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October 2008 Posts
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Join Bo, Ryan, Jason, and Special Guest Host, Dr. John Briggs, for a look at some of those confusing technical aspects of EVs that we never discuss, but often mention. What the heck is a kWh? What is the difference between AC and DC motors? And much more!
Don't just listen to the EVcast -- experience and be a part of it! Join us at 1:00pm Eastern, M-F, in our live video broadcast and chat along with us!
Here is the Tesla post where a lot of the information on AC and DC motors came from
http://www.teslamotors.com/blog4/?p=45 Wally Rippel
DC Brush
NmG DC 20KW, 30KW peakBugE DC, 3KWTango DC 42KW (150KW peak) Advanced DC FB1-4001
DC Brushless
Vectrix DC 7KW (20KW peak) (Parker Hannifin Divisione)Zap Xebra DC: 5KW Brushless (2008)Prius DC 50 KW, permanent magnetCamry Hybrid : DC Brushless 105 KWHighlander Hybrid DC Brushless 173 KWHonda Insight DC brushless 10 KWHonda Civic DC brushless 15 KW
AC Induction
Tesla AC Induction 185 KWTriac AC, 20 KW PMSMChevy Volt AC induction 111 KWGM EV1 AC induction 102 KW
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This was a good show- the more that is learned about how the technology works, the easier it will be accepted, even if it is not understood entirely. I think John hit it on the head when he said that most people are comfortable with gallons, miles per gallon and with horsepower, even if they do not really understand it completely. The new terminology of Volts, Watts and Watt-hours has to be learned so people will be comfortable with what they are buying. This is a bit like the acceptance of computer technology. Even if most users do not understand the terms, they have at least become aware of, and comfortable with, terms like Gigabytes, Gigahertz, RAM and Hard Drives. In fact, since the current generation has had to make that first, fast technological leap, I am hopeful that the leap to EV's will be even easier.
We need a new standard for measuring automobile efficiency. Instead of miles per gallon, we need a measurement that is common for every type of fuel. One that comes to mind is cost per mile.
We need to develop a consumer label for driving costs (maybe something like the energy star labels). On the label the specific fuel used by the vehicle in question would be listed in the standard unit of measure used to purchase the fuel. For example, if it were a gas powered car then the label would state that calculations are based on a cost of $3.30 per gallon. If it were pure electric then $0.19 per kwh. If it were hydrogen based then it might be $26.00 per MMBTUs.
Then an estimate would be made on the cost of driving 100 miles and driving one year (15,000 miles) using the EPA's famously inaccurate testing results. This would be in place of "miles per gallon". So we would have a city cost per mile, highway cost per mile, and combined cost per mile.
Using cost per mile completely eliminates confusion between fuels and allows a direct comparision across all vehicle types. It also allows the consumer to easily understand the cost to them since the efficiency is stated in cost.
Not a bad idea David, but the big problem is the greatly varing energy costs here in the US. In North Dakota at night a user can pay .05/kWh where as people in CA can pay up to .30/kWh.
I think Bo is right about the price of electricity varying by state would be a serious problem for these calculations. The cost of gasoline varies by state as well, but not nearly as much as electricity.
I don't think this is a problem for EnvergyStar labels. They calculate the cost to run your refrigerator based on 8.7 cent/KWH, and then you can compare refrigerators. The fact that it will cost you much more to run that refrigerator in Hawii, is not much of an issue, because you are using the number to compare two refrigerators. Also, they do give you the KWH/year, so you can do the calculation yourself.
Perhaps it will be necessary to leave something to the consumer. Supply KWH/mile city and KWH/mile highway and then some example cost of ownership data at 8.7 cents/KWH. Let the consumer adjust for the local price of electricity.
In the E-REV vehicles, this is going to be even more confusing.
Another entry for your chart:
Toyota Camry Hybrid: DC Brushless 105 KW
(Toyota refers to this motor (and that in the Prius) as a "permanent-magnet synchronous AC motor")
And the Toyota Highlander Hybrid:
Front wheels motor: 123 KW (167 Hp), 247 ft-lbs torque
Rear wheels motor: 50 KW (67 Hp), 96 ft-lbs torque
both permanent magnet (DC brushless / AC syncrhonous) motors
IwantAnEV,
Thanks for the information. I have updated the list of motors.
ThanksJohn C. Briggs
I'm not stuck on cost as the only solution for a common measure of efficiency. I'd like to hear other ideas that people might have. If we could educate the general public on a common energy unit (kilojoules?) and then have everything converted to that unit then maybe we could do the same thing. Sounds unlikely, though.
Concerning Bo's comment about the range of energy costs in the US, my point was that every car would contain a label stating what cost was used for the calculation. Maybe I wasn't clear but I meant that every car powered by gasoline, for example, would use the same national average cost for a gallon of gas. So a car sold in California and a car sold in Kansas would both use the same cost per gallon for the calculations. The average costs for each kind of fuel would be a national average set by the EPA (I assume) based on country wide sales. Every car that ran on gas would use one cost, every car that ran on electricity would use one cost. If the same method was used across fuel types to derive the cost of the fuel (for example the average price paid by a consumer at the "pump") the result would be a common method to compare efficiencies.
Even E-REV vehicles would be simpler to compare using cost instead of MPG. The only addition would be to estimate the amount of electric only operation verses range extending operation for city and highway driving.
We already see cheating going on with groups reporting "100 MPH in a plug-in Prius" for example. The 100 MPG comes from only the gasoline used and depends heavily on how many miles you drive on battery alone. And they don't include the cost of the electricity recharged from the home wall socket. And it's only going to get worse with everyone comparing "apples to oranges" in the next few years.
Granted, it's possible that the energy cost variation across the country may be too great to give meaningful numbers. If so, we may have to do regional calculations, or possibly state by state. And the comparisons may have to be updated more frequently that once per year. But at least money is a common unit we all understand.
Another point, we don't have to do only one thing. I would like to see both a standard "miles per energy unit" as well as cost per mile.
