GM Still Waiting for the Volt's EPA Rating
The decision could be key to consumer acceptance.
Kevin Bullis 04/12/2010
- 7 Comments
GM provided an update to its Volt program today. Everything is on track to start selling the first of these electric vehicles by the end of the year, but the big remaining question is how the EPA will label the vehicle's fuel economy.
Engineers are still tweaking elements of the design, such as the aerodynamics, and finalizing the manufacturing process, both for the car and for the battery pack, which GM has decided to make itself.
One of the first test vehicles has over 20,000 miles on it, and the battery system seems to be working fine--with about a 20 percent variation on vehicle range depending on driving conditions. In nice weather and on flat ground, drivers can expect to get slightly more than the 40 mile electric range GM is promising (the car also has an on-board gasoline generator that extends the range once the battery is depleted). In bad weather, or while driving up steep hills, they will get considerably less--according to GM, heating the vehicle can take just as much energy as propelling it down the road. This summer 300 GM employees will test-drive the cars to find glitches that haven't shown themselves so far in the testing process.
The EPA has yet to label the vehicle's fuel economy though. Last year the company announced that the Volt will get 230 miles per gallon, an all but meaningless figure Since, for the first 40 miles, the car does doesn't use any gasoline at all. As long as you can recharge the battery every 40 miles, you can skip the gas station entirely.
After you run out of charge, however, the car becomes a hybrid, something more like the Toyota Prius, using the battery to store power captured during braking and to help the gas generator operate more efficiently. (Unlike the Prius, however, the wheels are always powered by electricity--after 40 miles, the electricity comes from the gasoline generator rather than energy stored in the battery.) In this mode, the fuel economy is going to be something like 50 miles per gallon. The 230 mpg figure was calculated by guessing how much drivers were likely to exceed the 40-mile, battery range.
The EPA is still trying to figure out how best to label the car. Andrew Farah, the Volt's chief engineer says that what the agency decides could be key to how consumers accept the vehicle. "They have to know what they're getting," he says.
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dtutelman
116 Comments
Good news or bad?
"according to GM, heating the vehicle can take just as much energy as propelling it down the road."
This is an interesting aspect of transportation via engines other than thermal. Is it good or bad? Well, probably good. But not all good.
The reason it "costs" so much to heat the car is that electric propulsion is very efficient. Electric motors have very little waste heat. In order to heat the cabin, you have to explicity spend battery power.
The internal combustion engine, on the other hand, wastes so much heat that we can just use the spare heat to warm the cabin. But we're expending the energy to produce that heat -- and a lot more -- whether we use it to warm us or not.
This would be unalloyed good news for the electric car, except... The electricity has to come from somewhere. If the car's batteries are charged from plugging in (as opposed to fuel cells), then they most likely are wasting heat somewhere else -- the electric utility's generating plant. True, a large-scale generator wastes less heat than a small (single-vehicle) internal combustion motor. But the thermal efficiency is still well under 50%.
There are no easy answers. As usual.
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