Besides the Meteo Database included in the software, PVsyst now gives access to many meteorological data sources available from the web, and includes a tool for easily importing the most popular ones. These are summarised in the table below, and we have performed a comparison between their results.

Sources of Meteo data in hourly values

• Meteonorm hourly values are not measured, but synthetic data constructed in the same way as the synthetic hourly values in PVsyst from monthly values. Constructing hourly data in Meteonorm instead of PVsyst may give slightly more realistic results as the models (especially for temperature) have been slightly improved, and wind velocities are also generated (with which reliability?).

• Satellight provides real measured data in hourly values, over 5 years (1996-2000), for any pixel of 5x7 km² in Europe.

• US TMY2 data (Typical Meteorological Year) are compilations of measured hourly data chosen among  1961-1990, for 239 locations in the US.

• Helioclim-2 provides data in hourly values, measured by Meteosat, since February 2004. But these data are not free. Nevertheless the year 2005 is available for tests.

• SolarGIS climData provides fast access to high quality solar and meteorological data covering the last 17 years and updated in real-time. Hourly time series or Representative Meteorological Year (RMY) for any selected period are available for any location in Europe, Africa, Asia and parts of Australia and South America. The meteo variables are computed by the modern methods from satellite and meteorological data, and they are available in the PVSYST format. The recent IEA SHC Task 36 study performed by the University of Geneva (Dr. Pierre Ineichen) evaluated SolarGIS data as the best available on the market in terms of bias, RMSE and especially representativeness of a probability distribution of values (histogram). The data are paid for per-point bases. SolarGIS data specification 2011-03 [PDF]

Sources of Meteo data in monthly values

• Meteonorm monthly irradiance data are available for about 1'200 "stations", as averages of 1960-1991 (and also 1981- 2000 in version 6.0). All "stations" (i.e. with irradiance measurements) of the main European countries are referenced in the PVsyst database. Data for any other site may be obtained by interpolation (usually between the 3 nearest "stations").

• WRDC (World Radiation Data Center)  provides monthly irradiance for 1195 sites in the world, averaged during periods between 1964 and 1993. Many of them are only over a few years. These data don't include temperatures, which should be obtained from another mean.

• NASA-SSE (Surface Meteorological and Solar Energy Programme) hold satellite monthly data for a grid of 1°x1° (111 km) covering the whole world, for a 10 years period (1983-1993). 

• SolarGIS iMaps provide an unlimited access to long-term monthly averages of solar radiation and air temperature to Europe, Africa, and Middle East in PVSYST format. The data are accessible on the basis of paying the annual license. SolarGIS data specification 2011-03 [PDF]

• PVGIS-ESRA give monthly values interpolated for any geographical location from average of 1981-1990 terrestrial measurements for Europe, and satellite 1985-2004 data (Meteosat) for Africa.Helioclim-1 are satellite data from Meteosat, given for each year 1985-2005 independently for Europe and Africa. The public access - for tests - is restricted to the 1985-1989 data.

• Retscreen is a Canadian software which holds a complete database for any location in the world, optimised for using the best available data at each location from about 20 sources, the main ones being the WRDC and the NASA irradiance data. Temperatures and wind velocities are also provided probably with good reliability.

NB: All these monthly data are imported as geographic site  files,  and will require the construction of Synthetic Generated hourly data files for being used in the simulation.
NB: Monthly values are often given as averages over several years.

 

A summary of the meteorological databases available with importing tool in PVsyst

Comparison of the meteorological sources

We have performed a comparison between the different sources available in PVsyst, for several locations from north to south of Europe. For this, the annual available irradiation [kWh/m²/year] has been chosen as reference, and we refer to the Meteonorm data, which are the default data in the PVsyst database, for most of the comparisons.

All available sources for 12 locations in Europe

Sattellight yearly data differences with respect to Meteoteonorm

Climate evolution at Geneva from 1981 to 2007