What cycle is known as a "heat engine"?

Pls help and if you can please explain

In thermodynamics and engineering, a heat engine is a system that converts heat or thermal energy to mechanical energy, which can then be used to do mechanical work. It does this by bringing a working substance from a higher state temperature to a lower state temperature.

Explanation:

answer; round wood logs, building materials like (plywood),also pulp and paper products;

i think it's severe storms but i might be wrong