In a plug-in Prius, the gasoline engine is still the main thing that moves the car. Granted, there is an electric motor tied to the transmission, which is capable of moving the car by itself (unlike some hybrids). However, it can only get the car to ~53 mph, and takes a glacial 30 seconds to accelerate to that speed. The electric motor really only augments the gasoline motor, taking over at slow speeds and helping boost acceleration. Without the gasoline engine, the Prius would be a pretty sad car.
In the Chevy Volt, however, all of the power to the wheels comes from the electric motor. This motor puts out 160 hp, which is enough to propel the car from 0-60 in a respectable 9 seconds and give it a top speed you'd get pulled over for. As Chevy says, "Volt is an electric car that uses gas to create its own electricity," so the 1 litre engine is really just a battery in disguise. There is no mechanical connection between the engine and the wheels; its only function is that of a backup generator. In fact, you could rip out the engine and replace it with a diesel engine, a solar panel, a hydrogen fuel cell, a wind turbine, more batteries, a nuclear reactor, a cold fusion reactor, a bioreactor, or even a hamster wheel (I'm not even kidding, this would work), and the car would run in much the same way.
The design of the Chevy Volt holds some particular advantages over the plug-in Prius. The most important advantage is the aforementioned flexibility. As powerplant or battery technology changes, the drivetrain of the car can remain virtually untouched, saving a lot of R&D money. The motor also totally eliminates the need for a transmission, which improves efficiency and reduces weight and complexity. There's no gear shifting at all in this car, because unlike gasoline engines, which only work well at a very narrow range of speeds, electric motors work equally well at all speeds (sorry gearheads).
However, I have some nagging reservations, and one huge complaint (which has nothing to do with the Volt itself). My reservations deal mainly with how the gas engine will deal with not being run for potentially months at a time, with stale gasoline sitting in the fuel lines and tank. Anyone has tried to start a car thats been sitting in the driveway for a couple months knows that it's not easy. Modern fuel injection technology will likely help mitigate this problem, but I have a feeling that Chevy will end up recommending that owners deplete the fuel tank periodically.
I also wonder how the odometer will end up working. For this car, saying that it has 30,000 miles is more or less meaningless, as those miles could be all battery, all engine, or some mix of the two. To me, it makes sense for there to be two odometers, one for miles and one for "hours" the engine has run (theoretically at a constant RPM). Things like brakes, tires, differentials, suspension, etc, should be serviced on a mileage basis, while things like belts, hoses, oil, filters, gaskets, etc, should be serviced on an hours basis. Servicing based on hours isn't a new idea, as many recreational vehicles like ATVs and boats use that system.
My one big complaint is this:
In the early days of internal combustion engines, when diesel was just beginning to be tested as an alternative to steam in locomotives, engineers (the kind that designed the trains, not the kind that drove them) started running into some issues. Diesel engines had one very large disadvantage as compared to steam engines, being that they have an even narrower useful power band than gasoline engines (~600 - 1800 rpm). Steam engines on the other hand, like electric motors, have 100% torque available throughout their entire powerband. Engineers discovered that in order to be useful for accelerating hundreds of tons of freight up to high speeds, diesel engines would have had to be coupled to ridiculous transmissions, with perhaps even hundreds of gears, incredible material strength, and differentials capable of powering more than 4 axles. The construction and use of such transmissions bordered on impossible, so the widespread implementation of the diesel train seemed doomed to failure until the invention of the diesel-electric locomotive.
The idea behind the diesel-electric locomotive is the same as behind the Volt, namely, a diesel engine turns a generator, which provides electricity to power electric motors which turn the wheels. In one fell swoop, engineers managed to eliminate the need for a transmission and allow the diesel engine to run at its most efficient speed at all times (~740 rpm).
Now the reason I complain is that this technology had become almost universal by the 1930s. Aside from gradual improvements in diesel engines, electric motors, and control systems, the system has remained essentially unchanged for the last 80 years. The idea behind the Chevy Volt isn't "new" or "breakthrough" at all, its simply a very old technology that's finally getting adapted to a new purpose. I wonder, since this system has been proven to be reliable, efficient, and incredibly powerful, for 80+ years, why it hasn't been tried in a car until now.
They say genius is simply figuring out the obvious before anyone else, but to me, the magnitude of the obviousness of this approach makes it hard to credit Chevy with "genius."
0 comments:
Post a Comment