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[aprssig] Re: now, 1.5 Lptops Per Child : power options?

Ray Wells vk2tv at exemail.com.au
Mon Dec 31 23:19:07 UTC 2007


Richard Amirault wrote:

> ----- Original Message ----- From: "Scott Miller"
>
>
>> I was thinking about this the other day... when I was in Hong Kong, I 
>> saw tons of little gadgets hitting the market that have little 
>> hand-crank dynamos.  Smaller ones than I've seen before in 
>> flashlights and radios, too - little LED lights and cell phone 
>> chargers and such.
>>
>> My first thought was to try building a regular windmill with one, but 
>> perhaps a simpler mechanism like a cup vane anemometer would work.  
>> If you could get a couple hundred mW out of it, that'd be enough to 
>> power remote sensors and such where solar power might not be suitable.
>
>
> (snip)
>
> One thing you forgot .. when you are generating electricity with a 
> crank generator .. you are doing *work*.
>
> I bought one of those emergency radios with a hand crank as one of the 
> power options. When I got it the first thing I did is turn the crank 
> ... EASY .. in fact it was *too* easy.  The next thing I did was read 
> the  instructions .. then I plugged the rechargeable battery pack into 
> the charging circuit (it came unplugged from the factory) and tried 
> cranking again ... it was considerably HARDER to crank now!!   Hard to 
> tell but I'd say at least 4 or 5 times harder to crank.
>
> My point is that a windmill or anemometer needs to overcome this 
> resistance to generate electricity .. and it is a considerable amount 
> of resistance believe me. Unless your windmill or anemometer has 15 or 
> 20 foot arms .. or you plan on waiting for a hurricane .. I don't 
> think it will work.
>
> Richard Amirault
> Boston, MA, USA
> http://n1jdu.org
> http://bostonfandom.org
> http://www.youtube.com/watch?v=J7hf9u2ZdlQ
>
>
Remember how much harder it was to pedal a bicycle with one of those 
little tyre-driven alternators to supply a couple of lights.

Ray vk2tv




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