You may be right for gas cars, but the sweet spot will be much lower for cars that don't have to consume power at zero speed. See:
http://auto.howstuffworks.com/question477.htm <<...But the bottom line is, if you double your speed, this equation says that you will increase the power required by much more than double. A hypothetical medium sized SUV that requires 20 horsepower at 50 mph might require 100 horsepower at 100 mph. You can also see from the equation that if the velocity v is 0, the power required is also 0. If the velocity is very small then the power required is also very small. So you might be thinking that you would get the best mileage at a really slow speed like 1 mph. But there is something going on in the engine that eliminates this theory. If your car is going 0 mph your engine is still running...>> So I am still far from convinced that that tiny van can't possibly go 200 km in 10 h on 12 kWh mechanical energy. At constant 20 km/h this would mean 1.2 kW for 10 h, it doesn't sound totally impossible to me that two 600W power drills could propel that thing at this kind of speed... Michel ----- Original Message ----- From: "Jones Beene" <[EMAIL PROTECTED]> To: <vortex-l@eskimo.com> Sent: Friday, August 01, 2008 6:51 PM Subject: Re: [Vo]:Re: Cost per mile of CAT vs EV (was Re: Doubly disruptive?) > Well, it is generally assumed by automotive engineers > in the USA at least, that the most efficient speed in > terms of lowest gasoline consumption per mile traveled > is in the range of 55-60 mph. > > I see nothing in the operation of the MiniCat which > would change that assumption very much, unless Euro > roads have more friction at high speeds ;-) > > ... calcs notwithstanding. > > J. > > > --- Michel Jullian <[EMAIL PROTECTED]> wrote: > >> I was including air drag in the frictional losses, >> indeed it is their main component, and does go as >> the square of the velocity (air drag energy loss = >> work of the drag force = 1/2 * rho * Cx * Frontal >> area * v^2 * distance), so you may have missed my >> point, which is that 12 kWh is probably quite enough >> to run that small van 200 to 300 km at 20 to 30 >> km/h. >> >> Your 100 km/h figure is their top speed, not the >> speed for their range test, which as I said can be >> easily inferred from their "200 to 300 km or 10 >> hours of driving" spec as between 20 and 30 km/h. >> >> Cheers, >> >> Michel >> >> P.S. I am not particularly negative and have no >> special information on Negre and his company, I >> think the technology is very nice actually. >> >> ----- Original Message ----- >> From: "Jones Beene" <[EMAIL PROTECTED]> >> To: <vortex-l@eskimo.com> >> Sent: Friday, August 01, 2008 5:35 PM >> Subject: Re: [Vo]:Re: Cost per mile of CAT vs EV >> (was Re: Doubly disruptive?) >> >> >> > --- Michel Jullian wrote: >> > >> >> Note they say "200 to 300 km or 10 hours of >> >> driving", which indicates a range test speed of >> only >> >> 20 or 30 km/h, which is about 4 times less than >> the >> >> 100 km/h you have assumed, i.e. assuming friction >> >> losses going with the square of the velocity the >> COP >> >> could be as much as 4^2 = 16 times lower than the >> >> COP you computed, IOW a COP of 8/16 = 0.5 which >> is >> >> much less exciting! >> > >> > Ha false logic on several levels. Firstly - >> frictional >> > losses are small in comparison to aerodynamic drag >> - >> > which is far greater at the 100 km/hr, which in >> the >> > end make the conclusion actually far more exciting >> ! >> > >> > Jones >> > >> > Anyway, Michel - you are being unaccustomedly >> negative >> > in light of the "French Connection" to Negre... or >> do >> > you hear rumors that this company may not be on >> > up-and-up ? >> > >> > >> >> >
