By its acquisition of ScanWind, GE is incorporating combined European and American wind energy technology. In 2004 Finnish Arctic Wind Power contracted Norwegian ScanWind to supply gearless permanent magnet wind generators originally developed by German Siemens. It was imperative that these generators be highly reliable and require little maintenance in harsh environments.
Gearless generators were chosen since they offer high reliability especially in harsh environments. They also provide a higher efficiency converting rotational energy into electrical since the friction of a gear train is eliminated.
Permanent magnet synchronous generators have proven efficient with steam, gas, and hydro turbines. In these turbines, the shaft is usually synchronized to the grid frequency.
Since wind speed varies, the frequency of these synchronous generators varies and cannot be introduced directly into the grid. The output of each generator is converted to DC by diodes, which is then combined with that of other generators and fed to grid-tie inverters that converts DC to AC synchronized to the grid frequency and voltage.
Grid-tie inverters are also used to convert the DC output of solar photovoltaic panel into AC that can be fed into the grid. While the output of solar panels is a smooth DC, the output of a wind turbine is bumpy since it is obtained from rectified AC.
One of the advantages of ScanWind generators is that they operate over a wide range of wind velocities and will sometimes produce outputs of only a few cycles per minute. By combining the outputs of many generators a reasonable smooth DC ready for specially designed inverters can be obtained.
In these synchronous generators, the permanent magnets are on the rotor and rotated pass the stator or stationary part of the generator. There are no slip rings or commutators found in DC generators that will break down in harsh environments. There are no electrical connections to the rotor.
A similar move in technology occurred in automotive electronics about 50-year ago. DC generator commutators suffered from the harsh environment under the hood. These generators were replaced by “alternators,” which were synchronous generators utilizing diodes to produce DC.
While GE is the largest producer of wind generators, it has stiff competition. Mitsubishi has it own permanent magnet synchronous gearless wind generators. GE recently filled a patent infringement suit against Mitsubishi over wind generator claims (Bloomberg).
FloDesign Wind, a company in Boston claims to have greatly increased the efficiency of wind generator blades. While FloDesign has expertise in helicopter and et engine blade design, GE is a major designer and manufacture of jet engines and certain has it own aerodynamic expertise.
Certainly, the development of these turbines is a case of challenge and response since they were developed to meet the Scandinavian environment. GE and others will develop generators that will provide wind farms offshore where the windiest but harshest environments exist. Animal lover will be delighted to know that sea birds are able to avoid offshore wind farms.
Photo Credit: GE