eli5: if you need to put energy to rise the temperature of the substance, why cant you generate energy by cooling something down?

Question

eli5: if you need to put energy to rise the temperature of the substance, why cant you generate energy by cooling something down?

In: 6

Answer 1

I think that you are confusing WORK and ENERGY–they use the same unit.

Generating work from a difference in heat is what is called a heat engine. This is probably the largest category of engines (outside of electrical engines) with which you are familiar. Internal combustion (automobile), steam turbines, jet engines, rocket engines, etc are all examples of heat engines. They generate work from a difference in temperatures.