16. Lefdal Mine Data Center
If you need to keep something cool, what better place to put it than deep underground? The Lefdal Mine Data Center is just the place, and by converting an abandoned mine in Norway into a (literally) cavernous data center, Lefdal has managed an impressive 1.15 PUE.
The Lefdal mine uses water from a nearby fjord to keep itself cool and generate power, didn't need to build a new structure to house its computers, has zero CO2 emissions, and has a net water usage of zero.
The mine itself is huge, giving it plenty of room to expand for minimal costs and environmental impact.
SEE: Green tech initiatives: Best practices and breakthroughs (free PDF) (TechRepublic)