Energy systems with high shares of renewable electricity are feasible, but require balancing measures such as storage, grid exchange or demand-side management to maintain system stability. The demand for these balancing options cannot be assessed separately since they influence each other. Therefore, a model was developed to analyze these mutual dependencies by optimizing a concerted use of balancing technologies. This model is presented here. It covers the European electricity system in hourly resolution. Since this leads to a large optimization problem, several options for reducing system complexity are presented. The application of the model is illustrated with a case study outlining the effects of pumped hydro storage and controlled charging of electric vehicles in central Europe.
Energy storage is one option to provide the electricity grid with flexibility. Short-term storage can provide system services for power quality, whereas medium-term storage allows to shift significant amounts of energy over some hours up to days. Seasonal or long-term storage can, for example, be provided by the power-to-gas technology. Significant amounts of storage will be necessary, especially when a fully renewable supply is approached. New mechanisms are needed to ensure anticipatorily that sufficient flexibility is in the system at any time.