Abstract: Expansion machines in thermodynamic cycles operate at low pressures, i.e. below 10 bar. The interplay among components including gas generator, expansion machine, heat exchangers and pressure reduction device (absorber or condenser) is optimized, resulting in configurations operating at the lowest achievable cost level. A single stage radial turbine characterized by a pressure ratio of 5-10, a dimensionless speed of about 0.7 and a loading coefficient of 0.7 is a preferred expansion machine for certain thermodynamic cycles involving CO2 gas to permit such radial turbines to operate close to their optimum design specification and highest efficiency level. Methods to handle liquids which may condense within or inside the turbine are also disclosed, as well as methods to handle axial pressure on bearings and methods to protect lubricant in bearings.