corrado33

Ethics aside... Would humans producing power via stationary bikes connected to generators be viable in terms of net energy gain. Obviously you need to USE energy to feed the people and process that food, so could you produce the food using so little energy that you could produce an energy GAIN from people biking?

Spoonrobot 

No.

tcarl

I remember visits to science museums where they have a bicycle hooked up to a generator which lights a light bulb. My remembrance is that you get on it and pedal like crazy to get the thing lit. So, put yourself in an 80 inch gear and pedal at 100rpm for as long as you want to keep a light on.

StephenH

I guess it'd depend on the circumstances. In most cases, you'd probably be better off using solar cells.

For me, I'd crank away at that bike and optimistically generate 200w of power. Meanwhile, I'd have the AC sucking down about 2,500 watts to keep me cool while I did it. So not a good plan.

So maybe if you live somewhere where there's zero power available, and they raise all their food with hand labor and animal power, then maybe that'd be a decent way to power a computer on. But solar cells would probably be about as cheap to rig up and about as useful.

BlazingPedals

No. With the average cyclist generating 100 watts over a long-ish period of time (a couple of hours) you're not going to generate enough power to run a refrigerator or turn a grist mill.

wphamilton

I think that you come out behind fueling the body vs a power plant for generating electricity. In cost per kilowatt that is.

When you go on to include the energy cost of producing and distributing the food for your calories I think you'll be way behind. It's really the same reason why using biomass for generating electricity isn't a good idea, but even more inefficient that burning it directly in a power plant.

Elvo

They already covered this idea:

https://en.wikipedia.org/wiki/Fifteen_Million_Merits

fietsbob

Worked in the movie Soylent Green .. Soylent Green (1973) - IMDb


some pedal powered kiosks, let you charge your phone battery . in SNCF train stations . (as seen on web not there , myself)

Drew Eckhardt 

No. At best cyclists have a 25% metabolic efficiency (25% of what you feed them comes out the cranks), and we're worse at lower efforts which can be sustained for longer durations.

JohnDThompson 

Sure, it could be done. But humans generally decide they have better things to do with their time than power treadmills. Livestock were used to provide energy for plowing fields, grinding grain, etc. And more recently:

Odd Invention: Idle Livestock Hit the Treadmill to Generate Electricity For Farms | Popular Science

And as noted above, these are not particularly efficient means of producing usable energy. Photovoltaics and wind turbines are more efficient.

Doctor Morbius

Sure, why not? It worked on Gilligan's Island.

Sangetsu

Absolutely not. Think about the energy which was consumed to grow and transport the food you ate, and that this food provides the basic energy you expend on the bike.

intransit1217

https://www.youtube.com/watch?v=S4O5voOCqAQ

Problems I have with this video. A) He's a sprinter, not an endurance rider. B) I think they have the resistance set at max to make him put out max watts. C) Wouldn't gear reduction make it easier?


Separate idea: Spin bikes at gyms all plugged in to_______? Most spin bikes power themselves at least.

I'm going to say possible, but not efficient a this time.

PepeM

That would be the right answer.

coupster

And now for some real world results:

People Pedal to Power the 2014 New Year's Eve Ball : Discovery News

the answer is still no.

gregf83 

1 hour @ 300W = .3kWh of energy which is about 3c worth of energy around here. 300W for an hour burns about 1000 Cals. Try buying 1000 Cals worth of food for 3c. Even sugar costs about 12c per 1000 Cals.

FBinNY 

Human power will never be more than Plan C (or lower). It's useful when small amounts of energy are needed for short time frames. A classic example is hand crank powered emergency radios. Likewise a bicycle generator combined with a battery might make sense to power satelite radio receivers in very remote places.

But let's be real, a sustained 100 watts (if you could keep it up), doesn't go very far in term of meeting energy demands.

caloso

Watts are watts. Gears don't increase power.

FBinNY 

Yes, Watts is Watts. Force X Distance / Time. Changing the gearing lowers the force, but increases the distance by the same amount (percentage) the product (work) is the same.

Dave Cutter

Stationary bikes generating electric... not so much. But actual bicycles producing kinetic energy when ridden is very efficient... and easy to implement. Stationary bikes... are better for ruining otherwise lazy winter mornings.

blacknbluebikes 

There is no spoon.

intransit1217

Volts, Watts, and Amps

So how many amps was that german sprinter pushing?

Redhatter

There was a BBC programme that the ABC here rebroadcast it on their iView service, where they did an experiment exactly like this.

They had a team of cyclists with their bikes set up on rollers generating power for this one house and invited a family to try living in it for a day. The family were blissfully unaware of where their power was coming from until they met "the generators".

I can't recall what the program was called, might've been "The human machine" or something like that.

FBinNY 

Volts X amps = watts.

We can know the wattage, but that's not enough to answer that question, which depends on the specific circuit.

If, hypothetically, he sustained 600 watts, that could be 5 amps at 120 volts, or 50 amps at 12 volts.

Anyone who's ever worked on cars and seen the wire gauges used on battery cables, understands that it takes plenty of amps to get anything done at only 12 volts. By the same token, power transmission lines are run at high voltages so they can carry serious power without needing super sized copper wires.

Redhatter

Found it: BBC One - Bang Goes the Theory, 03/12/2009