A Rankine cycle system useful for the conversion of waste heat into mechanical and/or electrical energy is provided. The system features a novel configuration in which a first closed loop thermal energy recovery cycle comprising a first working fluid stream and a second closed loop thermal energy recovery cycle comprising a second working fluid stream interact but do not mix. The two thermal energy recovery cycles interact thermally via heat exchangers, a first heat exchanger configured to transfer heat from the first working fluid stream to the second working fluid stream, and a second heat exchanger configured to transfer heat from the second working fluid stream to the first working fluid stream. In one or more embodiments, the Rankine cycle system is adapted for the use of supercritical carbon dioxide as the working fluid.