Facebook has opened its first data centre outside the US - using 100 percent renewable energy on the edge of the Arctic Circle in Sweden.

Up to now many of Facebook's data centres in the US have been slammed by environmental campaigners for not using renewable energy, but the one in Sweden - located where the River Lule meets the Gulf of Bothnia - may go some way in turning things around.

The data centre at Lule is now handling live data traffic from around the world, with all the servers and other equipment powered by locally generated hydro-electric energy.

"Not only is it 100% renewable, but the supply is also so reliable that we have been able to reduce the number of backup generators required at the site by more than 70 percent", said Facebook.

In addition to harnessing the power of water, the Lule data centre uses the chilly Nordic air to cool the thousands of servers. And any excess heat from those servers is harnessed and used to keep staff offices warm.

All the servers used are also built using Facebook's Open Compute Project designs, which encourage the development of "vanity-free" hardware that leaves out "unnecessary bits of metal and plastic.

"These designs are then shared with the broader community, so anyone can use or improve them," Facebook said.

Facebook says the Lule data centre is averaging an impressive power usage efficiency (PUE) rate "in the region of 1.07".

Last year Facebook opened a new engineering centre in London, the company's first major engineering centre outside the US.