At NextBigFuture, Brian Wang discusses methods of converting low temperature waste heat into usable energy. One of the methods discussed is the Ener-G-Rotors (Schenectady, NY) rankine cycle approach which instead of using a turbine for energy recovery, uses a gerotor (internal gear motor) instead.

Ener-G-Rotors' technology is based on the Rankine cycle, in which heated fluid flowing through a tube heats a pressurized fluid in a second tube via a heat exchanger. The second tube is a closed loop; the so-called working fluid flowing through it (a refrigerant with a low boiling point, in the case of Ener-G-Rotors) vaporizes and travels into a larger space called an expander. There, as the name would imply, it expands, exerting a mechanical force that can be converted into electricity.

Instead of turning a turbine, the expanding vapor in Ener-G-Rotors' system turns the gerotor, which is really two concentric rotors. The inner rotor attaches to an axle, and the outer rotor is a kind of collar around it. The rotors have mismatched gear teeth, and when vapor passing between them forces them apart, the gears mesh, turning the rotor. _TechnologyReview

Anyone with the least exposure to fluid energy will recognise the internal gear pump/motor as relatively inexpensive, but far from frictionless, and not nearly as durable as a well maintained turbine. Ener-G-Rotors claims to have made their gerotor virtually "frictionless" and therefore extremely durable. If so, it would be a significant advancement in cost reduction for this type of heat recovery.