“uåX˜äŠÊ˜·³Ç

CSIC Haizhuang (HZ) of China has introduced a new 5MW pitch-controlled variable speed offshore turbine for low and medium wind speeds.

The turbine features a 154m rotor diameter and is suitable for both onshore and offshore sites. A sister model, CSIC H127, with a 127m rotor diameter will also be available for (international) IEC WC I strong-wind sites.

Dutch engineering consultancy, Mecal, worked with CSIC on the turbine design, and senior technical specialist, Martin Gemen, discussed the product’s specifications and key features with “uåX˜äŠÊ˜·³Ç Offshore.

High speed

CSIC spent three years developing the 5MW turbine, collaborating on the design with Dutch firm, Mecal, Denmark's KK-Electronic and German offshore specialist, Lehnhoff Consulting.

The CSIC H154 prototype was installed earlier this month at the Rudong demonstration intertidal wind farm, in the eastern Chinese province of Jiangsu.

The company’s latest and largest product incorporates a high-speed geared drive system with permanent magnet generator (PMG). The drive system, except the choice for PMG, is comparable to the drivetrain layout used in Bard Engineering’s Bard 5.0 offshore turbine, explained Gemen.

Both turbine designs feature a single rotor bearing with a short hollow main shaft and a direct flange connection to the gearbox, which is fitted with two torque supports one at each side. The combination with a cast main carrier is considered to offer a robust and compact turbine layout, without compromising serviceability, including gearbox exchange.

German bearing specialist Schaeffler is one of the suppliers. It delivered the huge double-row roller bearing for the prototype, measuring 3.2m in outer diameter and weighing 6.7t. Just a decade ago this was about the largest size that could be produced in series, but size-related manufacturing quality has advanced and serial production of more than four metres outer diameter is now feasible.

Schaeffler has worked with CSIC in the past, having collaborated with the turbine manufacturer on its 2MW and 2.5MW onshore turbine models.

Reliable solution

CSIC considers geared transmissions the most reliable wind turbine drive solution, according to Gemen. Claiming to be China’s second largest manufacturer of wind turbine gearboxes, CSIC has itself supplied the gearbox.

The CSIC H154 features 75m blades similar to the 6MW Siemens SWT-6.0-154. Together with a "modest" 5MW power rating this translates into a specific power rating of 270W/m², compared to 320W/m² for Siemens’ 6MW turbine with the same rotor size.

"The Siemens turbine has been designed for IEC WC I conditions with 9-10m/s mean wind speeds, said Gemen. "Such wind conditions do not prevail in Chinese waters. Off China’s coast, IEC III conditions with a maximum mean wind speed of 7.5m/s and sometimes IEC II (maximum 8.5m/s) are typical. Our turbine specifications also had to meet extreme weather conditions, including typhoons."

The CSIC HZ 154 design has been yield-optimised for Wind Class IIIB+ conditions, whereby the ‘+’ stands for additional built-in capability for extreme weather conditions as defined within IEC Wind Class II (50m/s). Interestingly, the recently introduced 3MW Vestas V126-3.0MW that was also developed for IEC WC IIIB wind conditions scores 240W/m2.

Head mass

CSIC claims a 15% head mass (nacelle + rotor) reduction compared to competing 5MW turbines, such as REpower’s 5M, Bard’s 5.0 and Sinovel’s SL5000 geared high-speed designs. This has been achieved through advanced design tools and optimisation.

Compared to specifications for the REpower 5M and Bard 5.0, the reduced head mass figure for CSIC’s 5MW turbine would correspond to around 360–370T. At the same time, it should be noted that Bard’s 5MW turbine was developed for demanding IEC WC IC conditions and within a record nine-month period. Insiders report that due to time pressures the Bard design was not fully weight-optimised. Furthermore, the Bard 5.0 features a 122m rotor diameter and 60m long rather wide and heavy blades weighing about 28.5t each. By comparison, Siemens’ 75m blades weigh ‘only’ about 25t. Specifications for the CSIC 75m blade were not available.