Renewable energies intermittency and electricity mix

As the share of wind and solar photovoltaic in the energy mix increases, the question of intermittency and the resulting need for backup capacity must be addressed. An efficient backup system would provide storage when renewable output is high and additional generating power when it is low. This article analyzes electricity production in France and Germany and develops scenarios using various shares of renewables. Properties of the resulting mixes are given, particularly requirements for the backup system, CO₂ emissions, footprints and investment costs. It shows the lack of adequate storage systems and the revival of fossil-fuel plants to adapt to strong transients. (authors)