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Just for fun - human-powered, bicycle-based generator

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Just for fun - human-powered, bicycle-based generator

Old 02-17-21, 07:47 PM
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Originally Posted by HillRider View Post
Years ago Buhl Planetarium here in Pittsburgh had, as one of its scientific displays, a bicycle powered generator that had the rear tire driving a friction roller. It was wired to a panel board with a series of household light bulbs from 25 to 150 watts. As you pedaled faster the bulbs lit in succession. The thing must have had huge drag losses since both the effort and cadence needed to light the 150 watt bulb were very high. Most of the kids who tried it could get the 100 and maybe the 150 watt bulb to light for, at best, a few seconds.
Hah HillRider, you and I must be the same Pittsburgh vintage! I remember that bike generator at Buhl Planetarium from a school field trip. I think I spun it up to the same 100 watts and maybe got a little flicker on the 150. At least I saw it flicker if no one else did!
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Old 02-18-21, 04:02 PM
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Over 20 years ago my wife and I stopped at the South Texas nuclear power plant visitors center. They a a bike powered generator and I lit a 60 watt bulb and powered a tv for a few seconds. It was a lot of work.
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Old 02-18-21, 04:08 PM
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someone should come up with a gym based power plant to serve its local area... could call it "power house" gym.......................................
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Old 02-18-21, 04:59 PM
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Not to put a damper on your project, but what are you planning on powering? I figure it would take half the peloton in the TdF to power my home for a day if they were put on stationary bikes capable of producing electricity for my home.

Twice to three times that many if they were average recreational cyclist like me.
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Old 02-19-21, 12:13 PM
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The bicycle is a marvellous invention for human transportation requiring very little power (and no oats, hay, vet bills, or stable clean-out). It helped expand the gene pool of small English villages which were too far apart to walk in search of a mate. Its virtue is its light weight compared to the weight of the payload and power plant yet still allowing it to exploit the efficiency of a wheel rolling on a road. Those virtues compensate ingeniously for the deficiencies of the human body as a power generator....and even then you can’t go very fast. So one should not expect great things from hooking a bicycle up to a generator unless you were just trying to salvage some energy expended anyway for some other purpose, like exercise or weight reduction.

We all know that bicycles are highly efficient in converting modest amounts of energy into locomotion. But you have to consider the cost of fuel. Food is expensive. Bottled water, not to mention energy drinks, is much more expensive than gasoline. How much does a quantity of, say, beans or canola oil cost that contains the same fuel energy as a litre of gasoline? The human body is about 23% efficient in converting food energy per second into shaft power, not much different from a car engine but less than a large modern steam power plant. (Gas turbines are even better because the “hot side” is hotter.). And remember many foods with high energy density have to be cooked, at a cost, to make them edible. Can’t do much with a bag of lentils till they’ve been boiled a while.

So even if you had a pretty good set-up for generating electricity with a bicycle for small jobs, you should figure out your cost per kilowatt-hour before declaring success, including amortization of capital costs just as the utility does. If you plan not to eat, and thereby lose weight, that’s different.

One could argue that electricity derived from food doesn’t require burning fossil fuels, if you care. (I don’t, particularly.) But it does require substantial consumption of fossil fuel and emission of GHGs to grow even beans, never mind beef. And if your grid electricity is pretty green anyway, your carbon footprint might rise from eating enough extra food to generate useful amounts of electricity yourself.

These quantities would all be trivial in the grand scheme of things. I just find the thought experiment interesting while waiting for the snow to stop so I can use my human-powered snow-clearing device on the driveway.
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