|Windmill farms abound in the West, like this one near Palm Springs in Southern California's Coachella Valley.
Wind farms, one of the most viable candidates to replace parts of our oil-dependent technologies, are growing in numbers in the U.S., and have the potential to become more efficient than they are today. One of the newest is a modest farm of five 1.5 megawatt wind turbines located in Atlantic City, New Jersey.
Completed in 2005, the Atlantic City site is the first coastal wind farm in the U.S., and the first wind farm in New Jersey. The turbines sit in an otherwise-unused (except by local fishermen) protected bay.
First Coastal Farm
A glance at a map of the nation's wind power resources (http://rredc.nrel.gov/wind/pubs/atlas/maps/chap2/2-01m.html) shows why New Jersey is new ground for wind turbines. Most of the sites with brisk, dependable winds are in the West, partly because of the abundance of high, exposed terrain. Favorable wind turbine locations in the East may be at relatively high altitudes, or along shorelines. Favorable locations without high mountains are mostly in the upper Midwest — in the Dakotas, for example — where weather comes sweeping in from Canada. The southeastern part of the country has few really good sites.
The Atlantic City wind farm is part of the Atlantic County Utilities Authority (ACUA) Wastewater Treatment Plant on U.S. Route 30. The wastewater plant will take about 50 percent of its electricity from the wind farm, and in doing so will use between 35 percent and 60 percent of the wind farm's output. The remainder of the output will be put into the main power grid.
Wind Is Fickle
One of the limitations of wind farms is the fickleness of the wind itself. When the wind dies, no power is generated. In the U.K., a partial answer has been developed. During times of high power generation, some power is used to pump water uphill into a reservoir. When the wind goes calm, the water is released to provide power from hydro turbines. This is not a new idea; several decades ago, New York State's Storm King Mountain was the focus of plans by the local power utility (Consolidated Edison) to create an elevated reservoir and build a pump storage power generator along with transmission lines. The plan never went through, being effectively blocked by conservationists.
At the University of Iowa, Dr. Andrew Kusiak is looking at ways to improve the efficiency of existing wind farms. He begins by data mining, analyzing the repository of wind speed and performance data generated by each turbine as it operates.
The result is an accurate computer model of a given wind turbine. Dr. Kusiak can then manipulate this model, and do such things as optimize the virtual wind turbine to gain maximum power.
He looks at the model of the turbine and asks, "Are we doing anything wrong with this turbine" Are we introducing stresses?" Sometimes the answer is yes. He may be able, for example, to increase power output by 10 percent.
Increasing the efficiency of existing wind turbines is important, he points out, because the demand for wind turbines is so great that production for a given factory may be sold out until the end of 2010 or 2011. Most of today's wind turbine production is in Asia; none are made in the U.S.
"We see how turbines behave as they go through different wind regimes," he says. "We think that we can improve power and improve torque ramp rates." By using computer models to optimize control, he thinks he can eliminate many maintenance problems. For example, a frequent problem in wind turbines is failing gearboxes. A single gearbox may cost $500,000 to replace.
A new wind turbine comes with a certified power curve that determines the relationship between wind and the power produced. "When you look at a certified power curve, it's like a function from a textbook; but the moment that you locate your turbine somewhere, that power curve disappears, and a different power curve takes its place. Moreover, that power curve is changing constantly." Most of the adaptation of the wind turbine to the specific site, Dr. Kusiak says, can be made with software, not hardware. It might be necessary, in a few cases, to redesign a few parts, but the payoff would be higher efficiency over the long term.
Smaller wind turbines are available for homeowners and business owners. They are usually installed directly to the building's electrical system, and when a surplus is generated, it can be fed into the power grid, running the electric meter backwards.