Wind turbines: the bigger the better?

The European Union investigates the feasibility of a 20-megawatt wind turbine. But do bigger turbines mean even bigger price tags? The UpWind Project says maybe not.

Wind farms, like Shepherd's Flat , aren't the only things getting bigger. The wind turbines themselves are growing taller, with blades stretching farther into the air. Just last month, Danish company Vestas debuted its 7-megawatt offshore giant.

But a European Union project recently released a report about going even bigger: the 20-megawatt, 500-foot-tall turbine, with about 400-foot blades kind of big.

The goal of a larger turbine is to increase efficiency by capturing more wind energy via longer blades. The goal of the $33 million UpWind project was to determine to what extent such turbines are feasible, and importantly, whether they make financial sense.

The results of the report? They are, and they don't.

After five years of research, the engineers at the Risø National Laboratory for Sustainable Energy concluded that the mega turbines would come with a 20-percent higher price tag than their 5-megawatt little siblings. That is, if these larger turbines were built in the same fashion.

From the tip of the turbine blade to its base to the grid its electricity travels to, the project examined several areas in need of tweaking to make mega wind turbines cost competitive.

Should future winds ever blow on the behemoths, UpWind says the turbines would need smarter blade design and materials to reduce load fatigue on the longer blades. Such modifications might include flexible trailing edge flaps (below), controlling the blades individually, or having the blade resemble an airplane wing with two different parts, each controlled separately.

Lead Researcher Peter Hjuler Jensen:

We have worked on developing several different types of sensor systems such as pitot tubes which are also used to measure the wind speed of aircrafts. Should we introduce these innovations to existing wind turbines, they would probably be more expensive, but if they are implemented on very large turbines the savings from load reductions probably would be competitive. Our conclusion is that upscaling opens up for new technologies.

Taking into account the design of the wind farm could also come into play. As wind blows through a farm, the whirring turbines often alter the wind conditions for their turbine neighbors, causing them to be less efficient. Placing sensors on turbines and enlisting laser-based devices called lidars (Light Detection and Ranging), which could provide 3-D maps of incoming wind gusts, might allow the turbines to adjust for wind shear, speed, turbulence and other factors in the breeze.

Much more research and testing would be necessary, but a turbine of this size placed in the North Sea, they say, could potentially power 20,000 homes. According to the European Wind Energy Association, by 2030 Europe could potentially get up to 34 percent of its electricity via wind on and offshore. If favorable financial winds strike these would-be bigger, smarter turbines—and this is a big if—the researchers say we might see them in action as early as 2020.

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Images: Flickr/Dieter Drescher, Vestas, and Risø DTU

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