Wind power is the most important source of renewable electricity worldwide. In Germany, it accounts for more than a quarter of total electricity consumption. In terms of installed capacity, China, the USA and Germany lead the world, closely followed by India and Spain. In the future, battery storage systems can play an important role in managing power generation that fluctuates with the wind: In centralised power grids, this could reduce the need for residual load power plants and grid expansion and increase the profitability of wind power plants. In decentralised or island grids, a stable energy supply can be realised with moderate land consumption.

Relevance of this field of application

Wind power is the mainstay of renewable energy generation in Germany. In 2020, 132 TWh of wind power were generated (105 TWh onshore and 27 TWh offshore), which corresponds to 27 % of total German electricity generation. Thus, electricity from wind power surpassed all other energy sources such as coal power (82 TWh or 17 %) and nuclear energy (61 TWh or 13 %) and contributed significantly to the share of renewable energies in total net electricity generation exceeding 50 % for the first time in 2020.¹ In the EU, wind power production amounted to 426 TWh in 2019,² globally it was around 1,263 TWh in 2018.³ The installed capacity here amounted to 63 GW in Germany (2020)⁴, 192 GW in the EU (2019)² and 622 GW worldwide (2019)³. The top five countries are China, the USA, Germany, India and Spain.⁵ Significant growth rates can also be expected in the future, especially against the backdrop of intensified climate protection efforts in the most important economic areas as well as efforts to achieve cost-effective decentralised energy supply in developing and emerging countries.

The success of wind power utilisation is driven by several advantages: The technology of wind turbines is mature, their energy payback time - i.e. the time in which the turbine has generated as much energy as is required for their production - is very short at a few months and their land requirements are comparatively low.⁶ In addition, the plants have good economic efficiency. A central disadvantage is that electricity generation fluctuates depending on the wind. Since generation and consumption must be constantly balanced in the electricity grid, regulation measures are necessary. In phases of low generation from renewable energy sources, the generation gap ("residual load") can be made available by other fossil-fuelled power plants, which, however, entail considerable costs for maintenance and operation. To a limited extent, adjustments on the consumer side (shifting electricity use in phases of high availability) are also possible. In centralised grids, a central role in dealing with fluctuating generation is also played by grid expansion, which can primarily connect areas with high generation (e.g. wind power in northern Germany) and areas with high consumption (e.g. industrial regions in southern Germany) with high-performance lines.

Use of battery storage

Recently, the storage of wind energy has increasingly come into focus. There are two approaches to this: Firstly, electricity can be used for the electrolytic production of hydrogen ("power-to-gas"). This can be stored comparatively well and transported via the existing gas grid. However, the production-related conversion losses are already considerable at around 30 %.⁷ If the hydrogen is to be used in motor vehicles, further losses occur during compression, at the filling station and during electricity generation in the fuel cell, so that in the end only about 15 % of the energy used to produce hydrogen is available for propulsion.⁸ Hydrogen production is therefore discussed primarily with a view to fields of application in which battery-electric storage does not appear practicable for capacity reasons.⁹ On the other hand, batteries can be used for much more efficient intermediate storage: Here, only losses in the range of up to 13 % occur for storage and retrieval (round-trip efficiency taking into account the power electronics).¹⁰ This, in combination with short provisioning times, makes battery storage an attractive third option for the management of fluctuating electricity generation, alongside generation and consumption adjustments. Their use can reduce the need for residual load power plants and the expansion of the existing electricity grid.

An interesting case is the so-called feed-in management of wind power plants. If high wind power generation threatens to overload the grid, the grid operator concerned in Germany can, under certain circumstances, initiate a forced shutdown of EEG-subsidised plants. The curtailed energy that would have been generated during normal operation ("outage work") is compensated via user charges. In 2019, the amount of outage work in the wind energy sector in Germany alone amounted to 6.3 TWh - or around 4.8% of total wind power generation.^11,2 In other words, 6.3 TWh could have been additionally generated and harnessed with the existing wind power plants if suitable battery storage had been used. This corresponds to more than half the annual electricity generation of a large coal-fired or nuclear power plant. In addition, there are also plants whose full potential cannot be used for electricity generation in the long term due to insufficient absorption capacity of the connected grid level. Here, too, intermediate storage with batteries is an ecologically and economically promising option.

In decentralised or island grids, electricity generation from wind power often plays a central role. Here, due to the smaller number of plants on the generation and consumer side, fluctuations are usually disproportionately greater than in interconnected grids. This makes the use of buffer storage all the more important for a stable power supply - especially when larger generation gaps have to be bridged.¹²

Performance requirements

The use of wind power promises an environmentally compatible and resource-friendly energy supply. Battery storage has the potential to further improve this: by balancing out fluctuating power generation as well as providing intermediate storage in the event of grid overload. However, they must also meet high ecological standards. This applies to the raw materials required as well as the performance of the battery: the "less battery" required per kWh of effective storage capacity, the better its ecological balance.

Particularly high demands are placed on the service life of the battery storage systems used. Wind power plants are planned for periods of around 25 years. With a view to investment security, the batteries used should have at least the same service life. Since the cycle frequency for storing wind energy can be relatively high, battery types that hardly age even under these conditions are advantageous.