Offshore Wind Turbine Vendors Unveil Next-Generation Wind Power Machines

At the recent EWEA Offshore 2013 conference and expo, turbine vendors displayed their latest and greatest turbines.

FRANKFURT -- EWEA’s biannual offshore wind conference and exhibition took place between 19 – 21 November in Frankfurt, Germany. International exhibitors and visitors could be clearly subdivided into typical marine and wind-industry related and additional companies and organizations offering specific products and dedicated offshore wind services such as a supersize HVAC submarine cable and several new foundation solutions.

ThyssenKrupp Mannex of Germany for instance presented a clever and innovative jacket foundation called Hexabase, described as the first industrial solution for offshore wind. The large-diameter open lightweight structure consists of so-called bionic elements, standardized pipes and pre-cast nodes, all of which mean a high automation level.

Here's a look at some new turbine product developments.

Integrated

Samsung of Korea had a prominent display at the show with a large booth dedicated to the 7-MW S7.0-171 offshore turbine, a prototype of which was recently installed in the UK. The behemoth is designed for 25-year operating life and features the world’s longest 83.5-metre blades offering a record 171.2-metre rotor diameter. The compact medium-speed drivetrain comprises a two-stage planetary gearbox designed and built by UK firm David Brown. A rather unusual design feature is that the gearbox has been integrated inside the large-diameter hollow main shaft, which in turn is supported by two rotor bearings.

The medium-voltage permanent magnet generator (PMG) operates at 3.3kV, and all power electronics including power cabinets, power-electronic converter, MV-transformer and switchgear are located in the tower base. According a Samsung spokesperson the turbine can achieve 73 percent capacity factor at high-wind sites, meaning that under the right conditions, on an annual basis, 63 percent of the time the turbine is producing power at more than 80 percent of its rated power, qualifying it as a “true power plant.” The company expects to receive certification in 2014.

High-speed PMG

Power engineering specialist ABB introduced a new 7-MW high-speed permanent magnet generator in Frankfurt. The generators come available in low voltage (690V)

and medium-voltage (3.3kV, and either water or air-cooled. All ABB high-speed generators for wind turbines (DFIG, PMG and induction-type) are based on a standard modular platform principle and feature an adaptable turbine interface. The modularity also allows changing from DFIG to PMG and vice versa depending upon customer preferences. Developing a new high-speed generator in the 7-MW high-end capacity range could come a bit as a surprise, because most new super-class geared turbine developments now seem to focus at medium-speed solutions.

Successor

REpower of Germany introduced the long-awaited successor to its 6.15-MW 6M (2009) flagship model, a product platform history that commenced in 2004 with a pioneering 5-MW 5M turbine, both with 126-metre rotor diameter. The new offshore model technologically builds on the 6M (now renamed 6.2M126, pictured right) and comes with unchanged power rating. New main features include the switch to a load-optimized cast main chassis and an enlarged 152-metre rotor diameter. This offers 46 percent more rotor swept area and, according Repower, a 20 percent higher yield at 9.5 percent average wind speed sites. The new slender blades are a dedicated REpower in-house product development. The 6.2M152 incorporates again a high-speed geared drivetrain with DFIG and 6.6kV stator voltage. 66kV transformer output voltage is now optional and is expected to become a new offshore wind standard for intra-array wind farm cabling.

Two-bladed and Downwind

German engineering consultancy aerodyn based in Frankfurt introduced an innovative two-bladed 8-MW SCD 8.0 down-wind offshore turbine with 168-metre rotor diameter. (SCD stands for Super Compact Drive.) The SCD 8.0 incorporates a medium-speed drivetrain with a single rotor bearing flanged to an in-house developed planetary

gearbox plus PMG. These main components in turn are flanged directly to a cast main carrier, and there is no separate nacelle cover.

One special product feature of the SCD 8.0 is a helicopter-landing platform integrated in the nacelle upper part, whereby actual landings are enabled only after locking the rotor in horizontal position. (See image, left, for an example of the 3-, 6-, and 8-MW products.)

Two-bladed turbines are new in the offshore market, but do offer specific advantages including easier deck stowage of fully assembled turbine heads (nacelle + rotor) plus time and cost-saving single-hoist installation. The SCD 8.0 is aimed at the European offshore market, and aerodyn owner/director Sönke Siegfriedsen firmly believes that a favorable 395-tonne head mass makes the turbine well-suited for both seabed-fixed and floating foundations solutions.

Optimization

SCD 8.0 is a further development and optimization of the 6-MW SCD 6.0, an IEC class IIB turbine featuring 140-metre rotor diameter. Aerodyn’s Chinese partner and licensee Ming Yang is currently finishing construction of the SCD 6.0 prototype, with installation planned for early 2014. The SCD 6.0 was specifically developed for the hurricane-prone coastal stretch between Shanghai and Hong Kong, which, according aerodyne, is one of the world’s largest future offshore wind markets. Ming Yang already operates several 3-MW two-bladed onshore upwind SCD 3.0 turbines with 110-metre rotor diameter for IEC class IIIA locations. (See image, right, for an example of an onshore two-bladed turbine.)

SCD was first presented at the 2007 Husum wind industry fair and was one of the world’s first medium-speed turbine designs.

SCD technology is built upon aerodyn’s (design) experiences with its patented 5-MW hybrid-type offshore turbine called Multibrid M5000. This groundbreaking turbine was developed and patented during 1996/7 and is comprised of a single rotor bearing and a highly compact fully enclosed cast chassis that incorporates a single-stage planetary gearbox and permanent magnet generator.

AREVA Wind commercialized the M5000-116, and an optimized 5-MW M5000-135 prototype with enlarged 135-metre rotor was installed this autumn.

Reducing CoE

Siemens Energy finally presented its new 4-MW and 6-MW offshore turbines in Frankfurt, including a new 4-MW SWT-4.0-120 model version with 120-metre rotor diameter. The company said that it wants to reduce lifecycle-based cost of energy (CoE, which equals turbine cost/kWh/20-25y) for both the 6-MW direct drive and 4-MW geared turbine models by up to 40 percent compared to today’s levels.

Substantially reducing CoE remains the offshore wind industry’s main overall challenge for the future of offshore wind power, and is a huge task ahead for all parties involved. Achieving this goal requires sustained combined efforts from project developers to wind turbine and submarine cable installation vessel designers/suppliers, foundation designers/manufacturers, advanced transport-logistics, installation contractors, and wind farm upkeep specialists.