Paul Kilduff, San Francisco Chronicle
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When it comes to renewable energy, a new wind may literally be blowing on the horizon: a small but growing movement to erect wind turbines on or near urban rooftops.
Once associated with farms and other rural environments, wind turbines are making their way to the city. Although still a tiny industry - the American Wind Energy Association estimates that just 1 percent of the 10,000 turbines purchased annually are of the small rooftop or residential variety - the current interest in wind as a renewable energy resource is undeniable. Celebrities like Jay Leno and Ed Begely Jr. have installed them. Boston's Logan Airport has a set. Even New York Mayor Michael Bloomberg is calling for wind turbines on the city's skyscrapers and bridges.
Closer to home, earlier this year San Francisco Supervisor Tom Ammiano created the Urban Wind Power Task Force to streamline the process of installing small wind turbines. In a city where steady 10 to 12 mph winds - ideal for small wind turbines to produce electricity - are not uncommon, the task force seemed like a no-brainer.
To date the city has signed off on the installation of a few residential turbines: three vertical-access ones (they look like corkscrews) and one horizontal-access model (it resembles a mini version of the turbines dotting the Altamont Pass alongside Interstate-580). Unlike the newer rooftop-mounted vertical-access turbines, horizontal turbines are generally mounted on poles.
"The beauty of wind power in San Francisco," she added, "is that because we have so much wind, we have the ability to produce power 24 hours a day, where with a solar system we're at like five hours a day" - unless you have the kind of solar panels that track the sun and move with it.
"My turbine has been going like crazy right now, and there's no sun for sure, so my solar system isn't doing anything. Wind is a greater resource," she said.
Where's the wind?
"People don't have money to blow, especially right now, on a device that may not give you the output that you need to make it a worthwhile investment," Partin said. "So if you really want to make a sound investment, then you're going to have to be willing to wait the six to 12 months it takes to test what your wind resource is."
Wilson, who also serves on the city task force, counters that the only real way to determine a home's wind-producing potential is through an on-site inspection, in which factors such as wind breaks (like nearby buildings) and the direction of the wind will be taken into account.
Because they are not rooftop mounted, horizontal-access turbines have to go through a 30-day public comment period before they are approved. This allows neighbors living nearby to voice concerns about noise, vibration, aesthetics or other issues. Turbines can generate a hum and some vibration, but whether it's enough to annoy neighbors is anyone's guess.
The alternative to the more established horizontal turbine is the vertical-access one championed locally by Bernal Heights resident Todd Pelman. His company, Blue Green Pacific, installed the first residential wind turbine in San Francisco last year. Since then, he's installed two more of the company's prototype vertical-access turbines on the home of Chris Beaudoin in the city's Castro district. Pelman is developing the next generation of his company's turbine.
Before putting up a wind turbine, consider this:
How big a turbine should you get? It depends on how much electricity you use and what you want to accomplish. The average PG&E customer uses between 6,000 and 12,000 kilowatt (kW) hours annually in San Francisco. A turbine rated at 2.5 kilowatts with winds of 12 mph should produce about 500 kilowatt hours per month (6,000 kilowatts a year) or close to 100 percent of an average household's needs.
Your wind resource. The ideal wind speed for a home turbine is 10 to 12 mph. You can test this yourself by putting an anemometer on your roof.
Guarantees. While no one can guarantee exactly the amount of wind your home will experience, turbine manufacturers will guarantee that your turbine will produce a certain amount of electricity given the proper amount of wind. They can make this claim because wind turbines have censors that track the amount of wind they're taking in.
Height. With wind turbines, the higher they're placed the better. Since most communities have building height restrictions, it's important to check what is allowed in your community.
Rebates. The California Energy Commission's Emerging Renewables Program offers a rebate of $2.50 a watt for turbines that are rated to produce less than 7.5 kilowatts. There is also a federal tax rebate on qualified turbines installed until the end of 2016.
Costs. The Blue Green Pacific vertical-access turbine, designed to offset 20 percent of the typical household's electric needs, will sell for less than $5,000. Systems sold by Whirligig that will produce 1.5 to 50 kilowatts range from $15,000 to $135,000.