Anyone have a rough estimate (or actual knowledge of) how much energy can be generated from a stationary bike?

Question

In Watts

Answer 1

Hmm that's an interesting question. Over how much time would you want to be generating this energy? You can calculate it on a mobile bike and assume the same amount could be generated from a stationary bike...

If you ignore energy lost as heat due to friction, the kinetic energy of a guy on a bike is 1/2 * total mass * velocity squared. Say the guy weighs 150 pounds and the bike weighs 50 - 200 pounds total, or close to 100 kg. Depending on how fast you can bike, you can get up to 25 mph. More realistically for a long bike ride let's say you go about 16 mph, or ~8 m/s.

So then total kinetic energy is 0.5 * 100 * 8 = 400 Joules. That's the energy you're putting out at any given time.

If you want Watts, that's actually a measurement of power, not energy. That's trickier, because you need to know how much force you're putting on the bike to counteract friction, as mechanical work is essentially force times velocity.

Let's just guess that if you stopped pedalling, you'd come to a stop in about 30 seconds. That's a deceleration of from 8 m/s to 0 m/s in 30 seconds, or about 0.25 m/s^2. Force is mass * accel, or 100kg * (-0.25 m/s^2) = -25 Newtons. So to counteract that, you're putting a 25 N force on the bike.

So then the power is basically 25 N * 8 m/s = 200 N-m/s = 200 Watts.

That's a very crude calculation, but it gives you a ballpark. Wow, I matched Bob's numbers pretty accurately. Nice.

Answer 2

An ordinary person can pedal one at 100 watts for maybe an hour, and hit a peak of 200-250 watts for a short time. An athlete can easily double those numbers.

Then, of course, there's Lance:

"Armstrong can ride up the mountains in France generating about 500 watts of power for 20 minutes, something a typical 25-year-old could do for only 30 seconds. A professional hockey player might last three minutes - and then throw up."

Answer 3

Good answers Bob and Dana.
If you want a real rough estimate, I would say if you wish to run your desk top with a CRT monitor on pedal power from a battery through an inverter then you probably have to pedal three hours to get one hour operation .
I'm looking at switching to alternative power soon and haven't done all the sums yet so that is just a wild guess.

Answer 4

not a lot..

A good analogy is the electric powered bicycle conversion kits... They use appx 400 to 600 watt motors.

If it takes about 6oo watts to drive a bicycle 20 mph on level ground... then you can figure that a person pedalling isn't going to provide more power output for any length of time.

Answer 5

Ed Bagley Jr uses his to make his morning toast.