In the solar industry, Clipping is a term used to describe lost power when an inverter cannot invert all the power that is available to it, it must throw away the excess energy. The typical ratio used in the industry is 1.2 as it represents very minimal clipping. Why not use an inverter than can capture all of it? Economics mainly, panels only output their maximum rated wattage at solor noon and for a couple of weeks when they're perfectly aligned, so why pay for more inverter than you'll typically use? Let's use a 400 W panel with a 350W microinverter as an example. |
The chart to the right is what the sun puts out, what you might see if you had a two-axis tracker. As an array will most likely be fixed, an actual curve would be much narrower. But it will give us the absolute maximum clipping might cost you. 87.5 is around a sun elevation of 65, so ~65 to 90 and 90 to 65, so that's 2x(90-65) = 50 degree span. 1 hour is 15 degrees, so 50/15 = 3.3 hrs you might be clipping per day. So, in a perfectly aligned 2-axis system on a perfect day you might lose up to 50W/hr for 3.3 hours. You need to calculate the area under the curve, we'll say it's .6. So, (400W - 350W) x 3.3 hrs x .6 area = ~100 Wh/d/panel. On a fixed panel system you'd see a lot less, typically only over the few weeks of the year the tilt was perpendicular to the sun. |
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