Introduction
The nacelle is the heart of a modern wind turbine, housing the drivetrain and all critical electro-mechanical systems that convert kinetic wind energy into electrical power. Located atop the tower, it contains the main shaft, gearbox, generator, power electronics, control systems, cooling units, hydraulic aggregates, and pitch & yaw mechanisms. Germany has long been a global powerhouse in wind energy component manufacturing, with a dense network of specialised suppliers spanning from the Ruhr region to Bavaria. This article profiles the key German companies supplying nacelle internals for onshore and offshore wind turbines, covering everything from forged main shafts to intelligent cooling systems.
Main Shaft & Rotor Support Systems
The main shaft (or low-speed shaft) transfers rotational energy from the rotor hub to the gearbox. It must withstand extreme alternating loads over a 20–25 year design life. German forging and heavy-steel specialists, many rooted in the country’s industrial heritage, produce main shafts in monolithic forged steels with integrated flanges. Precision machining and non-destructive testing (UT, MPI) are performed in-house. The main shaft is supported by bearing arrangements that are often supplied by Rothe Erde (Dortmund) in the form of large-diameter slewing bearings, or by IMO (Gremsdorf) for pitch and yaw bearing assemblies that interface directly with the main frame structure.
Key German Suppliers
Eickhoff – Bochum
Bochum, North Rhine-Westphalia
Core product: Wind turbine gearboxes and drivetrain systems.
Founded in 1864, Eickhoff Wind Power is one of the most established names in German gearbox
manufacturing. The company produces compact, high-torque planetary and hybrid gearboxes for
multi-megawatt turbines, including the 4–8 MW class. Eickhoff gearboxes are known for their
robust cast-iron housings, case-hardened ground gearing, and integrated condition monitoring
interfaces. The Bochum facility houses full-load test rigs capable of validating gearboxes up
to 15 MW, making Eickhoff a critical link in the offshore wind supply chain. Their drivetrain
packages often include the main shaft, gearbox, and torque support system as a pre-assembled unit.
Rothe Erde – Dortmund
Dortmund, North Rhine-Westphalia
Core product: Large-diameter slewing bearings for yaw and pitch systems.
Rothe Erde, a thyssenkrupp subsidiary, is the world leader in slewing bearings. In wind turbines,
their bearings are used for the yaw system (turning the nacelle into the wind) and the pitch system
(adjusting blade angles). These bearings feature integrated gear teeth on the inner or outer ring,
allowing direct drive via pinions. Rothe Erde’s induction-hardened raceways and optimised
internal geometries deliver the durability needed for 20+ year service intervals. They also supply
main shaft locating/non-locating bearing arrangements for gearbox-integrated drivetrains.
IMO – Gremsdorf
Gremsdorf, Bavaria
Core product: Pitch and yaw bearing assemblies, bearing sealing solutions.
IMO (Ingenieurgesellschaft für Montage und Organisation mbH) specialises in wire-race bearings
and four-point contact ball bearings for pitch and yaw applications. Their patented “Seal &
Sense” technology integrates sealing and sensor functionality into the bearing unit, enabling
real-time condition monitoring. IMO bearings are lightweight yet high-strength, contributing to
overall nacelle mass reduction—a key factor in tower top head mass optimisation. The company
also supplies main shaft bearing arrangements for direct-drive and medium-speed drivetrain configurations.
Siemens AG – Erlangen
Erlangen, Bavaria
Core product: Generators, power electronics, control systems (SCADA).
Siemens Energy (headquartered in Erlangen with a major wind hub) provides doubly-fed induction
generators (DFIG) and full-converter permanent-magnet generators for wind turbines. Their
electrical drivetrain portfolio includes medium-voltage switchgear, converter cabinets, and
the Siemens SCADA platform for remote turbine monitoring and control. Siemens also supplies
pitch drive inverters and auxiliary power supply units that fit seamlessly into the nacelle
electrical enclosure. With a deep installed base across German and global turbine OEMs, Siemens
remains the dominant electrical systems supplier for the wind industry.
Hydac – Sulzbach
Sulzbach/Saar, Saarland
Core product: Hydraulic systems, filtration, cooling and lubrication units.
Hydac is a leading supplier of fluid engineering solutions for wind turbines. Their nacelle
portfolio includes hydraulic power units (HPUs) for pitch and braking systems, oil filtration
and conditioning units for gearbox lubrication, and fan-fin cooling packages for generators
and converters. Hydac’s “WindFluid” range integrates pump stations, manifolds,
accumulators, and sensors into compact skids that mount directly to the nacelle frame. Their
condition monitoring sensors (particle counters, moisture sensors, temperature probes) allow
predictive maintenance on lubrication and hydraulic circuits.
Teufelberger – German Operations
Wels (HQ Austria), with strong DE service network
Core product: Steel wire ropes, lifting gear, and rigging for nacelle assembly.
Although headquartered in Austria, Teufelberger has a strong German operational footprint serving
the wind industry. They supply high-tensile galvanised wire ropes used in pitch systems, yaw
drives, and internal nacelle crane hoists. Their “WindLine” product family includes
rotation-resistant ropes and synthetic slings designed specifically for wind turbine installation
and maintenance. While not a drivetrain component supplier per se, Teufelberger’s products
are integral to nacelle internal handling systems and blade pitch actuation mechanisms.
Cooling & Thermal Management
Modern multi-megawatt nacelles generate substantial waste heat from the gearbox, generator, and power converters. German suppliers have developed dedicated thermal management solutions. Liquid-to-air cooling circuits, oil coolers with EC fan arrays, and glycol-water secondary loops are typical. Thermostatic valves and proportional bypass controls maintain optimal operating temperatures. Hydac and other German specialists provide modular cooling skids that are pre-filled, pre-tested, and ready for quick installation.
Hydraulics & Pitch Systems
Pitch systems adjust blade angles to control rotor speed and power output. Most utility-scale turbines use hydraulic pitch actuation, though electric pitch drives are gaining share. German hydraulic suppliers deliver integrated pitch cylinders, accumulators, rotary unions, and proportional valves. Hydac is a primary source for these systems. The yaw system—which turns the nacelle to face the wind—relies on hydraulic disc brakes (caliper units) and yaw drives that engage with the Rothe Erde slewing bearing teeth. Multiple yaw drives work in concert to provide smooth, precise nacelle orientation.
Control & Electrical Systems
The nacelle houses the turbine controller, typically a PLC or industrial PC running specialised wind turbine software. Siemens offers its Simatic S7-1500 series configured for wind applications, handling pitch, yaw, converter, and grid-connection logic. Communication to the SCADA master (often Siemens Spectrum Power or third-party platforms) runs over industrial Ethernet protocols such as PROFINET and IEC 61850. Condition monitoring systems (CMS) with accelerometers on the main bearings and gearbox are increasingly integrated into the control cabinet, enabling vibration-based fault detection.
Supply Chain Integration & Outlook
German nacelle component suppliers benefit from deep vertical integration and a highly skilled workforce. The cluster in North Rhine-Westphalia (Eickhoff, Rothe Erde) and Bavaria (Siemens, IMO) provides short logistics routes and strong R&D collaboration with Fraunhofer institutes and technical universities. As turbines grow beyond 15 MW for offshore applications, German suppliers are investing in larger test benches, advanced materials (e.g., high-strength low-alloy steels, carbon-fibre composites for bedplates), and digital twin technologies for predictive maintenance. The shift toward medium-speed drivetrains (gearbox + PMG) is creating new opportunities for integrated supply packages, with Eickhoff and Siemens jointly offering optimised gearbox-generator units.
For project developers, OEMs, and EPC contractors sourcing nacelle components, Germany remains a first-choice market due to its reliability, quality standards, and comprehensive aftermarket support. All companies listed above export globally and maintain service networks across Europe, North America, and Asia.
Summary Table
| Company | Location | Nacelle Components |
|---|---|---|
| Eickhoff | Bochum | Gearboxes, drivetrain systems |
| Rothe Erde | Dortmund | Slewing bearings (yaw, pitch, main shaft) |
| IMO | Gremsdorf | Pitch/yaw bearings, bearing sensors |
| Siemens AG | Erlangen | Generators, controls, SCADA, power electronics |
| Hydac | Sulzbach | Hydraulics, filtration, cooling & lubrication |
| Teufelberger | Wels (DE ops) | Wire ropes, rigging, pitch cables |
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