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The concept of Peak Sun Hours

The concept of Peak Sun Hours

Further to my recent post about the intermittency of solar power, I thought I’d tackle some of you more mathematically challenged and hopefully bring more light (no pun intended) to the problems facing those who believe in 100% renewables running complex civilisation.

If on a perfect cloudless sunny day you plot the output of a solar array between sunrise and sunset you’ll end up with a perfect bell curve. This rarely happens of course. Clouds come and go, and depending on where your panels are installed all sorts of things can shade your panels, like trees. The curve then comes out looking rather less perfect, a bit like this…:

The pale blue area is the cloudless curve, the darker one is real life. Around 8am there’s a dip, could be caused by a cloud or a tree; and by the way, it only takes partial shading of a single panel to cause s drop off in production for the entire array. So a shadow caused by a stink pipe protruding through one’s roof could cause this….

Back to the curve. The AREA under this curve is important. It represents the ENERGY generated by the power shown on the y axis multiplied by the time on the X axis. Energy is power X time, hence kWh is the preferred unit of energy when discussing electricity.

The variability of the sun’s input plus all the shading issues make measuring the energy generated on any one day kind of difficult. Luckily, we have technology….

Maximum Power Point Trackers (MPPTs) have white man’s magic built into them to not just measure energy but even store the data so that nerds like us can talk about it and even blog about it…!

…click on the above link to read the rest of the article…

Olduvai IV: Courage
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Olduvai II: Exodus
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