Michael e-mails: "Dear Mr. Answer Person: I've really come to en enjoy watching the wind turbine spin as I walk to work in the morning. As I've watched it respond to the changing weather conditions, though, I've come up with a few questions that seem right up your alley:
1) I've noticed that the base rotates in order (I assume) to align the blades with the wind direction. I've also noticed that sometimes it seems to be a little out of alignment, with the blades rotating at a direction not quite parallel to the direction that the wind seems (based on feel and the way the flag blows) to be moving, and at a speed that seems substantially slower than the strength of the wind. My question is about how the turbine "knows" to orient itself relative to wind direction. Is this an automated process, or human-controlled? Does the base move on a rotor, or does it swing freely with the wind?
2) 1.6 megawatts is kind of a big, abstract concept. Can you provide any more granular or familiar figures for how much power the turbine produces in a given day? Or even better, for example: take one complete rotation of the turbine blade. How much power does that
generate? How long would it power, say, a single 60-watt standard light bulb? A standard CFL bulb?
Mr. Answer Person responds:
Luther College has a web page devoted to answering questions about the wind turbine. You can find it at: http://www.luther.edu/sustainability/energy/windturbine/. It answers not only your questions, but other common questions and includes links to videos explaining wind turbines.
1) here's what the web page says: "Luther's wind turbine is classified as a 'down-wind' turbine. This means that the blades spin when wind is blowing directly at them, or when the turbine is facing into the wind. Because wind changes direction from day to day, the blades also need to be able to change direction in order to work best. A weather vane on top of the nacelle, the gearbox mounted on the tower, measures wind speed and direction. Using this information, the nacelle uses a series of gears housed in the tower to rotate into the wind."
2) Here's what the web page says about the electricity generated (although not in the terms you asked about): "The electricity from the turbine will serve Alliant Energy's customers on the west side of Decorah, including Luther College. The 5.2 million kilowatt hours of net electricity generated per year are enough to power more than 500 homes in Decorah and represents approximately one third of Luther's annual consumption.