Nowadays, diffrent solutions for increasing energy production are investigated in the world. One of the possibili- ties is using of renewable energy sources in cogeneration device – combined production of electricity and heat in one device, with a high overall effiency. The article deals with principle of hot-air engine, its basic division and use in combined production of heat and electricity from biomass. The basic principle of engine is conversion of heat into mechanical energy, that is subsequently used for production of heat and electricity. In the contribution is presented Stirling engine that driven by thermal energy from a concentrating solar collector and from biomass boiler.