5 ms·

So the car alternative is only 2.5x as much power as a bike, goes 100% the speed of a car, and is air conditioned? That seems like a worthwhile tradeoff.

by jsight 7y ago

sudosysgen 7y ago
2.5x?? There is absolutely no way a car uses 250w on average in city driving, even with regen. If that was the case, some Teslas would have an autonomy of 400 hours(!) in city driving. More like 25-100x more energy. And that's quite generous still. In a city, bikes are indeed multiple orders of magnitude more efficient than cars for personal transportation.
- soperj 7y ago
  They said 2.5x as much power as a bike, not car.
  - sudosysgen 7y ago
    Electric cars do not use 2.5 times the power of a car. Unless there is another electric vehicle that can go 100% the speed of a car, and is air-conditioned, that I don't know of.
    - soperj 6y ago
      the velomobile. literally what the topic of what this person is replying to.
- Retric 7y ago
  E-Bikes are already at 1,000+ watts. So the estimate is 2,500 watts for something like an enclosed golf cart with AC which seems possible, though I assume they mean car speeds inside a city not highway speeds.
  - sudosysgen 7y ago
    They are at 1000+ watts peak, but unless your average speed is of 45mph in a city all the time, you're not pushing 1kw on average. More like 100-200 watts on average.
    - Retric 7y ago
      I am referring to peak power. A highly aerodynamic human powered vechile can do 55 MPH on ~200w and got up to 89.59 mph. https://www.prweb.com/releases/2016/09/prweb13693869.htm https://www.prweb.com/releases/2016/09/prweb13693869.htm Something with better visibility and ergonomics is going to need more power, but 2,500w is plenty to get into seriously unsafe speeds in a small lightweight vechile.
      - sudosysgen 7y ago
        Sure, but the peak power of a human on a bicycle is not 100w, I personally can do 1100w for around 30 seconds on a road bike and accelerate up to 60kph. I have downhill in the city achieved speeds in excess of 70kph when I was younger and stupider, on a run of the mill unpowered bicycle. So I don't really get the safety argument, just don't be an idiot, it's not as if on a 30kg bicycle you're putting anyone in danger except yourself, really, or pedestrians in very rare occasions. Most jurisdictions prevent you from using an ebike with more than a kilowatt or less peak power without some sort of license, so unless you're talking about the tiny minority of DIYers, it's not an issue. Another thing that you have to keep in mind is that electric motors on bicycles are almost always limited in their top speed by their kv rating, that is to say, by their gearing. Once you get up to high speeds, power tends to drop off quite significantly as the battery and controller can't keep up with the motor and the ever-higher voltages required. So unless your ebike is specifically geared for that task or that you use a mid-drive with a ridiculous 72 speed transmission and gigantic pedal sprocket, you're not hitting 55mph on an ebike with a 250w motor, or with a 1000w motor for that matter. If it was actually useful to go that fast we would already do so. So in the end, the average power of someone riding an ebike around town is of 100w-250w, whereas cars use in the order of 10000w+ in town. This means bikes are on the order of 25-100 times more efficient than cars. If you want to build any sort of enclosed structure that can pass crash safety, it will likely have 4-5 times the frontal area of an ebike, and weigh the better part or upwards of a ton. And in the end, you will have an average power consumption, not peak, in a city in the multikillowatt range. Essentially, you would make an electric Smart Car, which already exists :)
- jsight 6y ago
  Yeah, you are right of course. I'm not sure why I compared a Wh/mile figure (which honestly amazes me) to a an average output figure. An average hour of usage would probably be ~250wh on the bike and more like 10Kwh in the car. I blame mornings and lack of coffee. :)
- m463 6y ago
  You should not prematurely optimize your solution. If you can charge your car from the sun, who cares? It might be that a bike is more efficient, but you have more risk of accidental injury or death. It's harder on your human body for say a 5 mile commute. You will arrive at work more tired, or more sweaty, or rained on. On the other hand, if you decide to use a bike for exercise, that might change the equation again. (I'm not trying to argue with you, just thinking from a different viewpoint)
adrianN 7y ago
250W is about 1/3HP.

So the car alternative is only 2.5x as much power as a bike, goes 100% the speed of a car, and is air conditioned? That seems like a worthwhile tradeoff.

by jsight 7y ago

So the car alternative is only 2.5x as much power as a bike, goes 100% the speed of a car, and is air conditioned? That seems like a worthwhile tradeoff.

sudosysgen 7y ago

2.5x?? There is absolutely no way a car uses 250w on average in city driving, even with regen. If that was the case, some Teslas would have an autonomy of 400 hours(!) in city driving. More like 25-100x more energy. And that's quite generous still. In a city, bikes are indeed multiple orders of magnitude more efficient than cars for personal transportation.

soperj 7y ago
They said 2.5x as much power as a bike, not car.
- sudosysgen 7y ago
  Electric cars do not use 2.5 times the power of a car. Unless there is another electric vehicle that can go 100% the speed of a car, and is air-conditioned, that I don't know of.
  - soperj 6y ago
    the velomobile. literally what the topic of what this person is replying to.
Retric 7y ago
E-Bikes are already at 1,000+ watts. So the estimate is 2,500 watts for something like an enclosed golf cart with AC which seems possible, though I assume they mean car speeds inside a city not highway speeds.
- sudosysgen 7y ago
  They are at 1000+ watts peak, but unless your average speed is of 45mph in a city all the time, you're not pushing 1kw on average. More like 100-200 watts on average.
  - Retric 7y ago
    I am referring to peak power. A highly aerodynamic human powered vechile can do 55 MPH on ~200w and got up to 89.59 mph. https://www.prweb.com/releases/2016/09/prweb13693869.htm https://www.prweb.com/releases/2016/09/prweb13693869.htm Something with better visibility and ergonomics is going to need more power, but 2,500w is plenty to get into seriously unsafe speeds in a small lightweight vechile.
    - sudosysgen 7y ago
      Sure, but the peak power of a human on a bicycle is not 100w, I personally can do 1100w for around 30 seconds on a road bike and accelerate up to 60kph. I have downhill in the city achieved speeds in excess of 70kph when I was younger and stupider, on a run of the mill unpowered bicycle. So I don't really get the safety argument, just don't be an idiot, it's not as if on a 30kg bicycle you're putting anyone in danger except yourself, really, or pedestrians in very rare occasions. Most jurisdictions prevent you from using an ebike with more than a kilowatt or less peak power without some sort of license, so unless you're talking about the tiny minority of DIYers, it's not an issue. Another thing that you have to keep in mind is that electric motors on bicycles are almost always limited in their top speed by their kv rating, that is to say, by their gearing. Once you get up to high speeds, power tends to drop off quite significantly as the battery and controller can't keep up with the motor and the ever-higher voltages required. So unless your ebike is specifically geared for that task or that you use a mid-drive with a ridiculous 72 speed transmission and gigantic pedal sprocket, you're not hitting 55mph on an ebike with a 250w motor, or with a 1000w motor for that matter. If it was actually useful to go that fast we would already do so. So in the end, the average power of someone riding an ebike around town is of 100w-250w, whereas cars use in the order of 10000w+ in town. This means bikes are on the order of 25-100 times more efficient than cars. If you want to build any sort of enclosed structure that can pass crash safety, it will likely have 4-5 times the frontal area of an ebike, and weigh the better part or upwards of a ton. And in the end, you will have an average power consumption, not peak, in a city in the multikillowatt range. Essentially, you would make an electric Smart Car, which already exists :)
jsight 6y ago
Yeah, you are right of course. I'm not sure why I compared a Wh/mile figure (which honestly amazes me) to a an average output figure. An average hour of usage would probably be ~250wh on the bike and more like 10Kwh in the car. I blame mornings and lack of coffee. :)
m463 6y ago
You should not prematurely optimize your solution. If you can charge your car from the sun, who cares? It might be that a bike is more efficient, but you have more risk of accidental injury or death. It's harder on your human body for say a 5 mile commute. You will arrive at work more tired, or more sweaty, or rained on. On the other hand, if you decide to use a bike for exercise, that might change the equation again. (I'm not trying to argue with you, just thinking from a different viewpoint)

adrianN 7y ago

250W is about 1/3HP.