I have been curious about this for some time now, and I figured I would run it by you fine folks to see what sort of response the idea gets.
Mods, if this is in the wrong forum, let me know.
Would it be possible, either from a physics stand point, a financial standpoint, or both, to make a power plant that generates electrical power via human effort?
My idea is that you would have a turbine based power plant, but rather than water or wind, the turbines would be powered by people on treadmills, or bikes, or something of that sort.
You would pay folks to run on a treadmill, or crank a bike for a shift. Proper gearing would insure that the minimal speed of a human could be upgraded to something that would actually create a decent amount of power.
I picture something the size of a good gym, or a big box store. No pollution, it could be placed anywhere, and as people currently pay money to go to a gym and do EXACTLY this for an hour, I can’t imagine you would lack for folks who would like to be paid a minimum wage to sit on a bike for an hour or two.
Basically you can’t get enough energy from humans to make any money. A reasonably fit person can produce somewhere around 100 watts of useful power for a sustained amount of time. With 10 people working for 1 hour, you can produce a whopping single kilowatt hour of energy. At current prices, that’s worth about 10 cents.
A quality exercise bike costs what, $500ish? If you only made money by selling energy, you wouldn’t even pay off a piece of equipment until someone’s used it for 50,000 hours. And that’s assuming free labor, and no other overhead costs.
Well, there’s no reason you can’t hook up a stationary bicycle to a generator, and no reason you couldn’t hook up a whole gym full of exercise machines to generators.
But you’re not going to get all that much power. Peak human mechanical power output for top athletes is about 1/2 a horsepower for short bursts. Long-term, lets’ very generously assume half of that, or 1/4 horsepower. That’s less than 200 Watts.
So you’ve got a huge gym with 50 people cranking away. That’s 10 kilo-Watts of power. Enough for maybe 2 or 3 houses.
Or to put it another way, that electricity – generated by 50 people – costs about $1-2/hour.
I don’t think you’re going to make it as a business paying for humans to generate power.
*ETA: Curses! darn your german ninja skills, lazybratsche!
At least I’m providing independent confirmation *
Humans need fuel to produce energy. Factor in all costs of food, delivery, maintaining supply, inventory, losses and the upkeep and depreciation of all equipment and related infrastructure and it’s a big-time loss.
There is increasing development in piezo-electric generators that produce electricity from people walking on sidewalks, cars traveling on roads, etc… Because these devices have no moving parts they are relatively inexpensive, and have low maintenance costs. But they don’t produce much power. The idea is to charge a battery sufficiently to power lights and signs, similar to the use of solar panels you see along the highway.
I have read of a few gyms that hooked the machines to generators, and used the power to help light the place. But it’s mostly just a gimmick: The exercisers aren’t even enough by themselves to keep the lights on; they still need to get the bulk of their power from the grid.
So far, we’ve been looking only at the power a human can expend while exercising. To operate the power plant in a more permanent way, you have to start counting the cost of feeding these people, which will probably make it even less efficient.
You may be better off just buying food, setting it on fire and using the heat to drive your turbines…
Not only is it possible, it has a history dating back to antiquity. At least if the definition of “power used to run machines” rather than “power used to generate electricity” is used. Take a read of this site on the history of the treadmill.
This paragraph jumps out:
Realistically, though, unless the power generated is continuous and above a certain minimum, it can’t do much of any value. That’s why it has always been forced out of crews of unwilling participants. Individuals can’t do very much. Even dedicated environmentalists like actor/activist Ed Begley Jr.
If it were easy to store electricity, this objection wouldn’t matter as much. That’s being frantically studied because it would be the answer to many problems. Until then, this idea gets proposed every day but nothing much comes of it because conglomerating energy in mass quantities is another one of those things that is always 25 years in the future.
I thought this would be a good idea for junior and senior high schools gym class. Let them play on their game boys and Xboxes while bicycle and treadmills produce energy for the schools. Exercise for the kids, they still get to play while NOT on the couch, and the school gets reduced energy cost.
A bbc tv programme called Bang Goes The Theory made a human-powered house as an experiment. Hard work for the team of cyclists they used, and brownouts were a constant threat.
The energy powering the humans doesn’t come free either, as the people will consume more food. Probably more efficient just to born the food to power a steam turbine or something.
That’s the part that I was going to mention…they’ll probably eat more then they’ll save do to the extra work out.
Whenever I hear about someone (that’s already in decent shape and doesn’t need the excercise) telling me they’ve decided to bike to work for the summer and then going on to tell me that since work is 5 miles away from home they’ll save $25 a month I always wonder if they’ll end up eating they extra $25 dollars. You’ve got to figure if someone that doesn’t work out suddenly starts biking 200 miles a month they’ve got to be eating more.
Did you even read my post? Electricity costs around 10 cents/kWh, exercise equipment costs hundreds of dollars, so it’d take forever to pay off. Going by my 50,000 hour payoff estimate, it’ll take 30 years of constant use whenever school is in session before the school makes back the cost of buying equipment.
Of course, most Americans already eat more Calories than they should, so the result might just be that they lose weight.
That said, a human on a bicycle is more efficient than a car, over a given distance, even when you account for the extra food. This is a combination of the bike being lighter, having a smaller cross-sectional area, and going slower.
I think the goal for optimal use of piezoelectric playground equipment is to install it when you’re first building the playground, i.e., you’d be spending the money on some kind of equipment anyway.
Likewise, as TriPolar notes, the fundamental idea with piezoelectric infrastructure is to harness power from energy that people are already expending anyway, in walking on sidewalks, pushing revolving doors, driving cars along roads, etc., rather than harnessing them to machines specifically for power-generating exertion.
See this site for some descriptions of innovative piezoelectric equipment in developing-world playgrounds and developed-world urban infrastructure.
:dubious: Considering that a 5-mile bike ride burns about 200 calories, the person would be using an extra 400 calories 5 days a week (not counting days off for bad weather, etc.). They could probably get that 400 calories for under a dollar.
Also, I think you need to make up your mind whether this person is someone who “doesn’t need the exercise” as you first claimed, or “doesn’t work out” as you subsequently stated. If they’re not already exercising enough to keep fit without the bike rides, then the bike commuting will be making them healthier, which on average means less expensive medical care.
However, you’re right that the overall savings on gasoline use from bike commuting are pretty much negligible. Avoiding car use only produces major cost savings when you manage to avoid owning the car at all.
I should have clarified that. By ‘doesn’t need the exercise’ I was implying that they don’t have some extra fat that they can burn for energy during the ride.
Later, when I said ‘doesn’t work out’ I meant to add on that that they aren’t replacing some daily workout routine with bike riding. It’s different if they currently get home from work and run on the treadmill for an hour and now, instead of that, they ride to work.
Basically, I just wanted to make sure that I’m being clear that some people will be able to ride to work every day without having to eat extra food (like people that will replace part of their workout routine), but some people will have to spend more on food if they are going to start riding to work (people that don’t work out and are going to start riding to work).
Yup, I read it. What makes you think I was talking to you? I didn’t see a cite for your numbers, and I was just making a comment. Geez, I love the way some posters love to jump all over it…
You were saying that your idea made a lot of sense, but a cursory look at the numbers (which had already been posted by that time) shows that it doesn’t make much sense.