This paper describes the design and testing of a high-efficiency turbo-generator for use in an Organic Rankine Cycles (ORC) with a power target of 30–100 kWe. The elegant yet simple design consists of a hermetically sealed, single piece rotor, with axial turbine and permanent magnet generator. The design employs compliant foil bearings (CFB), which eliminate the need for any external lubricates or dynamic seals and no contamination risk to the process fluid. A unique partial admission turbine concept is employed which provides better than 80% efficiency across a wide range of seasonal temperature variation, such as those occurring in northern latitudes, where summers can be hot (> 35°C) and humid and winters are extremely cold (< −20°C) and dry. We describe the design and prototype manufacturing as it pertains to micro and meso-scale turbines (< 100 kW) in terms of thermodynamic cycle considerations, turbine design, rotor-bearing dynamics, overall system design and scale-up considerations.

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