POSTSCRIPT:

I have gone back and looked at the dimensions more closely since I wrote
the material below. .
I have greatly downsized my initial size estimate, alas.
Rather than rework all the below by reducing power input to about 25% !!!
of what I first guesstimated. (I overestimated the total size and the
proportion of area that was PV panel.
Make the PV panel twice as wide and my comments below apply.

As it stands I calculate that it would take about 6 sunny days with full
sun on the panel all day to fully charge a 1000 mAh LiIon battery using
17.5% efficiency silicon monocrystalline PV cells - more or less the
current industry standard.

With 23% rear  contact cells it would take about 5 days.


                   Russell



I do not know their aim but ALL Yanko design devices that people have
referred to me so far break the laws of Physics severely.
BUT
This one might come closer to working than most.

   http://www.yankodesign.com/2013/04/26/plug-it-on-the-window/

To work adequately it MUST have sun shining directly on the WHOLE PVsurface=
..
If not then output will be typically 5-20% on a bright sunny day. Less if
worse weather.

If you can manage that:

Dia of PV is about 70mm based on hand holding the device.
Area is about 0.004 m^2.
Insolation in full sun with no filtering by glass etc is 4 Watts solar
INPUT.

Battery is 1000 mAh.
Assume LiIon.
Full charge energy is ~~~=3D 3.6 Wh.
Charge in 8 hours (they say 5-8)
Charge rate =3D 3.6/8 =3D 450 mW.
10% for encapsulant
20% for glass.
Area loss due to dead space =3D 10%

450/.9/.8/.9 =3D ~ 700 mW.
Insolation =3D 4W.
Efficiency of cells =3D 0.7/4 =3D 17.5%

That's the efficiency of top monocrystalline material in common use. You
can get 18% -18.5% for money

You can get 23% using new rear contact Si cells.

NOW allow for battery energy storage efficiency of say 80-90%.
Up conversion efficiency does not affect the above aspect.

If charge hours were 5 rather than 8 the efficiency needed =3D 8/5 x 17.5 =
=3D
28 %.

Can only do with GaAs or (hmmm) some of the thin films which are getting >
z than mono Si.

NREL PV cell latests zs (research)

  http://www.nrel.gov/ncpv/images/efficiency_chart.jpg

CIGS is doing well at present. CdTe lagging.
Alta thin film crystalline Si 29%.
Just right:-)

_________

These are "Sunshine hours" - hours of equivalent full sun hours per day.

         www.gaisma.com

7+ hours in Kabul in mid summer.

     http://www.gaisma.com/en/location/kabul.html

VariableJ FMA MJJ ASO ND Insolation, kWh/m=B2/day 2.29 2.833.86 5.066.38 7.=
40
7.30 6.675.66 4.232.95 2.17

5-6  in much of USA in summer.
1-2 in much of US in Winter.
Under 1 in some locations in mid Winter.

SO in summer this thing could come close enough to meeting its claims as to
not justify being on Yanko designs site.

Mains output is cute but silly.
Far better is 5V "USB" output.



        Russell
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