Scientific Advisory Board of the VGB: Battery storage - option for short-time grid stabilisation

To maintain the current level of security of power supply with the increasing feed-in of fluctuating power from wind and solar energy plants the need for additional back-up reserve capacities increases. These are - and will for the foreseeable future be - conventional power plants.
  • Renewable power from wind and sun requires appropriate back-up
  • Batteries for power compensations in the range of seconds are technically suitable

To maintain the current level of security of power supply with the increasing feed-in of fluctuating power from wind and solar energy plants the need for additional back-up reserve capacities increases. These are - and will for the foreseeable future be - conventional power plants.

In principle, storage technologies could also take over this task. In general, hydro reservoir and pumped storage power plants can be reliable options for power storage. Furthermore additional capacities for more electricity storage are necessary. Battery storage systems can contribute to possible solutions with their potentials.

The internationally lined-up Scientific Advisory Board of VGB PowerTech* examined the tech-nical potential of battery storage options. They noticed that – due to a relatively low energy den-sity of batteries (0.11 to 0.65 MJ/kg** in comparison to 10 to 50 MJ/kg for coal, oil and gas, thus about a hundred times the amount) – in future power systems battery storage could provide potentials for the so-called primary control (compensation of network frequency deviations in the range of seconds). The low energy density of battery storage materials and the associated high-level material costs produce natural limits and restrict the applicability for extended peri-ods. Hence, batteries are not suitable for a long-term compensation between demand and gen-eration in the range of minutes to weeks. Technological progress in the required range or rather a “technology leap” is currently not predictable.

The essential “instant grid stabilisation function“ (time range from zero/nanoseconds to about one second) will continue to only be accomplished by the inert rotating masses of turbine and generator rotors in power plants. As all electronic switching will need time of at least in the 10 milliseconds range, only they can meet the requirement to react instantly. Thus a certain share of rotating masses will remain necessary in every power system.

*) The Scientific Advisory Board of the VGB PowerTech consists of 34 directors of Chairs from the energy-generating sector from 12 European countries. He advises the association on technical issues with re-gards to power and heat generation.

**) One megajoule (1 megajoule (MJ) = 0.28 kilowatt hours (kWh)) is sufficient to e.g. watch five hours of television on a 42 inch LCD-TV or to drive 2 km with an electric car.