Optimum orientation change after simulation

[Wendy]

A Problem happened when I do the simulation located in 29.06N,92.2E.

Before simulation, I chose 33 degrees as the fixed angle of PV modules, while the loss by respect to optimum is 0%. However, after clicking on the simulation button, I came back to see the orientaion part, and found that the loss by respect to optimum and the global on collector plane changed. Please find the attachement of the sceenshot.

This problem may affect the result, especially "the global incident in collector plane" and the result is ~5% larger than the one my colleague got. We used the same virsion and simulated the same location.

This problem had never found before. PS, we used the metenorm 7 as the data source.

Have you ever met this problem and do you know how to fix that?

Look forward to your reply and Thanks!

Wendy

After simulation

Before simulation

[André Mermoud]

This tool is only a guide for helping you when choosing an orientation.

It is based on a very quick and rough calculation from monthly meteo values.

I don't know why you have such a difference: perhaps before the simulation the calculation was based on the Project's site, and after on the Meteo hourly file (according to its availability at the calculation time).

Or perhaps you have changed the transposition model from Hay to Perez.

By the way these rough values are not involved in the simulation process in any way. They are only indicative.

If you want a better orientation optimization tool, please use "Tools > Transposition factor" which provides a detailed calculation based on a hourly meteo file.

However if you have shadings (namely in a rows arrangement), please remember that these optimizations are no longer valid. In the case of rows, you should use the button "Optimization tool" just before the simulation.