[NoboruWataya]

I've often wondered if it would be viable to run a gym where all of the equipment is designed to harness customers' energy to help power the building. I suspect it wouldn't make enough of a difference to be worth it but have never seen anyone run the numbers.

[jck]

Let's say a person outputs 500W and we can somehow capture all of it. That would be 10cents worth of electricity in an hour.

Note that these are very generous estimates, but it does demonstrate how silly the idea of trying to generate electricity by capturing exercise output is (in a purely economic sense).

[WJW]

500W is an extremely high number as well. Pro cyclists can reach up to 400 Watt in short bursts, untrained people typically can't maintain more than 100-150W for long. We really use quite a lot of energy when measured in how many humans it would take to provide that much energy "manually".

[anon_123g987]

While it's true that the power of a human is not much (certainly not enough to power a house), but we have a lot of energy. Most of us carries at least 1 kg (~2 lbs) fat, which contains ~37 MJ of energy. For comparison, a stick of dynamite has ~1 MJ of energy.

https://en.wikipedia.org/wiki/Fat#Biological_importance

https://en.wikipedia.org/wiki/Dynamite#Form

[trelane]

Why stop there? The matter itself is energy, so combine a human with an anti-human....

[BizarroLand]

Sweet oblivion looks just like me

[Merad]

> Most of us carries at least 1 kg (~2 lbs) fat

It's a lot more than that. Even a fit (healthy, but not necessarily peak athletic shape) adult man will have about 15% body fat, 20% for a woman.

[yetihehe]

> Pro cyclists can reach up to 400 Watt in short bursts

I heard pro cyclists can reach up to 2kW. I managed to make 500W on a rowing machine for 5 minutes, but I'm a couch potato. I believe 400W is a normal rate for cyclists. When you are sitting, your body already produces about 100W of heat.

[SubuSS]

So cyclists measure their capability in terms of FTP - essentially what power output they can maintain at full throttle for an hour.

This hugely depends on body weight / gender / training levels etc., body weight being a big deal since that’s what you’re transporting. So the other way folks measure output is W/kg of body weight.

A beginner adult male will be in the 100-200W zone, around 0.5-1.5 W/Kg. Usually anyone can train themselves into the 200-300 (3-4 W/Kg) zone which is the recreational pace - the groups of cyclists you see on the road. Beyond 300 ftp (150lb body weight) (4-5 W/kg) you’re reaching race pace. The ones you see on screen have upwards of 5-6 W/Kg FTP output. They obviously have other constraints around putting this output at the end of a 200km ride for 20 mins etc as well, which makes it extra hard.

Finally we come to the KW numbers - all these folks have two kinds of muscles (fast twitch and slow twitch). The sprinters are saddled with a higher proportion of the kind of fibers that can allow huge spurts of power - they put out about 1000-1500W for about 5-10s. These are probably what you’re thinking of. This is pretty much an end of ride (or a sprint section) empty your tanks effort.

Semi related tidbit: track cyclists are a middle kind of beasts here: they put 600-1000W for a couple of minutes but don’t have to worry about riding 200kms to get there.

[a9h74j]

Yes, and the Wired graphic was particularly misleading in that it showed, as I recall, multiple dollar amounts accumulating on per-session treadmill displays.

On the other hand, it is possible to imagine lifestyles enhanced by various 10W contributions. 10W for heated clothing. 10W for a laptop. 10W average to power a several km electric bicycle or Aptera-size commute. And so on.

[pxndxx]

How are you proposing we produce 10W to heat clothes? we produce around 80W just by sitting idle, just wear insulating clothes! How do you produce 10W to power an electric bike? 10W is a laughable amount of power, just get rid of the electrics and pedal a bit. 10W is barely enough to charge a phone these days. Anything that gets moderately hot while in use is consuming more than 10W.

[a9h74j]

e.g., s/lifestyles/post-collapse lifestyles/

Based on Ali Express, heated clothing (5V power in a pocket) is popular enough in China.

[Flashtoo]

This isn't exactly what you are talking about, but this art/concept for self-powered student housing came to mind: https://www.humanpowerplant.be/human_power_plant/human-power...

[benj111]

In their defense this could be seen as a type of gamification. Ultimately you can put any dollar amount on a kWh of electricity. It's the kWh generated that matters.

Not saying it's a good defense though.

[SenHeng]

The Grand Tour has tried to answer that question. I thought the turnstiles idea was really good, especially if you place them in a building with heavy traffic. Though probably not really cost effective.

https://www.youtube.com/watch?v=WhwyH6tT-EQ

[CodeBeater]

As a quasi sidenote, most gyms already implement this on a smaller scale on their elliptical and spinning machines as they're usually self powered and you can regulate the resistance the machine offers, which I assume must increase or decrease the number of magnets around the flywheel.

[adwww]

However, most energy you burn in a gym is converted into heat energy, which the gym then burns extra electricity trying to air condition.

[agumonkey]

A dude did that, it didn't last long, but I'm still thinking about opening one. Just to avoid the double madness of powering lights and devices so people spend energy in the air :)

Even if you don't generate much, at least your biomechanical efforts are used somewhere.

[benj111]

Surely it's triple madness if you're driving to a gym to go on the running / cycling machine.

[a9h74j]

Not just driving to the gym, but driving twice around the parking lot to find a closer space for a shorter walk.

And wasn't it Mumford who observed that given the time it takes to earn the money to buy a car, on average it can be faster to walk than to drive.

[agumonkey]

Oh yes I forgot to mention this :)

[akvadrako]

You could have them power fans or keep the lights on. Things that can use just a few watts.

[agumonkey]

each one yes, but if you have 20 persons averaging 100W, you can power a kettle :)

[hinkley]

Having been to a gym, I sincerely hope any power scavenged is use to power the ventilation system.