The Electric Car
in [Design]
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From: Guy Macon on 31 Jul 2007 10:37 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/>
From: John Larkin on 31 Jul 2007 11:14 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
From: Jim Thompson on 31 Jul 2007 11:19 On Tue, 31 Jul 2007 08:14:21 -0700, John Larkin <jjlarkin(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 ;-) ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | America: Land of the Free, Because of the Brave
From: Charlie Edmondson on 31 Jul 2007 20:02 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... Charlie
From: MooseFET on 31 Jul 2007 21:05
On Jul 31, 5:02 pm, Charlie Edmondson <edmond...(a)ieee.org> 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... The power companies can't be counted on to build up the grid. Spending on new stuff would cut into this months profits. If it doesn't look like the grid will support it, people won't buy the cars. When people don't buy the cars no new grid is needed. |