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New York City Is Latest to Launch Solar Mapping Tool for Building Owners

The 3-D maps enable any building owner to go online and find out how much sunlight hits their roofs

By Brian Kell, SolveClimate News

Jun 15, 2011
NYC Solar Mapping

Successful marketing often involves putting a product's facts — literally — at customers' fingertips.

That seems to be the philosophy that city officials have brought to their online solar mapping services — and the results have been far reaching, they say.

Since March 2008, when San Francisco first put its map a click away from interested citizens, solar photovoltaic (PV) installations in the city have tripled, from 700 to 2,100 this year.

"[It] is the main solar outreach tool used in San Francisco," said Danielle Murray, the city's renewable energy program manager.

That may be so, but many observers say the City by the Bay's rooftop solar boom has been largely driven by California's tiered rate system, in which electricity bills rise as people use more power. And, according to Murray, the solar map has averaged a less-than-arresting 70 hits a day since debuting — though she insists this figure belies the project's impact.

Seventeen other U.S. cities and the German city of Osnabrük have published solar maps on the Web since San Francisco's site went live, enabling home and building owners to assess the potential of their roofs to generate clean electricity.

The map combines aerial images with calculators and other features to provide owners with facts and figures needed when considering whether to purchase a PV system, such as the pitch of the roof and the amount of shade cast by neighboring buildings.

Most of the maps were developed by Critigen, a technology consultancy based in Greenwood Village, Co., and were partly funded by the Department of Energy's Solar America Communities Program.

NYC Map Will Be the Biggest

The map of New York City, the biggest so far in terms of quantity of data and geographic area surveyed, is scheduled to go live on June 16, during the fifth annual New York Solar Summit.

Convened by the City University of New York (CUNY), the summit will bring together leaders of city and state agencies, the solar industry and utility Con Edison, with the goal of accelerating solar adoption in the nation's largest city.

"The map is an important part of this effort," said Tria Case, who heads the New York City solar map project as director of sustainability for the university. "It's a tool that building and homeowners, installers, city officials and Con Ed can use."

The map is exact. During night flights over New Yok in May 2010, a twin-engine plane equipped with lasers captured the architecture of the city. From these images, CUNY's Center for Advanced Research of Spatial Information created a 3-D model of the city.

"It's as if we shrink-wrapped the entire city in paper lined with a one-meter grid and got the exact elevation and horizontal location of each square meter," Sean Ahearn, the geographer who directs the center, told SolveClimate News.

Ahearn said the site incorporates so many bytes of information that it took a supercomputer with 10 processors some 50 hours to generate the map interface.

The website can calculate how much solar radiation hits every square meter of the city — every hour, every day for an entire year. For building owners it means they can size up of the solar energy potential of their rooftops within minutes.

The Web tool is just as useful to installers, its builders say.

"Before making a site visit, an installer can look the property up on a map and advise an owner," said Kay Schindel, an engineer who worked on the solar map for the city of Madison, Wis.  "The installer might, for instance, believe the house roof is too shaded, but there is an excellent location for a ground installation in the backyard."

Typically, the maps also estimate annual savings on electric bills, the time it takes to recoup the cost of a solar installation and the yearly reduction in CO2 emissions that a solar system will create.

Owners of a relatively modest home in San Francisco can learn, for instance, that a 2.5-kilowatt system can each year avoid releasing carbon emissions equivalent to driving their car 2,100 miles, or taking 467 trips across the Golden Gate Bridge.

Links embedded in the maps also provide information for how to qualify for federal, state and local incentives and for finding an installer. On some maps, users can share their solar experiences with others.

Nearly every site stresses the importance of adding solar panels only after owners have retrofitted their homes or buildings to be as energy-efficient as possible.

Maps Promote Energy Efficiency

In Boston, PV installations have increased five-fold since the city launched its map less than three years ago. Bradford Swing, director of energy policy for the city, believes the map was a driving force behind the boost, but says its main contribution may lie in getting people to think more broadly about energy efficiency.  

"The map is now part of Renew Boston," explained Swing, a new program aimed at "greening" residential and commercial buildings. "We have set an ambitious goal of reducing greenhouse gases by 25 percent by 2020. As important as solar is, we cannot do that with solar alone."

He continued: "For a lot of people, going green means solar, but we want these owners to recognize first that energy efficiency is the key to environmental responsibility."

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