Supercritical CO2 Electrical Generator Efficiency Trade Study

by R. M. Calfo, C. T. Farr, & G. E. Poole
Curtiss-Wright Electro-Mechanical Corporation

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Supercritical carbon dioxide (SCO2) provides unique properties for a power plant working medium which may have significant benefits in reducing the overall size of a power plant. The SCO2 power plant will utilize high speed turbo-machinery to maintain an overall high system efficiency. The electrical generators will also need to be high speed and operate inside the SCO2 pressure loop to minimize external seals and the potential to leak CO2 into the surrounding atmosphere. A dominant loss mechanism for high speed machinery is the friction and windage loss associated with the rotating parts. The generator efficiency can be maximized by minimizing the friction and windage loss. A range of SCO2 properties are examined in this paper to determine the optimum set of properties which provide minimal friction and windage losses while still being sufficient for good machine cooling. This paper will also identify the necessary auxiliaries which may be required to achieve higher efficiency. Generator efficiencies greater than 95% can be achieved for rotating machinery operating inside an SCO2 pressurized environment.