

the thing you’re missing is scale. what you’re describing is overgrown car radiator type scheme, and it works up to some couple MW if need be. when you have access to sea, or large river, you can just use that water as a coolant and dissipate some couple GW this way. this is the reason why so many nuclear powerplants are on seashore. because sea is generally very big [citation needed] temperature increase is slight and mostly harmless in usual cases
inland, in absence of large river, the other way to provide cooling is by evaporation of water. one form is to take that oversized car radiator and spray water on it, water evaporates taking away some heat. this arrangement allows for no-added-water operation in low load conditions. in principle this means that lowest possible temperature is not air temperature, but instead it’s wet bulb temperature, which is always lower, and difference is greatest when air humidity is low. in practice this doesn’t allow to reach this lower temperature, but the other approach does. for bigger scale still, instead of using heat exchanger, water is dripped in a tower of some shape and air is moved in some way against it. small part of water evaporates, and the rest, now cooled down, is collected at the bottom. this is how these large cooling towers near coal or nuclear powerplants work, but so do smaller towers that rely on fans instead of chimney effect. extra water is always needed, and temperature closer to wet bulb temperature is achieved in all load conditions. rarely used alternative is to make an artificial lake, and allow for evaporation from water surface
notice that if water is evaporated, it’ll leave whatever is dissolved in evaporator part, which means it has to demineralized at all times. in practice it means that some part of evaporated water is treated continuously by reverse osmosis, and the less saline input water is, the easier and more energy efficient it is to do it
the thing with heat exchangers is, without water evaporation, that they have some constant thermal resistance. if you want to dissipate more heat, you need more of heat exchanger, or alternatively have to allow for higher temperature. the former means more metal needed, the latter means limits to other parts of coolant loop, or using heat pump to cool down silicon, while increasing temperature of coolant. both of these mean extra capex and/or energy use, but evaporating water is cheap, so it’s done instead. it doesn’t help that one of dc ratings is ratio of how much energy gets into dc to how much energy powers actual silicon. evaporating water does not add to energy use, so designs chasing this rating are likely to use that solution










it’s not regulation, it’s a metric that looks nice to investors. but also lower energy use means lower cost