I think I get it. If we could convert 100% of the waste heat into useful power, then all good. And that would get interesting because it would effectively become "free" compute - you'd put enough power into the system to start it, and then it could continue running on its own waste heat. A perpetual motion machine but for computing.
But we can't do that, because physics. Everything we could do to generate useful energy from waste heat also generates some waste heat that cannot be captured by that same process. So there will always be some waste heat that can't be converted to useful energy, which needs to be ejected or it accumulates and everything melts.
I think I get it. If we could convert 100% of the waste heat into useful power, then all good. And that would get interesting because it would effectively become "free" compute - you'd put enough power into the system to start it, and then it could continue running on its own waste heat. A perpetual motion machine but for computing.
But we can't do that, because physics. Everything we could do to generate useful energy from waste heat also generates some waste heat that cannot be captured by that same process. So there will always be some waste heat that can't be converted to useful energy, which needs to be ejected or it accumulates and everything melts.