Since 2016 MND Energy Storage Germany GmbH has been operating two aquifer storages in Hessen, Germany (Hänhlein and Stockstadt) with a working gas volume of approx. 2.3 TWh.

Both storages are situated close to Frankfurt am Main and are connected to OGE (Open Grid Europe) grid in the node point of Gernsheim. For trading purposes they create one entry /exit point called “Zone MND ESG” in trading zone THE.

The underground gas storages Stockstadt and Hähnlein secure the gas supply in times of high gas demand

In the 2 underground gas storages (UGS) Stockstadt and Hähnlein, gas is stored for the supply of the Rhein/Main area. Both UGS belong to the group of pore storages where gas is stored in very porous and permeable sandstones which are located at a depth of 350 – 500m below surface.

The UGS Stockstadt started operation in 1969, while Hähnlein UGS was put in operation in 1973.

Gas injection into the storages normally takes place during the summer months to allow for withdrawal during cold winter month with respective high gas demand.

Cushion gas provides the necessary pressure

The gas content of the UGS consists of cushion gas and working gas. The cushion gas is essential, to deliver the required minimal pressure in the storage horizon for an optimal injection and withdrawal. The cushion gas makes up from 30 to 50% of the maximum gas volume stored and remains in the UGS permanently.

Working gas – a flexible Volume

Working gas is the gas volume which is injected in summer and withdrawn from the UGS in winter.

Pore storage

Pore storages are used predominantly for seasonal base load supply and not for short term peak gas demand. This is due to the physical storage properties which are best used for continuous production during the withdrawal period. Storage horizons into which the gas is injected are sealed off to the top by impermeable claystone rocks which prevent the gas from leaking from the storage structure. This mechanism ensures a safe storage operation.