The absorption refrigerator  is of unique importance in setting an autonomous quantum device.
Such a device requires no external power and operates without external intervention in scheduling the operations
. The basic construct includes three baths; a power bath, a hot bath and a cold bath.
The tricycle model is the template for the absorption refrigerator. 
The tricycle engine has a generic structure.
The basic model consists of three thermal baths: A hot bath with temperature , 
a cold bath with temperature 
and a work bath with temperature .
Each bath is connected to the engine via a frequency filter which can be modeled by three oscillators:
where ,  and 
are the filter frequencies on resonance .
The device operates as a refrigerator by removing an excitation from the cold bath as well as from the work bath
and generating an excitation in the hot bath. The term   in  the Hamiltonian is non linear
and crucial for an engine or a refrigerator.
where  is the coupling strength.
The first-law of thermodynamics represents the energy balance of heat currents originating from the three baths and collimating on the system:
At steady state no heat is accumulated in the tricycle, thus . 
In addition, in steady state the entropy is only generated in the baths, leading to the second law of thermodynamics:
This version of the second-law is a generalisation of the statement of Clausius theorem; 
heat does not flow spontaneously from cold to hot bodies.
When the temperature , no entropy is generated in the power bath. 
An energy current with no accompanying entropy production  is equivalent to generating pure power:
, where  is the power output.