[Power] Good day for a solar panel test

[Kim Blewett]

On 12/07/12 06:02, Richard Smith wrote:
>> First thing to note is the power cable is short but it is not far from an ideal length IMO.
> Yep.  That's going to be fixed in the production units.  Proposed
> length is 1.5 meters.  Just like the previous GP panel.  What do you
> consider the ideal length?
>
>> Too long is a pain I've found in the past.
> How so?  It needs to be long enough that the panel can go in the sun
> and the user or XO in the shade.  The samples that are getting used in
> Madagascar highlighted this because they were concerned about having
> the XO in the direct Africa sun.  It gets very hot and charging makes
> it even hotter.  The laptop is only rated for 50 degC operating temp.
Personally, I don't think 1.5m is long enough for our tropical 
conditions in PNG. 3m *might* be enough. I took a panel w/1.5m cord on a 
2-week trip and found that I had to keep moving around the shady hamlet 
to keep the panel in the sun and me in the shade. I have pics of 
"early-morning office", "late-morning office", etc. After "early 
afternoon" I could not find a place to sit and work while charging the 
computer. Αnd I usually had to work on my lap without a table-- not 
ideal for what we were doing.

If the cord had been long enough to set the panel on a roof (low, 
thatched house) and run it down through a window to a table inside or on 
a verandah, I could have used one side of the roof in the am, the other 
side in the pm. Now I've cut the wire and added an extension; we're 
using 5-6m for our adults, but that's

Granted, children have an easier time sitting on the ground to work than 
my older bones do, but if you're wanting children to share their 
computer work with their families it's a lot easier for a group to see a 
screen on a table rather than at ground level.

A longer cord would need to be heavier wire than what shipped with the 
original XO panels, I think. A hot, dry climate, with fewer tall trees 
shading the ground and even the rooftops, might provide more working 
locations where the panel could be in the sun for 1/2 the day at a time.

Kim
>
>> That Voc 18V, 1.140A Isc looks to make it ~15W @12V?
> 15W is the rated output of the panel but unless you have a lot more
> than 1000W/m^2 you won't get that.  When it gets to NOC it derates.
> See the data in my link below.
>
> Here's some more technical data on the samples.  This is for some
> pre-samples samples. :)  So you will notice some slight differences
> between whats in this info and what you actually have.
>
> http://dev.laptop.org/~rsmith/auria_solar_sample/
>
> Please don't copy it to the wiki.    Its for samples and not the
> official product.  Its not secret but I don't want people to use that
> info as the "official" info.  Just FYI for those of you who have
> panels.
>