Gas turbine on and off to run it only at high efficiency. The emergence of the continuously variable transmission may also alleviate the responsiveness problem. Turbines have historically been more expensive to produce than piston engines, though this is partly because piston engines have been mass-produced in huge quantities for decades, while small gas turbine engines are rarities; however, turbines are mass-produced in the closely related form of the turbocharger. The turbocharger is basically a compact and simple free shaft radial gas turbine which is driven by the piston engine's exhaust gas. The centripetal turbine wheel drives a centrifugal compressor wheel through
Turbine-electric transmission ships instruments and applications. A lot of these electricity-generating turbines are being produced to include integrated electrical propulsion. A good example of one of these systems is the COGAL (combined gas and electric) system. An alternative approach is to use COGES, Combined Gas-Electric and Steam, to improve overall efficiency. A gas turbine-electric primary transmission is used, with a heat-recovery boiler in the exhaust flow to generate steam and thus electricity via a secondary steam turbine. Electric driven propulsion allows for movement of the ship and provides power generation on-board of the ship. Heat lost by gas turbines is not practical