The AOC 15/50 Wind Turbine

Part 2 of 4


The 80-foot lattice steel tower lifts the wind turbine into stronger winds above the ground. Even without trees, there is some ground friction that reduces wind strength at lower levels. The tower is designed to withstand heavy ice loads and blizzard conditions.


Engineers working with the Department of Energy’s National Renewable Energy Laboratory helped develop the blades, or airfoils. An airfoil’s shape creates differences in pressure as the wind blows across it; those pressure differences cause the blade to spin around a hub. The blades are designed to spin at speeds that allow efficient electric energy production.

The design and length of the blades help determine the amount of wind energy that can be captured. These blades are 23.7 feet long, and sweep an area with a diameter of 49.2 feet. The blades and their hub make up the rotor.


The rotor is bolted to the main shaft, which enters the nacelle. The nacelle houses the components necessary for producing electrical energy, including the main shaft, gearbox, and the electrical generator itself. The main shaft transfers the wind’s power to a 30:1 gear transmission, which is coupled to a three-phase induction generator. The generator produces 480V alternating current (AC) power, which is fed into the utility’s system through transformers that raise it to regular distribution voltage of 7200V. Other transformers near homes and businesses reduce this voltage to 120V for use by consumers.

Shutdown/Braking System

The turbine has several braking mechanisms designed to keep the rotor spinning at proper speeds and protect the equipment from damage in high winds. Braking mechanisms include tip brakes on the ends of the blades to assist in slowing and stopping the rotor, a parking brake, and a dynamic braking system using the residual power of the generator to help slow the rotor.

Turbine Controller

A computer control system is used to operate the turbines. The controller reads wind speeds and the turbine’s status and then makes control decisions. It sends signals to regulate the speed or shut down the rotors when necessary, based on programming decisions made by utility personnel.

Part 1: Harnessing the Wind

Part 2: AOC 15/50 Wind Turbine

Part 3: Winds in Kotzebue

Part 4: Wind Energy Production