Solar dominates as an alternative to diesel because of cost, but Indian telecoms are also exploring aggregated renewable solutions (wind and solar, for example), fuel cells and bio-CNG digesters to power base stations. “They’re already giving diesel a run for its money,” Chattaraj says of the various clean energy solutions in India. But there is still a long way to go; Chattaraj notes that only about 9,000 towers have switched to alternative energy, a figure mandated to rise to 80,000 by 2015.
India’s directive could have the greatest impact on Africa, according to Chattaraj, where many countries have less than half of their towers connected to an electric grid. Chattaraj says that Greenpeace is already working in South Africa to produce a report similar to the one that helped bring the issue to the forefront in India. Programs by cellular networks, like Groupe Speciale Mobile Association’s (GSMA) Green Power for Mobile, are also trying to advance the use of renewables in off-grid locations.
In the U.S., which has an estimated 285,000 cell sites, less than 1 percent are powered by renewables, but that figure is slowly increasing. Verizon has about 20 solar-powered base stations. T-Mobile, one of the earliest big carriers to switch on a fully solar-powered cell site in 2011, has added renewables to more sites and sometimes uses solar energy as temporary backup power, a practice that the company said it will expand in the coming years.
One company that supplies solar generators to two of the major carriers (DC Solar) said that the move from diesel to solar generators, whether for planned maintenance or if after-storm damage cuts off grid power, is catching on as more providers become aware of the option and because it costs about 30 percent less. “I think the biggest thing is that the technology is now proven,” says Paulette Carpoff, vice president and owner of DC Solar Solutions.
Globally, the focus is on efficiency and low-power components, especially as bandwidth requirements strain networks. Lowering the energy needs of base stations could also help spur the adoption of renewables. “Energy efficiency is one way to make renewables economically viable,” says Thierry Klein, head of green research at Alcatel–Lucent’s Bell Labs.
The industry is working on more integrated chip technology and smaller radios to improve energy efficiency, including units that can turn themselves off when not in use. Alcatel–Lucent is also integrating energy monitoring capability into base stations, which can be used to make real-time adjustments to optimize power use and monitor renewables.
If the architecture of mobile networks moves to smaller, more distributed small cells, renewable power could be more attractive in developed and developing countries. Employing smaller cells is a growing movement in the mobile phone industry, which uses much smaller antennas and radios that in turn use far less energy yet allow carriers to increase network capacity. Klein noted that cost of digging and trenching to run power lines to cell sites can be a large part of the cost for stations connected conventionally to an electric grid, and running extra wires to many, very small sites might not be feasible.
“In the future,” Klein says, “if the carriers move to more small cells, you will need to install more renewables.”