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Thread: Edmonton plans to buy only electric transit buses beginning in 2020

  1. #1

    Default Edmonton plans to buy only electric transit buses beginning in 2020

    Phasing out the diesels.

    City council's executive committee was told on Tuesday that a purchase order was issued in July 2017 for 110 new diesel buses at a cost of approximately $45.7 million US.


    The greenhouse gas emissions from one old diesel bus are equivalent to the emissions from sixty of the new diesel buses, said Robar.


    "This is one of the older fleets in Canada," Robar said of the Edmonton Transit fleet.


    The current ETS fleet consists of 931 buses, including 46 small community buses, 852 large transit buses and 33 articulated buses.


    A report to the executive committee states that replacing the large transit buses at a rate of 40 to 60 buses per year would take approximately 18 years to replace the entire fleet of 852.

    http://www.cbc.ca/news/canada/edmont...obar-1.4276453

  2. #2

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    I have been a bit skeptical (I always thought natural gas is the way to go), but maybe the technology is there now.

    https://en.wikipedia.org/wiki/Battery_electric_bus

    Advantages

    Battery electric buses offer zero-emission, quiet operation and better acceleration compared to traditional buses. They also eliminate infrastructure needed for a constant grid connection and allow routes to be modified without infrastructure changes compared to a Trolleybus. They typically recover braking energy to increase efficiency by a regenerative brake. With energy consumption of about 1.2 kWh/km, the cost of ownership is lower than diesel buses.[3][4]

    Disadvantages

    As of 2016 battery buses have less range, higher weight, higher procurement costs. The reduced infrastructure for overhead lines is partially offset by the costs of the infrastructure to recharge the batteries. Battery buses are used almost exclusively in urban areas rather than for long-haul transport. Urban transit features relatively short intervals between charging opportunities. Sufficient recharging can take place within 4 to 5 minutes (250 to 450 kW) usually by induction or catenary.[3]

    The trolley bus folks will be happy - all of the benefits of a trolley bus (no pollution within the city), but none of the downside (high maintenance costs of system / driver dissatisfaction re regular wire dislocations / wire pollution / route inflexibility).
    Last edited by moahunter; 06-09-2017 at 10:22 AM.

  3. #3

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    I'm curious how the deep winter affects the charge of batteries on these buses, and electric vehicles in general in Edmonton. I know my cell phone bottoms much faster when the temperature drops below freezing, especially when it approaches -20. Does having the ranks of cells packaged together provide enough heat to counter the cold?

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    Pretty sure that modern vehicle battery packs require both heating and cooling, depending on their operation. Plus software controls which cells are being used to distribute heat and wear. What I find more interesting is the impact on our grid of hundreds of very high capacity batteries charging at night, every night. I'm not saying that's a bid thing, if anything it's good that they'll be charging off-peak as that's when power is cheapest. It gets in to the whole "smart grid" thing where potentially hundreds of these buses (and eventually, tens of thousands of cars) could be grid-scale storage or buffers when they're not being used. Buses wouldn't help much with solar intermittency as they're mostly driving around when solar is working, but it could help with wind.

    The power draw of bus barns equipped to charge electric buses are going to be incredible, although I suppose it's not as critical to charge them in only an hour or two, as they're mostly parked overnight.

  5. #5

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    Quote Originally Posted by Marcel Petrin View Post
    The power draw of bus barns equipped to charge electric buses are going to be incredible, although I suppose it's not as critical to charge them in only an hour or two, as they're mostly parked overnight.
    Yeah, it's gonna be interesting to see how they handle the needed upgrades, as that's a lot of juice to recharge hundreds of busses at once. A. Lot.
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  6. #6

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    Quote Originally Posted by Ustauk View Post
    I'm curious how the deep winter affects the charge of batteries on these buses, and electric vehicles in general in Edmonton. I know my cell phone bottoms much faster when the temperature drops below freezing, especially when it approaches -20. Does having the ranks of cells packaged together provide enough heat to counter the cold?
    No issues. There's a handful of Tesla owners in my area and they don't have any problems. Besides, buses won't be idling long enough to get cold. Those batteries will be constantly charging/discharging.
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    What if there is a serious power outage, how can this bus get recharged?
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  8. #8

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    The power requirements needed to charge 120 busses means they'd be looking at a direct tie-in from multiple substations, making a complete failure highly, highly, highly unlikely.
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    Hamster wheel.



    Top_Dawg says stick with the good ol' combustion engine.

  10. #10

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    Quote Originally Posted by noodle View Post
    The power requirements needed to charge 120 busses means they'd be looking at a direct tie-in from multiple substations, making a complete failure highly, highly, highly unlikely.
    I assume the buses will charge at night when not running? City should install solar with some batteries. Fill batteries during day, charge buses at night. Won't be enough to completely charge, but it would be an offset for sure.
    "Men never do evil so completely and cheerfully as when they do it from religious conviction" - Blaise Pascal

  11. #11

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    Here's a little envelope math for you based on my own usage.

    Currently you can buy a Tesla with a 100kWh battery pack. That's enough power to run my condo for about 8 days, if I plugged my panel into the car instead of the grid. If I recharge my car from flat to full in 8 hours, that means my usage (just for my one car) is ~8 days of my household usage compressed into 1/3 of a day, an increase of about 25x versus my baseline, no-Tesla consumption.

    And that's ONE Tesla.
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    Yup. It's likely those buses will have battery packs of 200-300 kWh to be able to drive 500 km a day, at a very rough guess. Multiply that by 800 buses, which is roughly the city's bus fleet, and that's about 200 mWh's that will need to be replenished overnight, every night. Assuming that it's over 8 hours, that's a continuous draw of about 25 megawatts to recharge the bus fleet, every single night. To put that in perspective, that's something like 3% of the power production of Keephills. It's a very, very significant amount of power. Again, I don't think it's any more of a problem than it is an opportunity, but there's practical realities to consider.

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    Some of the charging could be distributed to other parts of the day. A significant fraction of buses are back in the garage from 10:00 am to 3:00 pm, which would match nicely with the availability of solar power. Peak hour buses will also start returning around 7 or 8 pm, so those could be charged before the last of the fleet arrives in the early morning.

  14. #14

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    The 1800 panels on top of Londonderry Mall would be good for about 1900 charges a year & that's a large solar installation.

    Buying at off-peak times & storing the power in utility-scale batteries (outside of the bus batteries themselves) would be more cost-effective. Especially if the batteries used to store the power were the batteries that had been already used until their capacity shrunk beyond the requirements of the bus but still with plenty of capacity. Baseload generation in the middle of the night is around 2 cents/kWh currently & the batteries would be a common component whether we used grid or solar, but we can skip the dedicated panels.

    Solar is a fantastic power source, but given the high current requirements for vehicle charging it's a tough hill to climb, especially at transit-scale.
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    ^I don't need the point of storage. Nearly all the buses will be in the garage in the middle of the night when power is cheapest, and if solar is installed on the garage roof (more for feel-good environmental reasons than cost), half or more of the fleet will be parked there during peak generation hours and AC demand will create a good market for surplus power on summer afternoons when the buses are out.

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    A previous thread on electric buses provides useful context to this thread from the time period late 2014 to early 2016. Suffice it to say, the original timelines for phasing in electric buses starting in 2017 and ending in 2027 as stated in post #118 were a tad optimistic as tends to be the case when new (and not entirely proven) technologies are introduced.

    http://www.connect2edmonton.ca/showthread.php?35110-E-T-S-to-test-Chinese-electric-busses/page2



  17. #17

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    Quote Originally Posted by Marcel Petrin View Post
    Yup. It's likely those buses will have battery packs of 200-300 kWh to be able to drive 500 km a day, at a very rough guess. Multiply that by 800 buses, which is roughly the city's bus fleet, and that's about 200 mWh's that will need to be replenished overnight, every night. Assuming that it's over 8 hours, that's a continuous draw of about 25 megawatts to recharge the bus fleet, every single night. To put that in perspective, that's something like 3% of the power production of Keephills. It's a very, very significant amount of power. Again, I don't think it's any more of a problem than it is an opportunity, but there's practical realities to consider.
    There's a lot of start and stop on bus routes, and EV's get better mileage in cities because unlike ICE's they use practically zero energy when they're slowing or not moving. I would assume they'll have regenerative braking as well, so they'll recoup a fair amount of energy as well. Do city buses drive 500km a day anyway?
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    500 km is the number I saw thrown out in an article. But given that a bus's average speed is probably only 30-40 km/h, that does seem a bit high. And I understand the benefits of regenerative braking and how that explains why Tesla's get better range in a city. But keep in mind that transit buses weigh 5-10 times as much as a Tesla unloaded, so they'll take that much more energy to get going. Even if you're regenerating some power while braking, it's never going to be anywhere close to 100% efficient in doing so (I doubt the reclamation is much more than 30-40%, if it's even that high). And buses start and stop a lot, as you mention. Much more than cars typically do.

    In any case, it was just some napkin math to show how significant of a power draw an entirely electric fleet would be.

    Poking around on the internets, I found this website that range from 250 to 550 kWh: http://www.greenpowerbus.com/product-line/

    New Flyer's website does have product specs for their electric bus, but it didn't seem to mention the battery pack size that I could definitively see. There was mention of 300 or 350 in some of the specs, which might correspond to the pack size. edit: found a page on New Flyer where they say their buses range from 100 to 480 kWh: https://www.newflyer.com/buses/zero-...r-electric-bus

    So looks like my wild guess is in the ballpark.
    Last edited by Marcel Petrin; 06-09-2017 at 10:20 PM.

  19. #19

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    Quote Originally Posted by Titanium48 View Post
    ^I don't need the point of storage. Nearly all the buses will be in the garage in the middle of the night when power is cheapest, and if solar is installed on the garage roof (more for feel-good environmental reasons than cost), half or more of the fleet will be parked there during peak generation hours and AC demand will create a good market for surplus power on summer afternoons when the buses are out.
    And in the dark winter when insolation is at a minimum & power demands are at their maximum, what then?
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  20. #20

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    Quote Originally Posted by Marcel Petrin View Post
    Even if you're regenerating some power while braking, it's never going to be anywhere close to 100% efficient in doing so (I doubt the reclamation is much more than 30-40%, if it's even that high).
    It's actually north of about 60% battery-to-battery. A little north of 80% efficiency battery-wheel & wheel-battery, 80% of 80% is 64%.

    (Figures quoted are actually from a Tesla Roadster, so relatively ancient 10-year old tech, EV-wise)

    https://www.tesla.com/en_CA/blog/mag...rative-braking
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    The wording specifically says "at most":

    We must also remember that, even though the battery-to-wheel conversion efficiency is pretty good (up to 80% or so), the energy makes a full circle back into the battery and it gets converted twice for a net efficiency of at most 80% * 80% = 64%.
    I have a hard time believing that energy being converted so many times to different forms is going to be that efficient. I think they're playing games with that calculation or massively over simplifying. They seem to be saying that the same unit of energy used to originally accelerate the car is 80% efficient from battery to kinetic energy, and that if you use it to again accelerate the car, it is again 80% efficient. It doesn't seem to mention what the efficiency is of the conversion of kinetic energy back to electrical/battery energy at all. Unless I'm misunderstanding something. And actually, that 80% figure seems to be for the AC motor only, and does not take in to account inverter losses, which apply both during acceleration and braking.

    And that is assuming that ALL of the kinetic energy is being sucked up by regenerative braking. That might be the case with an extremely light footed, anticipating driver (lots of reviews of Model S's mention that if you're paying attention and driving conservatively, you'll hardly need to touch the brake pedal because it has quite a strong "compression" or regenerative deceleration when you lift off the accelerator). But any kinetic energy dissipated by actual brakes during harder stops simply goes poof.

    There is no way that 64% figure is reflective of real world performance. The energy path is roughly speaking as follows: chemical potential energy -> DC current -> AC current -> kinetic energy -> AC current -> DC current -> chemical potential energy. You lose energy every step of the way.
    Last edited by Marcel Petrin; 07-09-2017 at 10:03 AM.

  22. #22

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    Given that Tesla's powerwall uses the same inverter tech as the cars & is over 90% efficient round-trip we're actually looking around 95% one-way efficiency for a modern inverter.

    https://www.tesla.com/en_CA/powerwall?redirect=no

    That's also a 10-year old blog post I used to pull numbers out of, hence why it uses the older figure of 80% each way vs the more recent, real-world 95%. The actual real-world efficiency of a regenerative braking system is super duper hard to find, what with it being the "secret sauce" that helps differentiate between manufacturers & there actually being a lot of different ways to actually measure & quantify said efficiency. So a lot of people keeping their cards close to their chest & a lot of people trying to figure out the values of those cards in the first place.

    A transit bus is almost as ideal a platform for regenerative braking as you could ask for. Stop & go is the name of the game & a consistent driving profile is expected, with smooth acceleration & deceleration, plus plenty of room for large, efficient electrical systems (relative to a passenger car).
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    http://sites.uci.edu/haghpanah/files...Simulation.pdf

    Interesting study on the effects of regenerative braking on a hybrid bus.

    It is observed that in a drive cycle like Nuremberg using these strategies leads to recapturing 30%, 36% and 15% of overall output electric energy, correspondingly. These amounts of energy saving in addition to other advantage of hybridization provide an improvement of 32.7%, 34.3% and 19.6% in fuel economy for these strategies related to conventional bus, respectively. It shows that in such a start-stop drive cycle how much the braking strategy is important in order to fuel economy improvement.
    The employed drive cycle is Nuremberg R36 city bus drive cycle. It is a European standard drive cycle and has lots of start and stop conditions, so it can distinct the ability of each brake strategy.
    36% real world is still nothing to sneeze at & looks like your estimates were on the money for the final results.
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    Wild-*** guesses are my specialty.

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    We could string some wires, run a couple of trolleys...
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    Quote Originally Posted by noodle View Post
    Quote Originally Posted by Titanium48 View Post
    ^I don't need the point of storage. Nearly all the buses will be in the garage in the middle of the night when power is cheapest, and if solar is installed on the garage roof (more for feel-good environmental reasons than cost), half or more of the fleet will be parked there during peak generation hours and AC demand will create a good market for surplus power on summer afternoons when the buses are out.
    And in the dark winter when insolation is at a minimum & power demands are at their maximum, what then?
    Bus charging could be done entirely at night, or some at night and some mid-day. If solar is installed on the garage roof and the sun is shining, plug in all of the buses that come back between the morning and afternoon peaks. If there are no panels on the roof or it is cloudy, do all the charging at night when power demand and prices are lowest. Unless you wanted the fleet to be primarily powered by solar, there would be no need for storage other than in the bus batteries themselves.

  27. #27

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    There's no need for any sort of dedicated solar install whatsoever for the electric busses though, except as greenwashing, as the power requirements for the busses far, far, far, far, far exceed the available area for setting up panels.

    Solar is great & a generation source we as a province need to get on board with. It's just ill-suited to the transportation application.
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    Is solar needed? No. Would it be cost-effective compared to buying low cost off-peak power? Probably not. Could it supply a significant fraction of power needs for charging electric buses? Maybe. The new transit garage is supposed to have a nearly 50,000 m^2 footprint, giving enough room to install ~15,000 m^2 of panels before they start shading each other in winter. That would generate about 3 MW under good conditions. If 150 buses (1/2 of capacity) are parked there between 10:00 am and 3:00pm they could each get 100 kW-h of charging. So about half a charge for half the fleet, or quarter of total requirements. In winter, those hours account for most of the useful output of the panels. In summer, the additional power generated during the late afternoon when the buses are out would match peak air conditioning demand and could thus be sold for a good price.

  29. #29

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    Quote Originally Posted by Titanium48 View Post
    Is solar needed? No. Would it be cost-effective compared to buying low cost off-peak power? Probably not. Could it supply a significant fraction of power needs for charging electric buses? Maybe.
    No, no it wouldn't.

    Quote Originally Posted by Titanium48 View Post
    The new transit garage is supposed to have a nearly 50,000 m^2 footprint, giving enough room to install ~15,000 m^2 of panels before they start shading each other in winter. That would generate about 3 MW under good conditions.
    Which is not Edmonton winters. Optimized for winter effectiveness, you'll still see an ~80% drop off versus the summer months.

    3MW*5.5 hours a day (average year round) = 16.5MWh

    800 busses = 200MWh of batteries at 250kWh apiece.

    A full average day of sun at a 3MW solar farm is about 8% of the charging capacity of the whole fleet. It'd be higher in the summer & lower in the winter, but nowhere near enough to keep everything topped up.

    Quote Originally Posted by Titanium48 View Post
    If 150 buses (1/2 of capacity) are parked there between 10:00 am and 3:00pm they could each get 100 kW-h of charging. So about half a charge for half the fleet, or quarter of total requirements.
    150 is not half the fleet. It's not even half of half of the fleet, which is 200.


    Quote Originally Posted by Titanium48 View Post
    In winter, those hours account for most of the useful output of the panels. In summer, the additional power generated during the late afternoon when the buses are out would match peak air conditioning demand and could thus be sold for a good price.
    Except you're vastly overestimating the power generation of the panels while simultaneously underestimating the seasonal effects & bus fleet size.

    Here's a fun piece of info I got from a guy in the office while I was trying to get some real-world figures for all of this: It takes a similar calibre of service to supply a bank of Tesla Superchargers (capable of charging a whopping 12 cars) as the Milner library took, at peak, prior to the renovations.
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    ^
    I was assuming they would be optimized for maximum year-round production, mounted at an angle of 53░ above horizontal. Peak output would occur near solar noon (12:30 PM MST / 1:30 PM MDT) in March and September. Over 90% of peak output would be available near solar noon in June and December. Output would fall off fairly quickly in winter, but would still be above 75% of peak for 2 hours either side of solar noon.

    150 buses would be half of those that will be stored at that particular garage. The rest would be at other garages, which gives more room for solar panels.

  31. #31

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    Your math is still a little wonky.

    http://edmontonjournal.com/news/loca...ameron-heights

    12MW out of a 60-hectare site. 60 hectares is 600,000m^2 or twelve times the area of your bus barn solar farm. There's no way you'd get 3MW off of a 50,000m^2 roof. You're off by a factor of 3.
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    According to page 3 of the report that went to Executive Committee (Agenda Item 6.9) a 10 MW primary electric service, upgraded transmission and distribution, and a new 10 MW substation is required to support 200 electric buses (just over one-fifth of the current fleet).

    The initial RFP though is for up to 40 electric buses which will be based out of the new Northeast Transit Garage. If I understood Eddie Robar correctly, up to 40 buses can be accommodated without major electric system upgrades.

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    ^^I did find a math error, but it isn't that big - I used 16░ as the minimum noon sun elevation in December instead of the correct 13░. That reduces the useable area for panels to 12,000 m^2 before shading occurs in winter, and cuts the maximum output to 2.4 MW (assuming 200 W/m^2 peak panel output). I suspect Epcor's proposed solar farm does not have complete coverage over the whole site, reducing the output accordingly.

  34. #34

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    EPCOR's figures are for ~70,000 square meters of panels. Your latest round of corrections still have you assuming about 15% higher panel efficiency than EPCOR's figures, plus you're also quoting a significantly tighter spacing than what they're using, given that at 13 degree angle you're looking at ~4.3m of shadow for every m of height.
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    https://www.engadget.com/2017/09/19/...on-one-charge/

    The startup just drove a Catalyst E2 Max electric bus a whopping 1,101.2 miles on a single charge. That's the furthest any EV has managed before recharging, and well past the 1,013.8 miles driven by the previous record-holder, a one-seat experimental car nicknamed "Boozer." It's not hard to see how Proterra managed the feat when you know about the technology, but this still bodes well for eco-friendly public transportation. Not surprisingly, a bus can hold a much larger battery than just about any regular car. The Catalyst E2 Max carries 660kWh, or nearly nine times the capacity of a 75kWh Tesla Model S. Also, Proterra was driving in optimal conditions, with no passengers, no stops and a gentle test track. It'd be another story with a fully-laden bus wending its way through a city.
    Neat stuff & provides a real-world datapoint about possible pack sizes for a bus, even if the whole experiment is about as far from "real world" as you can get.
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