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Available solar power prediction


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I made a NodeRed flow that attempts to predict available solar power.

It does it using a node calls "Solar Power Forecast Plus" that takes your position, panel alignment etc and predicts the power that should be available.

I then took a www-request node to request weather info from darksky.net, and attempted to factor in the cloud cover to try to come up with a prediction.

The resulting info I send into MQTT to EmonCMS so I can chart it and so on.

My flow looks like so:


An export of the flow is also attached if anyone wants to play.

The MQTT message generated looks like so - EmonCMS can import it nicely:


You can see that right not the ideal available power is 3019W.  Darksky says there is 98% cloud cover, so my estimation gave 1243W achievable.  The formula is a guess, I used:

actual = ideal * (1 - 0.6*cloudCover);

I'm finding that Darksky overstates the amout of cloud - so my estimates are too pessimistic.

Still - here's how it came out compared to actual yield this morning:


You can see Darksky saying 98% cloud.  Nevertheless my actual yield was close to the "ideal" figure.

The actual weather reported at Cape Town Airport is FACT 060900Z 16011KT 130V190 9999 FEW030 21/11 Q1015 NOSIG - ie few clouds at 3000ft.  Looking out the window there seems to be high clouds but its a bright day.

Did anyone try to do something like this before?








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