Fulfilling the demand for broadband to millions of users across the globe takes more than just ingenuity, it takes energy -- lots of it. Accounting for nearly 1 percent of total power consumption in the U.K. alone, BT Group was faced with a dilemma: how to scale and roll out new services to take advantage of new market opportunities without overburdening its energy budget -- and the climate.

[ Discover the techniques used by other 2008 Green 15 winners to make their IT more sustainable. ]

"We do have a very huge carbon footprint," said Donna Young, BT Group's head of climate change. "How we mitigate against that is important as the number of customers using the networks increases."

Seeking to reduce the energy costs of its IP networks, the British telecom developed plans for network rollouts with sustainable IT practices in mind, setting into motion an ambitious, companywide initiative to cut BT's carbon footprint by 80 percent before 2016, as compared against 1996 levels.

Building new efforts the green was is not enough
But focusing on sustainability in new services would not be enough to achieve that vision. Significant efficiency gains, the company quickly realized, could best be obtained by reusing new ways of thinking about energy consumption in older environments.

"It was obvious that if we could take what we learned from the network build and transport it to our datacenters, we could make huge improvements in terms of energy efficiency," said Dave Needham, BT Group's head of datacenter strategy.

And so the BT datacenter team examined the chief energy-minded aspects of the company's IP network build-out strategy, assessed avenues for achieving requisite scale, and set about wresting inefficiencies from approximately 90 legacy datacenters on a targeted, site-by-site basis. The resulting 21st Century Network Data Center Project, which began in June 2004, is now the centerpiece of the company's strategy for fulfilling its carbon footprint mission.

According to Needham, 60 percent of the efficiency methodologies used in the IP build-outs have carried over to the retrofitting of datacenters, some of which were originally constructed in the early 1980s.

The two strategies that made the most difference
Two strategies in particular have had the most significant impact: a shift from forced- to fresh-air cooling, and a reduction in the number of power conversions employed across each infrastructure.

By knocking out walls between server rooms and hallways where possible, installing variable fans for fresh airflow, and tapping Britain's most abundant cooling asset -- its climate -- BT has already reaped 16 percent efficiency gains with its new approach to cooling. Moreover, by carrying alternating current (AC) as far as possible into its datacenters before transforming to direct current (DC) to power servers, BT has cut power-conversion energy loss by 12 percent.

Needham described the team's approach as a continual feedback-fueled process of improvements. Adjustments are made, effects are measured, and the team redoubles its efforts to cut down energy consumption even further. When all is done, Needham expects BT's datacenters, which combined house approximately 11,000 server racks, to be 70 percent more energy-efficient.