You wildly underestimate the size of the oceans. If they're going to be built anyway, and if they can have a long lifespan even in salt water, this would be far better for the environment than the currently popular method of using rivers for cooling - rivers can be warmed by perceptible and significant amounts until they carry that extra heat into the oceans, plus fresh water is more rare, precious, and in need of protection than salt water.

this is the current real solution on the ISS - three main computers doing everything.

About half of solar energy passes through the atmosphere, that factor of two isn't a good enough reason to use space-based solar panels for ground-based power grids.

Even though the microwave receiver power station in SimCity 2000 looked so cool.

Temperature is what matters. The same amount of heat out into a river can significantly warm the whole river downstream, but have no detectable effect on the ocean temperature, just because the heat is diluted so much.

Like, dilute a bottle of tequila with two liters of cola, sure you'll get drunk - but pour that same tequila into a full swimming pool, and you'd never get drunk even if you drink the pool water all day.

A 20KW data center is utterly feeble, barely worth the name, by ground-based data center standards, which easily go into tens of megawatts.

The effects of heat are all due to temperature, which is reduced by dilution.

The alcohol molecules represent heat energy (Joules), and the ABV% represents temperature (Kelvin).

Rivers are small enough to be negatively affected by data center waste heat, but oceans really aren't. They are being affected by the greenhouse effect though, because that is on a scale of petawatts, a million times the gigawatt scale of all global data centers together.

I'm not in favor of megawatt data centers being used for mostly-bullshit AI in general, but as I said "if they're going to be built anyway", then they'll do less harm in the ocean than most other places.

(That's assuming they can avoid problems due to saltwater corrosion.)