Reducing network energy use
The energy used to run our network accounts for around 80% of carbon dioxide emissions from our total energy use, and is therefore our main focus for reducing emissions.
Modernising our networks can significantly improve energy efficiency. Our energy strategy identifies a number of ways to further reduce network energy use:
Reducing the need for network air conditioning
Base stations use cooling systems to prevent equipment from overheating - extending battery life and reducing the chance of network failure. Cooling accounts for around a quarter of network energy use, offering the biggest potential energy savings in our 2G network. Average energy use in some base stations can be cut by more than 10% (depending on the climate conditions on site) simply by allowing the temperature to increase from 21°C to 25°C.
Our policy is to install ‘free cooling’ – a system that uses fresh air to cool network equipment – as the default option at new base stations. This reduces the need for energy-intensive air conditioning, saving an average of 7,000 kWh a year per base station. By allowing a further increase of 10ºC, to a maximum room temperature of 35 ºC, additional savings can be made, and the technology can be used in hotter countries. This requires upgrading technology to resist higher temperatures, for example, installing individual battery coolers rather than cooling the whole room. Vodafone Portugal increased the temperature to 35 degrees in all its 1,100 base stations in 2007/08. Free cooling at 35 degrees will be rolled out across the Group in 2008/09.
In hot countries where air conditioning is needed during the day, our Group guidelines recommend installing equipment that enables free cooling to be used at night. As existing cooling equipment reaches the end of its life, it is replaced with more efficient systems.
Improving network technology
We are working with our suppliers to improve the energy efficiency of network equipment. The average energy efficiency of new network equipment across our range of suppliers has improved by more than 35% since 2005/06. The focus is on two key items of network equipment – new, more energy efficient power amplifiers and remote radio heads. Vodafone Italy and Vodafone Germany have set a target to install remote radio heads at up to 90% of their base stations. This target will also be rolled out in other local operating companies.
The power amplifier is the most energy-intensive component of a 3G base station. The average energy efficiency of power amplifiers from our suppliers has improved gradually from around 9% in 2004 to 15% in 2007. Remote radio heads relocate the power amplifier closer to the antenna, rather than at the foot of the base station. This reduces energy use by an average 40% by preventing energy loss from the power cables.
In Spain, for example, existing equipment uses around 925W to produce an output at the antenna of around 20W. By upgrading the power amplifier and installing a remote radio head, base stations now use just over half the energy (480W) to generate double the power output (40W). This saves an average of 3.9MWh a year for each unit replaced.
Reducing diesel use
Several of our local operating companies use a significant amount of diesel to power their base stations. We are investigating ways to reduce this diesel use. By installing batteries, stored electric power can be used instead of diesel generators at times when grid electricity is unavailable. Intelligent controls are being developed to enable diesel generators to automatically turn on only when the base station room reaches a certain temperature when power for cooling becomes essential. We are also trialling the use of renewable energy alternatives in more than 150 of our remote sites.
Other network energy saving initiatives
Other examples of initiatives to save energy in our networks across the Group include:
- Deactivating unused rectifiers – devices that convert alternating current to direct current at base station sites. This reduced energy use by 110W (1-5%) per site in trials by Vodafone Germany, and is being rolled out in the Czech Republic, Italy and Spain.
- Categorising sites to optimise energy use – for example, not all base stations require battery backup or air conditioning.
- Remote monitoring and measurement of energy to help us manage usage more efficiently.
- Shutting down more base station sites in high density areas at times when demand is lower (at night, for example).
Online data storage
Data storage is the fastest growing part of the carbon footprint of the ICT industry, increasing at more than 50% each year. We are committed to minimising this impact, consolidating our data centres to cut the growth in online storage. See Reducing online data storage.