[OLPC-Peru] [Server-devel] solar Re: Extreme Linux Server Available to North America

[Sameer Verma]

Yama Ploskonka wrote:
> Hmm.  John's words sounded as if y'all had already a particular model 
> picked up.  I interpreted that from the "10 W" detail.  I am still at 
> the stage of figuring out the cost/performance sweet spot.
>
>  > 10W Solar panels will be deployed with the first
>  > laptops in areas without power.
>
> Price is a major concern for me.  All over-the-counter laptop solar 
> options I've come across seem to be priced for "Shibumi" compradores or 
> UN field projects. :-(
>
>   
Hi Yama,

I don't have specs for the "official" OLPC solar panels, but I've been
experimenting on my own. I have the red panel you've been using from
HarborFreight
(http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=44768)
and its output is only 1.5W peak. I didn't get much luck with that one.
Perhaps if we had two of those in parallel...

I looked elsewhere and found Volkswagen panels (part # 1 CO 915 687 D)
that cost me around $20 + shipping on E-Bay (YMMV). These are panels
that VW attaches to its cars' windows before shipping them. The panels
trickle charge the battery while the cars get transported. Apparently
this helps with not having to deal with a dead battery and resetting the
VW's onboard computer when the cars reach the dealership. The panel
comes with  charge controller that helps in preventing reverse flow of
current. The connector on the panel is an OBDII
(http://en.wikipedia.org/wiki/OBD-II#OBD-II) type, but can easily be
replaced with anything else. I chose RCA type phono connectors on a whim
and its paying off. See http://sameerverma.org/blog/?postid=171 for
details.

The older VW panels (silicon based) output 3.2 Watts at around 18 Volts
but the newer ones (looks like thin film) do 4 watts at around 12 to 14
Volts. I've had much success with the newer one. I usually park my car
on the upper deck at San Francisco State Univ. where my car gets much
sunlight. I typically get 9Volts + at 8:30am and it keeps going until
around 5pm. The voltage peaks around mid-day at 13.9 Volts. With this
setup, I go from zero (or close to zero by running the laptop until it
dies) to 20% approx in one day. About four days in a row, and I get 90%
+ charge. I have suspicions that the charging isn't linear, but I
haven't logged any of this.

A few days ago, I got a second panel and fitted it with the same RCA
phono connector. Next, I bought a Y-connector from Radio Shack so that I
could combine the power of both panels in parallel. These connectors are
designed for audio, but they work well for what I am doing. Now, with
two panels in parallel, I get 65%+ charge in one day! At peak, the
panels should be spitting out 4 + 4 watts.

On the other side of the equation, I also did some tests with a
Kill-a-watt device to see what the XO will pull in in terms of wattage
when charging, running, etc. I got:

XO turned off, empty battery: 21 watts
XO turned on, empty battery: 21 watts
XO turned on, battery removed: 10 watts (stays fairly steady during boot up)
XO turned on, battery removed, backlight turned off: 7 watts
XO turned on, battery removed, backlight turned off, camera+mic on: 8 watts

See more http://lists.laptop.org/pipermail/olpc-open/2008-March/000635.html

In all, its been a terrific learning experience. If this is something
that others find useful, I'll put it up on the wiki.

cheers,
Sameer

-- 
Dr. Sameer Verma, Ph.D.
Associate Professor of Information Systems
San Francisco State University
San Francisco CA 94132 USA
http://verma.sfsu.edu/
http://opensource.sfsu.edu/


> If OLPC (also very price conscious :-)) does come across a specific 
> provider, let's hear!
>
> Thanks,
>
> Yama
>
>
>
> Martin Langhoff wrote:
>  > On Sat, May 3, 2008 at 11:46 AM, Yama Ploskonka <yama en netoso.com> wrote:
>  >>  What is the provenance of those panels and is there any publicly
>  >>  available information on their performance re:XOs the rest of us 
> can use?
>  >
>  > I'm not sure which of the solar panels / blankets it is. There is
>  > really good infoin the wiki, but it's spread across several pages -
>  > the first 10 or so hits for
>  > http://www.google.com/search?q=site%3Alaptop.org%20solar%20panel are
>  > good
>  >
>  >
>  >
>  >
>  >
>  > martin
>
>
> Martin Langhoff wrote:
>   
>> On Sat, May 3, 2008 at 11:46 AM, Yama Ploskonka <yama en netoso.com> wrote:
>>     
>>>  What is the provenance of those panels and is there any publicly
>>>  available information on their performance re:XOs the rest of us can use?
>>>       
>> I'm not sure which of the solar panels / blankets it is. There is
>> really good infoin the wiki, but it's spread across several pages -
>> the first 10 or so hits for
>> http://www.google.com/search?q=site%3Alaptop.org%20solar%20panel are
>> good
>>
>>
>>
>>
>>
>> martin
>>     
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