How do you know what is a good solar panel.
Quote:
Originally Posted by
PhilipA
Warning ! boring for those not interested!
I have been trying to work out why nowadays that all solar panels seem to be over rated enormously.
I think I have the answer.
The manufacturers have a rating system based on an input of 1000watts per square metre.
It is printed on the panel as here.
Trouble is that the total input of sunlight is 1360watts per square metre at the edge of the atmosphere for a horizontal surface.
The ACTUAL daily watts input at Avoca Beach for a horizontal surface yesterday (source BOM at the Avoca Bowling club weather station) was 2800watts per square metre for the entire day midnight to midnight.
Seeing the main sunlight is for 6 hours lets assume , then the average watts per square metre are about 450watts per square metre.
So the output of any solar panel rated at say 200 watts will actually be less than half of that advertised if at Avoca Beach..
I really do not know how the industry got away with such a spurious set of claims .
Regards PhilipA
Testing output against 1000w/m2 is the correct basis for comparing solar panels as this normalises the results and relates to the published peak sun hours for your location which should be to the same standard.
The issue as you have noted Philip is some sellers are claiming false peak power figures. The efficiency of most of the cheap eBay mono cell solar panels will be around 17-19% at best. So the real peak power when tested at 1000w/m2 will be around 170-190w per m2. Even the most expensive panels only get 20-23% efficiency (or 200-230w per m2 under lab testing conditions).
In real life use you will then see less than this peak in the southern parts of Australia, but the power harvested a day will still be up to the peak power times by the peak sun hours for the specific location you are in. For places like Sydney and Melbourne this peak sun hours is less than 3 hours in winter and only gets to over 6 hours in summer.
Whilst it would be rare for us in the southern parts to ever see a peak of 1000w/m2 in real life, this standard just makes all the calculations simpler.