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EVs vs City Buses; which ones are greener?

Discussion in 'Electric Vehicles' started by minogully, Aug 18, 2017.

More threads by minogully
  1. minogully

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    I spent some time running some numbers on EVs vs Buses. Obviously, it depends on how the electricity is generated in your region. It also depends on the efficiency of the bus itself. But the general idea is, a bus is less efficient than a gas powered car, but it makes up for it in volume.

    So, how many passengers would you need to cram into a bus to have the greenhouse gas (ghg) emissions per person equal that of the ghg emissions of an EV driver?

    For a Heavy Duty Bus, the ghg emissions from...
    1 Coal Powered EV = 13 people on the bus
    1 Natural Gas Powered EV = 23 people on the bus
    1 Solar Powered EV = 215 people on the bus
    1 Nuclear Powered EV = 858 people on the bus
    1 Wind Powered EV = 1674 people on the bus
    1 Hydro Powered EV = 2489 people on the bus
    1 Geothermal Powered EV = 3262 people on the bus

    And since I live in Ontario...
    1 Ontario's Energy Mix Powered EV = 1187 people on the bus

    Of course, different buses have different efficiencies, but even the most efficient bus in my home town (a hybrid bus) is only about twice as efficient as the bus used above, so in my town you'd need 619 people on the bus to bring down the emissions of the bus per person to the levels that I'll be emitting with my Model 3.
     
  2. Brett

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    Yeah but even in your town you'd have to make 619 EVs versus ~15 buses. I would imagine the impact of making 619 cars would outweigh the per-mile advantage. Public/communal transport is almost greener.

    Of course no one wants to ride the bus so the the reality is that all those extra buses would just drive around empty. In the real world EVs are probably much better.
     
  3. MelindaV

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    and we have EV busses here....
     
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    • minogully

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      You're absolutely right, ghg emissions from manufacture isn't factored in here. And there's no doubt that EVs are hogs with respect to this.

      But one thing I didn't mention is the maximum capacity of the buses. The one that you'd need to fit 619 people into can only actually fit 40 people seated, so probably double that if you include standing room (I couldn't find numbers on max capacity including standing room).

      So, even if that bus is packed to the brim (assuming 80 people is the max), the EV is still 7.7x better on the environment than the bus. Not sure if this is enough to make up for the manufacturing problem you mention though.
       
    • MelindaV

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      The manufacturing is a one time thing though, vs an ice bus in your scenario is running daily. including the one time manufacturing emissions over there potential lifetime, their manufacturing probably isn’t even a spec in the co2 environment next to an ice bus.... Also in theory, the ev is in place of an ice passenger vehicle that would have had equal manufacturing emissions so unless you want to also compare an ice passenger vehicle cradle to grave to EVs...
       
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      • minogully

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        Manufacturing EVs produces more ghg than manufacturing ICE cars. The difference comes from the manufacturing the battery, which doesn't stack up well against manufacturing an ICE drivetrain. So, no they don't have equal manufacturing emissions... unfortunately. Here's a source (you may have to click on the 'full report' link to get the PDF that contains the stats on the manufacturing emissions):
        http://www.ucsusa.org/clean-vehicles/electric-vehicles/life-cycle-ev-emissions#.WZhLn9PyuX0
         
      • minogully

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        #7 minogully, Aug 19, 2017
        Last edited: Aug 19, 2017
        Hey, I found a study on the impact on manufacturing a bus. And it's 160t CO2e/bus. Since it can hold 80 passengers, it should be compared against the impact of manufacturing 80 EVs (assuming none of the passengers carpool). And here we see that manufacturing one EV produces 10 t CO2e. So, it's 160t vs 800t.

        But wait, there's more. Will an ICE bus last as long as an EV? Here it says that a city bus is expected to go around 250,000 miles. But Elon is projecting that his EVs might be able to go 1 million miles. But that's the drivetrain not the battery, which is expected to go about 500,000 miles. So, add an extra 4 tonnes per EV for the manufacturing of a second battery.

        In conclusion, when all things are equal, it's 4 ICE buses needing to be manufactured vs 80 EVs and an extra 80 batteries. Or:
        640t CO2e vs 1120t CO2e for the manufacturing processes. But then over that time the buses would have emitted 1,988 t of CO2 vs. the EV's 3t. Making the lifetime totals:
        Bus: 2628t CO2e
        EV: 1123t CO2e

        Making the EVs in my region 2.3x better for CO2 emissions than the best (hybrid) ICE buses from cradle to grave.
         
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        • Brett

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          Ok, WOW... I stand corrected. I didn't think the math would workout like that. Thanks for doing the research and math!
           
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          • minogully

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            With the latest information on the Model 3 chassis composition, it seems to me that it won't be able to go 1 million miles before rust deteriorates the car. Adjusting these numbers to a more conservative 500,000 miles for the lifetime usage of a Model 3 makes it a closer competition between ICE city buses and EVs in my region, but EVs still win.

            Here are the new numbers:
            2 Buses (enough buses to allow 80 passengers to go 500,000 miles)
            - Manufacturing : 320 t
            - Running : 994 t
            - Total : 1314 t

            80 Model 3s (enough EVs to allow 80 passengers to go 500,000 miles)
            - Manufacturing : 800 t
            - Running : 3 t
            - Total 803 t

            Meaning that my city buses produce 64% more ghg per person over their lifetime.
             
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            • garsh

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              Don't forget to account for:
              1. The cars can go exactly from each person's Point A and to each person's Point B
              2. Someone taking a bus still has to figure out how to get from their house to the bus's Point A, and from the bus's Point B to their destination.
               
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              • SSonnentag

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                Now factor in the bus maintenance and lubes and the additional wear on the roads that now have to be repaired. :D
                 
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                • Badback

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                  I also factor in the fact that I don't live in a city.
                   
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