Potential Energy

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an escalator driving a generator ? piezo-electric stair treads?

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When we go upstairs we spend a lot of energy that gets stored as potential energy. When we go downstairs we waste all the potential energy. Couldn't anyone invent a good way of coming down so the potential energy could be converted to other forms of energy that could be converted to electricity when needed??

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How much are you willing to spend on a contraption to power a 100W light bulb for less than 1 minute?

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Well in *theory*, yes you certainly could. Something as simple as a bucket and rope tied to a pulley turning a shaft. When you want to go downstairs you just climb into the bucket and let it lower you through a hole in the floor. Of course there will be *some* losses.

But lets look at just how much energy we're talking about. Raising a 200 lbm man up 10 feet in normal gravity would put 2000 ft-lbf of energy into the man. If you could recover *all* of that, that is a mere 0.75 watt-hours (not kW-hr, just watt-hour). So if he goes up the stairs 20 times a day for a year, he'll have used 20*365*.75 / 1000 = 5.5 kW-hr of energy. Recover

*all* of that perfectly and you have about \$1 worth of electricity for the year.

Going up stairs 20 times a day is great exercise, but it won't generate much energy for you.

daestrom

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"Charles" wrote in news:h0cdhv\$btv\$ snipped-for-privacy@news.eternal-september.org:

If you trained a bunch of st. bernards to keep doing it all day and night the dog food costs would still kill you :(

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And waste-disposal costs :)

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I worked on a program for defense dept. The idea was to keep soldier's battery packs charged (a modern infantryman carries a lot of battery weight). One idea we looked at incorporated piezo-electric strips in the sole of shoes. We didn't win the contract.

Modern magnetic design software is extremely good, and is allowing very efficient small generators to be designed these days. Notice the profusion of wind-up flashlights. If wearable computers ever make it to mass production something like that will likely appear to keep the batteries for those computers charged- or at least extend the life.

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But then there is the automatic watch whichh is wound up by a little pendulum inside the watch. Just moving your hands about keeps it wound up. Or did. I haven't seen one for years

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The difference is that you need some tens of watts to power a laptop (e.g., netbooks need up to ~30W, "regular" laptops need up to ~65W, and "high end"/gaming laptops might need ~90W or even more), whereas a match can be powered from milliwatts -- or even microwatts.

If it's done efficienctly, having a human directly generate 30W (by, e.g., peddling a generator) is not a huge burden (although it's certainly noticeable), but it's still huge compared to how much "incidental" or "waste" energy that we're currently harvesting from humans.

(Also note that you specifically want to harvest what is otherwise wasted energy from humans: Feeding humans more specifically with the intent of producing electrically is not particularly efficient at all. I've read somewhere that rice is a good, inexpensive food to use if you insist on this approach, though. And granted, there are many people out there with many megajoules of excess energy in the form of fat that we could spare to harvest, too...)

---Joel

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Liposuction all the fat from lawyers & politicians heads and we could solve the world's energy problems for at least a generation. ;-)

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Yeah, but if you set up triangular blocks of land and at one point you put a McDonalds, the second point a biofuel outlet and the third point the liposuction clinic you could fuel the world for ever.

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Its your idea, so run with it.

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You can't have a sense of humor, if you have no sense!```
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I think that McDonalds and shell have it all tied up.

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A lot of restaurants and gas stations closed down when gasoline hit \$4+ per gallon, so get busy,

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You can't have a sense of humor, if you have no sense!```
• posted

Be sure to capture the energy from rain falling too. Especially when it runs down the spout from your eavestrough.

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In alt.energy.homepower RogerGibb twisted the electrons to say:

One of the micro-hydro places near me has it's gutters set to dump the water into the mill-race it's on. Okay, I'm never going to claim it (or the micro hydro plant further down said mill-race) generates significant amounts of power due to this but I do think it's an elegant simple piece of design.

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So let's see, if you have a 45x28 roof, 20 ft up in the air and you get 4 inches a rain (quite a bit in most areas), and you manage 100% energy recovery, that rainstorm would generate about 522480 ft-lbf of energy.

A whopping 197 watt-hours.

In my case, I wouldn't bother.

daestrom

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