Considering wind energy but don’t have the space for a large turbine? Utility-scale models aren’t the only option that can turn gusts and breezes into renewable power. Unlike its taller cousins, a vertical axis wind turbine (VAWT) has a compact footprint and can be installed on rooftops or a corner of your property. This design flexibility makes it a suitable alternative for urban locations where a traditional turbine is out of the question. Learn how a VAWT can help your facility generate clean power when space is limited.
Spinning with Benefits
Though first designed in the late 1920s, vertical axis turbines aren’t as widespread as other renewable technologies. While modern engineering has ironed out some design challenges, commercial adoption has been eclipsed by systems with more established track records, namely horizontal axis wind and solar.
Vertical axis turbines come in two basic forms – those with S-shaped scoops or ones with blades that resemble an egg beater. Either version is omnidirectional, meaning they can accept breezes from any direction, says Paul Schneider, vice president of marketing for CGE Energy, a provider of wind solutions. This is a significant advantage over horizontal turbines, which must be facing into the wind to spin.
“Efficiency-wise, the capacity of these turbines approaches that of utility-scale models,” says Ryan Gilchrist, assistant director of business development for Urban Green Energy (UGE), a turbine manufacturer. “While not as high, the output is still high enough to gain strong economic returns.”
Though payback is variable depending on generation, utility rates, and quality of siting, owners can expect a 5- to 15-year payback, Schneider notes.
The petite stature, lower center of gravity, and lighter design of VAWTs also enable installation possibilities that simply can’t be achieved with a mega turbine.
Those on the shorter end of the spectrum are typically placed on rooftops. Less than 30 feet high on average, their height is unlikely to interfere with aviation traffic. Furthermore, their slim profile means that the weight can be supported by commercial roofs. They can be installed directly above an existing building column, though additional reinforcement may be required, explains Gilchrist.
If the roof isn’t an option, freestanding models can be located on an unused patch of your property. These turbines can be comparable in size to a standard area light pole or between 100-150 feet. This is still substantially smaller than utility-scale turbines, which are typically over 300 feet tall when measuring ground to blade tip.
Whether rotating overhead or gracing the edge of your parking lot, these vertical axis turbines are sure to stand out. Considering that solar panels may be obscured by parapet walls and geothermal is hidden underground, vertical axis turbines are an eye-catching way to position your company as an environmental leader.
“Companies looking to make a visual statement about their sustainability initiatives can attract positive attention with these turbines,” Gilchrist says.
As an additional benefit, VAWTs are quieter because their RPMs are lower than utility models, he adds. This means less vibration is carried through the building as well.
These turbines can also contribute to bird safety. Because the blades don’t spin as fast and their arms are shorter than a large turbine, they are easier for birds to see and avoid.
Lastly, access is far easier with VAWTs. Critical components such as the gearbox are often at ground level so no scaffolding or safety harnesses are needed to perform routine maintenance and inspections, says Schneider. Maintenance is similar to larger models with lubrication changes and blade cleaning. Some manufacturers also offer service contracts.
Ensure your warranty, which is typically two to five years, covers routine failures as these turbines are designed to move continuously, Schneider adds.
Hilton Fort Lauderdale Beach Resort
Hilton Worldwide wanted to attract green-minded customers to its resorts for personal lodging and events. Taking advantage of Fort Lauderdale’s strong coastal winds and the building’s 26-story height, the hotel installed six building-integrated turbines on its roof.
The 4 kW turbines stand approximately 52 feet tall and are strategically positioned on each corner and the center of the hotel’s rooftop to capture maximum wind velocity. The VAWTs are projected to produce 24,000 kWh, which supplements 5-10% of the resort’s energy needs.
At an investment cost of over $500,000, annual savings will be between $25,000-$50,000 with a payback of 10-20 years. The turbines are also expected to offset 70,000 pounds of carbon annually. Plans are underway to combine the installation with solar.
“The turbines will help us visualize the hotel as a place to be conscious of energy use. They will help to highlight the importance of conserving electricity and start dialogue,” says Randy Gaines, vice president of engineering for Hilton Worldwide.
INFORMATION COURTESY OF UGE AND HILTON FORT LAUDERDALE BEACH RESORT; IMAGE PROVIDED BY UGE
Quantify Your Wind Resource
As with any renewable, you need to have a firm projection of how much energy your site is capable of producing. For turbines, you should calculate your wind resource in order to capture as much of it as possible. The forceful winds on top of your building should produce enough torque to generate a suitable amount of electricity, but it’s best to confirm this before installation.
“We use a CFD (computational fluid dynamics) analysis to measure turbulence,” Gilchrist explains. “This helps us to model the building and take into account surrounding structures. What you want is laminar air, which will reliably spin the turbine.”
“Wind speeds can also be established by consulting wind maps or taking measurements with anemometers,” adds Schneider. Either way, you need this data to right-size your turbine and optimize its location.
Lincoln Financial Field
Lincoln Financial Field, home of the Philadelphia Eagles, is the first professional stadium in the U.S. capable of generating all of its electricity on-site.
The combination of 14 turbines and solar panels is projected to produce about six times the amount of power used during all Eagles home games on an annual basis. On non-game days, both renewables will offset 100% of all energy use, and any excess power can be fed back into the grid.
Located at opposing ends of the field, the turbines were strategically placed to provide “a visual representation of our commitment to sustainable efforts,” says Eagles president Don Smolenski. The system was also designed so that it doesn’t interfere with the fan experience. A custom braking system will ensure immediate stoppage if ever necessary.
INFORMATION AND IMAGES COURTESY OF UGE
A Collaborative Technology
Owners who want to significantly supplement a portion of their energy needs are unlikely to hit the mark with these diminutive turbines alone – this solution is best to implement when you want to diversify your renewable portfolio.
“Wind and solar go hand in hand,” Schneider says. “Sun is great during the day and in the summer months, but it’s also windier at night and during the winter season. These technologies are complementary and one can pick up the slack when the other is less available.”
“The combination of wind and solar can also address specific site conditions,” Gilchrist adds. “Say you have a tall building in a northern latitude where sunshine is inconsistent. The height of the building contributes to the wind siting and can pick up the slack for power generation when there’s cloud coverage.”
YMCA Storer Camps
The serene setting of the YMCA Storer Camps will soon be home to a vertical axis turbine.
Located in Jackson, MI, the rural campus is composed of a large dining hall, lodges and cabins, a nature center, and various outbuildings. Plans are underway to turn the camp into a net-zero site. A vertical axis turbine was specified for its quiet operation, safety for wildlife, and low profile.
The power purchase agreement (PPA) for the equipment eliminates upfront, installation, and maintenance costs. The YMCA will save on operating costs from day one, only purchasing the electricity generated at a discount from what it currently pays the utility.
“When we’re done with our vision, we’ll have a 450-bed campus that uses less energy than is generated on-site,” says Glen King, chief development officer for YMCA. “By having renewable sources like wind, geothermal, solar, and biomass at our camp, we will provide a total immersion learning environment to show real-world examples of environmental stewardship and sustainable energy.”
INFORMATION AND IMAGE COURTESY OF CGE ENERGY
Look for Financing Options
To help recoup a portion of your capital expenses, make sure to apply for the Federal Investor Tax Credit. Small wind turbines under 100 kilowatts that have been in service since December 2008 qualify. The credit is equal to 30% of expenditures and will be available to owners through 2016.
Already common with solar, PPAs (power purchase agreements) are also gaining traction with wind installations, says Schneider. These contracts allow property managers to avoid buying a turbine outright and simply pay for the electricity it generates.
Also ask your utility about net metering, an option that gives your facility credits when you have excess clean energy you can put back onto the grid. Otherwise any power you can use will go to waste or you’ll pay an avoided rate that eats into your ROI. Not every provider allows this type of arrangement, notes Gilchrist, and you may need to upgrade your connections to enable this functionality.
So is a vertical axis turbine a match for your facility? As performance data can be hard to verify given the limited amount of commercial applications, risk-averse FMs may not feel comfortable with this option. It’s worth noting that the Small Wind Certification Council, an independent accreditation body, has not yet certified any building-integrated turbines. The organization verifies energy output, rated power, sound level, durability, and safety according to industry standards set by the American Wind Energy Association. The good news is that several VAWT models have pending applications, showing promise that the technology is edging forward.
If a traditional wind turbine is out of the question, vertical axis models remain your next best option to turn a stiff breeze into renewable energy. Their installation flexibility and small profile can adapt to urban locations where real estate is tight but wind is plentiful.
Pearson Square Court and Bridge Street Apartments
In Long Island City, Queens, three vertical-axis turbines grace the top of the Pearson Square Court apartment building. Installed in May 2014 and projected to generate 9.6 kWh, the turbines produce power that offsets the common areas in the building, including the lobby, hallways, gym, and roof lounge.
At the 388 Bridge Street apartment complex in downtown Brooklyn, two turbines can be seen spinning atop the building from the Long Island Expressway and surrounding streets.
Before these installations were set in motion, UGE conducted a site analysis to evaluate which renewable energy solutions would generate the optimal amount of electricity. The turbines’ helical structure was determined to be well suited to extract energy from winds in urban settings, which tend to come from many directions. Both projects have unobstructed locations for the turbines to gain maximum winds.
INFORMATION AND IMAGES COURTESY OF UGE
Jennie Morton firstname.lastname@example.org is senior editor of BUILDINGS.