base station will roughly equal the fuel delivery at the base station, effectively doubling the market price for the diesel.  Some mobile network operators servicing many off-grid sites find that energy provisioning can consume up to 50 percent of their total operational cost.  Yet, despite these increased costs of operation, various forces including market driven demands for new subscriptions are causing mobile network operators to out-pace government programs of rural electrification.
|Table 1: Estimates total number off-grid and bad-grid base station tower sites in 2014 and 2020 categorized by region. |
In the face of the increasing diesel costs required for continued mobile subscription grown, network operators are increasingly exploring diesel generation alternatives. By the end of the second millennium, there were projects including 50 solar powered base stations deployed and in operation in North Africa.  Today the drive is often toward a hybrid approach, replacing or complementing diesel generation with renewable energy resources. For example, "WindFi", a low power base-station design relying on wind turbine and photovoltaic modules to power the system, and a system which adds micro-hydrology to solar and wind turbine power generation for rural base stations.  Although many of the programs are still at an experimental phase development, there are strong incentives for their success. The elimination of diesel dependence in 320,000 off-grid base stations would reduce about 0.175% of our global diesel consumption.
© Emily McMilin. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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