Over two weeks in April 2010, a light twin-engine plane flew low and methodically over the rooftops of New York City. It mission was to collect data, but not in the clouds. Affixed to the underbelly of the aircraft was an aerial LiDAR (Light Detection and Ranging) scanner, pointed at the ground, firing 50,000 laser pulses per second. Satellite and ground GPS measured the location of the aircraft every 0.1 seconds. An onboard Aerial Inertial Measurement Unit measured the pitch, yaw, and roll of the aircraft every 0.002 seconds.
The data collected—more than 15 million geographic coordinates—was used to generate the most detailed, three-dimensional map of New York City ever created. “It’s like shrink wrapping the city,” said Sean Ahearn, director of Hunter College’s Center for Advanced Research of Spatial Information (CARSI), whose lab managed the LiDAR acquisition and built the map.
The 3D map, however, served a larger purpose: creating a tool that estimates the solar energy potential of each and every one of the city’s nearly one million buildings.
That tool is the NYC Solar Map. And with its launch in June, New York City has taken a major step toward building a clean energy infrastructure.
The map is a product of the New York City Solar America Partnership, a group led by the City University of New York (CUNY) and its director of sustainability, Tria Case.
In it’s bid to become one of the Department of Energy’s Solar America Cities in 2007, the group developed a roadmap to accelerate the adoption of solar technology in New York.
As the city began to adopt the policies and incentives in the roadmap, Case said, “We recognized that a map—something that was out there and highly accessible to the public—would help people to understand what’s possible.”
So Case, and her partners at the Mayor’s Office of Long-term Planning and Sustainability and the New York Economic Development Corporation, asked the DOE to support a solar map, as well as the deployment of data acquisition systems around the city.
To make a map that can estimate, to a high degree of accuracy, the solar potential of nearly a million buildings requires a seemingly impossible first step: determine how much sunlight hits every square meter of New York City.
The Sanborn Map Company, experts in LiDAR acquisition and mapping, flew a total of 17 missions, crisscrossing 362 square miles of the city. The flights collected an extraordinary density and volume of data. According to Sanborn general manager Chris Genovese, it was one of the most data-intensive projects his company had ever worked on.
“We’ve done statewide LiDAR projects with far more area,” he said, “but in terms of density per square meter [New York City] was probably the highest.”
After the flights were completed, Sanborn turned over 535 GB of raw laser data to the lab at CARSI, which turned it into a 3D digital surface model. That model was used to calculate—with the help of a supercomputer—solar insolation data for the entire city. In other words, CARSI calculated how much sunlight was hitting every square meter of every surface of the city, every daylight hour, every day of the year. The isolation calculations took into account every conceivable variable: shading from surrounding buildings and trees, the time of day, the time of year, and even local weather conditions over the last 20 years.
Once finished, the model showed that two-thirds of the city’s buildings are suitable for solar PV installations. Together they could provide up to half the city’s power demand in peak times, assuming, of course, that the power could be funneled into New York’s electricity grid, one of the most complex in the country.
“Early on there were certainly a lot of questions about how solar might impact the network grid,” said Case. Even Con Edison, the local utility, didn’t have the answers.
So Case called in the National Renewable Energy Laboratory (NREL) to conduct an in-depth study on how solar could be integrated into New York’s network grid. Before it was even finished, said Case, the benefits of solar became clear. Con Edison embraced the project, and since then, “They’ve been great, great partners.”
Con Edison will be one of the map’s most important users, too. Now the utility can determine where solar can support a particular substation, and therefore delay adding more equipment that could mean more cost during peak usage times.
But with over 120,000 hits to date, Case says the audience for the map is “a myriad of folks with a myriad of perspectives.” She singled out the energy auditing community as a group that’s increasingly looking at solar potential in New York City. Likewise, city planners are using the map to study the potential for PV installations on schools and at landfills.
Still, Case is happy to report that most people who visit the map tend to look at their own homes first. She believes the widespread adoption of solar and renewable energy in New York City is all about breaking down the barriers to communication. Because now that the policy framework is in place and the NYC solar map is online, she said, “If the public doesn’t know about it, you’re only talking to the people who are already at the table.”
Visit the NYC Solar Map at www.nycsolarmap.com.
Posted on: December 22nd, 2011