Siemens has upgraded the rating of its direct drive 7 MW offshore wind turbine to 8 MW. Siemens says that the resulting machine, designated SWT-8.0-154, represents a significant decrease in LCoE (levelised cost of energy) for the technology and another step towards grid parity for offshore wind. The 8 MW turbine is based on the existing offshore direct drive platform, but incorporates some evolutionary improvements that will allow the 8 MW version to be brought to market very quickly.
A prototype SWT-8.0-154 will be installed at a test site in Østerild, Denmark, in early 2017, and will exhibit an up to 10% higher level of annual energy production (AEP) under offshore wind conditions as compared to the 7 MW model. The offshore direct drive platform, says its maker, enables a significant reduction in the LCoE, and at low risk – that is, very few components in the new model have been changed, which takes advantage of the established reliability and performance of the brand. Type certification for the 8 MW turbine is expected to be obtained at the beginning of 2018.
Siemensbelievesitiswellonthewayto reaching its goal of producing offshore wind energy at a total cost of less than ten euro cents per kWh by 2020. In fact, it expects that generation costs for offshore wind power plants will decline to less than eight cents per kWh by 2025.
The new turbine has a rotor diameter of 154 m, the same as its predecessor model, but in a suitable location can generate up to 10 % more energy per year. The upgrade has been made possible by installing more powerful permanent magnets than those introduced in the SWT-7.0-154, a step achieved by changing the magnet material, in co-operative effort with the manufacturer. To ensure that they can operate at the greater power level, design changes were also made to the converters, which have a modular design so they can be adapted to a variety of turbine power levels. It was therefore a relatively simple matter to extend them to the higher generator output.
Proven components of offshore direct drive technology, including the B75 blade and the medium-voltage transformer, remain the same. From long-term observations of the 7 MW machine, engineers concluded that the mechanical elements, such as the bearings, will remain stable when operating with the higher torques.
Siemens’ direct drive technology has a good track record. Approximately 150 offshore DD WTGs rated at 6 MW have already been installed and commissioned.