Danish Wind Turbines of the 1980s

Encouraged by tax incentives offered by the Federal Government and the State of California in the 1980s, developers placed over 4,200 wind turbines in the San Gorgonio Pass north of Palm Springs. The harsh, gusty winds greeted them without mercy. When the dust settled, the most rugged survivors hailed from Denmark, and all were surprisingly similar in design.

The Danish design is a three-blade upwind turbine with a drivetrain assembled from largely off-the-shelf components, including robust all-steel German gearboxes. The design is more akin to marine, not aircraft engineering. Fiberglass blades turn the main shaft that rides on a pair of bearings. This low-speed shaft drives a gearbox that spins the high-speed shaft coupled to an induction generator to produce electricity.

The Danish turbines included two other features that distinguished them. For one, many of them appeared in Palm Springs on cylindrical towers, offering access to the turbine from the inside (Vestas and Windmatic were notable exceptions). A door at the bottom opened the interior space where a technician would climb a ladder, exiting a small hatch near the top (or halfway, for some models). In addition to standing firm in harsh winds, the round towers proved a more durable and vandal-resistant approach than the lattice towers used in other designs.

Danish turbines of this decade also used large, rigid blades that turned relatively slowly. For example, the 65 kW machines spun at 47 rotations per minute, much slower than nearby downwind machines. Overspeed protection came from air dampers incorporated into the end of each blade or spoilers that extended from the downwind face of the blade. You saw these at Stop 2 (the upper blade with the tip dampers and the lower with a spoiler). Both automatically activate at high rotational speeds to slow the rotor. This approach proved reliable and likely contributed more to the success of the Danish machines than any other aspect of their design.

Most Danish machines in Palm Springs came from four companies: Bonus, Vestas, Nordtank, and Micon. Their designs shared many similarities and components, so the spare parts from early machines are still used today to keep others running. Still, they competed, leading to differences.

Windmatic turbines, based on a design by Christian Riisager, were distinctly different, using LM Glasfieber blades with spoilers that extended from the downwind side at high speed to slow the rotor. More significantly, they spun counterclockwise while most other machines turned clockwise. The Windmatic turbines standing among the clockwise-spinning machines quickly stood out.

Overall, the turbines from Denmark won many more battles against the wind than their competitors. Their design was also suitable for scaling up in size, paving the way for their growth and longevity that extends to this day.