Heat-to-Electricity With High-Speed Magnetic Bearing/Generator System

The development, testing, and application of a high speed permanent magnet generator in conjunction with a centrifugal expansion turbine supported on magnetic bearings for the production of electricity from waste heat recovery is described. This integrated power module (IPM) can recover waste heat from a number of heat sources including geothermal. The IPM operates between 15,000 rpm and 26,500 rpm depending on the energy available from the heat source. The varying frequency voltage supplied by the generator is connected to the grid using an active/ active power electronics package that can deliver power at 400-480 Vac (50 Hz or 60 Hz). Active magnetic bearings that were chosen for the application can operate directly in the working fluid of the ORC system, have low losses, and provide high reliability and remote monitoring capabilities. The shop testing procedure for quality control is described. The first field test unit was installed in April 2009, and since then some 100 units have been distributed worldwide for waste heat-to-electric production. This includes a commercial site for coproduced geothermal energy at a natural gas well in Louisiana.