Seasonic X-400 Fanless PSU
 

The Seasonic X-400 Fanless is based on the successful, 80 Plus Gold X-series platform introduced late last year. Company reps say the new fanless PSU was years in the making; ultimately, they had to await the development of a super-efficient platform. It was worth the wait.
http://www.silentpcreview.com/Season...00_Fanless_PSU