Storing Surplus Electricity

January 2019

With its 37 steel boxes, it might look like a storage depot for container shipping. But the 4,000 sqm site in a North Sea coastal town near Bremerhaven is actually home to a huge battery complex.

With a storage capacity of up to 25 MWh, the complex could theoretically supply energy to Varel’s roughly 24,000 residents for five days. But its real purpose is to store surplus electricity generated by wind turbines and to help stabilize any fluctuations in the grid by taking out or feeding in more than 11.5 MW of electricity when needed.

Of course, more than 40 similar complexes are either operating or in the planning stages in Germany. But this one is unique due to its two types of batteries: lithium-ion batteries offering quick access to stored energy, and sodium-sulfur batteries that store the energy for a longer period of time.

The EUR 27 million complex, which officially went into service on November 1, is part of a project launched by a consortium including Oldenburg-based EWE, Germany’s fourth-largest energy company, and three Japanese energy specialists – Hitachi Chemical, Hitachi Power Solutions and NGK Insulators – which believe that northern Germany offers ideal conditions for testing such technology. While EWE is supplying EUR 3 million in funding, the other EUR 24 million will come from Japan’s New Energy and Industrial Technology Development Organization (NEDO). In the spring of 2020, following a three-year demonstration phase, EWE will take over the plant from the Japanese free of charge and continue to operate it.