This depends a lot on local climate and topography.
Seattle has kind of been a bust with them because the hills really reduce the amount of charge, and on top of that the existing bus depots are already full, so switching to electric only would mean having to find and locate space for more bus depots, which is quite difficult.
I wonder if trolley busses will make a great comeback now. Seems so obvious to just put the overhead lines near a few central bus hubs, so buses can recharge during the shift.
Hills should never reduce the range, because the energy lost during climbing up is recovered when going downhill.
This is one of the great advantages of electric vehicles with batteries, when properly designed.
Electric buses with batteries are even more suitable for cities with hills than for cities without hills, because they provide greater energy savings over buses with ICEs.
While I have never used buses with batteries, I have lived in cities with electric trolley buses. Even with the primitive technology of many decades ago, they were doing great in cities with hills, recovering most of the energy when going downhill, unlike the buses with ICEs, which had excessive fuel consumption because of the hills.
Regenerative breaking is not perfectly efficient, so you may loose a significant portion of the additional energy needed. Better EV systems are what, 70-80% efficient on the breaking efficiency?
Okay, but gasoline is far more energy dense than batteries and a gas tank is a whole lot cheaper than a battery pack, so vehicles can have a gas tank big enough that that doesn't cause range problems. I don't know about buses, but you can buy a pickup with a 48 gallon tank. Even after assuming only about 1/3 efficiency, that's still equivalent to some 500 KWhr, which is several times more than any consumer EV I'm aware of.
That's efficiency, not range. Suppose hilly terrain reduces range by a third for electric vehicles and half for diesel. The diesel bus just fills up twice as often. The electric bus needs a 50% bigger battery in order to finish the same route without stopping to charge, and then it becomes 70% because it has to lug the bigger battery up the hills.
You can just... do that, but that doesn't mean it's not a thing you have to do, and it's not free.
It is impossible for a hilly terrain to reduce the range by a third for well-designed electric buses.
The efficiency of regenerative braking increases with the power of the vehicle. The electric efficiency should be well over 90%, perhaps even 95%. The mechanical losses will lower the total efficiency to much smaller values, but even so, the total efficiency should be over 80%.
A bus with an ICE will consume 5 times more extra energy for climbing the hill and it will also consume energy while going downhill.
Values like a 50% greater battery are unrealistic, and a heavier battery adds much less to the consumption than by how much it is heavier, even when going up the hill (because most of the extra energy consumption is also recovered).
In a certain city, it may happen that the bus routes are so long that batteries are not competitive with ICEs, at least for now. However, the presence of hills in any city can only make electric buses more advantageous, not less advantageous, due to much greater cost savings for fuel and maintenance. Buses with ICEs that are operated on hilly routes also need extra maintenance, besides increased fuel costs. Well-designed electric buses do not care whether they are operated in conditions requiring higher torque.
Like I have said, I have lived in cities with hills and with electric trolley buses and there was no doubt that the trolley buses were superior to buses with ICEs exactly on the routes that were going up and down over hills.
> The efficiency of regenerative braking increases with the power of the vehicle. The electric efficiency should be well over 90%, perhaps even 95%. The mechanical losses will lower the total efficiency to much smaller values, but even so, the total efficiency should be over 80%.
It's not just about conversion efficiency. Moving a vehicle up a hill requires several times as much power as traveling on level terrain, which heats the battery. Reaching the top of the hill and starting regen when going back down again, also heats the battery. On normal terrain that isn't all hills there will be level sections in between that allow the battery to cool. If the terrain doesn't have that then the battery gets too hot and the vehicle will disable regenerative braking and use friction braking to allow the battery to cool off. The steeper the hills are, the more heat is generated per unit time.
Batteries also have charge curves. In the extreme case you start at a higher elevation, go down a hill and can't use regen at all because the battery is full and there is nowhere to put it, but then you have to spend energy later to get back to where you started. The same is true even if the battery isn't fully charged, because extreme charge levels require charging to be done gradually and the battery might not be able to take as much power right now as a heavy bus would generate descending a steep grade.
> A bus with an ICE will consume 5 times more extra energy for climbing the hill and it will also consume energy while going downhill.
Modern engines will cut fuel entirely when descending a grade.
> the presence of hills in any city can only make electric buses more advantageous, not less advantageous, due to much greater cost savings for fuel and maintenance.
That doesn't contradict the point that they'll need to have larger batteries to achieve the same range on hilly terrain.
Regenerative braking is nice but as sibling pointed out it doesn't nearly recapture everything. Another factor is that the additional load whether accelerating up a hill or braking down one puts more current through the system. In fact nearly every part of the drivetrain will experience accelerated wear under those conditions, mechanical or electrical. Cooling systems, too. Properly spec'd, it's of course very doable, but it's true hilly terrain is more difficult.
The problem is that the hills in Seattle are quite large, so you are going up for a long period of time and possibly not able to regenerate before you run out of batteries.
The other problem is that because battery weight is so large, that in itself becomes a limiting factor for hilly operation where it is not really relevant for trolleybuses. And trolleybuses can feed current from uphill buses to downhill buses through the wires, but there's no such connection on battery buses.
> The problem is that the hills in Seattle are quite large, so you are going up for a long period of time and possibly not able to regenerate before you run out of batteries.
Is this deadpan sarcasm? Seattle isn't a mountain pass. The biggest hills are a couple hundred feet bottom to top. The "High Point" neighborhood, which is, uh, the highest point above sea level, is at 522 feet. Every other hill is smaller than that.
Total ascent time is measured in double-digit seconds, discounting lights/stop signs.
Not related to vehicle battery energy consumption, transit agencies have been reporting their BEBs struggling up hills due to drivetrain components not being good fits for their terrain. Surprising finding, with the OEM sending replacement parts as a result.
This is a weird multi-paragraph evangelical lecture seeing as any EV owner that’s driven in a hilly climate will tell you that this isn’t how things work.
Seattle has kind of been a bust with them because the hills really reduce the amount of charge, and on top of that the existing bus depots are already full, so switching to electric only would mean having to find and locate space for more bus depots, which is quite difficult.