Wednesday, April 13, 2011

A Little Testing on the Effect of Shadows on PV Array Output

There was a question on the Greenbuilding List the other day about whether shadows from a nearby power line would drop the power output form a PV array significantly.  I did a little bit of testing using my PV array and some pipes to simulate shadows, and thought the results were interesting enough to pass along.

My PV array is 10 modules and uses the Enphase micro inverters, so each panel has its own inverter, and the power output from each panel can be indepenently tracked.  So, I used pipes to make simulated wire shadows on some panels while using the output from the unshaded panels as a control.

PV array with 4 of the panels shaded.
Closeup of "wire" shading.
In a nutshell, its possible to get some pretty serious power drops when you use relatively lareg simulated wires that are pretty close to the panel (as in the picture just above), but when the wire diameters drop down to a bit over half an inch the effect (at least on my panels) becomes small.  As the distance from the panels to the wire increases, I believe the effect will become even smaller as the shadows appear to fill in with distance.

Here is the grand result showing power output form all of the panels for the two tests (big wires and small wires):

There is a lot more detail at the link below, with actual power drops for the eight different shading conditions I looked at.

All the details on PV array shading from power lines...

Another small shading investigation done earlier...

Gary

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