Aquasar
Aquasar is a supercomputer system from IBM Research which uses hot water cooling to achieve heat efficiency.[1][2]
The Aquasar computers are built from three BladeCenter H chassis with a mix of QSS22 Cell based modules and HS22 Xeon based modules.[3] It operates at about 6 teraflops, with a computational efficiency of about 450 megaflops/watt.[1]
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.
Cooling
The water cooling system is notable because micro-channels bring water directly over the processing units, rather than merely inside the computer case. This allows effective cooling even with water at 60 °C (140 °F), which has a side benefit of producing higher grade heat that can be used elsewhere.[1]