•  will_a113   ( @will_a113@lemmy.ml ) 
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    289 months ago

    Maybe the most surprising thing here is that regular biking is still twice as efficient as e-biking even given our mediocre metabolic efficiency and a physique that isn’t exactly designed for the bicycling motion.

    • It makes sense to me…

      For example if the the e-bike rider had to spend 1/5 of the energy of the unpowered cyclist (numbers chosen for the example’s sake) that would be 1.1Wh/km they exert.

      The remaining 12.9Wh/km would be what was discharged from the battery while riding (from using pedal assist and/or throttle features). This can be measured when you charge it back up at the end of the trip to the previous level.

  •  SkyNTP   ( @SkyNTP@lemmy.ml ) 
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    9 months ago

    Now do one where you A) normalize this to the same trip distance (not speed, so that these choices for a single trip become meaningfull) and B) convert the kWh into CO2 emissions, including the emissions in growing and transporting the various power and food production methods used (coal to solar, locally produced veggies-air shipped beef)

    • Trip distance is dependent on methods of transportation at the aggregate level. That’s only relevant for policy decisions or collective actions, not individuals of course, but if we are going to deal with climate change, collective action is necessary.

      Given the graph is normalized by km traveled, its overly generous to cars.

    • Yeah, if you account for the amount of CO2 that goes into producing food the ebike will be much more efficient in terms of co2/km than a regular bicycle. Even if you cheat by making the regular bicycle drive slower than the ebike, like they did for this chart.

  • The car is correctly represented, about 0.15 KWh / km is what one gets.

    However, the positioning of the e-bike looks strange to me. I’ve looked at previous studies and the e-biker has always been first in efficiency - because the efficiency of a motor far exceeds the efficiency of human digestion and muscles, while weight and speed remain comparable to an ordinary cyclist.

    I think someone has calculated food energy incorrectly, or assumed that e-bikes move faster than they do. :)

    • I guess it’s hard to gauge an e-bike since they often have a variety of operating modes ranging from progressively higher levels of pedal assist up to full throttle. But that’s fascinating to think that an all-electric ride may actual consume less energy in the grand scheme of things. I had never looked at it that way!

      • It is interesting, but remember we need food to live anyway, and we need exercise to stay healthy. If we ask used ebikes on max pedal assist to get around, but then go to the gym and pound the treadmill for an hour, what does that do to the numbers? Or if we eat less and burn less energy, but then lose bone density and need more healthcare as we age (just one effect among many of not getting enough exercise)?

        • Oh for sure, yeah. I have a sedentary office job, so the e-bike commute is my primary source of exercise (particularly after I quit the gym during the pandemic), so I tend to keep the pedal assist low and try to get a workout. There are exceptions though. Sometimes I’m just tired or sore, or it’s really hot with bad air outside, and I elect to go all electric on days like that. It’s nice to have the option!

    • I think many people peddle just as hard on an electric bike, so the 5.5 kWh/km is a given, the rest is the energy required to go faster. Since air resistance increases with the square of the speed, it might very well be the case that 14 kWh/km at 25 km/h is more efficient than what the human alone would need to deliver for the same speed.

      Edit: I failed to take into account that for the human at the same level of effort the power remains constant, not the energy per kilometer. Going faster at the same power output would reduce the energy expenditure per kilometer for the human to about 4 kWh/km, which would indicate that 10 kWh/km is being delivered by the motor to go faster.

      That being said, it might be the case that they just calculated the energy needed to move the bicycle without taking the energy efficiency of the digestive system into account.

      • I just did a quick of my statistics. My bike typically provides an average of 100W in my hilly 28km commute (both ways) that takes about 1h15 minutes. That’s less than 5Wh/km.

        I’m using a fairly high setting, too, and judging by the fact that I don’t break a sweat at all, I’m 100% sure I’m not pedaling as hard as I do on a regular bike.

        • If my calculations are right, at that speed with the numbers from the graph, that would put the energy requirement at about 10 kWh/km. That means that with your motor delivering half of that, the human output actually matches up pretty well with the graph. I’m saying output, because I’m convinced that the graph doesn’t take the calories being burned into account and only shows the work being done to move the bicycle.

  •  bjorney   ( @bjorney@lemmy.ca ) 
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    9 months ago

    Energy efficiency and carbon footprint are very different things - pretty sure the carbon footprint of 15 big macs (8500kcal) is substantially greater than 1L of gasoline (let alone an electric grid equivalent)

    • A quick googling tells me a burger is about 3kg of CO2 equivalents. 1L of gas seems to be about 2,5kg.

      Now if you were to eat local and seasonal food I’d guess you can get more efficient than burning oil.

      Edit: As @bjorney correctly pointed out a quick google in the morning, before the brain functions properly kick in, isn’t the best way to produce comments on numbers. I did NOT account for the factor of about 15 that a burger needs to get close the energy stored in a liter of gasoline.

      Edit to the edit: Just out of curiosity I did another quick google (please brain, be functioning now) and it seems that to get 8500kcal from oats you need about 2,5kg. This seems to produce about 1kg of co2 equivalents. I am certain that this does not include the amount of co2 the human is expelling in excess by using their muscles instead of a motor, so the whole discussion is probably moot anyways.

        • Damn, my brain got way to happy about the numbers being so close that I completely overlooked that. I’m gonna defend myself by saying that this was early in the morning ;)

          Edited my original comment to reflect this fact.

          •  bjorney   ( @bjorney@lemmy.ca ) 
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            9 months ago

            lol all good - I posted some napkin math above - https://lemmy.ca/comment/7747680

            Long story short this figure is just all around bad because it’s conflating energy efficiency with environmental friendliness.

            Electric vehicles, despite being greener, are probably less efficient (which is why ICEs are mysteriously absent from this figure), it takes a lot more watts of power to move a 5000 pound car than it does a 2000 pound one). Similar story with biking - based on my Garmin figures, biking is about 22x more energy efficient than driving an ICE car, but the carbon footprint of that energy source is much higher watt-for-watt, so if you eat a meat heavy diet, the bike is barely greener than driving (caveat: I didn’t amortize the footprint of constructing the car, which is a probably a huge deal - if cycling is actually an option for you, your mileage probably isn’t that high).

            Granted - you are spot on with oats, if you pick a greener crop like corn you are down to 0.5kg carbon per 1L of gasoline equivalent - as the guy below wrote, biking is a “greener choice” if you are vegan (3-6x less carbon footprint), but at the end of the day, manual transportation is a thing people choose for health or pleasure reasons, or when the distance is so low that other methods don’t make sense. if you are going to try and shame people into doing it out of a sense of environmental responsibility, you shouldn’t need to use dubious math to accomplish that end

  • Interesting. I’ve never owned an electric car, but just guesstimating based on those numbers, my daily commute would cost something like 25 cents in electricity. Not too shabby.

    I did buy an ebike a few years back and watched to see how much the bill went up, but frankly never noticed any change. At 2 cents per day, it’s basically a rounding error relative to other electrical usage, so that makes sense to me now.

  • While I like this chart, it’s useless without the tradeoff. It also needs to map speed to time spent. What is being given up for improved efficiency? The inflection point is how you move people from point A to point B.

    • Time efficiency in a modern urban area optimized for public transport and non-motorized transport modes compared to time efficiency in current typical urban areas, which are focused on individual motorized transport modes with severe lack of public transport:

      [Fancy chart: first case left, second case right]

      [Good] [Bad]

      • That’s nice, but in my town at least driving to work takes half the time of taking the direct bus and that’s with half the roads in the town being closed to private vehicles. To walk to work I have to walk for 2 hours without breaks down to the bridge and back up the other side or cycle for 50 minutes (at -10°C) this is compared to a 10 minute drive through the tunnel.

        I genuinely wouldn’t mind taking the bus if my kids daycare was open longer.

    • I get what you are trying to ask, and why, but unfortunately, such a comparison is not so trivial:

      Setting aside load (weight) and age differences, various transportation means use gear shifting in order to adapt the power output to the characteristics of the current load (as in “system load” this time). This adds a dimension of dynamism to the comparison, and most vehicles do not automatically and systematically impose an ideal efficiency constraint on the power output.

      To illustrate, using a single speed bike requires vastly different power than using a 7 speed bike. And different driving styles will radically change the efficiency of combustion engines.

      So, in addition to mapping the efficiency to various speeds, it should be mapped to various use cases (hence why combustion engines have different fuel economy in “urban” and “extra urban” situations).

      In the end, the graphic would not be 2D like this one, or 3D like it would be with “time per km” (or mile) vs energy requirement, and per type of vehicle, but there would be several 3D graphics, one per vehicle type, with time per km vs environment vs energy consumption.

      TBH I was gonna try and do that, but even with ADHD, I can see this is going to be mad time consuming. So yeah, no, I think I’ll pass. Good idea tho. “Someone” should do it. 😇

  •  Swarfega   ( @Swarfega@lemm.ee ) 
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    59 months ago

    EBikes are awesome. I live in a hilly area where riding is tough. EBikes allows people of all ages and abilities to get out. Even with the assistance you still burn calories… as long as it’s assisted peddling and not the illegal bikes I see delivery guys riding.

    I ride road bikes but when I get older and less capable I’ll certainly invest in an ebike.

  • Yeah but what about if a person is a massive hambeast? Ain’t no cycles going nowhere under that strain.

    Or what if they are a massive douchenozzle chud fuckwit?!? It would emasculate them to not have the largest most unnecessary truck possible?!?