Using PVGIS weather data
PVGIS is a free solar radiation database provided by the European Commission. SunSolve integrates directly with PVGIS through the Search for weather data wizard on the Weather tab — type a location name, and SunSolve fetches a complete Typical Meteorological Year (TMY) weather file for that site. This is the quickest way to set up weather data for a new location.
PVGIS TMY files have a subtlety: timestamps are written as HH:00, but the irradiance values may correspond to a different time within the hour, depending on the underlying radiation database. SunSolve detects the radiation database and automatically selects the appropriate observation period and timing adjustment — no user action is required.
Up to version 7.43.0 SunSolve used PVGIS version 5.2.
From version 7.44.0 onwards SunSolve uses PVGIS version 5.3.
See the PVGIS site for details on the changes.
How it works
Section titled “How it works”SunSolve selects the observation period and irradiance time offset based on the radiation database reported by PVGIS. The solar position is then evaluated at the appropriate effective time for all irradiance-dependent calculations: plane-of-array transposition, incidence angles, horizon shading, and diffuse irradiance decomposition.
For details on how each observation period shifts the solar position — including sunrise and sunset edge-case logic — see time steps.
Handling by radiation database
Section titled “Handling by radiation database”ERA5 irradiance values are hourly averages, representing the integrated irradiance over the previous hour, reported on the mid-hour (00:30). However, the timestamps received from PVGIS are on the hour (00:00), which is a thirty minutes earlier than the irradiance definition. SunSolve handles this by using the middle-of-hour observation period, aligned to the timestamp. The PVGIS irradiance_time_offset is ignored for ERA5 because the timestamps delivered from PVGIS are already adjusted by the same amount (i.e. 30 minutes).
SARAH2/SARAH3 irradiance values are instantaneous satellite observations at a small offset from the labelled timestamp. SunSolve uses the Instantaneous observation period with a time offset, applying the PVGIS-provided irradiance_time_offset directly. For example, with an offset of 0.1852 hours, an irradiance value labelled 10:00 is evaluated at approximately 10:11.
NSRDB satellite data is no longer used in PVGIS 5.3.
PVGIS weather loaded in versions of SunSolve prior to v7.44.0 may contain discrepancies between irradiance and sun position. It is recommended to reload the weather for the location using the latest API.