A method and an apparatus for producing power from a heat source comprising a nonane heater/vaporizer, an intermediate fluid vapor turbine mounted on a shaft that receives and expands the vaporized nonane, an organic fluid vaporizer that receives the expanded vaporized nonane for supplying heat to liquid organic working fluid present in said organic fluid vaporizer and vaporizes said liquid organic working fluid with heat from the expanded vaporized nonane to form vaporized organic working fluid and a nonane condensate, a seal of said shaft being cooled using the nonane condensate by cooling and condensing hot pressurized vapor near the seal, and liquid containing such condensed hot pressurized vapor being supplied to a condensate drain vessel, the drained condensate being supplied to a line connected to a cycle pump of the nonane intermediate cycle, and an organic vapor turbine that expands the vaporized organic working fluid.