= Target =
Power a 12V/2A (24W) system for 24h/24h, using an autonomous solar system in the Netherlands (read: not very sunny).

= Initial thought =
{{{ 24W * 24h =~  0.6kW and 2A * 24h =  48.0Ah }}}, so given ourself a {{{100 Ah}}} battery (AGM, deep-cycle), should last us to roughly 2 days of operation.

After first measurements my 20W Solar panel is preforming {{{50%}}} less if I put it a bit into the shadow (balcony fences). Putting it into fully into the sun makes it generate roughly 1.2A/12V which is indeed [http://humietrading.nl/index.php?option=com_content&task=blogsection&id=5&Itemid=34 as advertised]. The input should run at {{{17.5V}}} to make it take the full {{{20W}}}.

The change controller [http://www.stecasolar.com/index.php?Steca_Solsum_F_en Steca Solsum 6.6F] seems to regulate the input to {{{12V}}}, leaving me wondering if the panel will be fully utilized. Cause {{{20W/14W * 100% = 70%}}} e.g. loosing {{{30%}}} seems a bit to much. 

Taking this numbers into account we need at bare minimum at least {{{ 48Ah * (100% / 70%) =~ 69Ah }}}. Giving the fact that effectively we have 4 hours of sun in the Netherlands will this make {{{ 69Ah / 4 = 13Ah }}} which correspond to a 160W panel.

Estimated cost for bare minimum will be:
{{{
Panel 150W             : 600 EUR
Accu 100Ah             : 200 EUR
Charge Controller 10A  :  50 EUR
Connectors and cables  :  50 EUR
Measurement Electronics: 100 EUR
--------------------------------
Total                   1000 EUR
}}}

This setup is geared towards most optional numbers. Now take more realistic numbers into a account:
* The sun in the Netherlands will do roughly [http://www.zonnepanelen-info.nl/zonnepanelen/zon-nederland/ 1800 hour], but [http://www.vwkweb.nl/cms/index.php?id=1334&option=com_content&task=view 75(!) days] of the year I will not see any sun at all. If this period last for more than 2 days my battery will be depleted, so I properly need to add extra battery-pack to my system (+200 EUR).
* The panels are not always running at 100%, I expect average case to be 50% and worst case 25% (if sun is shying during the winter). Consequences will be that I need between 1 to 4 panels of 120W (which gives me +2400 EUR).
* Looking at [http://humietrading.nl/index.php?option=com_content&task=blogsection&id=4&Itemid=33 Wind Energy] might be a more suitable  

= Experiments =
* Using a dummy load (20W, I like to see if the panel is able to generate the full 20W).
* The Current Controller needs to be build/bought to be able to generate statistics on long running experiments.


= Idea/Brainstorm =
 * Use [http://www.geo-dome.co.uk/article.asp?uname=solar_mirror mirrors] to increase efficiency.
 * Measure DC current with an [http://openenergymonitor.org/emon/node/31 LT1495 and Arduino].
 * The [http://www.batterystuff.com/solar-calculator.html Solar calculator] suggests Power {{{25W/24h}}} using {{{2 * 120W}}} and {{{100Ah}}} accu. (giving 5h of direct sunlight). 

= Verbs =
{{{
Vpmx  : Voltage at rated power.
Voc   : Open Circuit Voltage. 
Lpmax : Current at rated power.
Isc   : Short Circuit Current.
}}}