Thursday 21 November 2013

Wind turbines are quieter than a heartheat, acoustical experts find
24 Sep 2013

One complaint voiced by wind turbine opponents is that the turbines create too much noise--even noise below the range of human hearing, known as infrasound. These concerns fuel claims about "Wind Turbine Syndrome", which advocates say is a medical condition that involves mental health problems, heart disease, and vertigo.

A study by an acoustic engineering group in Australia found that that infrasound generated by wind turbines is less loud than the infrasound created by a listener's own heartheat. It found that wind turbine infrasound does increase as wind speed increases, but this is often masked by the natural noise of wind moving through the area.

The Association of Australian Acoustical Consultants said that "those investigations conclude that infrasound levels adjacent to wind farms are below the threshold of perception and below currently accepted limits set for infrasound".

Those limits are levels of infrasound that people encounter already, created by natural sources like breathing, wind, and waves, as well as mechanical sources like aircraft, traffic, and fossil fuel industry. The study noted that wind turbine noise is all relative:

Our environment has lots of infrasound already in it, the levels generated by wind farms from our point of view are quite low in comparison and they're no higher than what is already out there in the natural environment.,.. "People themselves generate infrasound through things like their own heartheat, through breathing and these levels of infrasound can be substantially higher than an external noise source."

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Michigan's new tourist attraction? Like them or not, wind turbines
20 Oct 2013

DELAWARE TOWNSHIP, MICH.--Whether they are beautiful or a blight on the landscape is beside the point.

Michigan's wind farms are here, en masse. And travelers can't miss them. With nearly 900 commercial wind turbines dotting Michigan, especially in the Thumb where the wind is strongest and most consistent, a scenic drive can turn into a jaw-dropping experience. The Thumb alone has 618 wind turbines already operating or scheduled to go into service by next year.

"I was driving down the road when the sun was coming up one morning, and the sun hit the turbines and it was beautiful", says Scott Carr of Elkton, whose tiny community has been transformed in the last five years by 32 wind turbines. "Some people don't like them, but they don't bother me".

Wind turbines began sprouting in the state in response to a 2008 Michigan law that requires at least 10% of the state's energy be provided by renewable energy sources, such as wind, by 2015. The first phase of a high-capacity, 140 mile electric transmission line called the Thumb Loop was just completed in the region. It is capable of carrying electricity linked from at least 2,800 wind turbines.

Many things have been said and written about wind turbines. All over the world, they have changed tourist landscapes, adding strong man-made vertical elements to nature's soft horizontal vistas. Some travelers see wind turbines as engineering marvels and symbols of energy independence. Some see them as evil industrial fans ruining treasured landscapes.

Some see beauty in a sunset that makes the towers shine, or charm in a scene of a small house dwarfed by a turning blade. Other see turbines as too big and harsh--which they are, compared to a cow, a sugar beet or a farmhouse. Some are so tall that Michigan residents can even see turbines erected across the water in Canada.

At first, they dotted the landscape here or there. Then, they spread. Last summer, an operator in the Ludington and Scottville area did a lively business driving busloads of tourists out to see the turbines. That success has others asking: How does Michigan make the most of their breathtaking stature and the awe that they stir inside of us?

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GE wants to power up older wind turbines
18 Oct 2013

Earlier this year, General Electric Co (GE) launched a package of technologies and services to improve output from its newer wind turbines like the 2.5 120, calling them "brilliant" at predicting and producing wind power. Now it's bringing those same capabilities to its existing turbine fleet by packaging them into a new suite called "PowerUp" to improve older wind turbines' output and profitability.

Andy Holt, general manager of GE Energy's projects and services group, explained to us how it works: GE analyzes a customer's wind turbine capacity, turbulence, weight, its current condition and age, how hard it's been run, explore the on-site wind regime, and generates a list of possible improvements. "We'll put on as much as we can to optimize and maximize their output and revenue", he said.

One of these capabilities is the company's venerable WindBoost, which essentially nudges a turbine to run a little bit harder if conditions allow for it. Vortex generators, meanwhile, can be applied on the blade to decrease separation and increase lift. Other features that can be bundled with PowerUp run the gamut from trailing-edge serrations to reduce noise, to a winter operations mode that ramps down as ice forms.

Another aspect to PowerUp borrowed from the "brilliant" turbine setup is enabling predictability and condition-based maintenance, "having machines telling us when we have issues" to eliminate unplanned downtime, Holt said.

PulsePoint software monitors set points in the turbine to gauge factors including vibration, bearing temperature, and filter pressure. Other software awakens turbines to recognize when they're falling behind other turbines nearby and alert the dispatch center to find out why, or conversely notice if a turbine in the group (or groups) could be revved up to take advantage of current conditions

These types of tweaks take a page from what GE has done for its gas turbine customers, Holt pointed out.

The company especially sees a sweetspot for PowerUp in its flagship fleet of 9,000 1.5 77 turbines running nationwide, since "the technology has moved so far since we built the earlier machine", Holt said.

For just those turbines, GE claims that PowerUp could increase a wind farm's output by up to 5% and a 20% increase in profit per turbine--even a 1% energy output increase would add another 420,000 MWh annually, according to the company. Holt walked us through how GE came up with those numbers:

  • 2.3% more output per machine: Using WindBoost to run a little harder off the gearbox
  • 0.5%: Seasonal tuning, such as changing pitch parameters from summer to winter
  • 1.2%: Winter ice operations, sensing ice formation and derating/shutting itself down
  • 1.5-2%: Vortex generators on the blades
  • 0.5-1%: Blade cord extensions with slightly larger aerodynamic areas, increasing the velocity at the top of the blade
  • 0.5-1%: Trailing-edge serrations

Of course not every customer site will apply all of those improvements, but taking an average across GE's entire fleet the company calculates a 5% improvement in output.

That's "big enough to matter", Holt said, "and it's also just the beginning". Given the relative youth of GE's fleet of turbines in the US (averaging 5 6 years) repowering of entire hubs and nacelles isn't yet a big services business, but PowerUp could fill a big need for customers who are keen to know more about their turbines' performance in wind speed regimes of between 5-7 meters per second, shy of the rated output.

"We're taking advantage of the design life in the machine that's being underutilized because of lower winds, and that's given birth to a whole upgrade business", he said.

Customers will pay for PowerUp based on "validated performance improvements" i.e, the additional power that gets produced. "We just commit to selling MWs [to customers]", Holt said. "This is a simpler way to do business with us". PowerUp also can be incorporated into existing VICOSC&M contracts.