The employee was hit by a 12-tonne stator shield, which fell to the floor during lifting and repositioning at the plant in Aurich, Enercon stated.
Despite first aid being administered and the ambulance service being called, the worker died in hospital, the manufacturer confirmed.
The cause of the incident is currently unknown.
Enercon established MTA Metalltechnologie, which produces nacelle casings and cast components such as axle pins and blade adapters, in late 2007.
Both the Aurich police and MTA had launched investigations into the incident.
Aurich police has now closed the case. A spokesman described the incident as a "working accident", and confirmed that there had been no arrests and that no proseuctions would be made.