Dear Martin, Team Valentin,

Hope you had an great weekend.

We wondered how it is possible that the kWh/kWp ratio of PVSOL in a south-facing installation (0 degrees) can yield more than the outcome of PVGIS?

All factors that we can work with are the same; angle, orientation, location, etc.

 

Thank you in advance.

Greetingz!

 

Dear Remu,

there are a whole lot of reasons why simulation results differ between PVGIS and PV*SOL.

1. The climate data used is different. Most of all the irradiation data, which has the strongest influence on the results. The standard in PV*SOL are climate data from Meteonorm, while PVGIS uses its own compiled climate data. See these forum threads here:

 

2. The simulation models (and even the simulation approaches) are completely different.

• We follow a time-step based approach (in one-hour or one-minute intervals) that is simulating very accurately the irradiation on module, their temperature, shadows and so on, the electrical generation inside the PV module (with the two-diodes model), the interconnection of various modules and the superposition of their IV characteristics, the inverter behaviour, grid behaviour and what not.
• PVGIS is following a factor based approach, as you can read in their documentation. In the example you posted here, they just apply a loss factor of 15% to the results and that's it.

 

I'd say, PVGIS is more a tool for a first good guess of the energy yield of a PV system. They do a really good job in integrating meteorological data from various sources, and the web interface is superb. You can click very easily on every point in Europe and see how much a average PV system would generate. PV*SOL is more a tool for designing and simulating PV systems that you are really going to build in real life. You can select real world PV modules, inverters, choose and modify their configuration and so on. You can't really compare the tools, as the scope and the input data used are so different.

 

If you want to dig deeper in our simulation models, have a look here: https://help.valentin-software.com/pvsol/2020/calculation/

Here is also a link to the documentation of PVGIS: https://ec.europa.eu/jrc/en/PVGIS/docs/methods

 

Hope that helps,

Martin

Thank you very much Martin for your anwser. This give us more insight in making an choice between PVGIS or Meteonorm.

 

Yours sincerely,

Remu