harvesting energy

[Sameer Verma]

On Thu, Oct 27, 2011 at 12:00 PM, Paul Fox <pgf at laptop.org> wrote:
> alan jhonn aguiar schwyn wrote:
>  >
>  >
>  > I think that not is for "an adult athlete"...
>  > In Uruguay, in a site that not have electricity.. The childrens use this
>  > dispositive..
>  > And not need much effort than ride bikes for a while...
>  > Regards
>  > Alan
>
>
> bear in mind that the *minimum* time it takes to fully charge a single
> XO laptop is roughly two hours.
>
> once you're providing all the power the laptop can take at any one
> time, providing more (i.e., by being a stronger athlete) doesn't do
> any good (unless maybe you want to charge two laptops at once).
>

The playpump approach (somewhat like a cuckoo clock) is better because
it stores the water in a tank (potential energy) and can be used to
turn a wheel/crank as the water flows from the tank.

cheers,
Sameer

> two hours is a long time to engage in any, even moderate, physical
> activity.
>
> it's best to think of this problem in these terms:  what is the ratio
> of "usefulness time" to "charging time".  for the current laptop models,
> that ratio is about 2 to 1 -- if you charge the laptop for 1 hour, it
> will run for about 2 hours (very approximately).  this isn't a very
> good ratio -- clearly 10 to 1 would be much better -- charge for an
> hour, and get 10 hours of use, or, charge for just 12 minutes to get
> the same 2 hours of use.  as noted below, we hope for 1.75 to be much
> better (but probably still not 10 to 1).
>
> paul
>
>
>  >
>  >
>  > From: cjlhomeaddress at gmail.com
>  > Date: Thu, 27 Oct 2011 14:29:19 -0400
>  > Subject: Re: harvesting energy
>  > To: tony_anderson at usa.net
>  > CC: devel at lists.laptop.org
>  >
>  >
>  >
>  > On Thu, Oct 27, 2011 at 2:14 PM, Tony Anderson <tony_anderson at usa.net> 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 laptop.
>  >
>  >
>  >
>  >
>  >
>  > Tony
>  >
>  >
>  > That equation will likely change substantially with the XO 1.75.
>  >
>  > cjl
>  >
>  >
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> =---------------------
>  paul fox, pgf at laptop.org
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>



-- 
Sameer Verma, Ph.D.
Professor, Information Systems
San Francisco State University
http://verma.sfsu.edu/
http://olpcsf.org/