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Re: New transportation bills signed into law? All hail Scotty and "complete" streets?
Author: FUD
Date: 09-29-2024 - 09:25
EVs and hybrids do get better mileage in city traffic, because the speeds are low (resulting in less power demand for overcoming aero drag) and stop & go traffic makes more use of regeneration than constant-speed driving. Both vehicle types generally have higher EPA city mpg than highway.
BTW, the same thing happens with ICE, though at different speeds and with poorer mpg in stop n go because they have no regenerative braking. The ideal speed for ICE mpg is usually somewhere between 45-65 mph, constant speed, few or no hills. As speed gets above 60 -70, ICE mpg drops too, because of aero power demand. An ideal economy-oriented ICE vehicle reaches top speed in top gear at something below the maximum engine speed, aero drag limited, but above the engine-speed-limited next lower gear. If a ICE car has to have a limiter for top speed (above probably 90 mph or so) not related to maximum engine speed, it has (in principle) too much power. Same for EV, really.
Though of course the speed limit is the maximum speed; within reason, it doesn't limit how quickly you achieve it (see: difference between "quick" and "fast"). And "fuel" economy for both ICE and EV sucks if you use maximum performance frequently.
BTW, note that while most modern electric transit uses regenerative braking, sometimes almost exclusively, it's usually more "dynamic" (burning off the regen in resistors) than truly regen (back into the wire or 3rd rail) unless there are batteries to absorb it. Most LRVs don't have traction batteries, just small backups for low-voltage and critical safety systems. Regen only works if there's a load, usually another train accelerating in the same power block. Some lines have added wayside batteries or ultracapacitors at critical points, such as short, steep grades or major terminals, to "time-shift" the power generated by trains going downgrade or slowing from track speed, for use by later ones going up or exiting the terminal.
And BTW2: most hydrogen-fuel cell trains (and cars) are actually hybrids. The battery is used, as in a ICE hybrid, to harvest regen. It also provides instant response while the (slower-responding) primary generation builds up.
BTW, the same thing happens with ICE, though at different speeds and with poorer mpg in stop n go because they have no regenerative braking. The ideal speed for ICE mpg is usually somewhere between 45-65 mph, constant speed, few or no hills. As speed gets above 60 -70, ICE mpg drops too, because of aero power demand. An ideal economy-oriented ICE vehicle reaches top speed in top gear at something below the maximum engine speed, aero drag limited, but above the engine-speed-limited next lower gear. If a ICE car has to have a limiter for top speed (above probably 90 mph or so) not related to maximum engine speed, it has (in principle) too much power. Same for EV, really.
Though of course the speed limit is the maximum speed; within reason, it doesn't limit how quickly you achieve it (see: difference between "quick" and "fast"). And "fuel" economy for both ICE and EV sucks if you use maximum performance frequently.
BTW, note that while most modern electric transit uses regenerative braking, sometimes almost exclusively, it's usually more "dynamic" (burning off the regen in resistors) than truly regen (back into the wire or 3rd rail) unless there are batteries to absorb it. Most LRVs don't have traction batteries, just small backups for low-voltage and critical safety systems. Regen only works if there's a load, usually another train accelerating in the same power block. Some lines have added wayside batteries or ultracapacitors at critical points, such as short, steep grades or major terminals, to "time-shift" the power generated by trains going downgrade or slowing from track speed, for use by later ones going up or exiting the terminal.
And BTW2: most hydrogen-fuel cell trains (and cars) are actually hybrids. The battery is used, as in a ICE hybrid, to harvest regen. It also provides instant response while the (slower-responding) primary generation builds up.
