tony_anderson at usa.net
Fri Oct 28 01:16:19 EDT 2011
I think this would make a great problem for the kids to work on -
involves a lot of math and science (aside from phys. ed. benefits).
On 10/27/2011 07:16 PM, Hal Murray wrote:
>> Has anyone estimated the work required to charge an XO? Mike Lee gave a
>> demo some time back at the Washington D.C. Learner's Club which seemed to
>> show that it would be a difficult workload for an adult athlete to charge a
> You don't have to estimate. It's easy to measure.
> If you are interested in things like this, you should get something like a
> Kill-A-Watt. They are down to $20 (plus shipping and such).
> There are other similar units.
> It takes about 20 watts to charge an XO-1. Running uses 5 watts. The
> backlight is a few more. I think the limit is the front end so it will take
> longer to charge the battery if you are also using the XO.
> If it takes 2 hours to charge the battery, that's 40 watt hours.
> World class athletes can put out close to a horsepower for an hour or two.
> To do that, you have to use large muscles, so think legs rather than arms or
> hands. (Bicycles are really good at extracting energy from a human.)
> A horsepower is 746 watts. That's enough bigger than 20 that I think it
> would be reasonable for a normal person to charge an XO from a well designed
> setup. It will take a while.
> It might be hard work for a small kid, or take longer if they can't generate
> enough power.
> A good cyclist could generate .4 horsepower indefinitely.
> If you like human powered flight, Morton Grosser's Gossamer Odyssey is a good
> read. It's got a section on how much power you can get from a human but I
> don't remember any details.
> Bicyclists probably have lots of good data.
> There is a guy in Silicon Valley who runs most of his house from solar and a
> bicycle. He's got a stationary bike setup to feed power into his system.
> He gets 24 watt hours from his morning workout. He didn't say how long it
> More data from the same guy:
> Here are some more numbers:
> Scroll about 1/3 of the way down and there is a picture of an XO.
> There is an old joke/story about how to cure couch potatoes. Setup their TV
> so it is powered from a stationary bike. If they stop pedaling, the picture
> goes away.
> I have a couple of friends with their displays and keyboards setup so they
> can use their PC from a treadmill. It's a standard treadmill rather than a
> power generating setup.
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