LIGHTWIND: A disruptive drive-train for ultralight and lower cost wind turbines

At a glance

• As wind turbines increase in size, their material and maintenance costs increase disproportionately, particularly as far as the bearings are concerned. Significant costs are incurred when complete components have to be replaced.
• LIGHTWIND is an international project in which the project partners are developing a lightweight, modular drive train for offshore wind turbines on the basis of the patented OptiGen technology and testing its economic viability.
• Fraunhofer IWES is responsible for the development and validation of the test methodology.

The challenge

Floating offshore wind turbines (FOWT) have not yet achieved a breakthrough in the market. However, the technology, which can be employed in water depths of 60 meters and more, would make a key contribution to reaching the EU’s goal of 300 GW of offshore wind power in total by 2050 thanks to its enormous potential: in the EU alone, it would be possible to install almost 2,500 GW of floating offshore wind (FOW).

Technical challenges are one reason for FOW’s lack of success to date. For example, turbines located in deep water have to be particularly reliable and powerful to minimize the high operating costs. In the case of direct-drive wind turbines, the robustness of which makes them suitable for offshore use, the weight of the nacelle increases disproportionately with increasing generator power. This affects the whole turbine design, especially for FOW, which is currently reaching its limits at a system size of 16 MW.

Beyond this, increasing generator size makes it more and more difficult to guarantee that direct-drive turbines can maintain the size of the air gap, i.e., the radial distance between the generator rotor and stator. Technical solutions require either great care to be taken during component production or a stronger magnetic field, which, in turn, increases the weight and needs more rare-earth elements for the permanent magnets.

The solution

This is where the LIGHTWIND project comes in. Its objective is to develop a lightweight, segmented drive train for offshore wind turbines based on the patented OptiGen technology. This modular generator concept with roller-rail assembly results in a much more compact design and reduced weight even as the power increases.

OptiGen is to be integrated into the existing offshore wind energy technology in the course of the project and validated step-by-step via digital modeling and physical tests of components, subsystems, and a scaled-down prototype. The aim is to produce a preliminary digital design for a wind turbine generator system with 22 MW of rated power. Moreover, the scientists will quantify the advantages of OptiGen at a social, environmental, and general economic level, in addition to developing a strategy for the market launch.

Fraunhofer IWES is responsible for developing and validating the testing methodology. Furthermore, the experimental validation will be carried out using the institute’s existing test infrastructure. 

The added value

LIGHTWIND will lay the foundations for exploiting the potential of FOW at acceptable costs. At the same time, coastal offshore wind energy will also benefit from larger turbines and new technical concepts. The modular generator concept means that the number of suppliers will increase, as the requirements placed on production will become less demanding. This goes hand in hand with the avoidance of supply bottlenecks and project delays. LIGHTWIND will thus contribute to achieving the German goals for the expansion of offshore wind energy.