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Advancing wind power with the Pitch Bearing Unit
The energy transition is an important topic that has become an integral part of our present and our future. The aim is to convert the energy supply to renewable energy sources on a sustainable basis – and at competitive costs. The resulting economic and technical requirements pose new challenges for the industry. This is where thyssenkrupp rothe erde comes in and presents a groundbreaking product innovation: the Pitch Bearing Unit, or PBU for short.
In recent years, the number of wind turbines in onshore and offshore applications has increased worldwide – and a further rapid increase is planned to achieve the climate targets. With our rothe erde® slewing bearings, which are used in wind turbines for example, we are already making a decisive contribution to the energy transition. We think there is more to be done! That's why our experts have developed the Pitch Bearing Unit in a development project with HAWE Hydraulik SE and ITH Bolting Solutions, offering a customized solution for future generations of onshore and offshore wind turbines.
The structure of wind turbines at a glance
What do the components of wind turbines look like in detail? That's quickly explained! They are made up of three parts: the tower, the nacelle and the rotor. And this is exactly where our slewing bearings are used.
The tower ensures that today's wind turbines reach a hub height of more than 100 meters above the ground. This allows optimum use to be made of the wind, depending on the location. The rotor consists of a rotor hub, the pitch bearings and the rotor blades. The rotor converts the kinetic energy of the wind into mechanical energy for the drive train. The nacelle forms the heart of the turbine, as it contains the generator and the gearbox.
Wind turbines have become an integral part of the energy transition.
In focus: tackling the challenges of wind turbines
To understand what the Pitch Bearing Unit is and what advantages it brings, we first look at the current and future challenges facing wind power.
“A key challenge in wind power is the further development of the technology, especially in light of the growth in turbine size,” explains Dr. Daniel Becker, Head of Bearing Calculation & Tools. The engineer has been working at Rothe Erde for 13 years and, together with his team, deals primarily with calculation topics and corresponding development projects – including the PBU.
Dr. Daniel Becker and his team deal with calculation topics and development projects to further develop the technology of the Pitch Bearing Unit (PBU).
“These challenges apply especially to very powerful systems that are located offshore, i.e. on the sea. The focus here is not primarily on the logistics or transportation of the individual components or assemblies, but rather on the technological growth in size of the components,” Becker continues. This is the case, for example, with the rotor hub or the rotor blade itself, which in turn poses additional challenges for blade adjustment or pitch storage at component level. However, it is not only the further development of the technology that the industry has to deal with.
Among other things, the focus is also on the so-called total costs. These are the procurement costs for the component and the additional expenses for logistics, construction and on-site assembly of the module. This also brings more fundamental issues such as industrialization and productivity increases within the entire supply chain, from production to assembly, into the focus of developers like Becker and his team.
In addition, product development times are becoming ever shorter, while the need for coordination between individual suppliers is increasing, as is the standardization and modularization of individual components.
Die PBU ermöglicht eine gezielte Vereinfachung des Nabendesigns und damit der nabenseitigen Fertigungs- und Montagekosten.
The Pitch Bearing Unit opens new opportunities
With the Pitch Bearing Unit, thyssenkrupp rothe erde has added a new product to its own core competencies. Current development trends in multi-megawatt wind turbines show that deformations on the rotor hub and rotor blade side can have a significant impact on the performance and therefore the service life of the pitch bearings during operation. This is precisely where the Pitch Bearing Unit can help.
“The PBU also acts as a stiffening element between the hub and pitch bearing. It significantly increases the structural stability and rigidity in this area of the wind turbine, which is particularly evident with large and therefore potentially soft hub bodies,” explains Dr. Martin Neidnicht, Group Manager FEM Applications in the Bearing Calculation & Tools department at Rothe Erde.
In addition to the mechanical advantage, the PBU offers further benefits for the wind turbine of tomorrow. The Pitch Bearing Unit is a completely ready-to-install unit and combines three functions in one. The PBU combines the functions of conventional blade bearings, hydraulic or electric blade adjustment and the optimization of mechanical system stiffness. This means that the hydraulic or electric blade adjustment system can be integrated directly into the PBU without a connection to the hub. The advantage: the supply chains of the hub and pitch drive can be specifically separated. This saves logistics costs as well as machining and assembly work for the hub manufacturer. The blade adjustment system can already be adjusted and tested during the assembly of the PBU, which significantly reduces the complexity and overall effort involved in the final assembly of the wind turbine on site thanks to the plug-and-play concept.
The PBU also makes it possible to make hubs smaller without changing the rotor blade size.
But what is the difference in the hubs with and without the PBU? Thanks to its conical shape, the Pitch Bearing Unit makes it possible to completely rethink the design of hubs. “By using the PBU, for example, the hub can be made smaller without changing the rotor blade size. At the same time, the blade loads, i.e. the forces and torques that the rotor blades can withstand and which are used to generate energy, remain unchanged,” says Dr. Daniel Becker. Alternatively, the PBU can be used to increase the rotor blade diameter without changing the hub size, for example to use different materials on the rotor blade side, to install different rotor blades or to increase the rotor blade length in a targeted manner.
A simpler and smaller hub also ensures less complex production, which reduces manufacturing costs. However, transportation costs are particularly relevant for onshore turbines, as the components are usually transported by road in special transports. Increasingly larger components have special requirements on the means of transportation due to their size and weight. And on some routes, long detours must be accepted, for example due to low bridge heights. Smaller hub bodies using PBU can bring cost benefits here.
Another advantage of the Pitch Bearing Unit is the possible standardization and modularization of the hub component. This means that standard hub designs could be used for certain size ranges of wind turbines in the future. Initially manufacturer-specific, i.e. platform-dependent, and in a further step even manufacturer-independent. Such standard hubs could be adapted to different rotor blade diameters and pitch concepts using different PBUs. “By standardizing the hub and modularizing the pitch unit, optimizations and cost savings in the supply chains of wind turbine manufacturers are conceivable, similar to the automotive sector,” says Dr. Becker.
Hub with pitch drive without PBU (left hydraulic, right electric)
Hub, smaller in comparison, with PBU (left hydraulic, right electric)
3 in 1 – The Pitch Bearing Unit combines blade bearing, blade adjustment and stiffening element in one ready-to-install unit.
Full wind power: New opportunities and prospects for the future of the wind energy sector
The Pitch Bearing Unit developed by Dr. Daniel Becker and his team opens up a number of opportunities and areas of development for the wind power industry. This primarily concerns the supply chains of wind turbine manufacturers against the background of standardization and modularization, which allows further cost optimization. Other starting points include less on-site assembly work during the installation and commissioning of wind turbines and the targeted reduction of manufacturing, processing and road transportation costs for hubs.
You can find more insights into sustainable processes and technologies at thyssenkrupp in our stories.