Tuesday, 15 May 2012

"Edge of Cloud Effect" & Solar Panels.


If, like me you have a home solar electric system that runs off of photovoltaic solar panels you’re constantly hoping for clear skies so that the system's output of solar electricity will be at its maximum. Cloud cover will naturally lower your solar systems output, but have you found that some partially cloudy days give high solar electricity outputs? 

I had a comment from Geoff07 on my post Red-letter-day-for-solar-output. He mentioned that he got a higher than normal reading one day which he thought was due to clouds acting as reflectors. This got me thinking if my system acted in the same way?
I noticed that on some cloudy days my solar system's output was increasing and decreasing rapidly, sometimes the output actually exceed what the solar panels output would be on a fully clear day. This phenomenon is known as the ''edge of cloud effect." This can be explained by the occurrence of the sun's rays being momentarily intensified as they pass through the outer edges of nearby clouds. This magnifies the light and pushes more solar electricity out of your photovoltaic solar panels. Other factors that will increase your solar systems solar electric output are reflections of sunlight off snow or water.
This sounds great doesn't it? Something for nothing…. 
I'm not so sure that my installers took this effect into account? A solar panel's output is commonly 70%-80% of its average rating.  I have a Sunny Boy 2500HF inverter which I assume means it will handle 2.5kW’s of output?
 Installers normally take the solar arrays output rating and multiply it by a factor of 1.25 to take into account increases in solar electric output. If my system exceeds its manufacturer's rating it will cause electrical clipping and solar electricity generated will be lost.this will slowly reduce the life of  my inverter and other electrical devices connected to the load.
SMA inverters have an excellent efficiency and reliability rating; I’m hoping that any spikes in solar output won’t compromise the life expectancy of this expensive device. Does anyone have experience of "Edge of Cloud Effect" in relation to Inverter life? I'd also be interested in your views regarding my inverter size related to a 2.66kW system.

Icarus
Twitter: (@solaricarus)

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