To cool its next generation of commercial servers, HP is using electric-ducted fans (EDFs), originally developed by model airplane hobbyists to power radio-controlled jets. Essentially propellers in a box, the fans run so fast and produce so much air pressure that they should be able to provide the cooling needs for the next several generations of HP servers, according to Wade Vinson, an engineer in the company's Industry Standard Server Group.

Of course computer servers don't need thrust, since they generally don't go anywhere. Instead, Vinson and his team showed that EDF blades can be redesigned to produce pressure. The fan blades on their prototypes force air into a server's chassis, so that a certain volume of air per minute flows past the heat sinks (aluminum or copper fins attached to most CPUs) and carries away heat through convection.

The end product is HP's Active Cool Fan, scheduled to debut in its next generation of BladeSystem servers. At their most efficient setting, according to Vinson, the fans consume just one-third the power of traditional computer fans; and they're smaller than regular fans, which means engineers can make the servers thinner and pack more electronics into them. "If you have 10 traditional servers today, we could put 16 servers in the same space," says Vinson.