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107 comments on On likely alternatives to conventional oil

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copperweaver on November 28, 2005 - 8:06pm Permalink | Subthread | Comments top
I have a kookie idea........

It seems logical to harness the energy that so many N. Americans produce while exercise on stationary bikes and stepping machines. What if we were to build exercise machines equipped with generators( linear alternators perhaps ) and stored the energy burned into batteries.  I know it's been done to some degree and would only produce a tiny fraction of the electricity we use, but it would be one tiny pice in the huge puzzle.  The best applications for this electricity would probably be lighting(LED?) and electronics.  I have envisioned wiring a whole health spa this way, but a home personal use model would be much easier to maintain than whole network.......  

What if we had tiny hydro powder generators in skyscrapers that harness the energy of wast water flowing down to the sewer?

I know these are not solution to PO but they might lead to greater efficiency.............

Please pick it apart and tell me why it would not be practical.  

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DIYer on November 28, 2005 - 8:40pm Permalink | Subthread | Parent | Comments top
When I was small, my dad used to have an old hand-crank ring generator from a military surplus field telephone, of WWII vintage. He was a radio ham and had lots of such stuff around.

Anyway, and to get to the point, it was a surprise to me how much effort is required to light a 15-watt incandescent bulb. The generator made about 200V p-p at about 10-20 Hz depending on how fast it was cranked. If you put a bulb across the terminals it would suddenly get much harder to crank and the voltage would drop. Granted, I could probably light a 60 watt bulb now, given the right kind of generator on a stationary bicycle. But it's a -lot- of work.

The output of all those sweaty gym dwellers probably wouldn't be enough to keep the lights on at the gym, much less put out on the grid. And waste water is also not particularly energy-dense.

Bottom line is that any devices for collecting this small amount of energy would cost quite a lot, and could be put to better use harnessing, for example, wind power.

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jkissing on November 28, 2005 - 9:13pm Permalink | Subthread | Parent | Comments top
The lights in the gym are nothing compared with the ac load. Each person normally puts out 600w of heat, no doubt larger when riding a bike. Then, there are the (hot) showers taken afterwards, and then the ac necessary to cool the shower rooms, etc. Huge net loss. Most can't imagine how much energy it takes to run modern machines.
THink about it like this... Most cars have peak output of at least 100hp, some much larger. Now imagine 100 horses, all expending max energy as they try to pull the car uphill at 30 mph.  Next, imagine feeding the herd, cleaning out the stable, etc.
Back to a light bulb... One horse at full throttle can generate the energy to light around 10 100w bulbs.
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copperweaver on November 28, 2005 - 9:25pm Permalink | Subthread | Parent | Comments top
Your points are valid, but I still see possibilities for home use.    Advances in efficiency could be used to provide an alternator that would fit the job.   My old landlord use to design and build linear alternators for NASA, Dod, and private firms, and from what he told me, they had very high efficiency.   LED's would probably be a better choice  than incandescent bulbs for such a small source of power.  

I think the biggest hurtles to finding uses for micro power generation, are economics.  So many consumer products are designed to be disposable.  I suppose that makes them cheeper to manufacture.  If products were made to last, we would consume less, but that would not be good for the economy.............

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mcain6925 on November 28, 2005 - 9:48pm Permalink | Subthread | Parent | Comments top
An article summary here reports that Floyd Landis was measured over the entire course of the Tour de France. Average output, 232 watts. During the final time trial, where he finished sixth, 379 watts for 75 minutes. While training, maximum of 649 watts for five seconds. Figure that the average person at the gym comes in way below those figures... I know that the Tour racers average at least twice the velocity that I can manage, and energy goes up as the square of the velocity, so I figure I would be pressed to put out 60 watts for any kind of sustained time.
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Boof on November 29, 2005 - 2:49am Permalink | Subthread | Parent | Comments top
We could have a new unit of power called the 'metabolic'. Normal air pressure of 14 psi or 101 kilopascals is called an 'atmosphere' which is a little more than 1 bar in metric units. To illustrate the term you might put 2.5 atmospheres of air pressure in your tyre. If say 1 metabolic = 200 watts then a middle class person may burn more than 10 'metabolics' or 2000w in continuous averaged use of food, fuels, electricity and embodied energy depreciation of houses and large items. Seen that way that makes us by far the most wasteful animal that ever lived.
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Engineer-Poet on November 29, 2005 - 7:10pm Permalink | Subthread | Parent | Comments top
Per-capita use of energy in the USA is about 10 kW, so you'd be closer to 50 "metabolics".

OTOH, the choice of reference is problematic.  Do you pick an athlete or a couch potato?

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Twilight on November 28, 2005 - 10:36pm Permalink | Subthread | Parent | Comments top
And in a dark room a 7W nightlight bulb puts out a lot of light.  Around the holidays we often have a single 7W bulb in a couple of windows in a room - once your eyes adjust, it's surprisingly bright.  Imagine what someone from the 1800's would have thought of a 7W bulb!  My point being that we need to consider revising our expectations of power use - and we have the advantage of things like compact fluorescent bulbs.  For like 15W I get 60W equivalent of light.  

BTW - the 6 pack of these bulbs at Home Depot is quite a deal at under $10.  The color temp is pretty good too, and they start a little slow when cold, which is nice in the morning!  I've got at least 24 of them now, too bad they don't have any that fit in the small-base candle sockets of that brightness.

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Stoneleigh on November 29, 2005 - 11:37am Permalink | Subthread | Parent | Comments top
They have ones that will fit candle bulb sockets where I live. I got mine at IKEA. They're more expensive than the regular compact fluorescents though, and they don't look anything like candles.
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rtz on November 28, 2005 - 9:01pm Permalink | Subthread | Parent | Comments top
In the 1973 movie Soylent Green, it appears there was a bicycle that was used to charge up some batteries to power their lights and TV...

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107 comments on On likely alternatives to conventional oil

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