Most wind turbine costs are headed in the wrong direction. A few years ago, according to one industry insider, a typical U.S. turbine installed cost $1.4 million/MW and a goal was to bring that figure down to $1 million. But costs are now closer to $2 million/MW for those onshore, and reportedly $3 to $4 million/MW for offshore turbines. Larger turbines are only part of the cost issue.
At least one company is working to keep costs under control and with a simple idea: Eliminate one blade, lighten the structure, and costs tend to drop. Although manufacturers tend to keep costs confidential, Nordic Windpower (nordicwindpower.com) claims a higher-than-average return on initial investment than at least two larger OEMs. For instance, company figures from 2009 list equipment prices of $1.2 million/MW, and an estimated annual operating cost of less than $15,000. Nordic reports that installations are coming in at less than $2 million per turbine including balance of plant. These figures tend to be on the low side when compared with those for three-blade designs. So for its cost-control efforts, the Nordic N1000 is Windpower Engineering’s Turbine of the Month.
The two-blade design also simplifies construction. Unlike three-blade turbines, the two blades are attached to the hub before lifting the nacelle. This makes ground assembly safer, faster, and easier to QA. Even with an attached rotor, the nacelle can be lifted in higher wind speeds, says the company, thereby reducing weather delays. Reduced component complexity and a relatively roomy nacelle interior (0.8-m wide passage around the machinery) make service and maintenance easier.
The company says gearbox durability is key to turbine reliability. Nordic says gearboxes in its N1000 show low wear even after years in service. Several design features reduce gearbox loading, such as the lower hub weight, which in turn reduces drive train loading. That unusual teeter or pivot-hub dissipates loads before they reach the gearbox. Main drive-shaft bearings are built into the gearbox for greater strength. A cylindrical steel housing holds the gearbox, drive shaft, and generator in alignment, forming a lightweight, load-absorbing unit.
Because of the flexible, two-blade design, the tower and foundation are lighter than those needed for more rigid and weightier turbines. The company says that overall, the N1000—including tower, nacelle and blades—is as much as 20% lighter than other turbines with the same output.
In addition, the company reports it is completing projects of 1 to 20 MW in community wind and DG markets in North and South America. As the company develops two-plus MW machines, it expects even more favorable cost savings ratios for small and large projects. WPE
The N-1000 by the numbers
|Nominal power||1,000 kW|
|Rated wind speed||16 m/s|
|Operation range||4 to 22 m/s|
|Extreme wind speed||52.5 m/s|
|Rotational speed||23 rpm|
|Blade dia., tip speed||59 m, 66 m/s|
|Blade material, weight||GRP, carbon, 4.2 tons|
|Nacelle with hub||40 tons|
|Pivot bearing||±2° elastomeric dampers|
|Power factor||0.98 at 100% power|
|Turnable blade tips
Centrifugal force, hydraulics
Disc brake with two calipers
Springs on, hydraulic-pressure off
|Gearbox||Two planetary, one-stage helical, integrated turbinew bearings
|Yaw system||Hydraulic drive motors|
Welded steel tube, 3.2-m dia bottom, 1.9-m top
|Tower height, weight||60m, or 70 m at 63 tons|