Sorption heat engines: Simple inanimate negative entropy generators

The name ‘sorption heat engines’ (SHE) is proposed for simple negative entropy generators that are driven by thermal cycling and work on alternating adsorption and desorption. These generators are not in general explicitly recognized as heat engines. Their mechanism is applicable to the fields of engineering, physics, chemistry, geology, and biology, in particular the origin of life. Four kinds of SHEs are distinguished depending on the occurrence of changes in the adsorbent or adsorbate during the thermal cycle.