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Wind Energy Center requires transmission line

Jan 6, 2007 - McClatchy-Tribune Regional News - Kevin Bonham Grand Forks Herald, N.D.

The $250 million Langdon Wind Energy Center near here could not begin to deliver wind energy throughout eastern North Dakota and northwestern Minnesota without a new $10 million transmission line.

The 115-kilovolt line will replace a 41.6-kilovolt transmission line owned by Otter Tail.

At Hensel, it connects with other transmission lines that transfer power throughout the region.

How wind turbines work

Wind turbines capture the wind's energy with two or three propeller-like blades, which are mounted on a rotor, to generate electricity. The turbines sit high atop towers, taking advantage of the stronger and less turbulent wind at 100 feet (30 meters) or more above ground.

A blade acts much like an airplane wing:

-- When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade.

-- The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift.

-- The force of the lift actually is much stronger than the wind's force against the front side of the blade, which is called drag.

-- The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity. Overall, the wind energy centers works like this:

-- A computer automatically controls each turbine.

-- The computer turns the rotor consisting of three blades and a hub inside a nacelle (enclosure) to face into the wind.

-- The rotor turns (depending on the type of wind turbine) at 11 to 22 rotations per minute. As the wind blows, the pitch of the rotor blade adjusts to suit the changes in the wind speed. For safely purposes, the turbine shuts down automatically if the wind speed exceeds 56 miles per hour.

-- The blades drive the main shaft, which drives the generator through a gearbox to convert the mechanical power to electrical power.

-- The electricity is cabled down the turbine tower, then through a series of transformers and underground distribution lines before entering the main substation.

-- At the substation, the voltage is stepped up and delivered to the electric grid. The step-up enhances the efficiency of energy transmission to homes and businesses.

Wind: How reliable?

Sophisticated monitoring and wind resource analysis allow wind developers to estimate with a high degree of certainty "when" and "how much" wind energy is available, so customers can plan their wind power purchases. When the wind blows, it can displace fossil-fueled generation such as oil and gas. Studies have shown that when a utility diversifies its power portfolio with the addition of wind energy, it can meet demands more reliably.

What if it's not windy?

When the wind is calm, the turbine is at rest. However, at the hub height of a utility-scale wind turbine -- usually more than 200 feet above ground -- on a site selected specifically for its good wind resources, it is rare for the wind to be totally still.

Are there wind seasons?

Yes, but they vary by region. In California, the peak wind season is summer; in the Midwest, it's fall and winter, and in Texas, spring is peak. Each wind plant has specific daily and seasonal variations. Each wind site also has specific wind patterns, which are determined through wind studies conducted during early development of a project.

Source: FPL Energy