Under the deal, Deutsche Bahn will buy the power produced from a 25MW portion of the 48-turbine project at a fixed price.
The supply and trading unit of Innogy’s parent company RWE will act as the contracts and retail partner.
Nordsee Ost consists of 48 of Senvion’s 6.2M126 turbines and was commissioned in 2015.
State-owned railway operator Deutsche Bahn plans to source 100% of its electricity from clean sources, up from 57% today.
Its CEO Torsten Schein said Deutsche Bahn plans to replace expiring fossil fuel-based contracts with power deals for renewable energy "over the next few years", and intends to launch a Europe-wide tender for clean energy contracts by the end of the month.
Corporate PPAs remain rare in Germany — even for onshore wind — but more deals are anticipated beyond 2021 as support schemes expire.
Innogy is due to be carved up under a complex asset swap deal between its owner RWE and utility E.on.
RWE will acquire the renewable assets — including Nordsee Ost — and gas storage businesses of its subsidiary Innogy, as well as those of E.on.
Meanwhile, E.on will buy 86.2% of Innogy and its grid and retail business, and RWE will receive a 16.67% "effective participation" in E.on in return.