###### Abstract
Uranium and other nuclear fuels are also finite, so nuclear energy is not an alternative to fossil fuels due to limited resources [6]. Therefore, a sustainable energy policy must rely on biomass, geothermal energy, hydro power, ocean energy, solar energy, and wind energy. As renewable energies are to a large extent not permanently available and depend, for example, on the weather, grid stability must also be considered when expanding renewable energies. For example, the locations and technical characteristics of the plants influence grid stability, as does the quality of the grid. In addition, grid stability depends on the respective short-term power flows in the power grid, which in turn depend heavily on the weather in a renewable power supply. The grid is considered stable when frequency, voltage, and angular stability are satisfied. While voltage stability can be maintained by distributed generation facilities and communication systems, maintaining frequency stability is more complex. To date, the rotating masses of the power generators support the grid frequency in the first moments of a power loss (frequency-response reserve). Such a power deficit can occur, for example, due to the failure of an offshore wind farm. The foreseeable absence of rotating masses raises the question of whether there will be sufficient frequency-response reserve in the power system in the future, or whether the system will have sufficient inertia in the event of abrupt power plant or line failures to allow sufficient time for the deployment of spinning reserve [7; 8]. If the mismatch between consumed and generated energy exceeds the time horizon of the frequency response reserve, primary control power is used to ensure that frequency stability is not affected. If the energy demand is higher than predicted, power plants already in use are first operated at a higher working point and, if necessary, additional power plants that are in standby mode are brought online. The demand for control power that needs to be held in reserve increases with the increasing amount of weather-dependent renewable energies, whose output can only be predicted to a certain extent [9]. In principle, the possible power gradients of weather-dependent solar and wind power plants are sufficient to react quickly compared to large power plants. However, it should be noted that the availability of control power is only possible if there is sufficient wind or sun. As the allocation of control power by weather-dependent renewable energies is only possible by throttling, free available energy remains unused, which applies to the allocation of negative and positive control power. In the case of positive control power, however, the extent is greater, as the plants must be permanently throttled in order to be able to increase output if necessary [7]. Hence, for a complete roll-out of renewable energies, alternatives for power control must also be considered in order to ensure a safe system state of the grid. Due to the fast activation and reaction time, battery systems are ideal for providing the necessary control power. The time required to provide or consume energy is mainly determined by the used power electronics and reaches full load in the range of 20 ms. This means that battery systems can provide both frequency response reserve and operating reserve. To a certain extent, it is even possible to generate the replacement reserve with batteries. Therefore, the energy transition can only be achieved by a massive expansion of battery storage power plants. Already today, battery storage power plants are used to a significant extent. For example, in 2017, about 700 battery storage power plants with a capacity of over 2.5 GW were in operation. The majority of these use lithium-ion batteries with the problems already described [10].