Good data needed for small-wind turbines to spin

Massachusetts stiffens the requirements for its small-wind rebate program, a sign that people, aided by online tools, can better choose locations for home turbines.

Massachusetts has revamped its small-wind rebate program with more stringent requirements, a reflection of how important brisk wind is to small-wind turbine installations.

Dozens of companies have developed turbines designed to supply a portion of a home or business' electricity, which has fueled a surge in small-wind turbine installations over the past three years. Now, installers and consumers are being nudged toward picking only the best locations, a shift that is being aided by the emergence of better online tools.

The Massachusetts Clean Energy Center, which administers renewable energy grants, temporarily suspended the state's small-wind program to phase in measures, expected in the coming weeks, that include a more rigorous assessment of available wind.

The state now demands a wind assessment be done at the tower height of the turbine the customer plans to install, rather than a single height for all grant applicants. That change, which follows others instituted last year, is meant to better reflect the actual wind conditions at a given location, rather than the general wind resource in a region.

"At the end of the day, wind speed is the critical factor that determines performance, so we want to be focused on that," said Andy Brydges, program director in the renewable energy division of the Massachusetts Clean Energy Center. "We think it's a viable market. We just want to do everything we can to protect consumers and pick good projects."

Massachusetts decided it first needed to stiffen the wind resource requirements after a review it did last summer of small-wind turbines in the state. It found the actual performance was disappointing, with about one-third generating the expected output. A U.K. review of roof-mounted microturbines found disappointing results as well.

Massachusetts homeowners, small businesses, or communities exploring wind turbines now need to use an online software program, developed for the state, to assess the available resource. Also, the rebate is based partly on ongoing performance, which is another way to ensure good locations are being chosen.

"The difficulty has been that it's very hard to model the wind. It's not that people were intentionally picking locations that didn't work," Brydges said.

Growing pains
Most wind turbine manufacturers provide a required speed, typically a minimum of 10 miles per hour, for turbines to generate at their stated capacity. Distributors of the home Swift turbine , for example, says it can generate 1,200 kilowatt-hours a year with average wind speed of 11.2 miles per hour and that it starts generating at 7 miles per hour. The Helix wind turbine, meanwhile, recommends 14 mile-per-hour wind, preferably gusty wind, and an electricity rate of over 15 cents per kilowatt-hour. One company, Windtronics, this year plans to release a small-wind turbine optimized for very low wind speeds .

More available products and interest in on-site energy have led to a steady rise in sales the past three years. Sales of small-wind turbines, defined as 100 kilowatt capacity and less, grew 15 percent in 2009, representing $82.4 million in sales and almost 10,000 new units, according to the American Wind Energy Association (AWEA). Sales were aided by a 30 percent federal tax credit for renewable energy investments and state incentives.

Often installers and homeowners have relied on satellite data to get an idea of the available wind resource. Data from wind maps is typically given at 80 meters, and installers need to extrapolate available wind at the height of towers, which are usually 20 meters to 30 meters, said Ron Stimmel, the manager of legislative affairs and small systems at AWEA.

But now the tools for measuring wind are improving, one of the factors that are making small wind more viable, according to AWEA.

Small-wind turbine maker Southwest Windpower last month launched an online wind assessment tool that uses data from 3Tier, which provides data to estimate wind, solar, and hydro power potential. The tool is designed as a way to quickly separate locations into three types: high potential, moderate, and those not worth pursuing.

"We're trying to make it with a very high degree of probability that when you install a wind turbine, it works," said Ken Westrick, the CEO of 3Tier, which sells its weather data and makes it available through a Web service. "It's a tremendous leap forward from what the industry was doing even a year ago."

The data, which is accurate within about 1 mile per hour for a 3-mile square region, should improve over time, said Westrick.

Site-specific
These online tools are an improvement over wind maps that classify regions based on available wind, said Westrick. They are also significantly less expensive than installing a meteorological, or "met," tower to gather data over several months, said Stimmel.

Small wind turbines for homes need to be above nearby obstructions, making them best suited for rural areas of plots with a significant amount of land. American Wind Energy Assocation

But a good installer is also needed to check out location conditions, including understanding where the prevailing wind is from. The placement and the height of a turbine can make a significant difference in performance, say experts. For example, there should be no obstructions, such as trees, nearby. Roof-mounted turbines are often plagued by turbulent and unpredictable wind around rooftops.

The North American Board of Certified Energy Practitioners is establishing a certification for wind site assessors, a move that should help homeowners make better decisions on turbine location. AWEA has also created a set of safety and reliability standards for small turbines.

There are other barriers to small-wind installations besides getting good wind data, including zoning laws that limit the height of towers, or even finding qualified installers. Massachusetts is particularly strict in its requirements, said AWEA's Stimmel, but it's part of the maturing that industry is going through in the U.S.

"The market has grown exponentially in the last three years, so these issues are coming to the fore and how to optimize for turbine productivity is certainly an important one," he said.

 

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