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Hourly values for different orientations (azimuth): weird results


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Hello,

Today I tried playing with the azimuth orientation of a circular solar park my company has in development. Basically, I rotated the configuration and generated hourly values to compare. I got the following (see figure). All numbers are grid feed-in (kWh). I have two questions arising from these numbers:

  • Generally, the yield looks approximately the same during the day for all configurations (not as much deviations as I would expect), which is weird I would say. I would expect that for example a 270 degrees orientation (so the panels aimed in east direction), the grid feed-in would be bigger in the morning than in the afternoon. Does anyone of you maybe understand what's going on?
  • I also noticed that for a south orientated configuration, the specific yield and hourly grid feed-in numbers are lower compared to 150/210 degrees orientation (especially in winter, first picture), how can that be? The Spec. Annual Yield for the 180 degrees orientation was 890 kWh/kWp, while for the 150/210 degrees orientation it was 950 kWh/kWp. I would expect a south configuration always to have a bigger yield.

All configurations have the some properties (except the orientation of course). The configuration is also circular, so rotating has no effect on the used space. Some properties of the configurations:

- Inclination 30 degrees

- Number of vertical modules: 1

- Depth of row: 0.863 m

- Mounting Support Clearance: 0.937 m

- PV generator output: 629.68 kWp (1852 panels)

gridfeedin-question.png

 

gridfeedin-question2.png

Thanks in advance for the help!

Kind regards,

Bas

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Hi Bas,

in order to be able to identify what is going on it would be helpful if you could provide the project file. You can send it by private message to me here in the forum.

The instantaneous output of PV systems with varying orientation is depending strongly on the diffuse fraction of the solar irradiance and the sun position. The diffuse fraction changes from time step to time step, so does the distribution of the diffuse irradiance over the sky dome. And of course, if there is direct irradiance, it gets more complicated. So without these data it is impossible to understand why a given PV systems performs differently than another at a given point in time.

Kind regards,

Martin

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