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Comment by king_magic | Hacker News Reader

With this (absurd) line of thinking, we should probably just not generate any power at all.

The point is that even if unlimited cheap heat becomes possible, turning that heat into useful forms (e.g. electricity) has limits that we are already close to.

I don't see how that observation is in any way absurd. It's actually quite helpful to counter the "fusion as a panacea" narrative with a dose of reality of how power plants actually work.

We put the plant near a river. It intakes river water, which is heated to steam to make the electricity, and is then cooled and reused or released. I don't see how that is terrifically destructive; I must be missing something. Explain it to me, please? (Serious question.)

Imagine that we decide to increase energy usage by 5x-10x, and increase size of the plant, and the change in river eater temperature goes up by that much. Eventually the plant starts to change the river water temperature to the degree that it changes the ecosystem.

This is already regulated, see for example this discussion of monitoring systems for proving compliance:

https://www.power-eng.com/articles/2007/01/external-temperat...

How do you cool it down? The only way to cool one thing is to heat another. Evaporative cooling is usually the method if you must cool your water, but it has diminishing returns and isn't practical to cool all the way to inlet temperature (because source water is colder than the air wet-bulb temperature). This results in water above ambient being discharged to the environment, which affects fish and plant life in the water body.

We already do that, and those nuclear power plants (and other thermal plants) already have to shut down under certain climate conditions to avoid damaging the local ecosystem by overheating it. [1]

[1] https://www.chicagotribune.com/news/ct-xpm-2012-08-20-ct-met...

Wind and solar do not require cooling or have problematic thermal emissions. It is possible for solar to have a slightly lower (or higher) albedo than ground it is situated, and possible for wind to cause some local heating from air mixing (with corresponding distance cooling) but these effects are much less intense than thermoelectric plants essential need to release Gigawatts of heat in order to produce gigawatts of electricity (in addition to the heat which the produced electricity ultimately results as).

Even if solar albedo is equal to the ground it was on, that will cause a net cooling at the solar collection site, since ~20% of the absorbed solar energy is converted to electrical power, not heat. The power then eventually gets converted to heat by the consumers, but that's true of power from any source.

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