Study: Microwind turbines a tough sell in Mass.
BOSTON--Despite the growing enthusiasm for home wind turbines, an analysis of microwind turbines in Massachusetts found that they fell short of performance expectations.
The Massachusetts Renewable Energy Trust commissioned a study last year to review electricity output from 21 small wind turbines in the state and the results were surprising: the data showed that the estimated production was about three times higher than the turbines' actual production.
The analysis is not the final word on small wind generators, but is significant because few states have done similar reviews, say the study's authors.
The Swift wind turbine from Cascade Engineering, one of many new small wind turbines now available or being developed.
(Credit: Cascade Engineering)The Massachusetts Renewable Energy Trust was "taken aback" at the discrepancy in expected versus actual performance and made changes to its "small wind" rebate program earlier this month to address the issue, said James Christo, a program director from the quasi-public state agency. Christo spoke on a panel on small wind--defined as less than 10-kilowatt capacity machines--at the Northeast Sustainable Energy Building Energy Conference here last week.
"We're certainly disappointed by the performance we've seen to date but we believe there is potential for microwind," Christo said. "People just need to take a more critical look and be cautious."
With the growing interest in clean energy, dozens of different small wind turbine types have emerged from sources as varied as designer Philippe Starck to Aerovironment, a company with roots in military aircraft.
The problem is not that the technology doesn't work. Aerovironment's roof-mounted turbines installed at Boston's Logan airport and other spots, for example, have performed well. The challenge is finding--and choosing--sites with sufficiently strong wind, particularly in cities.
"One of the challenges as an installer is that everyone has a windy site," said Mark Durrenberger, the president of New England Breeze who also spoke at last week's "small wind" panel. "But what you feel on the ground has nothing to do with what you have 100 feet up."
Higher is better
Most small wind turbines are scaled-down versions of giant utility-scale turbines, which look like a fan with three blades. Southwest Windpower's Skystream, for example, is rated at 1.8 kilowatts with at least 10 mile-per-hour winds, which should offset a large portion of a home's electricity consumption.
But there are many other types, including vertical axis wind turbines, such as Mariah Power's Windspire, where a structure spins on a pole to generate electricity.
Having already installed a few turbines in Massachusetts, Durrenberger offered a few simple rules of thumb on small wind turbines. He doesn't recommend roof-mounted models because of the vibration they cause in a home. "It will be like having a sub-woofer in your basement," he said.
When it comes to optimizing for capturing wind energy, higher is usually better. His company will not install a turbine unless it's 30 to 40 feet above any other obstructions, such as buildings and trees.
Good sites are places with smooth terrain like a field with minimal obstructions, according to the Cadmus Group, a consulting firm that performed the analysis for the Massachusetts Renewable Energy Trust. (Click for a PDF with slides of the study). Massachusetts as a whole has only an average wind resource.
Data problem
The Massachusetts state analysis tried to pinpoint the reason for the underperforming turbines and found that installers often worked without sufficiently good information.
Area wind maps for the region tended to overestimate on average by 10 percent how good the wind was for certain locations, according to Shawn Shaw, an analyst at the Cadmus Group who worked on the study.
Another problem is the rated capacity--how much electricity a turbine can produce--that manufacturers publish aren't always reliable for extrapolating expected performance, Shaw found. Industry associations are trying to come up with standard ways of reporting capacity which will help, he added.
"You want to be internally honest about your (wind resource) assessments," Shaw said. "The economics are going to probably be the best driver in Massachusetts."
A state like Massachusetts has a good wind resource near the coast, but its hilly and woody terrain means that finding a good site requires some investigation.
Installers and customers should be aware, for example, that nearby obstructions can have a significant impact. A 100-foot wind tower placed next to a 50-foot tree is effectively the same as a putting turbine on top of a 50-foot tower, which means it will get a lot less wind, Shaw said.
The results from the Massachusetts study echoes a similar survey done in the U.K. over the past two years, called the Warwick Trials.
That study focused specifically on urban microwind turbines, some of which were roof-mounted. Overall, it found that the performance of these systems fell below expectations as well and that a number suffered technical glitches.
"The truth of the matter is that (urban wind) hasn't been studied very much, at least in the U.S.," said Shaw. "There's a tremendous amount of uncertainty."
To test urban wind turbines, Christo said the Massachusetts Renewable Energy Trust is sponsoring a "science experiment" to put up five turbines from different manufacturers at the Museum of Science, a project expected to go up this spring.
NIMBY and urban wind
Massachusetts on average is far from having the best wind resources in the U.S.--it ranks right in the middle of pack compared to other states.
Following this review, the state revamped its wind power program with the hopes of getting only the best projects developed, said Christo. To get a rebate, installers are now required to do a more stringent wind study and use a specially designed software tool to assess the wind resources in a projected site.
At the federal level, the tax credit for small wind turbines was increased this year, giving investors a 30 percent credit on the installation cost.
Performance issues aside, Durrenberger said that inconsistent zoning and not-in-my-back-yard (NIMBY) sentiment are also serious barriers to erecting a turbine.
Some cities, such as San Francisco and Seattle, have passed bylaws to specifically enable microwind generators. But the rules vary from town to town or are ambiguous.
In an unscientific survey of the 351 towns in Massachusetts, Durrenberger found that 60 percent had no rules for or against wind turbines. Twenty percent specifically allow them and 20 percent have rules, such as height restrictions, that either disallow them or make it difficult to get permitting.
"I promise you, if you want to put one of these things up, you will hear from your neighbors...so contact them before the building inspector does," he said. But "despite NIMBY and the folks in Nantucket (opposing the offshore wind project Cape Wind), there is still a lot of support for wind so you could change your town's bylaws."
Martin LaMonica is a senior writer for CNET's Green Tech blog. He started at CNET News in 2002, covering IT and Web development. Before that, he was executive editor at IT publication InfoWorld. E-mail Martin. 
could power 60% of the households in the world - they're not as rich and fat
So it's a good thing for the world that we're subsidizing the technology?
Sanenazok, I believe you are confusing a kilowatt with a kilowatt-hour. If your house pulled a constant 1.8 kilowatts, then you would use 1.8 kilowatts in 24 hours, which would be roughly 43 kilowatt-hours in a day. At 8 cents, that would cost you $3.46 a day to power your home. Over a 30 day period, you would be charge $103.68 (before taxes, fees, etc), which is probably a pretty typical electrial bill for a mid sized home in an area with your power rates (depended on the weather, etc)
I don't think their math is wrong, but I'm sure that turbine doesn't put out 1.8 kW consistantly. The 1.8 kW is more likely a peak output. I would guess most of the time it is significantly less or none at all, depending on the wind speed.
A 1.8 KW turbine only produces 1.8KW at the turbine's rated speed, which is typically about 25-30mph - few places receive sustained wind of those speeds.
I am a fan of alternative energy, but these small turbines are simply cute and expensive toys.
The Swift 1.5KW wind turbine has peak output at 14m/s ... meters per second ... isn't that convenient that they disguise this in meters per second? Which turns out to be 31.3 miles per hour. So, the Swift Turbine is only cranking out 1.5KW when there is a 30MPH wind. How many places do you know that consistent 30MPH sustained winds.
For those who don't know, stronger winds don't help - if a turbine has a certain peak output at a certain wind speed, the turbine does not produce more electricity. Obviously, it would for a short time, but the electrical components would burn up.
The standard rule is longer blades, as high up as possible.
Sanenazok - If you happen to read this, may I ask what state you live in? Nebraska is about 5th cheapest which is part of the reason we don't have much investment in alternative energy here. It is just that much harder for home or business owners to justify. (Also, our entire state is public power, so we cannot take advantage of any tax benefits for installing alternative energy.)
I am a fan of wind turbines, and have done quite a bit of research on the topic. If you ask the experts - not the people trying to sell these units, they will tell you that these "micro" wind turbines are simply expensive ornaments.
http://news.cnet.com/8301-11128_3-10075828-54.html
"It can generate 1.5 kilowatts with 31 mile-per-hour wind (or 14 meters per second) and about 2,000 kilowatt-hours over a year, the company said. U.S. households typically consume between 6,500 and 10,000 kilowatt-hours in a year, according to the U.S. Energy Information Administration.
At a cost of $10,000 installed, it's a bit lower than the typical per-watt cost of solar electric panels. But state rebates, the cost of electricity, and the wind or solar resource make a big difference on the actual up-front cost. Cascade estimates the payback on the upfront cost can be as low as three years, but that it varies widely. "
How about this idea:
Every time an airplane takes off there is a tremendous amount of wind created from the engines, lift, and take-off. It's dependable. Instead of on top of a building, put a few hundred around the end of a runway on each side. Any big city has enough planes taking off to keep these turbines running consistently, thus giving enough reliable data to make these turbines even better.
My biggest concern would be safety. Crashing a 747 into all these turbines probably wouldn't matter much overall, but crash a small plane like a Cessna? The wind turbines would have to be really tough and extremely breakable... and how would you get the emergency crews to a crash with pieces of broken wind turbines all over the place.
Hmmmm... interesting idea, but I think I already killed it.
What do you think?
- by markrd1 April 6, 2009 7:41 AM PDT
- Martin, thanks for the write-up and nice job being faithful to what I said at the NESEA conference.
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(13 Comments)To the other commenters, A typical US home uses about 500-1000 kwh per month. A Skystream will generate anywhere from 100-300 kwh per month on a decent site. Install costs for the Skystream are roughly $15-20k depending on tower and foundation needs (here in MA). DIYers can do it closer to $10K.