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The Energy Cost of Electric and Human-Powered Bicycles (2004) [pdf] (ebikes.ca)
58 points by jeremejevs 20 days ago | hide | past | web | favorite | 44 comments



Interesting!

> The above figures were all produced by assuming average or typical cases. To be fair, it is entirely possible for a bicycle rider to deliberately eat only locally grown and unprocessed foods. In that case, the ratio of primary energy to food calories is closer to 1:1 (Günther 3). Combined with a metabolic efficiency of 25%, this increases the human energy efficiency to 1:4, slightly better than the lithium-ion electric bike.

> ...

> Conclusion: ... Despite the intuitive sense that electric bikes would require more resources than regular bikes, life-cycle analysis shows that they actually consume 2-4 times less primary energy than human riders eating a conventional diet. This conclusion is largely due to the considerable amount of transportation and processing energy that is associated with our western food system.


But that’s an ideal case.

People eat a lot and exercise to lose weight. They don’t eat to only replenish expended energy. They over consume then often compensate with exercise. So a particular rider might eat more or might eat the same regardless of whether they pedaled or they used electric power.


> People eat a lot and exercise to lose weight. They don’t eat to only replenish expended energy. They over consume then often compensate with exercise. So a particular rider might eat more or might eat the same regardless of whether they pedaled or they used electric power.

Some diets aren't as efficient as others though. Feeding corn to cows then eating the cow meat is going to be vastly less efficient than eating the corn directly for example.


Well, a steak has more energy density than corn. Plus, it has nutrients that simple corn doesn't have.


Recognizing it was first-order approximation, two significant problems with the comparison: 1. E-bike riders likely to travel much faster. Since drag is quadratic, change in consumption significant. 2. The important energy comparison might not be manual bikes, but other modes of transit. A current driver/transit-rider might choose to bike 15 miles each way only if on an e-bike.


"A current driver/transit-rider might choose to bike 15 miles each way only if on an e-bike." This is absolutely the case for me - an e-bike makes the difference between my 27km commute being viable in a sensible time frame, or having to drive.


> E-bike riders likely to travel much faster.

I'm not sure that is significant. In most countries e-bikes are constrained not to exceed 25 km/h when under power. I've commuted by bike for some parts of my life (I now work from home) and I usually overtake e-bikes unless I'm climbing a pretty steep hill.

On the other hand your second part is probably correct: I recall reading that when Canada started mandating helmets it had a negative effect on life expectancy because people were using bikes less and that had an impact on cardiovascular health that exceeded the increase in safety. So you might be right that the increase in usage overweights the change in efficiency.

On the other hand I would never leave a bike that is worth more than 100 euros parked outdoors on a pole in most European and American cities even with a decent U-lock. Add to that weather and electrical components and you end up with something you can use only if you have an indoors parking.


"Despite the intuitive sense that electric bikes would require more resources than regular bikes, life-cycle analysis shows that they actually consume 2-4 times less primary energy than human riders eating a conventional diet. This conclusion is largely due to the considerable amount of transportation and processing energy that is associated with our western food system."

And obviously, caveat lector: there are huge assumptions going on here, because the "real" cost of stuff like food and batteries aren't trivial to calculate at all. It's not like you can feed em both the same resources anyhow, so at best this is an analysis that the efficiency is sort of comparable. In 2004.


> And obviously, caveat lector: there are huge assumptions going on here, because the "real" cost of stuff like food and batteries aren't trivial to calculate at all. It's not like you can feed em both the same resources anyhow, so at best this is an analysis that the efficiency is sort of comparable. In 2004.

This is what I was thinking as well. My naive guess is that the extra energy expended to build an electric bike blows the efficiency improvement completely out of the water. It would take a truly enormous amount of usage to make up the difference in the expected lifetime of the battery (which then has to be efficiently recycled, else it's yet another environmental hazard).

Of course the real issue is the fact that I can't travel even 1km toward my workplace on a bike without seriously fearing for my life. Cities in the United States are extremely unfriendly to bikes.


Yes, does it take into account the energy cost of the ambulance that comes to collect you after you had a heart attack after getting fat because you didn't burn off what you were eating....

On the other hand, from what I understand in the Netherlands, ebikes help older people keep cycling for longer so ebikes are still good?

I would guess overall, the difference between bike and ebike is a rounding error compared to not riding at all. Both environmentally, and from a health pov.


In any case I definitely know nobody who ate more because they rode a bike. Some might get a bit more exercise or will get a bit less fat but I m firmly against the assumption that you'll et more if you ride in current wester societies.


My eating logs show a dramatic calorie increase when cycling to work vs not. Eye balling looks like ~20% increases are common


When I cycled to work I did eat more, but that was 30+ miles a day up and down hills. It was also on an ebike (whatever that proves) and I would say it was more carbs than air freighted fresh veg and meat, so not the most carbon intensive food.

But yes I don't think most people eat their full extra cycling energy expenditure when they take up cycling.


I've been an e-bike advocate since the first time I rode one. It's an amazing feeling being able to effortlessly overcome hills and riding as fast as 28mph on flat terrain without struggling too much.

The major downsides are: weather extremes (that are going to be more common). The bike is generally heavier (much more effort to get it into the building or onto a bus).

And of course, the biggest one of them all - you are now vilified by both car drivers and pedestrians, while taking on more risk than either one. And of course suburban sprawl being the center-point of US culture, anywhere takes too damn long to get to even on an e-bike.

It's unfortunate that the US isn't more dense, which would make an ebike an ideal mode of transport in ~80% of cases.


Bottom line is that bikes are efficient because they’re slow and light, not necessarily because they’re human powered.

In both cases the energy use is lower than lots of things that we don’t think of in terms of energy.

By way of comparison, a hot shower used about 300 Wh (a full charge on a smallish ebike battery) every minute.


Long ago I measured how much water I needed too. Two steps:

    - soaping: 1 glass of cold water
    - cleaning: 1 glass of cold water
head to toe


Frugliness is next to Godliness.


> To travel one kilometre by bike requires approximately 5-15 watt-hours (w-h) of energy, while the same distance requires 15-20 w-h by foot, 30-40 w-h by train, and over 400 w-h in a singly occupied car.

Since the rise in popularity of electric cars 400wh/km is actually quite high.

Most electric vehicles are rated city/highway 15/20kwh/100km (150 w-h/km / 200 w-h/km)

On this page:

https://forum.abetterrouteplanner.com/blogs/entry/13-model-3...

it shows the model 3 gets 143 Wh/km at 110 km/h


In Germany about 2% of the cars are electric, half of those are hybrids. I think in the US it's similar.


I think he forgot the production cost of a human.


> The metabolic efficiency of a human on a bicycle is remarkably good. Calorimetric studies have shown that a properly trained athlete will have efficiencies of 22 to 26% depending on pedal cadence and power output.

Anectdote about this, is that my watt meter on my bicycle gives out the total amount of work done in kJ at the end. To convert that to kcal in food, one can convert 1-to-1, as the metabolic efficiency matches roughly the ratio between kcal and kJ.


I assume it's the same for elevators?

"Save the environment, take the elevator"?


I wonder if elevators are even better because they're counterweighted, whereas when you take the stairs, you squander all of the potential energy you gained going up on your way down.


human: 1.2 (0.9) kcal/floor ascending (descending) [0, 1] elevator: 2.5 W•h/floor [2, 3]

Let's assume 15 floors since otherwise you'd probably save time walking.

The article suggests a grid efficiency of 50% and a motor efficiency of electric e-bike motors as 75%. It looks like elevator motors are actually more efficient (increasingly so as more people are loaded) [4]. It's only about 5 percentage points higher, so for simplicity let's keep 75%.

Ignoring the transportation and manufacture cost of the elevator assembly (not totally unreasonable since it has a long lifetime), elevators have an energy ratio of 2.5:6.7 or 1:2.7, which looks far better than the 1:28 that the article quotes for humans.

Gee, that kind of upends my worldview... I guess I'll just wait until bodies are deprecated in favor of high-efficiency cybernetics.

[0] https://captaincalculator.com/health/calorie/calories-burned...

[1] https://www.livestrong.com/article/301539-calories-burned-cl...

[2] https://www.quora.com/How-much-electricity-does-an-elevator-...

[3] https://fatknowledge.blogspot.com/2007/02/how-much-energy-do...

[4] https://www.me.ua.edu/me416/LECTURE%20MATERIALS/MotorEffic&P...


> Let's assume 15 floors since otherwise you'd probably save time walking.

Not many people would consider walking 15 floors either up or downstairs. Actually many people pant heavily when climbing (from their point of view) 3 floors to my place.


anecdotally i get about 60 miles to the burrito.


Is that city or highway burritos?


I think it's more an issue of whether it's a metric or imperial burrito


Depending on the formulation of the burrito, I may produce undesirable hydrocarbon emissions.


this reduces the duration of pulling time! it’s a strategic asset in a paceline.


I think they should count energy savings associated with health benefits of riding normal bike. Hospitalisations use ton of single use items that bound to have some energy cost.


The author lost me at the assumption that humans on electric bikes eat less than humans on pedal bikes.

Personally I eat about the same whether I drive or bike, just ride to avoid getting fatter.


People definitely unnoticeably adjust their diet to their exercise level.

It's apparent when they stop doing exercise and they gain ton of weight until they adjust their diet again. Usually that requires concious effort.

My buddy seen that when he quit judo.


Yah but humans want to spend energy as they’d prefer not storing it on their bodies because of social and longevity pressures.


That's from 2004. Are the numbers still valid?


I’m guessing Li-ion is way better today than it was in 2004.


They want to sell electric bikes, so they found an obscure point of view from which they may be preferable to the ordinary one. Ignoring the obvious points of view from which they are not - health disservice to the rider, battery tech non-monetary costs, increased electricity consumption of the owner.

Electric bike has its legitimate target group - elderly or ill or handicapped people. If you're fine, get that ordinary bike and build some form.


>health disservice

The point of transportation is to take you places, not to make you healthy.

>increased electricity consumption

The biggest ebike battery you're likely to find is 500 Watt-hours. That's about 6¢ for the average American to fill from zero to full, and that'll carry you 50 miles.


I agree with the cheap energy part, electric bike is a very efficient mode of transportation, better than car. However, when you compare impacts to health of the rider and the environment, the ordinary bike wins as the better choice.


No, it doesn't, see the article you're commenting on. Regular bikes are more expensive and produce more carbon because of the extra calories the rider has to eat.

The purpose of vehicles is transportation, not exercise.


The purpose of ordinary bicycle is both transportation and exercise. You can't just dismiss benefits of the other choice because your choice does not have them. We are comparing ordinary vs. electrical bike, with all benefits and drawbacks.

The analysis in the paper is flawed right from the start. For regular overweight people, which is the majority of people in U.S. and some other countries, unless getting to high speeds and high heart bpms, a little increase in energy expenditure in moving the bicycle does not increase food consumption in the linear way the paper assumes. The food is gonna be consumed anyway.

And even disregarding that, there are more important considerations here than alleged increase CO2 production, which is laughably negligible in comparison to car, plane and ship transportation. Ordinary bicycle has lower price, better health effects, lower environmental cost of manufacturing/disposing of batteries.


People don't buy ebikes for exercise.


They shouldn't buy them because of bogus CO2 efficiency reasons either.


I think this is one of the few edge cases where gifs could improve the comments on HN

https://tenor.com/view/walle-humans-lazy-eve-disney-gif-5471...




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