In 2021, the Grohnde nuclear power plant in Lower Saxony on the Weser River was shut down. Now, immediately next to it, the Emmerthal energy cluster is growing with three very large battery storage systems, ground-mounted photovoltaic systems, and a new substation for several 380-kilovolt high-voltage lines.

The villages of Grohnde and Kirchohsen on the Weser River belong to the municipality of Emmerthal. This municipality has decided to approve up to three battery storage systems (BESS) on a maximum of 35 hectares of land in the “Energiecluster Emmerthal”.

According to public documents from the municipality, three BESS projects from the operators Green Energy Storage Initiative (GESI), FRV, and Elements Green have already received commitments for their respective grid connections.

The connection to large power lines will be via the new Emmerthal substation (UW), which the grid operator TenneT is building. It replaces the previous Grohnde substation, whose capacity is no longer sufficient. The Emmerthal substation will couple two 380 kV power lines, which are also to be reinforced, with several 110 kV lines. The future RheinMainLink power line runs close by.

In this region, the RheinMainLink runs parallel to the SüdLink, which is already under construction and is also designed as a 525 kV underground cable with High Voltage Direct Current (HVDC) transmission. The two lines are only about 19 kilometers apart in this area.

Apparently, the operators of BESS near the two new north-south power lines hope to buy wind power surpluses from northern Germany cheaply and sell them at a higher price to southern Germany when needed.

Potentially up to 1.87 gigawatts of power

The operators GESI and FRV have already published relatively concrete plans for their BESS in the Emmerthal energy cluster. GESI intends to install containers with Lithium Iron Phosphate (LiFePo) batteries, which will store a total of 3.84 gigawatt-hours (GWh) of energy and deliver up to 870 megawatts (MW) of power. This is referred to as a 4-hour system because a complete discharge would take that long.

FRV is also planning a 4-hour system: The BESS “Grohnde III” is intended to store 2.4 GWh and deliver up to 600 MW. It cooperates with a 53-hectare ground-mounted PV system operated by Solizer in direct proximity, which is supposed to deliver a peak output of 72 MW (MWp). Due to changes in tender conditions, large solar power projects and battery storage systems are increasingly being planned together. The two BESS from GESI and FRV alone, with 1.47 GW, deliver more power than the former Grohnde nuclear power plant with its net 1.36 GW.

The British project developer Elements Green, on the other hand, has not yet provided any data for Emmerthal. However, Elements Green plans to invest two billion euros in Germany and is building, among other things, a 400 MW BESS in Elsfleth. If Elements Green also builds 400 MW in Emmerthal, the site will have a total capacity of 1.87 GW and store 7.8 GWh.

Update: According to the website battery-charts.de, large battery storage systems with a total capacity of 5.2 GWh are currently in operation in Germany, capable of delivering around 3.2 GW of power. According to this, another 10 GWh are to be put into operation by the end of 2027. So-called home storage systems in Germany currently already have a capacity of more than 21 GWh. The figures on battery-charts are derived from the Market Master Data Register (MaStR).

Planning still in flux

It is still unclear when exactly the battery storage systems in Emmerthal will become operational. The operators mention years starting from 2026. However, the 25-hectare Emmerthal substation is not scheduled to be completed until the end of 2030. RheinMainLink could provide a transport capacity of approximately 8 GW from 2033. SüdLink (4 GW) hopes for completion of construction work by 2028.

The respective project developers are often not the operators of a BESS in the end. For example, Allianz Global Investors (Allianz GI) recently acquired 51 percent of GESI. The 137 MW BESS currently being built by Kyon Energy in Alfeld has in turn been sold to the Danish investor Obton. It is located at the Godenau substation, about 27 kilometers as the crow flies from the Emmerthal energy cluster and near the SüdLink line. However, it is connected via the Lamspringe substation to the new 380 kV Wahle-Mecklar line.

Originally, the companies Hansa Battery and Kyon Energy had also planned two other, smaller BESS in Emmerthal, but have abandoned these plans.

The Emmerthal energy cluster also provides for commercial areas to attract businesses. The municipality intends to favor local and medium-sized companies to avoid causing too much additional road traffic. The nearest motorway connection to the A2 is more than 30 kilometers away.

Stronger conductor cables

The grid operator TenneT intends to strengthen the existing 380 kV lines in the region through “re-stringing”. According to information from the provider Wiretec, special aluminum-steel overhead line cables can withstand temperatures up to 150 degrees Celsius and thus higher currents. This means that the current-carrying capacity of the “hot cables” should be up to 50 percent higher than that of old cables with the same diameter and similar weight per kilometer. Additionally, a black coating can improve heat radiation.

From the previous Grohnde substation, a 90-kilometer-long 380 kV connection leads, among other things, to the substation at the former Mehrum coal-fired power plant, which is currently being demolished. A large data center, also a BESS, and possibly a new gas-fired power plant are planned there.

(ciw)