Why is Global Horizontal different in final results report and the actual meteo data?

[dimitar.tashkov]

Hello,

I have a problem with my simulation. I've created a new location and imported both NASA and Meteonorm irradiance to it (Inverness, Scotland). When the location is defined and meteo data imported the annual global horizontal is given as 843 kWh/m2. However, after the simulation ends the report suggests the global horizontal is a lot higher - 969 kWh/m2. Screenshots below:

 

 

Could you give me any advice on what has gone wrong or how to interpret that? (I think these two values should be the same, as far as I am aware the resulting value should still be equal to the meteo data)

Thanks,

Dimitar

[André Mermoud]

The data specified at the beginning of the loss diagram is the Irradiation on the Horizontal plane. This is taken from your Meteo hourly file *.MET

The data in the orientation of the optimizing tool is the Irradiation in the plane of the array. It is normally different. But in this particular case the plane is horizontal, so that it should be identical.

For technical reasons, the Meteo data used for this optimization tool are taken from the Meteo data of the site you have specified in your project. As I understand you have imported data from Meteonorm and from NASA. Probably the Project's site data are from one source, and the meteo file *.MET is from the other.

NB: the values provided by the orientation optimizing tool are marginal in the software: they are just here for an estimation of your orientation with respect to the optimal, not for an absolute irradiation evaluation.