Quote:
Originally Posted by jamesqf
Suppose it's not a few long trips per year? Suppose you have an EV with (just for instance) an 80 mile electric range, and you regularly make trips of 100 miles. So you drive 4/5 of the way on electricity* and 1/5 on the generator: even if the generator is only half as efficient as using a plain IC-engined car, aren't you still cutting fuel use by 60%?
*Though of course you would not really run the batteries to empty, then run a generator big enough to drive the car, but instead would have a much smaller generator running most of the time.
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I only see it as a ~60% ICE Fuel savings if:
- ICE only provides energy for 1/5 of distance
- Generator ICE is equally as efficient as the ICE it replaces.
- ~90% efficient Generator
- ~90% efficient Control Electronics
- ~90% efficient Motor
- None of the generator electricity gets buffered by the batteries
If you buffer the generator through the batteries I see it closer to ~47% ICE Fuel Savings ... If:
- All above
- ~90% efficient battery cycle Charge to discharge
- ~90% efficient 2nd set of control electronics
In your example trip the battery is already providing 4/5 = 80% of the energy for the trip.
60% less ICE fuel + 80% of Trip from Battery = 120% of original energy ... a ~20% efficiency loss.
47% less ICE fuel + 80% of Trip from Battery = 133% of original energy ... a ~33% efficiency loss.
Even if the Generator ICE can be operated more efficiently than the ICE it replaces ... how much more efficient would we expect the ICE generator to be ??? Could we expect more than a ~33% increase in average ICE operating efficiency? ... that seem optimistic to me.
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My perspective:
The additional size and weight of the ICE means giving up ~50 Miles worth of battery space and weight ... if you are only need another ~20 Miles adding more batteries will be smaller , lighter , and give better vehicle energy efficiency than adding the ICE Generator.