Solar powered data geek

[Let’s draw a veil over a blogless January and February]

On the day that the government lost its Feed-In Tariff appeal in the Court of Appeal, the guys from Sungift Solar started to install PVs on my house. I still don’t know how much I’ll be paid for what I generate, as the government is now taking its appeal to the Supreme Court. But leaving that aside…

My installation is:

  • 11 panels totalling 2.7 kW, manufactured by Siliken, model SLK60M6L 245Wp monocrystalline
  • SolarEdge SE3000 inverter
  • 11 SolarEdge widgets that smooth the output from each panel and improve efficiency

A friend has exactly the same system installed, except for the widgets. I’m hoping to be able to calculate the efficiency gain by comparing generation totals. BUT the widgets also provide data on power output at 15 minute intervals and daily generation totals, so I can be a renewable energy geek and a data geek at the same time!

Here’s a pretty picture of daily totals. So far, the maximum power output has been 2.47 kW on 3 March, and the maximum daily generation 12.82 kWh on 29 February.

Daily totals

It’s interesting to note that the highest power output does not necessarily take place on the sunniest day. Compare the 15 minute data for 19 and 26 February. The 19th was a low pressure day – sunny and cloudy intervals, and very good visibility. The 26th was a high pressure day – sunny all day, but so hazy that I could barely make out the Haldon Hills across the estuary. So although total generation was higher on the 26th, the better visibility meant that power output peaked higher on the 19th.

15min intervals

All this information leads me to wonder whether it might be a useful proxy for some weather observations – most obviously sunshine hours, but also possibly cloud cover, and a measure of visibility or haze. A model of reduction in power output below expected, as a function of cloud cover or visibility, would need to account for: location of installation and time of year, i.e. position of sun throughout day; pitch and orientation of panels; shading; any lying snow; outages; degrading efficiency of panels over time. Might be possible. Whether the information is worth anything would also depend on the number of installations which include these sort of widgets, and whether the companies and the panel owners are willing to provide the data.

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