One of the main factors that makes Solar Power so popular over here (apart from the Aussie Pollies throwing wads of money at in in the form of Solar rebates and Solar Feed In Tariffs) is the fact that the Sun is so damn strong down here.
It’s not rocket science to work out why Solar Power hasn’t really taken off in less sunny climes like my homeland; grey, drizzly old England.
In fact the same 1.5kW system on a roof of my Mum’s quaint cottage in Northern England will produce 45% less energy than if it was on my roof here in Sunny Adelaide.
So does that mean the more sun the better, when it comes to generating Solar Power?
That would kind of make sense, right?
Unfortunately, as with most things in this life, it is a bit more complicated than that.
In fact when it comes to solar power you can have too much sun.
The problem is, most solar panels’ power outputs start to degrade if the temperature of the panel goes over about 25°C.
This is why, if you look at the specification label on a solar panel, most manufacturers quote the solar power output at a panel temperature of 25degC.
So does that mean that if it is 25°C outside and a clear blue sky then your panels will be performing to their rated output?
Because, if the air temperature outside is 25°C, that dark solar panel baking on your roof is going to be closer to 50°C.
So how much solar power will you be losing on a 25°C day if the panel manufacturer has quoted power output at a solar panel temperature of 25°C?
To work that out we need to know the solar panel’s “Max Power Temperature Coefficient”, which should be on the solar panel’s specification sheet.
A typical value for this is 0.4% per °C.
Which means that for every degree that the solar panel is above 25°C the power will fall 0.4%.
So on a cool 25°C day where the panel is cooking at 50°C, you will be losing 10% of your solar power.
Here’s the calc:
0.4% x (50°C -25°C) = 0.4% x 25°C = 10%
And on days when the mercury breaks 40°C you can be losing close to 20% of your solar power.
Which is why you can often find that on the hottest days tho