This is 100% the right answer: Microsoft’s Chiller-less Data Center. The Microsoft Dublin data center has three design features I love: 1) they are running evaporative cooling, 2) they are using free-air cooling (air-side economization), and 3) they run up to 95F and avoid the use of chillers entirely. All three of these techniques were covered in the best practices talk I gave at the Google Data Center Efficiency Conference (presentation, video).
Other blog entries on high temperature data center operation:
Microsoft General Manager of Infrastructure Services Arne Josefsberg blog entry on the Dublin facility: http://blogs.technet.com/msdatacenters/archive/2009/09/24/dublin-data-center-celebrates-grand-opening.aspx.
In a secretive industry like ours, it’s good to see a public example of a high-scale data center running hot and without chillers. Good work Microsoft.