A power conversion system comprising: a first working fluid circuit having a high pressure side and a low pressure side and configured to flow a first working fluid therethrough; a heater configured to circulate the first working fluid in heat exchange relationship with a heat source to vaporize the first working fluid; a first expander arranged between the high pressure side and the low pressure side of the first working fluid circuit, configured to expand the first working fluid therein and generate mechanical power therewith; a first pump or compressor arranged between the low pressure side and the high pressure side of the first working fluid circuit; a second working fluid circuit having a high pressure side and a low pressure side and configured to flow a second working fluid therethrough; a heat transfer arrangement, configured for transferring heat from the low pressure side of the first working fluid circuit to the high pressure side of the second working fluid circuit and vaporize the second working fluid; an expander arrangement (24; 25) arranged between the high pressure side and the low pressure side of the second working fluid circuit, configured to expand the second working fluid therein and generate mechanical power therewith; a second pump or compressor arranged between the low pressure side and the high pressure side of the second working fluid circuit; wherein the first pump or compressor is drivingly coupled to the expander arrangement (24; 25) and driven by mechanical power generated therewith; the power conversion system is characterized by comprising a second heat recuperator, with a heat-dispensing side in heat exchange relationship with a heat-receiving side, the heat-dispensing side being fluidly coupled to the second working fluid circuit and the heat-receiving side being fluidly coupled to the first working fluid circuit, such that heat is transferred from the second working fluid, circulating in the heat-dispensing side of the second heat recuperator, to the first working fluid circulating in the heat-receiving side of the second heat recuperator. a first working fluid circuit having a high pressure side and a low pressure side and configured to flow a first working fluid therethrough; a heater configured to circulate the first working fluid in heat exchange relationship with a heat source to vaporize the first working fluid; a first expander arranged between the high pressure side and the low pressure side of the first working fluid circuit, configured to expand the first working fluid therein and generate mechanical power therewith; a first pump or compressor arranged between the low pressure side and the high pressure side of the first working fluid circuit; a second working fluid circuit having a high pressure side and a low pressure side and configured to flow a second working fluid therethrough; a heat transfer arrangement, configured for transferring heat from the low pressure side of the first working fluid circuit to the high pressure side of the second working fluid circuit and vaporize the second working fluid; an expander arrangement (24; 25) arranged between the high pressure side and the low pressure side of the second working fluid circuit, configured to expand the second working fluid therein and generate mechanical power therewith; a second pump or compressor arranged between the low pressure side and the high pressure side of the second working fluid circuit; wherein the first pump or compressor is drivingly coupled to the expander arrangement (24; 25) and driven by mechanical power generated therewith; the power conversion system is characterized by comprising a second heat recuperator, with a heat-dispensing side in heat exchange relationship with a heat-receiving side, the heat-dispensing side being fluidly coupled to the second working fluid circuit and the heat-receiving side being fluidly coupled to the first working fluid circuit, such that heat is transferred from the second working fluid, circulating in the heat-dispensing side of the second heat recuperator, to the first working fluid circulating in the heat-receiving side of the second heat recuperator.