Those figures came up in various reports/studies. The one I studied in most detail was from Fraunhofer on the German energy transition. One good book regarding

Those figures came up in various reports/studies. The one I studied in most detail was from Fraunhofer on the German energy transition. One good book regarding napkin math was the following (in German unfortunately): https://www.amazon.de/Erneuerbare-Energien-zum-Verstehen-Mitreden/dp/3570104583/ https://www.amazon.de/Erneuerbare-Energien-zum-Verstehen-Mit...