Patent ID: 8400005

Claim:
An apparatus comprising: a first turbine generator apparatus, comprising: a first turbine wheel configured to receive a working fluid and rotate in response to expansion of the working fluid flowing from a first inlet side of the first turbine wheel to a first outlet side; and a first electric generator having a first stator and a first rotor, the first rotor coupled to the first turbine wheel to rotate at the same speed as the first turbine wheel when the first turbine wheel rotates; and a second turbine generator apparatus, comprising: a second turbine wheel configured to receive the working fluid from the first turbine generator apparatus and rotate in response to expansion of the working fluid flowing from a second inlet side of the second turbine wheel to a second outlet side; and a second electric generator having a second stator and a second rotor, the second rotor coupled to the second turbine wheel to rotate at the same speed as the second turbine wheel when the second turbine wheel rotates, and wherein the first outlet side of the first turbine wheel is coupled to the second inlet side of the second turbine wheel.