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Solar Irradiance [TMY vs Actual data]

asked 2021-09-14 17:32:04 -0500

Aly ElHefny gravatar image

updated 2021-09-14 18:07:42 -0500

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 ?

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

Debayan93 gravatar image

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

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Asked: 2021-09-14 17:32:04 -0500

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Last updated: Sep 23