Wikipedia
Aquasar
Aquasar is a supercomputer system from IBM Research which uses hot water cooling to achieve heat efficiency.
The Aquasar computers are built from three BladeCenter H chassis with a mix of QSS22 Cell based modules and HS22 Xeon based modules. It operates at about 6 teraflops, with a computational efficiency of about 450 megaflops/watt.
The first Aquasar system became operational at ETH Zurich in 2010, and another is planned at SuperMUC, Munich. The heat from the supercomputer is used to warm the buildings at the university campus at ETH.