Automatic inverter de-rating?

[alisdisco]

Hi all, very quick question. I have an install that is capped at 3.69KW, it is a SMA Sunnyboy 3800 inverter. What I want to know, the last time (only 2 months ago,) British Gas told me that the whole system is running at 133%. Brilliant. Anyway, with this recent hot and very bright weather that were having, I have noticed that when midday is apon us, a few months ago, we would be hitting the 3.69Kw, but at the moment we are only achieving 2.7Kw. Is it because the sun is much higher in the sky, our panels are just off of south facing, so the hottest/brightest part of the day is not shining directly at the panels, or is the inverter derating, is this where we're not generating the full amount? If anyone can answer this, because Google cant!!!

Many thanks

Alistair

 

[sunshine_eggo]

Could be derating, but the summer sun on panels causes them to heat well above 25°C STC conditions. Cells are likely as hot at 50°C, possibly more, if you don't have good ventilation on the back of the panel. Typically, if an array is producing 70-80% rated power in summer heat, you're doing good.

2.7/3.69 = 73%

 

[alisdisco]

Hi sunshine_eggo, thank you for replying to my question. So maybe they are working to their potential then, and its just the summer heat that is affecting their output. There is a good 10" or so clearance under the panels to the roof to provide a good airflow. Thinking about it, there hasn't been much wind either to cool things, nor rain to wash the panels down. It all adds up when you think of all these factors doesn't it. I have been reading how much temperature affects outputs of panel - its all about trying to shift electrons when they are hot to begin with, bit like us when its too hot, we don't want to be bothered or told to to move and be happy about it....