You also need a big enough battery to get through slow hours.
So you can get the Zero-emissions Off-the-grid gym!
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
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.
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.
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.
i just want a stationary bike that can charge my phone.
Most stationary bikes have a flywheel. You could 3D print a gearing set to run a small generator (like this one or DC) off if it. There are tutorials out there about how to set up it up.
I actually did that with an actual bicycle and one of those “make any old bike a stationary bike” stand things. Harvested an old motor out of…what was it, a printer or something? Photocopier? It was the upper-left third of something that used to be office equipment, and built the circuit out of a 7805’s datasheet with an extra big capacitor on the generator side. It charged phones. It was jank AF though. All it did was offer 5V at I have no idea how much current on the power pins of a USB Micro-B cable.
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.
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.
Something like this has been prototyped by a group including the peeps behind low tech magazine: https://www.humanpowerplant.be/ It’s really cool!
