Energy storage
Battery storage
Storage energy capacity
The total stock and monthly additions of battery storage systems in Germany are shown below. The data is based on the Market Master Data Register (MaStR) of the Federal Network Agency. The preparation and categorization into home, commercial and large-scale storage systems largely follows the methodology of the Battery Charts of RWTH Aachen University. Home storage systems are currently mainly used to optimize the self-consumption of PV systems (prosumers), but not for arbitrage in the electricity market. The same is likely to apply to larger industrial storage systems. A significant proportion of large-scale storage systems are likely to be active primarily in the balancing power market. Home storage capacity has recently grown strongly in parallel with the strong growth in rooftop photovoltaics (see Deep dive photovoltaics). The flattening of the expansion at the current margin is due to incomplete data and is likely to change as a result of subsequent reports.
Storage power
Due to the typical dimensioning of the batteries, the picture for the cumulative battery power rating is very similar to that for energy capacity.
Pumped hydro storage plants
Storage energy capacity
Pumped hydro storage plants have been in use for decades and are still the most relevant large-scale electricity storage systems in Germany. However, their capacity has stagnated in recent years, while battery storage has recently grown strongly (see above). The last major addition in Germany was the Goldisthal pumped hydro storage plant in 2004. The pumped storage facilities installed in Germany mostly have artificial upper reservoirs without a natural inflow. The figure also shows pumped storage power plants in Austria and Luxembourg, which are directly connected to the German transmission grid and are therefore also included in the Federal Network Agency's Market Master Data Register (MaStR), which forms the data basis for the figures shown here. The total installed energy storage capacity of pumped storage in Germany is currently a good 35 GWh, plus 19 GWh in Austria and Luxembourg, making a total of 54 GWh.
Storage power
The installed power rating of pumped hydro storage plants has developed similarly to their storage capacity. The plants installed in Germany have a total capacity of just over 6 GW, plus almost 4 GW abroad, i.e. a total of almost 10 GW.
Storage operation
The following figures illustrate the average daily operating mode of pumped hydro storage plants in Germany since 2015 for the winter and summer half-years (top panel in each case). In the past, pumped storage usually had one charging and discharging cycle per day. They were regularly charged at night and discharged during the day, the latter mainly in the morning and evening hours. In recent years, this pattern has changed significantly, with the exception of the pandemic year 2020. Pumped storage plants now generally have two cycles per day, with storage taking place both at night and during the day and discharge in the morning and evening. The reason for this is the strong growth in solar energy, which is regularly accompanied by a high supply of electricity during the day and correspondingly low prices on the wholesale electricity market. The comparison with the average daily price distribution (lower panel) shows that the storage operation has directly followed the changing price patterns in the electricity market.
The influence of solar photovoltaics is particularly pronounced in the summer months, which is why prices are particularly low during the day and storage is particularly high. Recently, there has hardly been any storage at night in summer, but almost only during the day. This was still the other way around in 2015.