Increasing energy efficiency conserves fossil fuels, cuts down on pollution, and saves money. Steam turbine power plants reduce their energy or heat loss by insulating pipes and by returning condensed steam to the boiler for reheating. New combined-cycle plants increase energy efficiency by using hot exhaust from gas turbines to produce steam for steam turbines in the same plant. On-site electricity generators often increase energy efficiency by cogeneration, or by combined heat and power (CHP), in which waste heat is captured to heat buildings. Cogeneration is employed in many different industries, with chemical, paper, and petroleum refining plants being the largest users. A number of colleges have also installed CHP generators. Improved technologies, the use of catalysts, renewable or recycled raw material, and recovery and reuse of waste in industry increase energy efficiency.
In transportation, fuel efficiency or miles per gallon (MPG) depends on vehicle design, on reducing air resistance by reducing the weight of a vehicle, and on the type of fuel used. Carbon-fiber composites are strong, extremely light materials that could significantly increase fuel efficiency if employed in the manufacture of vehicles. One such material is waiting to be patented, and research into reducing composite production cost, using agricultural and paper-manufacturing waste, along with recycled bottles and plastic car parts, is ongoing. New technologies, such as regenerative braking, which converts momentum to electricity when the brakes are stepped on in hybrid electric vehicles, also increase energy efficiency. Advances in engine-technology design include Compression Ignition Direct Injection engines, which result in less heat loss in gasoline burning engines and which also increase fuel efficiency.
Hybrid electric vehicles, as well as alternative fuel vehicles, use less gasoline and cut down on pollution. Flex-fuel vehicles can use gasoline, ethanol, or methanol for fuel. Bifuel vehicles have two tanks—one for gasoline and one for natural gas or propane. There were over 100,000 vehicles fueled by natural gas on the road in the United States in 2000, according to the U.S. Department of Energy.
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