Con Edison makes a solar leap
By Patrick G. McHugh and Margarett L. Jolly
Con Edison has worked with Mayor Michael Bloomberg and other partners for a decade to encourage solar energy in New York City and Westchester County, N.Y .
Adding a few kilowatts here and a few there with residential installations and moderate-sized commercial projects drove solar production from 8.5 megawatts in 2010 to 30 megawatts today.
Now Con Edison’s engineers have invented smart grid technology that could spawn a dramatic escalation in the amount of solar energy in Greater New York.
The innovating began when Jetro Cash and Carry's Restaurant Depot, a food service supply company connected to an isolated spot network in the Bronx, applied to install a behemoth 1.56-megawatt array of 4760 Sunpower E20 panels atop its store and warehouse.
Con Edison’s distributed generation engineers and planners quickly recognized the opportunity. Such a large installation would provide a benefit to the electrical grid during sweltering heat waves like the one that enveloped the city for seven days last July.
In addition, the utility has committed to robust efforts to shrink its carbon footprint and keep New York a clean, livable city. The generation of electricity with the sun’s rays instead of with fossil fuels keeps emissions out of the air.
But the utility also saw a stubborn problem standing in the way of that opportunity. Jetro—like nearly all solar customers—planned to send excess electricity generated by the panels back into the grid, selling it to the utility for distribution to other customers.
The backwards flow of such a large amount of electricity would cause the Con Edison network protectors associated with Jetro to open as if they recognized a fault, blacking out the customer.
Con Edison programmed the network protectors associated with Jetro so that they do not open when power flows from Jetro’s panels into the grid. Those protectors will still open if they detect an actual fault.
As a backup, the new relays allow Con Edison control operators to monitor the operations of the solar panels. The operators can isolate the feeders remotely if needed.
The application of this supervisory control and data acquisition (SCADA) computer- controlled communications system to an isolated spot network is a significant step for Con Edison. The utility is the first in the industry to use this technology to manage flows on an underground network system.
Jetro, which chose Ross Solar Group as its installer, is the first beneficiary. The panels are expected to generate 1.8 million kilowatt hours of electricity annually, saving the company $220,000.
With its government incentives, tax breaks, electricity savings and depreciation, the company expects a return on its investment in the panels in about three years.
Other Con Edison customers may follow with super-sized installations that take advantage of the new technology. The utility has applications for even larger installations in the queue.
It’s another example of Con Edison’s commitment to working with customers who want to install photovoltaic panels. The company provided technical assistance for the New York City Solar Map (www.nycsolarmap.com), which provides information on the solar potential of buildings. Con Edison also shortened the approval process for customers who want to install residential systems (under 25 kilowatts).
Patrick G. McHugh was Con Edison’s chief engineer, distribution engineering, during the Jetro project and has since been promoted to vice president, Brooklyn/Queens electric operations. Margarett L. Jolly was Con Edison’s distributed generation ombudswoman and has since been promoted to director, research and development.