Keeping Weight Down Key to Boosting Turbine Performance

The Vestas V90 improves over previous designs by requiring fewer and less demanding service calls.

The V90-3.0 MW turbine from Vestas Americas improves on previous designs thanks to lightweight carbon fiber in  blades and stronger steel for a lighter tower. What’s more, a microprocessor controlled pitch regulator and  redesigned nacelle further improve the turbine’s performance. The company says minimizing weight was a matter of high priority.  As weight goes up, so do costs for production, materials, transportation, and installation. The payoff for the V90-3.0  MW: It takes only two to three hours for it to supply an average European family with electricity for a year. Although the  V90-3.0 MW design is not the company’s most recent design, it was a significant step forward when introduced, has  proved itself a workhorse for wind farm owners, and provided a spring board for additional designs.

The blade design is shared with the V90-2.0 MW turbine, also a 90-m rotor. The blade structure is said to differ from  previous designs by using new materials, most notably carbon fiber for the load bearing spars, and a revised blade  profile. Carbon fiber is lighter than the fiber glass it replaces and its strength and rigidity also reduce the quantity of  material needed which further reduces overall weight. Even though the V90 has a 27% larger swept area than the V80,  the new blades weigh about the same. The final blade design, in part due to a collaboration with Risø National  Laboratory in Denmark, features a plane shape and a curved back edge. The resulting airfoil improves energy  production, while making the blade profile less sensitive to dirt on the leading edge, and maintaining a favorable geometric relationship between successive airfoil thicknesses. Blade features include the microprocessor-controlled pitch regulator. OptiTip constantly adjusts the angle of the turbine blades for best position in relation to prevailing winds. This capability is used in all but one Vestas  turbine. Despite the larger rotor and generator, the V90-3.0 MW weighs less than the V80-2.0 MW turbine.

The nacelle represents a radical redesign, says the firm. Even though the 3-MW generator is larger than the unit in the  2-MW design, nacelle weights are almost equal. This was done by combining the hub bedplate directly into the  gearbox, eliminating the main shaft and thus shortening the nacelle. The result is a nacelle that can generate more  power without an appreciable increase in size, weight, or tower load. Tower improvements come from a stronger steel which requires using less of it. Towers are now constructed in fewer sections than previous designs, with significant  savings in material, transportation, and installation.

Since its introduction in 2002, the company says it has installed more than 1,000 V90 3.0 MW units around the world. The design has been a springboard for the V112-3.0 MW unit a recently introduced on and off-shore turbine. The V112,  however, will not see service in the U.S. till about 2011 and later in Canada.