I know a train runs on an electric engine powered by a diesel generator. Would something like this be feasible for cars?
It really isn't the best way to go. Anytime you convert energy, some efficiency is lost. It is more efficient to propel the car directly with the engine, rather than propelling the car with an electric motor that is powered by a generator powered by the engine. Despite this loss of efficiency, this setup is appealing for use in trains because of their heavy loads. To drive a train directly with a diesel engine requires a massive transmission. Designers ran into problems with the transmission gears breaking due to the massive forces associated with moving a train. Instead, they propel the train with electric motors, which require no transmission. But the motors require power, so they use diesel powered generators. So there you have it. The diesel/electric setup is not appealing for cars, because stresses are low enough that a normal transmission can be used, and there is more efficiency by driving the car directly by the piston engine. The diesel/electric setup is appealing for trains because it eliminates the need for a transmission, which is bulky and prone to breaking.
Not at the present cost of diesel. Nothing mechanical is 100% efficient, and when you start converting the different power sources - diesel to electric, electric to rotary, for instance - the torque and power may be sufficient for a particular application, but the inefficiencies simply add up from one source to the next.
You still have the inefficiency of the gasoline fueled engine. Gas cars break down like this: 1/3 of the energy goes out the radiator as waste heat 1/3 of the energy goes out the exhaust pipe as waste heat 1/3 of the energy actually turns the crank shaft Now subtract from that final third the power to turn the water pump, oil pump, alternator, power steering pump and air conditioning. Then loose some more energy through friction losses in the drive train. If the car has an Automatic Transmission (A/T) add a little bit more loss to turn the fluid pump and the energy loss in the torque converter while the car is stopped. That constant push you feel while the A/T is in gear is lost energy exiting in the form of heat in the transmission fluid. That's why A/T have oil coolers. So only 20% to 25% of the total energy in that gallon of gas actually goes to pushing the car forward. I've seen reports that it is as low as 15%. See the waste?
running a small engine to power an electric motor? yeah, that'd be feasible. not sure how effective it would be. i'd need to do some research before i could even guess
Chevrolet is coming out with something similar in 2010. The Chevy Volt is an electric car (axle driven only by an electrical motor powered by a bank of Lithium Ion batteries), but has a gasoline engine on-board to generate electricity to power the car when you run the batteries down. The gasoline engine in the Volt is not mechanically linked to the drive train and cannot be used to directly move the car. As far as diesel-electric hybrid cars go, Mercedes Benz is coming out with a Bluetec Diesel Hybrid S300 sedan next year. It's a mild hybrid though-- The primary motive power is the Bluetec diesel engine, with an electrical motor only assisting the engine when extra power is needed.
