Shouldn't treadmills produce instead of consuming electricity?

[ScienceNostalgia101]

We have coal, oil, gas, nuclear, and thermal!solar power plants that work by burning these boiling water, and turning turbines.

 

We have wind and hydroelectric power plants that use their respective fluids to turn turbines directly.

 

And yet, when people want to work out, they get on devices that USE electricity to run a motor. Something isn't right here.

 

Is there any way to design a treadmill and/or stationary bicycle that can generate electricity from the user's motion?

Edited August 28, 2019 by ScienceNostalgia101
Replacing "energy" with "electricity" in subjectline.

[QuantumT]

Back in the days (80's) we had dynamo lights on our bicycles. Small turbines that rubbed against the front tyre, producing a small current, enough to make light.
They stopped making them, because they don't work when you stop your bike. So in a badly lit area, you could get hit by a car.

But the general concept is still equally valid.

Edited August 28, 2019 by QuantumT

[koti]

12 minutes ago, ScienceNostalgia101 said:

And yet, when people want to work out, they get on devices that USE electricity to run a motor. Something isn't right here.

 

Is there any way to design a treadmill and/or stationary bicycle that can generate electricity from the user's motion?

It;s not so simple. In order to effectively work out on a tredmill it needs to move under your feet. It would be useless to effectively work out on a tredmill that converts kinetic energy produced by your moving feet - a stationary gym bike is not a bad idea on the other hand.

[swansont]

1 hour ago, ScienceNostalgia101 said:

We have coal, oil, gas, nuclear, and thermal!solar power plants that work by burning these boiling water, and turning turbines.

 

We have wind and hydroelectric power plants that use their respective fluids to turn turbines directly.

 

And yet, when people want to work out, they get on devices that USE electricity to run a motor. Something isn't right here.

 

Is there any way to design a treadmill and/or stationary bicycle that can generate electricity from the user's motion?

Yes. The issue is how much, and is it worth the fuss. QuantumT mention a bike dynamo, which lit a small light and added a noticeable load to one’s pedaling. I remember a demonstration in high school where a tandem bike was hooked up to a generator. The pair struggled lighting up an incandescent bulb, and a hair dryer basically brought them to a stop.

Humans just don’t generate all that much power. There’s a reason we went with animals and machines.

A 100 kg person going up 3 flights of stairs - 10 meters - does just under 10000 joules of work. If that happens in 9.8 sec, that’s a kilowatt. How long can a person do that kind of exercise? In an hour, they will have generated around 10-12 cents worth of electricity (it will vary with local market conditions) 

 

1 hour ago, koti said:

It;s not so simple. In order to effectively work out on a tredmill it needs to move under your feet. It would be useless to effectively work out on a tredmill that converts kinetic energy produced by your moving feet 

Not sure why you think this. The dynamic would be different, pushing the tread around its track, but it would work. It would be more like walking up an incline even when it was flat. In fact, an incline might be the way to make it work best.

[koti]

1 hour ago, swansont said:

...an incline might be the way to make it work best.

I agree.

[Endy0816]

They exist to a degree.

https://www.gosportsart.com/product/n685-verde/

 I'm not seeing any commercially available ones that power more than a smartphone however.

 

The  penal treadmill deserves an honorary mention. Used them to pump water and mill corn.

https://en.m.wikipedia.org/wiki/Penal_treadmill

More efficient when you use mechanical motion directly like that.

[Art Man]

If you had a loose track on frictionless rollers when you accelerated the track would continuously spin faster with each step. With a mechanical roller the speed is determined so the danger of the track constantly changing speed is avoided. If you could somehow build a powerless roller track with a speed control the machine would require much more maintenance than an electric one.

2 hours ago, Endy0816 said:

The  penal treadmill deserves an honorary mention. Used them to pump water and mill corn.

https://en.m.wikipedia.org/wiki/Penal_treadmill

More efficient when you use mechanical motion directly like that.

And then there is the mouse wheel, which would accomplish what you want without tracks and rollers.

Edited August 29, 2019 by Art Man

[J.C.MacSwell]

I use a simple set up in the winter to heat my house; a stationary bike with frictional resistance.

100 % efficient!

(no, not thermodynamic efficiency)

[Endy0816]

2 hours ago, Art Man said:

And then there is the mouse wheel, which would accomplish what you want without tracks and rollers.

Actually about what they had, though walking on the outside of the wheel.

They also had single man ones which were more a sideways wheel.

40 minutes ago, J.C.MacSwell said:

I use a simple set up in the winter to heat my house; a stationary bike with frictional resistance.

100 % efficient!

(no, not thermodynamic efficiency)

 A very sound use

Edited August 29, 2019 by Endy0816

[moth]

Wikipedia has some examples of "cramps to Amps" too.
I'd be happy if i could just interface my stationary machine to trigger the next image from google street view so i could take a walk anywhere on earth. 

[swansont]

8 hours ago, J.C.MacSwell said:

I use a simple set up in the winter to heat my house; a stationary bike with frictional resistance.

100 % efficient!

(no, not thermodynamic efficiency)

Yes, it all shows up as heat.

_ _ _ _

If you calculate how much it costs for the fuel, it’s rather expensive. Which means if you use human effort to generate thermal or electrical energy because you were going to exercise, i.e. you are reclaiming waste, that’s fine. But if you are doing it specifically for that purpose, it’s incredibly inefficient.

[Janus]

20 hours ago, ScienceNostalgia101 said:

We have coal, oil, gas, nuclear, and thermal!solar power plants that work by burning these boiling water, and turning turbines.

 

We have wind and hydroelectric power plants that use their respective fluids to turn turbines directly.

 

And yet, when people want to work out, they get on devices that USE electricity to run a motor. Something isn't right here.

 

Is there any way to design a treadmill and/or stationary bicycle that can generate electricity from the user's motion?

One issue is that, with a electrical generator, the fast it turns, the greater the current it produces, which in turn results in it taking more effort to turn it.  The faster you walked or ran, the greater the resistance of the treadmill would be.   Generally, you want to set the resistance of your electrical equipment and have it remain constant no matter what speed you are going.  So a direct treadmill to generator hook-up isn't the best option.

Instead, you would need to add some sensing equipment that measures the current output and makes adjustments accordingly.   Some elliptical machines are designed to do just this.   Many models use magnetic braking; the machine moves magnets either closer or further from the flywheel in order to create the resistance.   There are also "green" models that use this to generate the electricity operate the electronics for the machine and allows you to use it with having to hook it up to an exterior power source.   This scheme would likely work for a stationary bike, using the same idea.  Both of these completely rely on the user for setting the pace.

However, when it comes to the motorized treadmill, the idea behind the motor is that it sets and maintains the pace for you.  It is a means of forcing you to a steady constant pace.  Manual treadmills require the user to control the pace.  You might be able to create a hybrid manual treadmill, which works like like the green elliptical. where the user provides the energy for moving the treadmill, and generates electricity for a electronics display used to track your progress.

[ScienceNostalgia101]

On 8/28/2019 at 2:27 PM, swansont said:

Yes. The issue is how much, and is it worth the fuss. QuantumT mention a bike dynamo, which lit a small light and added a noticeable load to one’s pedaling. I remember a demonstration in high school where a tandem bike was hooked up to a generator. The pair struggled lighting up an incandescent bulb, and a hair dryer basically brought them to a stop.

Humans just don’t generate all that much power. There’s a reason we went with animals and machines.

A 100 kg person going up 3 flights of stairs - 10 meters - does just under 10000 joules of work. If that happens in 9.8 sec, that’s a kilowatt. How long can a person do that kind of exercise? In an hour, they will have generated around 10-12 cents worth of electricity (it will vary with local market conditions) 

Which suggests it would take a long time to turn a profit, but doesn't suggest that it won't eventually do so, especially if someone would otherwise exercise a comparable amount of time anyway. Why does no one want to invest in this?

[dimreepr]

54 minutes ago, ScienceNostalgia101 said:

Why does no one want to invest in this?

Because it's a lot of hard work.

[Janus]

1 hour ago, ScienceNostalgia101 said:

Which suggests it would take a long time to turn a profit, but doesn't suggest that it won't eventually do so, especially if someone would otherwise exercise a comparable amount of time anyway. Why does no one want to invest in this?

Maybe because the energy produced wouldn't even be enough to heat the water for the shower you'd need afterwards.   At best, you'd would be off-setting the power usage of your exercise equipment,  and I already pointed out,  there are already elliptical machines out there that do this.  

[swansont]

2 hours ago, ScienceNostalgia101 said:

Which suggests it would take a long time to turn a profit, but doesn't suggest that it won't eventually do so, especially if someone would otherwise exercise a comparable amount of time anyway. Why does no one want to invest in this?

If it takes longer than the expected life of the product, it’s a nonstarter.

Make your business case. Let’s see the math.