Generating electricity with a bicycle

John taking kids for a ride
Any one who knows me, knows that I have used bikes as a major part of my transportation for much of my life. I supose this comes from living for over 25 years in Taiwan and Japan where bike riding is  not a sport but a form of transportation. I own a dozen or more bikes. One for each occasion. As well as have 1/2 doz bike trailers. Both commercial and ones I have built. As a experment in Japan I  onces did a house move using nothing but my bike and bike trailer I had built. Yes, even for the Japanese this was extreme and did get me strange looks.

My son on way to his painting job
People often ask me what about generating electricity with pedal power. I tell them I'm going to start an exercise gym. Instead of people just "throwing" away their energy I'm going to charge them to generate my electricity as they loose pounds. Of course this would never work because as soon as they found out I was going to sell what they were throwing out they would not pay me any more.

One of my students taking his moms bike home.
Anyone who has dabbled in energy know that pedal powered electricity isn't a very good idea. Pedal powers greatest strength is in mechanical energy. That is why bikes are such an amazing efficient tool. A very good explanation of why generating electricity is not such a good idea can be found at an excellent site called Saving Electricity. Here he says:

"Yes, you can make energy with a bicycle. But it's unlikely to save you any money, because it generates such a tiny amount of electricity versus the cost of the setup. And it might not even be green energy, once you consider the energy that's used to produce your fuel (food).

A typical bike generator can produce 100 watts. If you pedal for an hour a day, 30 days a month, that's (30 x 100=) 3000 watt-hours, or 3 kWh. Since the average cost of U.S. electricity is 12¢/kWh, that one month of pedaling saves you $0.36. Congratulations. If the system cost $400, it would take only 93 years to pay for itself.

And that's before we consider the cost of food. If you're overweight, like most Americans, then you can consider your biking energy "free" since you could be burning fat. Likewise, if you ride the exercycle instead of doing some other kind of exercise that you were going to do anyway, then the cost of your energy is also free. But if you're not overweight and not exercycling instead of some other exercise, then you'll be buying more food to fuel your effort. Since it takes about 1 calorie to produce 1 watt-hour of electricity, your month of pedaling would require 3000 calories. With the cheapest food you can buy, oil or flour, you're looking at $0.85 to create $0.36 of electricity. Some savings. Other foods are even worse: Figure $5.41 for Cheerios, $6.15 for bananas, or $22.22 for Big Macs.

But money aside, isn't bicycle power a form of green energy? The answer is that it depends on where you get your calories. Just as with the money costs, if you're overweight or exercycling instead of other exercise, then yes, the (piddling amount of) energy you create is indeed green. But if you're already at a decent weight and not substituting for some other kind of exercise, then you're going to eat more food to power your effort, and the pollution caused to produce the food for your cycling is more than the pollution caused by geting the energy from the grid. 3000 extra calories from what a typical American eats will make 30 lbs. of CO2e, or 15 lbs. for a vegan. By comparison, the energy from the power plant makes only about 5 lbs. of CO2e to generate the same amount of electricity.

But what about putting the generators in gyms where people are exercycling or using ellipticals anywway? Okay, let's take a look at the numbers: Texas State University put generators on 30 elliptical machines at a cost of $20,000. If we generously assume that each machine is used 1/3 of the time over a 12-hour period, that's 30 machines x 1/3 utilized x 12 hours x 100 wH/hr x 1 kWh/1000 wH x 360 days/year = 4320 kWh/year, which is not enough to power even one typical American house for the same period of time. And cost-wise, the energy saved at 12¢ per kWh is worth $518 per year, so the payback time is close to 40 years, not counting maintenance or opportunity cost. Yeah, it's green energy, because otherwise the exercisers' energy is wasted."

As he states and those around me constantly hear me preach when they try to promote new solutions to our energy problems. The far easier solution is to just stop using ridiculous amounts of energy in the first place. A single family can easily save more energy by making some modest changes than the entire fleet of ellipticals at TSU can produce. His website gives concrete examples of how to do this.

PS: I learned this lesson well when one of my jobs in the solar industry, was monitoring solar houses for the US government, to determine if the solar was working as advertised. My data showed me that once you reduced the amount of energy need by. incorporating simple energy savings design (2 x 6 walls, more insulation, building a smaller house, solar orientation, etc,) you saved so much money and energy it wasn't worth installing solar.


  1. I have been trying to reduce my energy (read: fuel) consumption by riding my folding bike to work - at least part of the way. I still have to drive sometimes, but since the bike fits in my trunk, I don't have to drive nearly as much - I just take the bike out, unfold, and I'm on the road, pedaling away.


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