  The topic of microscopic heat engine has undergone intensive research in
recent years. Microscopic heat engines can exploit thermal as well as active
fluctuations to extract thermodynamic work. We investigate the properties of a
microscopic Stirling's engine that uses an active (self-propelling) particle as
a working substance, in contact with two thermal baths. It is shown that the
presence of activity leads to an enhanced performance of the engine. The
efficiency can be improved by increasing the activity strength for all cycle
time, including the non-quasistatic regime. We verify that the analytical
results agree very well with our simulations. The variation of efficiency with
the temperature difference between the two thermal baths has also been
explored. The optimum region of operation of the engine has been deduced, by
using its efficient power as a quantifier. Finally, a simple model is provided
that emulates the behaviour of a flywheel driven by this engine.
