How can one power supply work without any fans at all, you might ask, when other power supplies routinely use three and sometimes even four fans? For one thing, units without fans don't cover the whole range of power demands. Passive cooling power supplies usually only offer a maximum power rating of up to 350 watts. In fact, the highest output from any power supply that uses only passive cooling is the Yesico power supply reviewed here, which is rated at 420 watts.

Passively cooled power supplies use external heat sinks (Yesico) or have cooling fins designed to be built right into their aluminum enclosures (Antec and Silverstone). Likewise, these devices use as much aluminum for their internal components as possible, to help increase radiant cooling or to conduct heat to special cooling surfaces. Enclosures also typically incorporate special conductors to transport heat to the case or to heat sinks, so as to maximize heat transfer to the neighboring environment.

The Antec Phantom's big passive cooling fins are big and easy to see.

Special heat conductors transport heat to the Antec's built-in cooling fins

The Antec's coils transfer heart to the aluminum case/cooling fins

The Antec incorporates a big, but nice-looking heat sink into its design.