Alternative Technology Assn Forums

1. 

   cool at home
   Member

   Our SGU of 3.24kW was installed on Monday on N-W facing, completely unshaded roof. Yesterday and today have been sunny and cloudless, yet even at midday today my system is showing 2300W PAC and around 13kWhr power generation for the entire day yesterday. This seems a little low for what I feel are pretty 'ideal' conditions... or am I expecting too much?
   Susan

   Posted Wednesday 12 May 2010 @ 2:34:49 am from IP #
2. 

   rsigmund
   Member

   Average 4.5 Sun hours per day. Given the sun is not at its zenith you will be getting lower KWh output unless your PV pannels are at a very steep angle...If yours are directly on the roof it more than likely optimised for summer!

   2300W PAC I guess you mean Peak AC that is AC peak output after losses even the best inverters are getting only 96% at best and maybey quite a bit less.

   Also is 3.24kW figure Standard operating conditions? I think this means cell temperature of 25C I would guess your pannals were hotter than that so you need to apply a derating factor as well

   Since you have 3.24kW and only getting 2.3Kw peak it seems like your getting around 70% but as I have detailed that may be ok...

   Your best option IMHO (unless you like reading specification and doing math) would be to post a question like this "3.24kW rooftop solar - How many KWh are you getting?".

   Posted Wednesday 12 May 2010 @ 3:08:05 am from IP #
3. 

   cool at home
   Member

   Many thanks - a great help.

   Posted Wednesday 12 May 2010 @ 4:33:44 am from IP #
4. 

   alfresco24
   Member

   PV performance depends on several factors, 90% of which comes down to;
   - Where are you? The further south the less solar exposure you get because the sun has to go through more atmosphere to reach you.
   - Can you be a little more specific than NW facing? Too far off solar north centre line can reduce total generation 10%-20% for every 10 degrees off line.
   - What is the inclination of the panels? The correct inclination for PV's is usually set for maximum exposure between December to February in the southern latitudes - and so output power is much less in May through August months. Unless you can track the sun.

   Posted Wednesday 12 May 2010 @ 6:57:41 am from IP #

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