Williams Energy Services integrated two Capstone Model 330 microturbines and one PowerBlock energy storage system to power an oil derrick near the Denver airport. Most microturbines are typically single-shaft machines, with the compressor and turbine mounted on the same shaft as the electrical generator, which produces 25 to 300 kilowatts. Engineers equip the unit with a single rotating part to eliminate a gearbox and associated moving parts, thereby reducing maintenance. The shaft itself is mounted either on two oil- lubricated bearings or, in some cases, air bearings. Shaft speeds range from 60,000 to 100,000 rpm.
Engineers mount the stator into a common casing with the turbine and compressor.
Digital power controllers convert the high-frequency power produced by the generator into 50 to 60 hertz grid quality power. These electronic components also control all of the microturbines' startup and operating functions, including full control of the turbine, signal conditioning, data logging, and diagnostics. A key microturbine component is its recuperator, which transfers heat from exhaust gas to air that is sent to the combustor. Preheating combustion air reduces the fuel consumption of the microturbine and increases its overall efficiency. In addition, microturbines provide high operating efficien-cies of 25 to 30 percent, high reliability, and perform as long as 50,000 hours without stopping for maintenance.