Usinge measurement data of diffuse and direct irradiation

[demanding_client]

Hi forum,

so I searched for a way to use my meteo data of direct and diffuse irradiation (only GHI). I did not find any possibility for that, please correct me if I missed something.
This means I would need to use a standard model and lose a lot of accuracy when using PV*SOL with accurate irradiance (dir/diff) data from sources like SolarGIS e.g.
When comparing results in my example to pvsyst the yearly irradiance on the tilt plane (25°) is lower by 6% (due to wrong ratio (dir/diff)).
How is it not possible to set those crucial values or did I just not find the right option?
 

[developer_bh]

Hello,

you can change the used model to get a better accuracy depending on the situation in the simulation options. You can also adjust other parameters in that dialog.

You will find detailed explanations here :
https://help.valentin-software.com/pvsol/2019/calculation/irradiation/diffuse-irradiation/
https://help.valentin-software.com/pvsol/2019/calculation/irradiation/irradiation-onto-inclined-plane/

Here is a quick overview of some models.

• Erbs model: This model uses empirical correlations to derive the diffuse radiation from the total radiation. It is often used for hourly or daily data and is well suited for mid and low latitudes.
• Liu-Jordan model: A simple and widely used model based on the assumption that the diffuse radiation is evenly distributed from the sky to the solar modules. It takes into account the solar constant and the zenith angle of the sun to separate the components.
• Hay-Davies model: The Hay-Davies model takes into account both the direct radiation and the diffuse radiation components caused by scattering in the atmosphere. This model differentiates the diffuse radiation into isotropic and anisotropic components, with the latter being preferentially scattered in the direction of the sun.
• Perez model: The Perez model is an advanced model that divides diffuse radiation into several components, including isotropic sky diffusion, anisotropic scattering by clouds and reflected radiation. It is particularly suitable for accurate simulations under different atmospheric conditions and is often used in complex PV simulation software.
• The Hofmann model is usually a good choice. You find more details about it f.e. here https://www.mdpi.com/1996-1073/10/2/248

 

At the moment you can only use models based on GHI data.

Best regards,
Ben