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
Westinghouse Combustion Turbine Systems Division is typically adequate energy in the exhaust of the gas turbine to generate enough steam to produce about 50% of the gas turbine power, or, in this case, only 75MW. In this way, the original PACE plant design had built-in steam turbine capacity to enable the water/steam side of the plant to remain essentially the same as the gas turbine power rating evolved through to the 100MW-plus W501D5, when the rating of the plant was 300MW without supplemental firing. The PACE 260 was initially offered with a heat rate of about 8,100 Btu/kWh (42% efficiency) LHV on natural gas fuel.