  Integrating a high share of electricity from non-dispatchable Renewable
Energy Sources in a power supply system is a challenging task. One option
considered in many studies dealing with prospective power systems is the
installation of storage devices to balance the fluctuations in power
production. However, it is not yet clear how soon storage devices will be
needed and how the integration process depends on different storage parameters.
Using long-term solar and wind energy power production data series, we present
a modelling approach to investigate the influence of storage size and
efficiency on the pathway towards a 100% RES scenario. Applying our approach to
data for Germany, we found that up to 50% of the overall electricity demand can
be met by an optimum combination of wind and solar resources without both
curtailment and storage devices if the remaining energy is provided by
sufficiently flexible power plants. Our findings show further that the
installation of small, but highly efficient storage devices is already highly
beneficial for the RES integration, while seasonal storage devices are only
needed when more than 80% of the electricity demand can be met by wind and
solar energy. Our results imply that a compromise between the installation of
additional generation capacities and storage capacities is required.
