The more efficient power supplies get, the less heat they produce, that is a positive side effect of that reality. Seasonic has now released three new power supplies that have no fans whatsoever, passively-cooled power supplies.
Of course, it's not a new thing, but typically only the higher rates Wattage products have been passive. well, Seasonic now offers a 600W, then a PRIME Fanless TX-700 (80 PLUS Titanium certified), the PRIME Fanless PX-500 (80 PLUS Platinum certified) and an unannounced 450W model. Seasonic will hand out a handsome 12-year warranty. The prices, however, have not been announced, but yeah they aren't going to be cheap, no Sir.