Something like this has been prototyped by a group including the peeps behind low tech magazine: https://www.humanpowerplant.be/ It's really cool!
this post was submitted on 22 Jan 2025
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It's a tough ask. A bicycle generator will be 70% efficient, and a healthy amateur could do 100w over an hour of effort generating 70w. A treadmill would have a lot more friction, and a rowing machine gets nowhere near the power you can generate from your legs. A linear "foot press" exercise machine is not as efficient as the circular motion of cycling.
Power requirements of a gym might also include music systems, outside lighting. Heat/hot water could come from gas.
It can still be worth adding generators and wiring to exercise machines to offset energy consumption, including batteries to prevent peak TOU rates. But it is a tough ask to disconnect from grid, without solar.
It can still be worth adding generators and wiring to exercise machines to offset energy consumption
It seems like a lot of extra overhead for marginal benefit.
There is a YouTube video around of a sprint cyclist powering a toaster and he can barely do it. I don't think you could do it "reasonabley".
600w electrical output requiring 700w cycling power output is not sustainable human power output. TdF riders will usually output 1kwh over their full (4hr ride) day. Enough for 100 toasts
yeah. it still amazes me how much it takes to actually burn calories and its mostly heart rate that does it. I was thinking how you won't get anything from the free weights or aerobics classes along with swimming and heating pools, sauna, hot tub is not insignificant. I think it could be done as long as what the gym offers is limited and it uses very energy efficient things.
Eh if you want to go real efficient you just drop the heating music and light and have only non electric machines and voilà! 0W used :D
I’ve considered instead of energy generation which is pretty hard for human biomechanics to do, we could have a gym where you build stuff. Like today’s workout is you have to build a wall.
Carry a bunch of wood around (squat, deadlift, carries ). Do some sawing (row, push up). Lift wood overhead (press).
And at the end of the workout you’ve got a wall!
My first factory job was a workout. I spent all day taking bundles of ice cream products off a conveyor and placing them on skids. I liked that aspect of the job, or any job that involves physical activity.
The first week was brutal with muscle pain, but then my body got used to it.
I do white collar work now but kinda wish I could do that kind of work like one day a week or something.
Well, exercise equipment makes for terrible generators. The amount of modifications and the added load to the user would make them much larger and more difficult to use.
the added load to the user
Isn't that the purpose of a gym?
Generators have a significant amount of load to make them viable and work best at constant speeds.
Huge amounts of load at the start and then momentum usally makes it more efficient. This is great for endurance training, but you would have to mess with a fair bit of engineering for weight machines to work well.
At that point you might as well just make them preform labour like splitting wood.
Might be difficult.
Bicycle riders make 30-70 watts from memory. That'll run a few LED lights, but if you want the fridge you need five cyclists, and for the aircon about 30 to 50 I think.
A brand new rider makes around 50w off the couch. 100-200w functional threshold power is normal for someone who rides casually but regularly. Pro racers are doing like 5 w/kg so around 300w for a smallish person.
but if you want the fridge you need five cyclists
Your numbers suggest the fridge uses 5 * (30 to 70), or 150 to 350 watts. Which are reasonable numbers when the compressor is running.
But, the duty cycle of a fridge is typically less than 30%. It only draws a couple watts with the compressor off and the door closed.
In a long enough "race", two cyclists should be able to drive the electric meter backward faster than the fridge drives it forward.
70 W is very casual riding, like 15 km/h or so. Anyone actually training (20-25 km/h or simulating anything with hills) will be more in the 100-150 W range. My fridge uses 70 W as an example, and only when actively running, with a duty cycle of 40% or so. Obviously this isn't an industrial fridge or freezer.
If they generate that much just from their memories, imagine how much they must generate when they pedal the bikes!
Hehe. Good one.
Actually I think the brain uses 30 watts so you're not far off :)
I really should check my sources! Slacker me.
What if you have anxiety?
I do! How did you know?? I'm stressing out
Here's an Olympic sprinter powering a toaster. He generates 0.021kWh going flat out: https://youtu.be/S4O5voOCqAQ
~~ONE~~NAUGHT POINT 21 ~~JIGA~~KILOWATTS!
Damn Marty!
Kilowatt-hours, not kilowatts. And it was 0.021.
He was basically going full blast for just under two minutes, and generated 0.021 kWh.
but a relay team could do 600watts "continuous".
It would have to be a pretty big relay team. The recovery time for 2 minutes of all-out power exercise is pretty long.
Look at the size of this guy's thighs. He's a freak of nature (in the positive sense of the term) who trains for this specific type of exercise and had to stop after 2 minutes because he was in so much pain. I can't imagine he'd be ready for another all-out run in less than a couple hours, and after two in a day, probably would need a day's rest.
6 guys simultaneously doing 100w for an hour has a much larger "relay pool" of available athleticism.
That's fair. But that's still a lot of work for so little work, if that makes sense. Which is kind of what the demonstration showed.
A man at the peak of human athletic capability could barely put in enough energy on his own to slightly toast a piece of bread. Of course 6 people could put in one sixth of the effort, but that's six people still working such a small output.
For a 2 slice toaster, they could make 60 toast per hour. Primitive human hunters had an endurance advantage over all prey, as sweat is a cooling system. They could run long enough to exhaust the prey. I still imagine horses could produce more electricity. Though apparently a horse can travel just 20-30 miles per day, while an average cyclist could do 60+.
That's 1440 slices of toast per day. Using random numbers from google, that's 110k Calories worth of plain white bread. Assuming 6 people putting in the work, that's a bit over 18k per cyclist for 24 hours cycled, who each would require about 12k Calories for the work put in.
However, this is just to toast the bread, not to make the bread. I'm being a little dumb and taking this hypothetical a bit too far.
I love how the channel is dedicated to just this experiment
Nice demonstration of how much power this actually is
But couldn't they fix the handlebars better or are they this wonky on purpose?
I once saw a TV program where they tried something like this. They had a few dozen people on exercise bikes try to power a normal family home. They barely managed even going flat out with a lot of people. Humans aren't very good for generating electricity. I think it's basically impossible to get more out of them than you have to feed them. Our future robotic overlords won't have much use for us.
Demonstrations like that really emphasize just how much energy a modern lifestyle requires. Switching from human power to fossil fuel power let us scale energy use so high without a second thought, just keeping food cold inside a warm room, nevermind traveling at 400 mph.
Great idea. As others have pointed out, it wouldn't be enough power on its own, but maybe it could supplement the gym's power and you could award people points for how much power they generate. Then maybe you can use those points to pay for all the things you need for daily living. https://en.m.wikipedia.org/wiki/Fifteen_Million_Merits
Many of the stationary bikes power their own display. I think thats about all you can do with so little energy.
It does feel like all that wasted effort would be good to use for something productive. The energy used probably wouldn't even heat the water for the showers though.
Maybe just charge people's phones while the work out is better than nothing though.
The energy used probably wouldn’t even heat the water for the showers though.
Not even close. Someone posted a video of an Olympic cyclist going all out running a 700 Watt toaster for 2 minutes, and he was exhausted after that. A water heater would be like 3000 Watts and would need to run for a long time to heat up an entire tank of water, which would last for just a couple quick showers.
Hey that’s exactly what I’ve wondered for years. Just get rid of all those useless weights, and replace them with generators.
And watch all the lights turn off.
At the door there’s a bike. Start peddling to turn the lights on.
After a quick warmup, you can find your way to the rest of the gym. All the other machines also power the lights, air conditioning, showers etc.