The Electric Car
in [Design]
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From: John Larkin on 1 Aug 2007 02:09 On Wed, 01 Aug 2007 00:45:24 -0500, Spehro Pefhany <speffSNIP(a)interlogDOTyou.knowwhat> wrote: >On Tue, 31 Jul 2007 21:29:24 -0700, the renowned John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Tue, 31 Jul 2007 18:08:26 -0700, MooseFET <kensmith(a)rahul.net> >>wrote: >> >>>On Jul 31, 8:19 am, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- >>>Web-Site.com> wrote: >>>> On Tue, 31 Jul 2007 08:14:21 -0700, John Larkin >>>> >>>> >>>> >>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >On Tue, 31 Jul 2007 14:37:31 +0000, Guy Macon >>>> ><http://www.guymacon.com/> wrote: >>>> >>>> >>Jim Thompson wrote: >>>> >>>> >>>I don't ever recall saying "more-efficient-at-higher-speed". >>>> >>>> >>>But I guess it WOULD depend on your definition. The engine is >>>> >>>optimized right around 3000RPM (85MPH), but external drag is higher. >>>> >>>> >>Assuming that "optimized" means maximum efficiency as opposed >>>> >>to maximum power or torque, wouldn't it be more efficient at >>>> >>3000 RPM in first gear? >>>> >>>> >>Part of me thinks about the far lower drag and says that it >>>> >>would. Part of me thinks about those pistons moving up and >>>> >>down more times per mile and sucking in about the same amount >>>> >>of fuel per cycle and says that it wouldn't. Maybe it needs >>>> >>an engine sized for 3000 RPM in first gear to make it work? >>>> >>>> >>Also, I can't prove it, but I suspect that hard accelerating >>>> >>to some speed (don't know how fast) and then shutting down >>>> >>the engine and coasting down, then repeating, gives the >>>> >>maximum fuel economy. >>>> >>>> >Interesting curve: >>>> >>>> >http://www.fueleconomy.gov/feg/driveHabits.shtml >>>> >>>> >And it is reasonable to also factor in the value of your time. >>>> >>>> >John >>>> >>>> "Remove excess weight"... don't give a leftist weenie a ride ;-) >>> >>>At those speeds it is drag not weight that matters. You shouldn't >>>wear a dress while driving. >> >>You get the best mileage if you wear nothing at all. > >I suspect Spandex is better than nothing. More slippery than hairy >surfaces and it could prevent the energy-sapping oscillation of fatty >and/or dangly bits. Well, I suppose some people are more viscous than others. > >Interesting that modern hybrids apparently get better gas milage in >city driving rather than highway. We have a friend who bought a Toyota hybrid. But hauling all those batteries up and down the hills here apparently isn't efficient... her mileage is mediocre. >Eg. Prius 60mpg city, 51mpg highway People don't buy Prius' to save gas, they buy them to be hip and stylish. So instead of smog, we have clouds of smug. John
From: Glenn Gundlach on 1 Aug 2007 02:52 On Jul 31, 7:37 am, Guy Macon <http://www.guymacon.com/> wrote: > Jim Thompson wrote: > >I don't ever recall saying "more-efficient-at-higher-speed". > > >But I guess it WOULD depend on your definition. The engine is > >optimized right around 3000RPM (85MPH), but external drag is higher. > > Assuming that "optimized" means maximum efficiency as opposed > to maximum power or torque, wouldn't it be more efficient at > 3000 RPM in first gear? > > Part of me thinks about the far lower drag and says that it > would. Part of me thinks about those pistons moving up and > down more times per mile and sucking in about the same amount > of fuel per cycle and says that it wouldn't. Maybe it needs > an engine sized for 3000 RPM in first gear to make it work? > > Also, I can't prove it, but I suspect that hard accelerating > to some speed (don't know how fast) and then shutting down > the engine and coasting down, then repeating, gives the > maximum fuel economy. > > -- > Guy Macon > <http://www.guymacon.com/> Some guys thought the same as you and went and did it. http://origin.www.toyota.com/html/hybridsynergyview/2005/fall/marathon.html This is absolutely not for real roads but it proves your point. GG
From: Glenn Gundlach on 1 Aug 2007 03:06 On Jul 31, 11:09 pm, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: <snip> > We have a friend who bought a Toyota hybrid. But hauling all those > batteries up and down the hills here apparently isn't efficient... her > mileage is mediocre. > > >Eg. Prius 60mpg city, 51mpg highway > > People don't buy Prius' to save gas, they buy them to be hip and > stylish. So instead of smog, we have clouds of smug. > > John I did and do. What I REALLY want to do is tell them thar arabs I don't want to use any more of their oil than I have to. Between my work commute and _not_ using the wife's ML350 on weekends, the household fuel use dropped 13 gallons a week with no fewer miles used. It consistently hits 50+ MPG and you can see the gas records to verify BUT my commute is almost ideal for a Prius. 25 miles each way, moderate stretches of 35-40 MPH, not much freeway, no hills >400 feet, 7-8am so not hot, car parked underground all day 5-6pm going home, also not hot so little A/C needed. Blah blah blah. Not smug, just trying to do something better than before. I'm too old to be hip and stylish though it does get washed. GG
From: Nobody on 1 Aug 2007 04:03 On Tue, 31 Jul 2007 00:39:09 -0700, Glenn Gundlach wrote: >> > That is not the point, work out how much energy it takes to move say 1 >> > ton of metal a 100Km, with all the normal losses, like traffic lights, >> > and going around bends in the road. > > > > Much of the energy required for acceleration is recoverable upon > > deceleration via regenerative braking. It's just a question of efficiency. > > The amount of kinetic energy is related to the speed, not the > acceleration. If you accelerate more rapidly, that extra energy is > not recoverable. No. The kinetic energy is related to the speed; how you got to that speed only matters if it affects the efficiency of whatever generates the kinetic energy (engine, motor). > Modest acceleration is less wasteful. Only insofar as some power sources will be less efficient when run at higher power. This is particularly true for ICEs; typically less so for motors, although copper losses will increase as I^2*R, so twice the current for half the time will produce double the loss for the same total energy. My main point was that these aren't "inevitable" losses. E.g. using thicker wiring or using higher voltage/lower current will reduce copper losses, better MOSFETs will reduce conversion losses, etc. OTOH, losses due to drag are inevitable. Given that the vehicle has to carry passengers, you can only reduce the drag so far. > > The inevitable losses are friction and air resistance, primarily the > > latter, especially at high speeds. For stop-start urban driving, failure > > to recover kinetic energy upon deceleration (i.e. lack of regenerative > > braking) is a significant efficiency loss. > > > > Realistically, we aren't going to see electric vehicles becoming > > widespread until battery (or equivalent energy storage) technology > > improves. > > > > Taxis and buses are a different matter. For heavy use in an urban > > environment, the efficiency gain from regenerative braking could make it > > worthwhile developing the necessary infrastructure (i.e. places where you > > can swap flat batteries for fully charged ones every couple of hours). > > Got a Prius last year. So far 52+ mpg for 15000 miles. It's the best I > can do. Conventional hybrids are hampered by transferring the motor power through a conventional mechanical drivetrain. An all-electric drivetrain (e.g. directly attaching a motor to each wheel) would be more efficient, and also removes some layout constraints which may allow drag to be reduced.
From: Eeyore on 1 Aug 2007 06:51
Jim Thompson wrote: > Charlie Edmondson wrote: > >Eeyore wrote: > >> MooseFET wrote: > >>>Guy Macon <http://www.guymacon.com/> wrote: > >>>>Martin Griffith wrote: > >>>> > >>>>>If they could recharge in 10 mins, the US power grid would burn out > >>>> > >>>>To a first aproximation, given a large number of electric cars > >>>>on a power grid, the load on the power grid is almost the same > >>>>whether they recharge in ten minutes or ten hours. In the > >>>>later case, you have 60 times as many cars being recharged at > >>>>any given time, each of which is drawing 1/60th as much power. > >>>> > >>>>Short recharge times would, however, have a large effect on the > >>>>time of day that the charging would take place. At ten hours > >>>>everyone will plug in when they get home. At ten minutes a > >>>>large number will try to recharge in the morning right before > >>>>leaving for work. And the grid has to be sized for peak load, > >>>>not average load... > >>> > >>>At 2 seconds, people will recharge it just before they set out. At > >>>ten minutes, they will plug the charger in when they get how. Nobody > >>>wants to wait an extra ten minutes before they start on their hour > >>>long commute. > >>> > >>> > >>>>Either way, I don't see the total capacity of the current power > >>>>grid being enough. Household nuclear reactors, anyone? :) > >>> > >>>The owners will get a better deal on the power if they let the power > >>>company control the charging current. The feature will be built into > >>>the charger and most people will use it. > >> > >> > >> That's a very sensible idea actually. The recharging rate could be dynamically > >> modulated to provide a full charge quite quickly whilst at the same time > >> minimising peak load on the grid (and obtaining optimal use of spare capacity) . > >> That'll keep the power generators very happy indeed. > >> > >> Plus, you're presumably get a discount for plugging it in earlier rather than > >> later. That might provide the required incentive to do that. > >> > >> I'd patent it FAST. > >> > >> Graham > >> > >> > >Also, it isn't like 10 million cars will suddenly appear overnight, they > >would be added over a period of many years. During this transition, > >power companies will slowly be building up the grid, esp. in areas that > >have more electric vehicles... > > Just think of the litter, cars with dead batteries stalled on the > freeway, and no where to plug them in ;-) Hybrids will never be stalled anywhere unless their fuel tanks run dry. Graham |