Stirling engine and biomass combustion plant

A Stirling engine (1) comprises four working pistons (3) all at right angles and a planetary drive (4) to convert to a drive shaft (5) rotation via an external toothed crank (11). Two equalizing masses (14,14') equalize mass forces and moments so that the work pistons and gear have a common center of gravity in the shaft axis. An independent claim is also included for a biomass combustion unit comprising a Stirling engine as above.