USA – Wind monitoring tower captures wind statistics

On an undeveloped parcel of land just beyond the Mat-Su Central Landfill, a 100-foot tower silently measures the wind while seagulls and bald eagles that frequent the dump fly overhead, taking advantage of wind currents. Two employees of Alaska Energy Authority, which loaned the wind-monitor tower to Valley Community for Recycling Solutions, raised the 4-inch-diameter aluminium pole using a battery-powered winch Tuesday afternoon. AEA loaned one of its wind-monitor towers to VCRS for a year-long study of the wind. A computer chip in the monitor records wind velocity, wind direction and temperatures. There are three anemometers on the pole, measuring wind speed. Two are located at 30 meters and the third was placed at 20 meters. The tower also sports a wind vane and a temperature sensor, according to Doug J. Vaught, AEA consulting engineer. The new data-collecting tower will provide great opportunities for field trips for school-aged children, said Mollie Boyer, VCRS's executive director.

"It's something people can see. It's tangible," Boyer said. "This is one of the first steps toward getting our green building." VCRS hopes a new recycling centre constructed according to green building standards will fill the empty space next to Mat-Su's Animal Care and Regulation shelter. One of the requirements for green buildings hinges on the use of alternative energy such as wind or solar energy. So, the data gained from the year-long study should help shape the up-and-coming facility. The Mat-Su Borough gave VCRS a free lease of the parcel for the new facility. Another advantage of the wind monitor: Data will become accessible to the community, Boyer said. AEA can use the information for other projects, although the data are site specific, she said. The reason two anemometers have been positioned 30 meters up the tower is for redundancy - to double-check the information gathered, Vaught said. The anemometer is placed at 30 meters because that's the height of the hub of turbines most likely used in rural Alaska, he explained. The energy wind produces depends on wind density and wind speed and the size of the rotor. The proportions of the turbine blade will determine how much wind is swept with each rotation; the more wind gathered, the more energy produced.

The energy developed through wind energy relies heavily on wind speed. To apply the mathematical formula, wind velocity is cubed. That means wind speed is multiplied by itself three times. "It's wind speed times wind speed times wind speed," Vaught said. "If you double the speed of the wind, you increase the potential energy by eight times." Temperature also proves to be a variable. "Colder air is denser so the rotor blades produce more lift. For example, 10 degrees below zero with a 25-mph wind will produce more energy than 25-mph wind on a 70-degree day," Vaught said. AEA supplies wind-monitor towers to rural Alaska villages for one complete seasonal cycle, usually from summer to summer. Four villages generate some percentage of their energy needs from wind turbines, according to Mia Devine, AEA assistant project manager. Kotzebue installed 13 turbines, Selawik erected four wind-catching devices, and Wales' energy needs are partially sustained by two turbines. Wales has constructed a foundation for the third one. St. Paul gathers some of its energy from one large wind turbine. In the next couple of years, a wind turbine could be capturing this invisible source of energy and fuelling part of the energy needs of a new recycling centre. For now, the wind monitor stands alone in a field of reawakening wild rose bushes and dried Alaska grasses. And already, it is doing its job: Gathering valuable data for future needs. "We get phone calls from people in Palmer wanting to know about wind generation. The wind monitor will tell us a lot about the wind energy in this area. It's possible that someone could put a personal wind turbine in their yard to generate electricity to a small cabin," said Reuben Loewen, Alaska Energy Authority project manager. "The Valley has two nice glaciers that produce a lot of wind."