Principle of operation

With the brine4power project, EWE GASSPEICHER is pursuing a green vision and a forward-looking idea: creating the world’s biggest battery for electricity sourced from green energy in two caverns under the North German Plain: b4p storage. This mega-battery could store up to 700 megawatt-hours of energy in the future – enough to supply 75,000 households with electricity for a day.
The expansion of renewable energies as part of the energy transition presents energy utilities, towns, cities and municipalities with a new challenge. Because until now, it was very difficult to store electrical energy. When electricity was primarily generated using fossil fuels, it was relatively easy to regulate the difference between the volume of electricity generated and the volume actually consumed by increasing and decreasing the output of the power plants. The right balance was struck with the help of positive or negative balancing energy.

Renewable energies are low in emissions and climate-friendly, but their capacity depends on the weather. On sunny and windy days, the amount of energy fed into the electricity grid can be well above the amount needed. But when the wind isn’t strong enough or there is not enough sunshine, the amount of energy available may be insufficient. The only thing that helps in this case is storage facilities that balance out any shortfalls between supply and demand.

EWE GASSPEICHER specialises in the area of large storage facilities. With b4p storage, storing large volumes of wind and solar energy will be possible for the first time. The innovative technology is founded on redox flow battery technology, which has been further developed at the Friedrich Schiller University in Jena. This involves electricity being stored in saline solutions containing polymers.

Here’s how it works: a battery consists of two tanks containing the storage liquids and a number of electrochemical cells. The two saline solutions in the cells – the catholyte and anolyte – are separated by a membrane. When the battery is charged, the polymers in the catholyte surrender their electrons to the polymers in the anolyte via the electrical connection. When electrons are lost, this is called oxidation, and when they are gained, this is called reduction. The charged polymers are then pumped out of the cell and into the tanks in a constant flow, and are replaced by uncharged polymers. When the battery is discharged, this process is reversed – the anolyte loses its electrons, which become available as electricity and are then passed to the catholyte. An exchange of ions takes place through the membrane at the same time so that both electrolytes have a neutral charge.

What makes the new redox flow batteries unique is that their maximum storage capacity is limited only by the size of the tanks. Their power depends on the throughput and on the number and size of the electrochemical cells, which are also known as stacks.
EWE GASSPEICHER is planning caverns with a volume of 100,000 cubic metres, but they can be made considerably bigger. As they are located in salt domes, the brine needed for the mega-battery is sourced directly from the caverns.

The cost of a cavern battery per kilowatt of power is approximately equivalent to that of pumped-storage power plants or conventional batteries. The new mega-batteries do have a major advantage, though: b4p storage will be unbeatably affordable as it is able to store large amounts of energy.
The brine4power project pursues the idea of affordable, safe and, above all, sustainable and long-lasting energy storage. In combination with a wind farm of an appropriate size, each battery replaces a regulatable 120-megawatt power plant.

b4p – brine for power: the missing piece of the puzzle to make the energy transition a success.