There are many reasons to get a rooftop solar power system, from the attractive state and federal incentives to the potential for dramatically lower electricity bills.
Unfortunately for solar developers and potential clients, those pluses aren't always enough to make a rooftop system a reality.
"There are a hundred different reasons why a lot of roofs will never host solar in New Jersey," said Mark Warner, president and CEO of Sun Farm Network, a solar developer in Flemington.
Some pitched roofs face the wrong direction, while others have limited available space due to air-conditioning units or other rooftop obstructions.
Trees or other sun-blocking structures make other rooftops impractical. But while an unsuitable roof used to be a deal-breaker, Warner and other developers are now pitching another option — the parking lot, which can be outfitted with solar-paneled canopies, turning a field of asphalt into a solar-power plant.
To date, only a small fraction of New Jersey's 11,000 megawatts of solar projects are on parking lots. Warner said that's because parking-lot systems require expensive steel racking structures, driving the cost up to 30 percent higher than a rooftop system.
Lately, though, the prices of solar components and steel have dropped, and manufacturers have made strides to optimize racking-system technology. That's given Sun Farm and other developers a more attractive alternative for so-called "solar-challenged" clients with unviable roofs.
Sun Farm is currently installing a 2.1-megawatt system at St. Peter's University Hospital, in New Brunswick. More than 90 percent of the generation capacity of that project comes from panels atop the hospital's parking lot and parking garage.
William Paterson University, in Wayne, also took advantage of its parking lots when it launched a solar initiative last year.
Stephen Bolyai, vice president for administration and finance, said about 1.7 megawatts of the 3 megawatts worth of solar power generated at the school comes from panels installed on parking lots. The school is planning to add another 500 kilowatts worth of panels in its second phase; about one-fifth of that phase will be on a parking garage at the school.
"We were trying to maximize the output," Bolyai said. "We're on 370 acres, and most of that is wooded, and we have parking for 4,000 cars and over 40 buildings."
Bolyai said some of the school's parking lots were ruled out because of tree coverage, or for aesthetic reasons. He said the school also was careful to design the canopy system in such a way that it didn't detract from the campus' natural setting. For instance, it opted for an off-white coat of paint on the steel, in order to avoid the cold, gray look of an overpass or battleship.
The school also built lighting fixtures into the array, so the panels wouldn't darken the lots. Because the array was built under a power-purchase agreement, the school didn't have any upfront costs, and the project's developer, Nautilus Solar Energy LLC, will maintain the system.
Joe Sullivan, vice president of energy policy and development at Concord Engineering Group, in Voorhees, said parking lot solar canopies also align with state and local policy goals.
He said the state's energy master plan encourages "behind-the-meter" solar — that is, solar power generated on-site for use by the property owner. Parking-lot solar also creates a second use for land that's already been developed, which can make it easier to get the approval of local zoning boards.
"You're putting something on top of a surface that's already impervious," said Sullivan, a former Board of Public Utilities official. "You're basically getting two uses out of that space."
That said, Sullivan said property owners need to think about how the canopies will affect snow removal, and make sure the panels are high enough off the ground for the tallest vehicle that could enter the area. Warner, for instance, said the canopies at St. Peter's University Hospital are 18 feet off the ground, to accommodate fire trucks and other emergency vehicles.
For those and other reasons, Warner said, canopy solar is generally more complicated to design than rooftop solar. But with falling prices and a still-growing market for solar, Warner believes parking lot canopies have plenty of potential.
"This is a relatively new development in New Jersey," he said, "and it has profound market implications because it, in essence, opens up a whole new opportunity for people to go solar that didn't exist before."
E-mail to: firstname.lastname@example.org
On Twitter: @JaredKaltwasser