Question Any solar power experts here?

[JohnN]

I have a 12.6 KW solar array but the Inverter limits at 10 KW. The company that did the install said this is industry best practice, because of decreased efficiency when the array is making less than max output.

Sounds like BS since I get peak output about 4 hours/day, the balance of the time the inverter is operating at less than max

Comments?

 

[Still Kicking]

Same here. I have a 16 panel array (not sure of capacity) but the inverter caps out at 4kw. Here's the graph for a typical day.

I complained to the contractor and they gave me the best practice line. I know it's not a significant amount but it irks me that I could be selling more power back to the grid.

 

[broncobowsher]

Well, you don't get peak for 4 hours a day. Do you have a solar tracker? Rated output is at STC, Standard Test Conditions. Not real world conditions. It is done at 1,000 watts per square meter solar intensity, which is rarely seen. There are also temperature constraints, when the panels get hot the output drops.

Can you monitor the inverter performance? Are you really maxing out the inverter at 10kw?

Running a larger inverter will have more, well lets just call it "pumping losses". Self consumption is another name for it. Dark current. The invertor is not 100% efficient. The efficiency conversion isn't linear either. How many watts go in, how many watts come out, it is a curve, not a line.

It would take a lot of engineering to look at your location, panel placement, average cloud cover, inverter conversion curves. You may be missing a little at the peak on the summer days but make up for it with less losses through the rest of the day and over the whole year when you don't have ideal sun angles.