Transmission system operators must assess precisely the supply of electricity from renewable energies for the next day in order to market this electricity on the European Power Exchange (EPEX) as effectively as possible. The sharply fluctuating supply of solar and wind energy makes reliable forecasts even more difficult. For this reason, Fraunhofer researchers, working jointly with TenneT TSO GmbH, developed a high-performance software -- the EMS-EDM PROPHET -- that takes multiple forecasts and combines them with each other to generate one single, highly reliable projection. Sun and wind power fluctuate sharply -- this is why transmission system operators try to forecast, as accurately as they can, how much renewable energy will be stored for the upcoming day. In this respect, the growing volume of solar and wind power is a challenge, because they are subject to strong natural fluctuations. From a large number of individual forecasts, the software generates an optimized overall projection. The entire computing process consists of roughly 15,000 individual steps -- a massive challenge that requires a high degree of automation from the software.