Harvesting Winds of Change

Rooftop Windfarms

By Jonathan Barnes

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Thirty-three years ago, during the summer of 1976’s energy crisis, 40 people gathered on the rooftop of 519 East 11th Street in Manhattan’s East Village, beers in hand, determined to create their own power source. With enthusiasm, flavored with leftover 1960s activism, plus a good bit of pushing and hoisting, the group erected a windmill fashioned from a 30-foot farm turbine on the roof of their building.

The experiment in wind energy so impressed the public that politicians applauded it and the MacNeil/Lehrer Report filmed an installment of its television show on the building’s roof. The turbine supplied part of the building’s electricity needs for years before it was dismantled, but the idea that inspired that first rooftop windmill lives on.

The new energy crisis has made co-op and condo administrators scrutinize their bottom lines, and alternative energy sources are figuring more prominently in their solutions to their cash crunches. These days, developers are constructing residential buildings with the intention of having part of the building’s energy needs supplied by wind power. Some consider these forays into alternative energy experimental, but others feel that they are viable solutions to a very pressing problem.

Old Ideas Anew

Alternative energy sources are in the news these days thanks to high fuel prices, the recession, and the growing number of residents interested in decreasing their own environmental impact. To meet those growing demands, a handful of New York City buildings have installed miniature “wind farms” on their roofs to utilize air power to supply them with energy and save residents money. Early adopters of this green technology are pioneers of a sort, openly experimenting to determine how wind technology works best in a vertical urban environment.

Les Bluestone, a partner with Manhattan-based Blue Sea Development, has done enough research to expect that the wind farm his company is planning for The Eltona, a five-story, 63 unit residential development at 429 East 156th Street in the Melrose section of the Bronx, will work. His company began introducing LEED-certified green projects about eight years ago, and was the first in the state to offer Energy Star buildings back in 2001. The idea of using wind power technology piqued Bluestone’s interest early on. “We ran across a California company that had these prototypes,” he says, and the company began working on ways to introduce it to the New York market. Enrolled in NYSERDA’s Multifamily Performance program and the U.S. Green Building Council’s LEED for Homes program, The Eltona will also be the subject of a Mount Sinai School of Medicine study, analyzing the effects of green living for those families suffering from asthma.

Bluestone’s building, which is finished, will feature an array of sealed turbine components needing no lubrication, each rated at one-kilowatt and having a 40 to 50-year life span. The turbines are mounted on its parapet walls, a system recently approved by Con Edison. The project will also include a co-generation facility that will use throw-off heat from the building’s boiler to heat water. The co-generation system includes two five-kilowatt units. Together, the rooftop turbines and co-generation plant will enable the building to have a zero carbon footprint.

According to Bluestone, “We estimate that between the wind and the co-generation facilities, we ought to be able to provide a constant load, onsite.” The system was just turned on nine months ago, and Bluestone says, “The turbines are very, very quiet.”

A Viable Option?

The case for onsite residential energy production is that such buildings will be less dependent on the city’s power grid and old forms of energy (such as coal), while reducing the amount of carbon spewed into the atmosphere. Small wind power projects provide “clean” power, with no harmful emissions. The benefits provided by rooftop wind power generation systems are driving interest in the systems, and according to the pros, more people are willing to pay for the technology, seeing it as a smart buy.

Assuming a building has a good wind source, it might offset its electric usage significantly with a rooftop wind system, says Eric Nevala-Lee, GreenHomeNYC spokesperson and program coordinator of the nonprofit organization that promotes the adoption of sustainable building methods and materials by owners of small residential and commercial buildings in New York City.

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However, their are several factors involved and a lack of sufficient case studies which makes it difficult to estimate the amount of power a fully functional wind farm can produce. “Assuming you’re talking about rooftop micro turbines, these can be rated from .5-20 something kilowatts maybe,” says Nevala-Lee. “This rated output isn’t what the turbine will actually produces though, but the maximum. Actual production depends on factors like placement, consistency of wind, obstructions of other buildings, etc. It then depends on how much space you have. Maybe you have room for one turbine or maybe you have room for 100.”

Jennifer Harvey, senior project manager for the New York State Energy Research and Development Authority (NYSERDA), contends that the amount of power produced is contingent on the size of the windfarm.

That said, residential wind technology is relatively new, and can represent a major capital investment, so thus far only a handful of buildings have implemented it.

According to Harvey, another hurdle for wind energy has to do with hardware. There just aren’t many small-scale wind systems on the market. Another reason may be that wind patterns in urban areas are complex, and don’t always provide the force needed to make a rooftop system viable. A residential building might be situated amidst a group of tall buildings, and thus not get the full benefit of a wind power generation system.

“National experts in small wind power…recommend that you measure the wind speed on your building,” Harvey says. “Right now, there is no accepted process. There’s not a lot of good information on siting small wind facilities. One national expert recommends measuring wind speed on buildings using an anemometer.[...] Much work needs to be done in this area to further understand the complex wind and help determine what sites could be good candidates. You want a situation where there aren’t a lot of obstacles for the wind to get around.”

There are also structural issues that must be taken into account, Bluestone adds. “The building has to be designed for the loads of the wind turbines,” he says. While, installing heavy equipment on a rooftop not constructed to withstand it can spell all kinds of disaster. Bluestone adds that the turbines’ weight isn’t the entire issue. “It’s the loads,” he says, “the lateral loads. The particular model that we used really is better suited for pre-cast concrete production.” Therefore, it’s vital that any building contemplating the installation of turbines commission an exhaustive engineering survey to determine whether their roof and walls can actually handle it.

In terms of retrofitting building to bear the weight Bluestone says, “although it can be retrofit there are certainly structural reinforcements that have to take place. But there are other models out there probably better suited for retrofits to existing buildings.”

If you don’t have adequate wind potential around your building, Harvey has another environmentally savvy suggestion. “It may be that your building is a good candidate for solar,” she says. “Both types of green energy lower a building’s carbon footprint.”

According to Bluestone, low- to mid-rise buildings are best candidates for rooftop wind power generation are low- to mid-rise buildings. When wind hits the vertical surface of a building, it accelerates as it goes over the top of the structure. “The obvious benefit [of the energy produced] is that some coal-fired plant in Ohio can relax a bit,” he says. “It reduces demand overall.” Without engaging in a complex physics discussion, Bluestone explains that the turbines are a generator. “It’s not unlike an electric generator that would be run by a gasoline engine the only difference is that the wind is spinning the turbines instead of a gas motor.”

Wind Drawbacks

The potential of having part of a building’s energy needs provided by rooftop power generation sounds good—but it’s not hassle-free. For some buildings, the up-front expense of installing a rooftop wind farm moves the idea out of reach, Nevala-Lee says.

“There is a big upfront expense to this,” he says.

Bluestone explains that the price tag may vary depending on the model and the manufacturer. “That would really would depend on what you selected. I could say that roughly speaking it’s about $10,000 a kilowatt for us. That includes the equipment, the installation and the wiring and whatever other stuff.”

Harvey agrees that price ranges can vary depending on tower height and other factors. “ A 10-kilowatt turbine costs in the area of $60,000 to purchase and install,” she says.

The feasibility of installing a wind power generation system on a co-op or condo building is largely a question of which way the wind blows and how hard it blows. If a building doesn’t have the wind coming toward it consistently and at the right speed, even the most sophisticated technology is unlikely to generate enough electricity to offset its own installation costs.

Maintenance and life span are another issue. Nothing lasts forever, and rooftop wind systems are no exception. Some can have a 40 to 50-year life span, given good maintenance. But while some may think that maintaining turbines, housings, and other components may be beyond the standard qualifications of a building super or handyman or that malfunctions could be expensive, others disagree.

“In terms of maintenance they’re not different than most generators,” says Bluestone. “They do require periodic maintenance, but they are really fairly maintenance free. There are scheduled maintenance periods, but really nothing that is any more or less involved than any other part of the building system. The safety, sure, is always an issue. There are lots of companies making these things, some of whom are a little more established and have a little more science and background and experience than others. So that is kind if key for us on our decision on whom to select- a company that we felt comfortable with. There are no third party testing standards for wind turbines. So that is a little bit of a problem. So you do really have to do your research and homework an make sure that the company that you’re go to is legitimate and has some background.”

“It’s a mechanical system, and must be maintained like any other mechanical system,” Harvey says. “You want to make sure you have a fairly good estimate of the energy your system will generate before deciding to go with such a system.”

Windy City?

Could the future of New York be small windmills on apartment buildings? Some of those interested in the green movement hope so—and hope such systems will be in wider use on houses, too. Through her organization, Harvey is doing her part to make that dream a reality. She helps with a program to assist residents who want to explore installing a wind system to offset their electric usage. You can learn more about the program by visiting www.powernaturally.com.

The sales value added to a building by implementing a rooftop wind power system is hard to measure, though the value added by the power generation facility should be calculated to the kilowatt. Having such a facility will be helpful in marketing the building, Nevala-Lee says. “This is something that is expensive right now. But the more that it’s out there, the more prices will come down for this stuff. It’s something you invest in, but you’ll get a payback,” Nevala-Lee says.

So it may not be a question of whether the average New York co-op or condo owner lives in a green building, but when. Co-generation, wind power and other green forms of energy production are increasingly popular in residential developments. Over time, as popularity drives down the cost of implementing such systems, the skyline of the Big Apple may be alive with wind power.

Jonathan Barnes is a freelance writer and a frequent contributor to The Cooperator and other publications.

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