Individuals and commercial businesses around the world are increasingly drawn to small wind turbines to supplement energy consumption, according to a report released Wednesday by Pike Research.
The niche industry of small wind turbines, which saw $165 million in revenue in 2008 and $203 million in 2009, will grow to $412 million by 2013, according to Pike's "Small Wind Power" report.
It can be attributed to the fact that on a cost-per-watt basis many are finding small wind turbines to be less expensive than solar panels, David Link, senior analyst at Pike Research, said in his report.
This is especially true in the U.S. and the U.K. where government support in the form of incentives, tax credits, and municipal height restrictions for structures being lifted for small wind turbines.
There are still places that see wind turbines as "visual pollution." But Pike's report found legislative reviews and incentives indicating that government support for wind turbines is increasing.
However, there are still hurdles.
Because of wind energy's intermittent nature, wind turbines are usually seen working in conjunction with another energy source such as diesel generation. This, coupled with permitting issues depending on a resident's municipal rules, could provide a holdup to market growth, according Pike.
The report is in keeping with the American Wind Energy Association's assessment of the U.S. small-wind industry market that came out in May. It found a 78 percent increase in sales from 2007 to 2008, but that seemingly impressive percentage figure is largely due to a modest starting place. Despite the jump in growth, the report estimated that only a total of 10,000 small wind turbine units were installed in 2008.
Helix Wind's The S322 vertical wind turbine
(Credit: Helix Wind)Helix Wind announced Wednesday that it's beginning a trial run in Southern California to see if its wind turbines might be useful for powering cell phone towers.
The manufacturer is becoming known for its small vertical-axis wind turbines that can generate electricity with winds as low as 10 mph, as well as its unique business model to finance them.
The pilot program, conducted in conjunction with cell phone tower operator Core Communications, will experiment with whether the turbines powering cell phone towers could also generate surplus energy to sell back to the energy grid.
If they generate enough surplus power, small wind turbines could provide a new source of income for cell phone tower operators as well as a new power source.
Helix Wind's turbines, which will be installed in early 2010, will run for up to three months before being re-evaluated.
According to statistics provided by Helix Wind, there are approximately 3,500 cell phone towers in Southern California, and another 1,000 expected to be added in the next five years to cover consumer growth.
Now you can test whether you're both techno-chic and an ecogeek by combining the iPhone with home wind turbines.
Small wind turbine maker Mariah Power has teamed up with software developer Create with Context to make an iPhone application designed to measure wind speed.
The application, which is due "any day," uses the iPhone's microphone to get a read on wind speed. It translates that into how much power a small wind turbine could offset. For example, a wind that averages 12 miles per hour is enough energy to run your refrigerator and freezer for a year, according to Create with Context.
The iPhone small wind application uses a microphone to get a read on wind speed.
(Credit: Create with Context)The application was written to get people excited about wind power. But it strikes me that actually buying a turbine based on an iPhone application is a bit risky.
Small wind turbines do indeed work, but experienced wind installers will tell you that they only deliver on their stated performance when there is a sufficient wind. That means placing a turbine far above and away from obstructions, such as trees and rooftops, in addition to getting that 12-mph average wind speed.
Two studies--one in the U.K. and one in Massachusetts--found that early buyers of pole-mounted wind turbines and roof-mounted turbines did not get the electricity output they expected. The primary reason was that the turbines weren't getting enough wind in their locations.
So an iPhone wind speed application could be fun to play with and even give you a decent idea of wind speed. But if you're serious, I'd suggest consulting a wind map from 3Tier or others and gather more data with an anemometer.
There are at least two other iPhone applications for measuring wind speed, called Wind Meter and Wind Speed, the New York Times notes.
Twister 300-T
Twister 1000-T
Vertikon H50
(Credit: Venco)Helix Wind has signed a definitive purchase agreement to acquire Venco Power, a Germany-based manufacturer of vertical axis small wind turbines, for $3.9 million in cash and common stock, the company announced Thursday.
With Venco comes greater access to the small wind residential market in Europe, along with three new products the company plans to add to its small wind product line, according to Helix Wind CEO Ian Gardner.
While all three models are for the small wind market, each has a distinctive look and different capacities. The Venco Twister 300-T produces power at wind speeds as low as 3.5 meters per second (7.8 mph); it starts rotating at 3.0 meters per second, and its claim to fame is that it's "virtually quiet." The Twister 1000-T makes the same noise and power claims as the 300-T, but has a different look and begins to start rotating at a wind speed of 1.5 meters per second. The Vertikon H50 will begin generating power at speeds as low as 2.5 meters per second.
Venco also has an online calculator (for Java applet-friendly browsers) for estimating how much power one can expect each particular turbine product to generate. Potential customers input average wind speeds for each month of the year at their location, and can change which turbine the figures are applied to.
"We're also excited to bring German engineering talent and technology to the quest for alternative energy," Gardner said in a statement.
The news follows Helix Wind's August announcement offering a unique financial fix for the initial cash outlay that residential customers and dealers face when getting into wind power.
MUSKEGON, Mich.--Tucked in the back corner of a nondescript office park is an early shoot in the budding green-energy economy--a start-up with big plans for small wind turbines.
Last month, I took a detour from a summer road trip to visit WindTronics and see a prototype of its wind turbine designed for individual homes and commercial buildings. The company's lab, housed in a nearly empty warehouse, is a glimpse into the fervent experimentation going on among green-tech entrepreneurs and, specifically, in small wind.
With people looking for clean and cheaper forms of energy, sales of small wind turbines are brisk and projected to grow in the coming years. There are now dozens of different small wind turbines available in a dizzying number of designs, although most commercial products are just smaller versions of big turbines--a propeller with three blades.
Despite all the activity, there's some creeping doubt about the ultimate potential of small wind. A study in Massachusetts and one in the U.K. found that many residential locations don't have sufficient wind to meet the promised output of small turbines.
In WindTronics' lab, a protoype of the Honeywell Wind Turbine, which is 6 feet tall and weighs 95 pounds.
(Credit: Martin LaMonica/CNET)WindTronics has designed a turbine that addresses that wind speed issue head on. While most wind turbines start to work when the wind blows at seven or eight miles per hour, its machine--to be sold for $4,500 as the Honeywell Wind Turbine--starts to generate electricity at only two miles per hour. That, say company executives, means small wind can make sense economically in many more locations.
Kilowatts versus kilowatt-hours
Entering WindTronics' lab, there wasn't much to see except for a spartan office and conference room. A design drawing of its wheel-like turbine on the wall gave me a clue I was in the right place. After a moment, the turbine's inventor and chief technical officer, Imad Mahawili, greeted me and brought me into a warehouse.
At the back end of the cavernous room, there was the 6-foot-high turbine, a table with some testing equipment, and a truck trailer that had been converted into a low-cost wind tunnel.
WindTronics has designed its turbine, which is now going through certification testing and will be available later this year, to be mounted on rooftops or onto free-standing poles. The most striking thing about seeing the turbine up close is how big it is. At 6 feet high without the mounting gear, it would be a conspicuous addition on a home's roofline, although I imagine less so on a pole.
The turbine is built around a wheel with long spokes, each of which has a specially shaped, bendable nylon blade attached to it. Around the rim of this big wheel is a "shroud" that covers the blade edges. This is where WindTronics' design differs from most other wind machines.
Wind tests on the cheap--a wind tunnel built inside a tractor trailer container.
(Credit: Martin LaMonica/CNET)Most turbines have a gear box at the hub of the rotor. As the wind turns the blades, the gear box turns a generator to make electricity.
WindTronics turns things inside out by having the electricity generation happen at the rim of the turbine. Permanent magnets attached to the blade tips spin past stators--essentially wire coils--attached to the shroud to generate a current. Without the resistance of a gear box at the hub, WindTronics says its turbine will spin--and generate electricity--at low wind speeds, which over the course of time will add up to more power than other turbines, company executives argue.
"The reality is because most turbine makers sell to utilities, they have to specify the maximum power," said Mahawili. "The other companies don't give details on how many kilowatt-hours a turbine will make, just the plate power (in kilowatts), which doesn't signify much. We're really not telling the story as we should."
WindTronics says its turbine will generate 2,000 kilowatt-hours in a year for a home with a very good--called Class 4--wind resource. That's between 15 and 20 percent of the annual electricity consumption for the average U.S. home.
Green collar industry?
Mahawili then cranked up the wind tunnel, which is used to measure the output of the turbine. Rather than pay a lot of money to test its turbines in commercial wind tunnels, it built its own with a giant fan placed at the front of a semi trailer.
As the fan cranked up, we could see on a laptop how much power the test turbine produced at different speeds. With about 10 mile-per-hour wind, it generated about 100 watts and kept climbing upward with higher speeds.
Part of its system for capturing wind power at low speeds is a battery--a standard issue 12-volt car battery--that stores electricity at very low wind speeds. As it speeds up, the turbine can directly feed an inverter to produce household current, Mahawili explained.
When I walked into the wind tunnel itself, there was no noticeable vibration. The fan for the wind tunnel made noise but I couldn't distinguish the sound of the WindTronics test turbine, which the company says will operate very quietly at 35 to 45 decibels.
After the wind tunnel slowed down, WindTronics CEO Reg Adams told me about the company's business plans. It has a partnership with Ace Hardware to distribute the turbine starting this fall. The first units will be manufactured in the Netherlands but the company is looking for factory sites in the U.S.
There are already tax incentives offered from Michigan, a state that's desperately seeking out new manufacturing industries, notably wind. WindTronics was incubated in the Michigan Alternative and Renewable Energy Center in Muskegon, a city known in the past for its lumber industry.
Although it has the support of government officials plugging for "green-collar jobs," WindTronics has a long way to go before it can claim to be a commercial success. In addition to finalizing its product, it has to develop the distribution channels and ensure enough people are trained to install the turbines.
Also, the small wind category is relatively immature. Although there was a big jump in sales last year, there were only 10,000 units installed, according to the American Wind Energy Association. Even with its ability to spin at low speeds, WindTronics' turbine should be placed in good locations for wind, said president and CEO Reg Adams. Typically, that means well above and away from any obstructions, including trees, in a site with steady wind.
Still, the company's goal is to bring the cost of distributed wind down significantly and get a toehold in this relatively new market. When compared to other turbines or solar panels, the yearly energy output of WindTronics' turbine will compare favorably on price, said Adams. "We want this to be mainstream, not a specialty item," he said.
Homeowners this fall will be able to buy a wind turbine at hardware stores that tackles the small wind industry's bete noire: slow wind.
WindTronics, based in Muskegon, Mich., has developed a wind turbine sized for individual homes that it says can operate at speeds as low as 2 miles an hour.
It will be sold for $4,500 as the Honeywell Wind Turbine and distributed through Ace Hardware stores in the U.S. starting in October. WindTronics developed the turbine and licensed the technology to buildings systems giant Honeywell.
The fan-like turbine will generate 2,000 kilowatt-hours in a year for a home with a very good--called Class 4--wind resource, according to the company. That's between 15 and 20 percent of the annual electricity consumption for the average U.S. home.
Turning a turbine inside out: rather than having power generation occur at a gear box in the shaft, WindTronic's turbine has magnets at the edges of the fan to generate a current.
(Credit: WindTronics)The turbine is rated at 2 kilowatts, but WindTronics executives say that most turbines' rated capacities--the amount of power they can produce at a given moment--are misleading.
"We say if a turbine only works between 8 and 25 miles per hour, you have a very limited range of operation," said Brian Levine, the vice president of business development at WindTronics, a division of EarthTronics. "Our device is rated to address a wider range at the low and high end."
The 95-pound turbine, which is 6 feet in diameter, can be mounted on rooftops, attached to chimneys, or put on a pole. The company hopes to sell the turbines through Ace Hardware stores or through contractors--who are needed for the installation--to homeowners or businesses.
Spinning magnets
With people seeking out alternative forms of power generation, there's been a surge in interest--and sales--in small wind turbines in the past year. But it's still not clear that these small wind turbines are cost-effective enough to be used beyond a niche of green-minded buyers.
Two studies--one in Massachusetts and one in the U.K.--discovered that many small wind turbines far underperformed manufacturers' specifications.
The tests found that people often chose locations that didn't have sufficient wind or obstructions that blocked wind. In most cases, turbine makers rate products assuming a very good wind resource--anywhere from 12 to 25 miles per hour.
By using a novel design, WindTronics' turbine can generate electricity between 2 miles per hour and 45 miles per hour, the company says.
Typically, turbines convert the mechanical energy of spinning blades to electricity with a gearbox and generator in the turbine's nacelle, the enclosure where the rotor's shaft is mounted.
WindTronic's turbine has small magnets at the tips of its fan blades. When they spin from the wind, equipment in the fan's housing captures the current produced.
The installation kit also comes with an inverter to convert the direct current to household alternating current and a "smart box," which regulates the flow of electricity and monitors wind speed. At 45 miles per hour, the unit turns itself sideways to avoid damage.
Levine, who said the turbine was originally developed for developing countries, said WindTronics expects it can produce 50,000 units in its first year. A number of utilities, including Duke Energy, are testing the turbine, he added.
He said that mounting the turbine on a house should not cause vibration because the unit is lighter than most turbines. The sound is rated at between 35 and 45 decibels, which is quieter than normal conversation, Levine said.
Right problem
There is a growing number of companies designing turbines to operate in less-than-ideal wind conditions. A wind map from the Department of Energy shows that most of the fair and good wind--class 3 and class 4--is in the plains states and on the coasts of the continental U.S.
One technique to squeeze more power from available wind is to concentrate the wind to increase the speed of the air going past rotor blades. OptiWind, FloDesign Wind Turbine, and Green Energy Tech are among the companies exploring that approach in small or mid-size turbines.
Other turbine manufacturers, like WindTronics, use permanent magnets in a direct drive design rather than gearboxes to generate electricity.
WindTronics has only built prototype systems, which it first showed at a hardware show last month. But if its turbines can operate in low wind with little vibration and sound, the company could make small wind turbines economically attractive to a much larger audience.
Updated on May 29 at 7:25 a.m. PT with corrected figure of installed turbines last year.
Sales of turbines big enough to serve a single home or office building grew rapidly last year and are poised for even faster growth this year, according to a report from the American Wind Energy Association.
The report, published on Thursday (click for PDF), found that sales of small wind turbines smaller than 100 kilowatts grew 78 percent last year, even though there was a sharp drop-off at the end of last year and beginning of this year.
The actual number of small turbines installed, though, is very small at over 10,000 units last year, comprising 17.3 megawatts of added capacity.
The stimulus act passed earlier this year gives people who buy a small wind turbine a 30 percent tax credit on the installation, which addresses the challenge of the upfront costs, which can be several thousand dollars to install.
Apart from policies, the other important factor to making a small wind turbine economical is siting. A study done that analyzed small wind installations in Massachusetts and one looking at roof-mounted turbines in the U.K. found that the machines underperformed manufacturers' claims.
The best location for small wind turbines, most of which are mounted on poles, is an area with an average wind speed of about 12 miles per hour, said Ron Stimmel, the small wind advocate at AWEA.
"It all depends on your wind resource to get a decent payback," he said. "You need a little bit of land so you're not talking cities, but mostly suburban and rural locations."
Many municipalities have height limitations on structures but turbines generally perform well when they are 30 feet above any structures in a 500-foot radius, he said.
"If you find the wind annoying or have trouble keeping things on your porch, then you probably have enough," Stimmel said.
Unlike large turbines, you don't need to put up a tower to get data on wind speed but customers should look at wind maps and rely on installers to assess the resource, he added.
The dominant small wind turbine design is essentially a smaller version of the three-blade horizontal axis large turbines used in wind farms. But there are now hundreds of different small turbines, some of which are designed for homes or structures such as streetlamps.
Southwest Windpower, which makes residential wind turbines, said on Monday it has raised $10 million from existing investors and General Electric to expand its operations.
With the money, the Flagstaff, Ariz.-based company said it intends to grow its European operations and invest in product development.
Southwest Windpower makes the Skystream tower-mounted wind turbine, designed for individual homes or buildings. It was originally developed at the National Renewable Energy Laboratories.
These relatively small turbines have a rated capacity of up to 3 kilowatts of electricity. With a good wind source, a homeowner could offset more than half of their electricity use and make electricity cheaper than retail grid rates, according to the company.
Its product plans call for making the Skystream, which has an integrated inverter, more efficient at converting wind to usable electricity. The company is also looking at designing new products, such as wind turbines mounted on street lights.
Other investors that participated in the funding are Altira, Rockport Capital Partners, NGP Energy Technology Partners, and Chevron Technology Ventures, Chevron's venture capital arm.
GE expects to see rapid growth in small wind turbines. Federal renewable energy incentives were changed earlier this year to give investors a 30 percent tax credit for small wind turbines, the same level as solar power.
"In many applications, Southwest Windpower offers the most economic distributed renewable generation technology, and GE is helping the company accelerate adoption of that technology," said Kevin Skillern, managing director and leader of venture capital at GE Energy Financial Services, in a statement.
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."
Small wind turbines attached to individual homes work fine unless you have lousy wind.
That's the upshot of a multi-site study called the Warwick Microwind Trial project, a year-long survey on the performance of roof-mounted turbines done in the U.K. done by Encraft, a low-carbon technology consulting firm.
The researchers picked 26 sites in the U.K where microturbines tied to the power grid were attached to people's homes to offset their electricity use. Many of the consumers clearly purchased the turbines to lower their fossil fuel energy use as some already had solar panels and ground-source heat pumps.
One of the building-mounted roof turbines tested in a year-long study of urban wind turbines in the U.K.
(Credit: Encraft)But the Encraft study, which came out last month, found that many of the turbines didn't meet manufacturers claims for power generation. Some turbines needed to go offline at times because of technical problems or complaints over noise.
"The gap between average performance (or expectation) and reality is much larger than people could reasonably expect," Encraft managing director Matthew Rhodes said in a summary.
The survey doesn't conclude that small wind turbines, in general, are uneconomical or unsuitable for the U.K. Instead, the data points to the need for accurate wind measurements before installing microturbines, particularly in cities.
From the study: "Overall the trial has painted a picture of an industry and technology that is still at development stage and is likely to make a tangible contribution to energy and carbon saving only on the most exposed sites and tallest buildings. The combination of this reality, aggressive and over-optimistic marketing by some suppliers, and the enthusiasm and credulity of the market (and regulators) has potentially led to an unfortunate outcome where the wind industry as a whole is in danger of suffering from a setback in credibility."
In response to the report, the British Wind Energy Association noted that many of the urban sites chosen in the study have wind lower than 5 meters per second (or 11 miles per hour), considered the lower limit of commercial viability. It also said that the British government's online wind assessment tool overstated the available wind in cities.
"The overwhelming majority of small wind system installations are a success--when they are sited properly they save money and energy. The Warwick trials do not show that small wind is not viable. We know that it is, and the experience of thousands of UK users bears this out," said Alex Murley, BWEA Small Systems Manager, in a statement.
Poring over wind maps
In the U.S., urban wind turbines account for only one percent of installations but there is growing interest, according to the American Wind Energy Association (AWEA). In a report (click for PDF) on how municipalities should permit small wind turbines, the AWEA said understanding one location's particulars and how high a turbine is placed--which in general, means more wind--is crucial in urban locations.
"Siting becomes especially important for turbines in urban settings. Wind patterns behave very differently around buildings and in densely-built areas, so a turbine must be sited very precisely in order to gain access to wind of sufficient quality," according to a report by AWEA.
Small wind turbines overall are a fast-growing segment of the wind industry. Incentives to install small wind turbines improved last year, boosting the federal tax rebate to up to $4,000. Politicians, including New York City Mayor Michael Bloomberg, have called for placing turbines atop skyscrapers and public buildings.
To get a read on the suitability of a location, start-up 3Tier offers a free, Web-based wind and solar assessment tool, which gives people an idea at a high level how good wind is. There are state-level wind programs, and the Energy Information Association and National Renewable Energy Laboratories both publish national maps.
In isolated areas, a pitched roof causes wind to speed up. But the presence of nearby buildings in an urban setting can cause wind to slow down when it hits a roof, according to research from the U.K.'s Centre for Renewable Energy Systems Technology.
(Credit: S. Watson, Loughborough University)Southwest Wind Power, which makes a small wind turbine that typically is mounted on a pole rather than a roof, offers guidance on minimum requirements, which include 10 mile-per-hour average wind and 20 feet clearance above obstructions.
Another manufacturer, Cascade Engineering, publishes specifications that assume a very good wind resource. The specifications for its roof-mountable small turbine indicate that it can turn out 1.5 kilowatts and the 2000 kilowatt-hours per year--or about one third or one quarter of a U.S. home's electricity. To meet that that threshold, however, a site needs 31 mile-per-hour wind, or 14 meters per second.
Some customers, meanwhile, don't do rigorous economic analysis beforehand. The Museum of Science in Boston, for instance, is now working on an educational project to put eight small wind turbines from different manufacturers on its roof
Harvard University, which plans to put some small turbines on an office complex and on a parking garage, told The New York Times that the installations are experiments and "outward symbols of our commitment to renewable energy and sustainability here on campus."
Aerovironment is targeting commercial customers for its small-wind turbines that are optimized for gusty wind coming off buildings.
(Credit: Aerovironment)Small wind manufacturers say that the payback on small wind turbines--rooftop or pole-mounted--varies greatly based on how a machine is sited, which points to the importance of a good installer.
With good wind and high electricity rates, a homeowner could recoup the upfront investment of a small wind turbine in five or six years. But low electricity rates and marginal wind could mean 15 or 20 years, Andy Kruse, the CEO of Southwest Windpower, said last month.
Kruse is lobbying for government-sponsored work to make wind and solar maps that offer more specific information. "How do we create a new generation of maps so that we can understand resource, to make sure it works and stop guessing?" he said.
