I recently had a discussion about ACs and how they heat up cities.
Then I found an article about theoretical increase of efficiency of acs by using the heat pulled from a room to run a thermoelectric device and getting some of the energy back that was used in the ac.
I‘ve had this downstream thought many times already: since hot air is basically just energy stored. Could we theoretically pull (all?) the energy from the air (depending on desired temp) to cool it and casually fuel our society’s energy needs?
The problem with this is entropy. Heat dissipated to the environment is highly entropic (more disorganized, less useful heat/energy), and to effectively extract it, you’d need to reduce the entropy, which requires more energy that you would get from the heat you recovered.