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Potential Energy - Page 2

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Posted by z on June 6, 2009, 4:56 am

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

Posted by Lawrence Statton on June 6, 2009, 2:24 pm

And waste-disposal costs :)

Posted by Don Stauffer on June 6, 2009, 2:38 pm
 karela wrote:

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.

Posted by harry on June 9, 2009, 8:46 pm
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

Posted by Joel Koltner on June 9, 2009, 9:29 pm
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,


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