Turbines of the year -- Offshore turbines

WORLDWIDE: The competition hots up as offshore development moves into deeper waters and more challenging weather conditions

MHI Vestas V164-8MW…Winning combination of evolutionary and innovative design features
MHI Vestas V164-8MW…Winning combination of evolutionary and innovative design features


GOLD MHI Vestas V164-8.0MW

The world's most powerful turbine combines a clever mix of state-of-the-art and innovative solutions in a largely evolutionary design and scaling process.

The tube-shaped MSG-PMG drivetrain is self-supporting, with the twin-bearing main shaft housing mounted directly on a cast main chassis. Flange connections virtually eliminate misalignment risks, while a flexible shaft coupling promotes "pure" rotor torque transfer to the planetary gearbox and generator. The unusual combination of a cast chassis and welded spaceframe elements contributes to achieving a favourable head mass of about 500 tonnes.

An E-module incorporated in the tower foot consists of the power inverter, MV-transformer and switchgear. The helicopter-hoisting platform incorporates a passive cooling system without moving components.

The joint venture with MHI has also provided a huge boost to the financial strength and leverage of the new 50/50-company in winning new offshore wind farm contracts, with the trend for wind projects becoming increasingly bigger and built further from shore. Such conditions are also believed to favour the application of large powerful turbines.

Despite only one operating prototype, product-market expectations for the V164-8.0MW are high with multiple references made to the favourable business case this turbine will provide.

SILVER Ming Yang SCD 6.0

Expert opinions on the pros and cons of two-bladed downwind turbines continue to differ. But German design consultancy Aerodyn deserves credit for developing a product with the potential to meet China's complex typhoon-prone offshore conditions.

The medium-speed 6MW SCD 6.0 offshore turbine has a 140-metre rotor diameter and a total installation length (hub and nacelle) of only 11.2 metres. Offshore-specific features and benefits include a favourable 308-tonne head mass, easy onshore assembly, transportation and complete head single-hoist installation. A helicopter landing deck integrated into the nacelle aims to enhance working safety and reduce operations-and-maintenance access cost. It also eliminates the need for a separate nacelle cover. The prototype was installed in September 2014 in China with Aerodyn-designed main components, including gearbox, PMG and blades.

SCD-licensee Ming Yang is aiming the turbine at the typhoon-prone coastal stretch between Shanghai and Hong Kong, potentially one of the world's largest offshore markets. Typhoons are characterised by fast continuously fluctuating wind-flow patterns incorporating both vertical and horizontal components. Aerodyn developed a mathematical model in-house as such software simulation tools did not exist. When a typhoon approaches, the rotor is locked in a horizontal position with the hydraulic yaw system released. This allows the rotor to yaw freely and follow rapid wind direction changes with minimised structural loading. Optional is a 6.5MW SCD 6.5 with 130-metre rotor for IEC I.

BRONZE Siemens SWT-6.0-154

Last year's winner in the larger turbine range, the 6MW Siemens turbine started life in 2011 as an offshore turbine prototype with a new direct-drive generator and a rotor diameter of 120 metres. This model, followed a year later, with lightweight 75-metre blades for a 154-metre rotor diameter. Prototypes were installed in 2013.

The novel water-cooled outer-rotor PMG has a 6.5-metre outer diameter and a stator built in segments. A cast main carrier allows easy hub access via the hollow generator shaft and single rotor bearing.

Two power-electronic converters and the MV-transformer are located inside the nacelle, an arrangement that potentially reduces internal power transport losses and offers the additional benefits of onshore pre-commissioning.

Despite the nacelle-based converters and transformer that add weight to the nacelle, the SWT-6.0-154 manages to maintain a reasonably light head mass.

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