Comment by CorrectHorseBat
6 hours ago
What is waste heat depends on your usecase. Using waste heat from industrial processes for district heating is done in some places.
6 hours ago
What is waste heat depends on your usecase. Using waste heat from industrial processes for district heating is done in some places.
Yes, because there is a heat delta. A heat difference.
Using higher heat to raise lower heat is just the most simple case.
But purpose isn't relevant to this constraint, it is a physics constraint. Regardless of purpose, you can't extract useful energy from heat without a heat difference to work with. (And without a heat difference, even "heating" with heat doesn't do anything.)
Yes you can, that is exactly what heat pumps do. As long as the total entropy increases it is not in violation of the laws of thermodynamics.
But I don't really see how that is relevant to the question of using waste energy to heat homes. We don't have ideal Carnot machines so there's always energy wasted, which most of the time is still good enough for residential heating.