German company Linnhoff Offshore has developed floating foundations for wind turbines that self-adjust their positioning to the wind. These newly designed platforms are easy to build in water depths of up to 200 m
The construction, installation and maintenance of durable foundations is responsible for much of the costs associated with offshore wind farms[ds_preview]. These expenses rise even further when turbines are to be installed in deep water. One solution to this problem is the use of floating foundations that are moored to the seabed.
Until recently, however, this idea had not made it past the prototype stage of various projects. Now, German company Linnhoff Offshore is offering the first commercially viable floating turbines. The technology is being developed and tested in cooperation with renowned Hamburg University of Technology, Institute for Fluid Dynamics and Ship Theory, Institute for Ship Structural Design and Analysis as well as DNV GL, Aerodyn and Unterweser Industries.
The project is funded by the German Federal Ministry for Economic Affairs and Energy. Linnhoff expects immediate cost reductions – for investment, construction and installation – of up to 40 % per unit.
High stability, reduced complexity
The Linnhoff Offshore Floating Turbines (LOFTs) are semi-submersible, self-adjusted platforms stabilized by 5,000t of ballast water – even in conditions of high wind and five-meter waves the movements at the hub height of 100 m do not impair operations. Holding the foundation in position is a single-point mooring hook-up that is also utilized for power transport. The hook-up, which is based on proven technology from the offshore oil and gas industry, is also part of an elaborate design that ensures continual alignment of the LOFT rotor to the wind – this self-adjusting process is aided by the symmetrically profiled tower and blades.
In combination, these factors allow to dispense with the 360-degree yaw bearing required in traditional turbines, therefore reducing production and maintenance costs significantly. At the same time, the cantilevered towers eliminate the danger of blade impacts. Linnhoff’s floating turbines also promise considerably easier installation in water depth of up to 200m. The completed, ready-to-operate LOFTs can be towed to their positions. In a simple maneuver they are hooked up to the single-point mooring connectors without requiring jack-up vessel assistance. For large repairs or upgrades, the units can be towed back to the shore. Major offshore maintenance and construction work is eliminated.
Whenever tasks need to be performed at sea, the LOFTs are boarded via their leeward floaters, which – in comparison to a fixed body – can be accessed in rougher weather conditions. The approach and transfer maneuvers are easier and require less sophisticated equipment, therefore increasing safety and bottom line results at the same time. Additionally, marine life will be grateful for the use of Linnhoff’s floating foundations. Underwater construction noise, a serious problem for some animals, is a matter of the past. The suction bucket anchorage system is easily installed – or removed. Also, the mooring system covers only a small area of the sea floor, leaving it almost completely intact.
The LOFT family currently consists of three models with strengths under different conditions, such as a two-blade turbine that is particularly well suited for high-wind regions. The units can be built at ship yards anywhere in the world. Their simple design enables the use of automated yard modules production methods.
RD
