Tilting at Windmills - Is wind energy right for Philadelphia?


Story by Samantha Wittchen | Illustration by Melissa McFeeters

Following the announcement late last year by the Philadelphia Eagles that Lincoln Financial Field would become the greenest stadium in the world—in part due to the 80 helical wind turbines to be installed on the rim of the stadium—the concept of harnessing wind power in an urban environment feels like less of a pipe dream.

Conventional wisdom has long held that cities are ill-suited for wind power because the wind speeds required to operate turbines efficiently simply do not exist within an urban area. However, with the growth of the small-wind industry, it has become more practical for homeowners to harness the power of the wind for individual use. Small-wind turbines are classified as those that have capacities of 100 kilowatts (kW) or less. According to the American Wind Energy Association (AWEA), the U.S. leads the world in the production of small wind turbines; in 2009, 95 percent of all small wind systems sold domestically were made by U.S. manufacturers.

One California-based manufacturer, Helix Wind, the planned provider for those Lincoln Financial Field units, builds turbines specifically designed to operate at the lower wind speeds found within the urban environment. Helix Wind’s turbines are compact vertical-axis wind  turbines (VAWT), which is to say they don’t require the vast amount of space that the monolithic, horizontal-axis wind turbines (HAWT) you’ll see on distant ridges from the Pennsylvania Turnpike do.

Although this new technology is promising, switching to wind energy is a complicated question. The U.S. Department of Energy (DOE) considers regions with average annual wind speeds of 6.5 meters per second (m/s), or 14.5 miles per hour (mph), to be suitable for wind development. According to data from the National Renewable Energy Laboratory (NREL), Philadelphia’s average wind speed is only 5m/s (about 11 mph), and that’s at a height of 262 feet above the ground (higher than the roofs of most rowhomes) where urban wind turbines would likely be mounted.

But don’t give up yet! Helix Wind makes a turbine designed for an average wind speed of 5 m/s, perfect for Philadelphia. And remember: The NREL data is only an average. Wind speeds vary by location and topography, so before completely discounting wind power, you may want to gather more data. You can do this yourself by purchasing a recording anemometer and mounting it at the height you’d mount a wind turbine, or by hiring a professional. The DOE suggests measuring wind speeds at your specific location for a year to get an accurate picture of the wind resource available. Once you have that data, you can decide if it’s worth pursuing.

If the Eagles already have you sold on wind power, here are four things to do before setting up that windmill:

1) Right-size your system. There’s no point in oversizing a renewable energy system for an inefficient home. Make sure you do the efficiency work first to save money on the size of the system. The AWEA estimates that small wind turbine installation costs $3,000 to $5,000 for every kilowatt of generating capacity, so it’s worthwhile to install as small a system as possible. According to the DOE, a wind turbine rated 5 to 15kW would be required to make a significant contribution to a typical home that uses 10,000 kilowatt-hours of electricity per year.

2) Check the local zoning codes. Are you allowed to place a wind turbine on your property or will you need a variance? Consider engaging your neighbors to address their concerns before you

start construction so they don’t throw any obstacles in your path.

3) Know your grid options. Contact your electricity provider or distributor to find out if and how you can connect your wind energy system to the grid. The American Wind Energy Association (awea.org) is a good resource for utility interconnection requirements.

4) Take advantage of incentives. The federal government offers a tax credit of 30 percent of the cost of the system.

While wind may not be the right answer for all Philadelphians right now, there’s no telling what the rapidly developing small wind industry will build in the near future. We may be tilting at windmills today, but tomorrow we could be powering our city with them.