It's fine and dandy to be satisfied that the Chevy Volt "works," but I would think that engineers ought to be curious, and ask "how"?
Did you guys listen to this?
The GM powertrain engineer uses a bit of techno-babble, if you ask me, saying that the engine must always "react against" an electric motor. Whatever that means. But what it comes down to, wading through the fog bank, seems to be this: The two electric motors have their outputs combined by a planetary gear arrangement, to reach the wheels. The internal combustion engine ALSO feeds this planetary gear arrangement directly, i.e. mechanically. However, the electric motors must remain engaged even when mechanical power from the engine is mechanically feeding that planetary gear arrangement. (E.g., is one of the motors acting as a generator at this time? Probably that's all "react against" means.)
To me, sorry Chevy, this makes the car a plug-in hybrid. Not saying this is bad, not saying the design tradeoff was not well thought out, just saying it ain't a pure electric car. Notice how the engineer defines it as an electric car, more than once, only by mentioning the first 40 miles of driving.
At relatively how output, internal combustion engines become most efficient. So okay, that's why they did it this way. I'm hoping for fuel cells to become feasible soon.
Etmax - yes this make perfect sense (within limits)! Higher speed definitely uses more fuel. However, at low loads ICE's waste a lot of energy via pumping losses across the throttle plate (efficiency plummets). The most efficient throttle setting is usually about 3/4 open throttle - where these losses are minimized, but "power enrichment" fuel mode has not started to add more fuel. So... moderate accel + constant speed would seem to be optimum. In fact, most ICE "Eco-Marathon" competition vehicles have no throttle, and just accelerate / coastdown repeatedly. ICE's don't throttle-down efficiently (but diesels are much better in this regard !) see: http://en.wikipedia.org/wiki/Eco-marathon
For more detailed data and discussions on related topics - try checking out the blog of the 100 MPG automotive X-Prize winner (Edison2). This car used an ICE (burning E85) and beat all the electric vehicles in its class (even though the rules actually favored EV's): www.edison2.com/blog
BMW did a study into what type of driving saves the most fuel. They tried 1. accelerate rapidly to the desired speed and maintain. 2. accelerate beyond the desired speed and coast back down to it. 3. Drive like a granny (my apologies to all the grannies out there) ie. accelerate slowly to the desired speed. They found that No. 1 on average offered the best fuel consumption. This was of course for a conventional ICE. This makes a lot of sense when you think about it. It would be interesting to see this done for pure EV's and Hybrids to see whether there are differences
`(Somewhere above here it was said that it takes 5 HP to run at 70mph?) I believe one experiment is worth a 1000 expert opinions. Remember mechanics in physics? A reasonable approx is Energy/time = ((1/2)(mass_of_car)(70mph^2) - (1/2)(mass_of_car)(60pph^2))/time Measure the time.....I got about 22HP for my station wagon. (If U assume the drag is directly proportional to velocity and not the square of velocity, you can come up with an exponential curve as a function of speed.)
It's going to be very difficult to compare electric to gas or hybrid but comparing gas to hybrid is simple since the same fuel is dumped into the tank. In the case of the civic, you can also throw in CNV. the Fueleconomy.gov site can give practical info. After almost 150K on my Civic hybrid (originally purchased only for the car pool sticker), I've used about 3300 gallons of gas, versus 6600 for my 23mpg caddy I was driving or 5000 gallons for my 30mpg ford focus (these are my actual commute mileages, not the EPA estimates). A "normal" civic would have used the same as the focus (also a 30mpg combined). The CNG version gets 26mpg of CNG. So whether it's the Atkinson engine, the regen braking, or whatever, it amounts to a very signficant gas savings. I expect the Volt to have similar overall savings. As far as cradle to grave, time will tell..
"Once a high percentage of the grid is powered by renewables - THEN (and only then) will EV's make sense. For those that don't care about the cost - hybrids (or plug-in hybrids) are an OK mid-term solution."
Totally agree on that. I'll add: if one really needs an energy intensive vehicle (SUV or van) and/or plans to drive mostly on highway, he/she should go for a diesel. In the meanwhile, let's study how to reduce energy waste of homes (thermal end electrical).
NASA's Orion Flight Software Production Systems Manager Darrel G. Raines joins Planet Analog Editor Steve Taranovich and Embedded.com Editor Max Maxfield to talk about embedded flight software used in Orion Spacecraft, part of NASA's Mars mission. Live radio show and live chat. Get your questions ready.
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