The electric wind turbines built 30 years ago, after the 1970s oil-price shocks increased interest in the industry, often experienced serious problems. Some came apart in bad storms, some did not work well, even in good weather, and still others found insects piling up on the blades, slowing power production. Bird deaths at some early wind farms were alarmingly high.
Challenges remain, but the technology has come a long way in recent years, and wind farm operators have learned plenty of tricks, too, like the importance of shutting down the machines in high winds and the best places to put them to begin with.
The turbines have grown larger, and more effective. One model made today by Vestas, a Danish turbine manufacturer, can produce 300 times as much power as a turbine sold 15 years ago, according to Finn Strom Madsen, the president of technology research and development for Vestas.
But experts say that vast improvements in wind technology still lie ahead – which makes sense for an industry that is about 100 years behind, say, that of the automobile.
To date, many manufacturers have focused on making the machines bigger, so the towers can reach faster and steadier winds and the blades can cover a larger area. The biggest onshore turbine in Europe, according to Peter Sennekamp, a media officer with the European Wind Energy Association, is a 7.5-megawatt machine made by the German company Enercon.
It is 135 meters, or 440 feet, tall – one-third the height of the Empire State Building’s 102nd-floor observatory – and its three blades sweep an area 127 meters in diameter. The Enercon machine’s power potential dwarfs that of most turbines in the United States, where the average capacity is 1.77 megawatts, according to the American Wind Energy Association.
For wind companies, buying larger turbines (as opposed to putting up more of them) makes sense because it reduces overall transportation, logistical and operational costs, said Dan Radomski, co-founder of Kinetik Partners, a company that advises companies in the clean-energy sector.
But turbines destined for onshore wind farms may not keep getting bigger as quickly as they have in the past, experts say, because of logistical hurdles. As towers get to be 100 meters high and more, and blade length increases, shipping them gets challenging. Trucks carrying big towers and blades must sometimes move with police escorts and avoid certain overpasses or small roads.
(One potential solution is for blades to arrive in segments and be assembled on site; the tubular towers are already shipped in several sections, but even they face limits because taller towers generally need very thick foundations.)
Mr. Madsen, of Vestas, said that offshore turbines – less encumbered by roads and bridges – will keep growing more rapidly than their onshore counterparts.
Earlier this year, Vestas unveiled its plans for a seven-megawatt offshore machine, with a rotor diameter (the diameter of the area swept by the blades) of 164 meters. A March report, “Upwind: Design Limits and Solutions for Very Large Wind Turbines,” prepared with support from the European Commission, found that a 20-megawatt turbine – with each blade probably more than 120 meters long – was “feasible.”
But sheer size is not the only way that turbines will improve. Research and development work has proliferated around matters like how to pitch, or angle, the blades and how to monitor wind speed and direction at a turbine more accurately, using lasers.
“This is probably the most exciting time in the industry as far as companies launching new product platforms,” Mr. Radomski said, adding that much of the research and development work was happening in Europe, where the modern wind industry grew up.
Partly, he said, the flurry of development work is a result of the increasing number of manufacturers, which are looking for ways to differentiate themselves. Also, many of the best wind sites have already been claimed, and that has forced developers to build in places that are not quite so windy – making innovation all the more crucial for cost-effectiveness.
Wind turbines are complex machines. Each contains about 7,000 or more components, according to Tom Maves, deputy director for manufacturing and supply chain at the American Wind Energy Association. (That figure counts items like fasteners.)
In places like Texas, the U.S. wind-power leader, the turbines must withstand all kinds of weather extremes, from heat of 100 degrees Fahrenheit (38 Celsius) or more in the summer to frigid temperatures in the winter, along with occasional snow- or hailstorms.
The weather is even a little different at various parts of the turbine: The wind speed at the tip of one blade may be considerably greater than the wind speed at the tip of another. Suzlon, an Indian manufacturer, had trouble with blades’ cracking several years ago.
One turbine part that has remained especially problematic over the years has been the gearbox, which speeds up the wind-powered rotations in preparation for the electrical generator.
“Gearboxes are really the Achilles’ heel of the system,” said José Zayas, senior manager of renewable energy technologies with the Sandia National Laboratories in New Mexico.
Some manufacturers, like Siemens and General Electric, have begun using a technology called direct drive that eliminates the gearbox and uses a lower-speed generator. However, that technology uses rare earths, among other drawbacks, according to Mr. Madsen, who said that Vestas’s gearboxes were reliable and that the company was not using the direct drive technology.
Many of the forthcoming improvements to the big, three-bladed turbines may not be easily visible to people outside the industry. Vestas, for example, is working on a “stealth” system that will significantly reduce the turbines’ interference with radar (something the military often complains about). It is likely to be commercially available by the end of 2012, according to Mr. Madsen.
One more physical change is that turbines of the future may have flaps on the blades – “like an airplane has flaps,” Mr. Madsen said. Those will allow for better control of the load the turbine handles and should make it easier to build larger ones.
Mr. Zayas of Sandia said that many recent innovation initiatives were focusing on reliability and “serviceability.” For example, he noted, several manufacturers, including Clipper Windpower, a U.S. company, have devised a way to work on turbines without needing a huge crane. That is useful because cranes are expensive.
Companies are also starting to use more sensors to monitor things like the properties of oil in the gearbox, Mr. Zayas said – in the same way that newer cars may have sensors to tell the driver to change the oil when it is necessary, as opposed to the old pattern of changing it every few thousand miles.
Mr. Radomski said that manufacturing processes for turbines also could become much more efficient. Far too many tasks are still manual, he said, like making molds for the blades or sanding and polishing them. “There is no fully automated blade plant today,” he said.
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