Digital Chirps Will Make It Easier to Site Wind Farms

SOMERVILLE, Mass.--(BUSINESS WIRE)--A Massachusetts company has perfected a way to measure wind speed by sending a digital chirp into the sky - lowering development costs and improving power predictions to make the siting of wind farms easier.

Second Wind Inc. is introducing the Triton® sonic wind profiler, a device designed to address the limitations of sodar technology for identifying wind farm locations. The product was introduced today at North America's premiere trade event for the wind energy industry, WINDPOWER 2007 in Los Angeles.

Background

As wind energy becomes a more competitive option for generating electricity, modern day prospectors hunt for productive wind sites the way forty-niners used to hunt for gold. Their tools include U.S. wind maps, used to identify places where wind speeds and proximity to the power grid may support a commercial "wind farm" - where scores or hundreds of turbines generate electricity for sale to utilities.

To verify a site is practical, prospectors have to measure the wind speed over a period of at least a year. For this measurement, the primary tool is a meteorological mast or met mast - a tower laden with anemometers and other weather instruments.

The met mast creates two kinds of concerns for developers. The first is political: Because met masts are highly visible precursors to a potential wind farm, their visibility can often generate public concern even before the developer has decided whether the site is worthwhile.

Second, most met masts are 60 meters tall, or just under 200 feet. The reason is that any tower over 200 feet requires aircraft warning lights and separate approvals through the Federal Aviation Administration. Most of today's wind turbines are 75 or 80 meters high, and the trend among turbine manufacturers is heading even taller. So a 60-meter mast only measures the bottom 20 percent or so of each turbine's "blade sweep"- and wind can change at higher elevations, which dramatically changes the potential energy calculations for the site.

How Sodar Helps

To address the height challenges wind developers have recently enlisted another tool called sodar. Sodar stands for sound detection and ranging, and is similar to the sonar technology used by submarines and ships. Instead of a "ping" through the water, sodar sends an audible "chirp" up through the air, and wind turbulence sends a portion of the sound back toward the ground. By precisely measuring the frequency and time delay of the chirp's echo, the sodar device measures the wind speed and direction at various heights up to 200 meters.

Prospectors are currently using sodar products selectively to "profile" a selected site, gathering wind measurements at specific heights and turbine locations. However, existing sodar designs have multiple limitations for wind profiling. Current systems work only in good weather, generally require on-site support to operate, and deliver wind data in formats that require expert interpretation.

Benefits of the Triton Sonic Wind Profiler

Numerous Triton innovations address the shortcomings of previous sodar products to provide unattended wind profiling in all weather.

* A hexagonal transducer array and a tri-lobed acoustic enclosure combine to provide exceptional accuracy. They improve signal-to-noise ratios and beam focus, making the device more accurate and the chirp almost inaudible twenty feet from the unit.
* Its rugged plastic construction with stainless steel hardware and polyester lining allows the Triton to work in all weather.
* Data is delivered in a format familiar to wind developers, without expert interpretation and with a GPS stamp to verify time and location.
* A sensor adjustment system provides automatic orientation correction on uneven ground.

As the technology gains acceptance, company officials believe that it eventually could replace met masts in numerous wind assessment applications. Other potential applications include detection of wind shear at airports.

"Sodar has become an essential technology without a commercially viable product," Second Wind President Walter Sass said. "The Triton profiler will make it much easier for the wind energy industry to locate and create successful wind energy plants."