Solar Irradiance [TMY vs Actual data]

Hello everyone, I hope you are in good health.

The following plot presents the global horizontal solar radiation from the TMY file for a specific location compared to the actual measured global horizontal solar radiation for the same station. I expected that the averaged irradiance trajectory from the TMY file will correspond to the measured data of the same year. But even the peak is significantly shifted.

image description

What is the best way to approximately predict the hourly averaged global horizontal solar radiation trajectory for a future day ?

Hi Aly,

It is better to plot a 'sunny day' (less cloud interference) to compare the actual vs TMY or a few continuous days. This shift could be possible due to two reasons:

1) Locations are slightly different

2) Local interference during the measurement period while TMY averages it out over the year.

Meteonorm is a commercial source for availing future climate data. There could be other services available depending on the region.

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Debayan93

answered 2021-09-23 08:28:27 -0500

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Hey Debayan, For the location, I'm using the exact station location for the both cases. I understand that TMY presents averaging values but I expected (or hoped) the average would at least have a peak close to the actual one rather than that shift. I know of a number of payed services available which include meteonorm for predicting the solar irradiance but I'm more interested in opensource with sub-hourly increment if available.

Aly ElHefny (2021-09-23 08:37:23 -0500) edit

For the comparison, I suggest then use a different source of TMY data (ex: PVGIS). Alternatively, you can utilize PVLIB package implemented in Python to simulate GHI on your station location to compare against measurement data.

Debayan93 (2021-09-23 08:41:44 -0500) edit

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Solar Irradiance [TMY vs Actual data]

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Solar Irradiance [TMY vs Actual data]