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ISSUE 118 VOL 2 PUBLISHED 9/24/2004

Taking adfantage

By Kyla Bauer
Contributing Writer

Friday, September 24, 2004

Wind, according to Webster's Ninth New Collegiate Dictionary (1983), stems from the Middle English language and is related to the Old High German wint, the Latin ventus, the Greek aeani, and the Sanskrit vati. In all of these languages, the meaning of wind is similar: it blows. Sometimes it blows quite a bit at St. Olaf. With the addition of wind turbines, however, St. Olaf can utilize the wind for its own benefit. How exactly does a wind turbine convert wind's energy for our electrical consumption, and where does wind come from in the first place?

Wind is a culminating effect of three processes: the rotation of the earth, the sun's warming of the earth and the impact of topography.

The earth makes a complete rotation daily and this spinning produces wind. While the earth spins on its axis, it also revolves around the sun. At different times of the day and year, certain regions of the earth are closer to the sun than others. The sun's radiation better reaches areas that are closer to it than farther away, causing an uneven warming of the earth. For example, areas surrounding the equator are warmer than the North and South Poles. As the air heats up near the equator, gas particles that compose the air expand, causing the air to become less dense and rise; hence the saying that heat always rises. On the other hand, the air near the poles is cooler and denser. The cooler air from the poles slides toward the equator to replace the warmer air that has risen and is journeying toward the poles. This continual circulation of air between warmer and cooler parts of the earth creates what are known as convection currents, or -- more broadly defined -- as wind.

Differences in air temperature that cause wind also occur between large bodies of water and land. Land heats up more quickly than water so that during the day air above land is generally warmer than air above large bodies of water. Wind blows inland during the day. At night, the reverse is true because land loses heat more easily than water.

Lastly, topographical features such as mountains contribute to wind. Mountainous regions sometimes form wind tunnels in which the land forces lower winds into tighter passageways, triggering the winds to gain momentum. Winds at higher altitudes tend to be stronger as well.

In the southeast corner of Minnesota, St. Olaf lies in the wake of turbulent winds because of its distance from the ocean and relatively flat surroundings, explained Gene Bakko, a biology professor at St. Olaf aiding with the turbine project. Minnesota experiences larger temperature fluctuations than land on the coast because it is not near oceans that tend to maintain a constant temperature, which moderates weather effects. No tall land formations exist around St. Olaf to impede the wind either. Locally, the wind gains strength on the Hill because it becomes compressed as it moves upward over the hill. At its height, the turbine can easily catch this wind at either of its proposed locations. How does the wind turbine capture this energy to produce the campus's electricity?

A basic design of a wind turbine is a tower that stands on an underground foundation. Most of the turbine's functional machinery hides inside of a nacelle, which connects the rotor, the part with three spinning blades, to the tower. Pete Sandberg, director of facilities, said that St. Olaf is purchasing a NEG Micon NM 82. The blades on this model actually adjust hydraulically to capture the most wind energy available. To do so, the turbine must first know the wind's direction and speed. A wind vane and anomometer on top of the nacelle remit this information to a computer known as a controller. Depending on the information it receives, the controller commands what is known as a yaw motor that attaches to a large bearing or wheel to turn the rotor into the direction of the wind.

Typically with this model, the rotor, which is 82 meters in diameter, makes 14.4 revolutions per minute (rpm). The rotor connects to a large main shaft inside the nacelle that turns a gearbox. The gearbox increases the revolutions to over a thousand rpm via a smaller shaft that powers a generator. Approximately 1650 kW surge from the generator down into large cables within the tower that extend below ground to give St. Olaf what it has been enjoying for almost 100 years: electricity.

Information about the production of wind and the basic components of a wind turbine come from the website of Danish Wind Industry Association at www.wind

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