European Commission Joint Research Centre in all these years has been mapping the PV solar electricity potentials in various parts of the earth to facilitate and accelerate solar power generation for countries and the private sector. PVGIS was developed 10 years at the European Commission Joint Research Centre, in Ispra, Italy. The focus of PVGIS has been to do research in solar resource assessment, photovoltaic (PV) performance studies, and the dissemination of knowledge and data about solar radiation and PV performance. The most famous outcome of their research is the online PVGIS web application and maps. Here you have a direct link to download the high-resolution map of PV solar Electricity Potentials in Europe.
If you are curious about the calculation and estimation of the solar radiation intensity, please read more here.