VALLEY FORGE, Pennsylvania — Every day, as dusk falls over the United States, millions of street lights blink on in towns and cities across the country.
These quiet moments require a vast, unseen balancing act, because electricity demand and supply must be matched every second.
Perhaps no one carries more responsibility for getting this balance right than PJM Interconnection, a private company which manages the flow of electricity to 60 million customers in 13 mid-Atlantic U.S. states.
As one of the oldest businesses of its kind, PJM often advises neighboring regions or developing nations on how to manage complex energy-transmission systems. Its success is of special note in a week when a series of power black-outs have brought much of India to a standstill.
PJM's control center, in Valley Forge, Pennsylvania, is like a traffic officer for the region's electric power grid. Every day, it ensures that more than 1,600 power plants share more than 100,000 kilometers of transmission lines fairly, efficiently and reliably.
To do this, PJM runs an electricity marketplace where power plants declare the lowest price for which they would generate power the next day. Based on these prices and ever-changing demand and transmission line sizes, PJM tells each power plant exactly when to turn on or off.
“We’re looking in at one of the two PJM control rooms,” says Mike Bryson, PJM’s director of operations. "They’re both staffed 24 hours a day, seven days a week. If one of the rooms is disabled, the other can operate independently.”
Centers of power
Bryson runs the company’s twin command centers. Each windowless underground room contains 10 desks, an American flag and a 20-meter-wide screen crowded with constantly-updated data.
At the screen’s center is a multicolored map, which shows, "the bulk electric system, with generators on the system, direction of flow on all the transmission lines, and then the red dots on there show you the generators," Bryson says. "Red is online. Green is offline.”
That's right, red is on. Green is off.
“That’s electrical engineering," Bryson says. "It’s the opposite of what’s intuitive.”
Scorching summer days can be the hardest to manage. With millions of air conditioners driving electricity demand up, PJM will sometimes offer generators 50 times the usual non-peak price for electricity.
“That’s really telling everybody ‘Hey, we need everybody on because we don’t want to lose any customers,’” Bryson says.
Planning ahead is more important than ever in the digital age.
"The reliability of electricity is much more important than it was...25 years ago, before we all had computers and the Internet and all kinds of electronic devices," says Terry Boston, PJM’s President and CEO. "We keep building... new infrastructure each and every year to make sure it's reliable."
Just as America’s energy needs are changing, so are its energy sources. Coal, hydro and nuclear are still key, but natural gas use is growing rapidly. PJM is also working to integrate wind and solar, even though these renewable sources produce power at varying rates.
“When I started my career, I was writing software to optimize the generators to match the load," says Boston. "Now I’m trying to match the load to the variable generators.”
For instance, when supply gets tight, PJM can now alert colleges or factories to turn off equipment. That’s called “demand response” and Bryson is glad to have that flexibility.
“We have, going into this summer, over 9,000 megawatts of demand response throughout the system," Bryson says. "That’s the equivalent of nine nuclear plants.”
That sort of highly-interactive communication has its risks. And, in recent years, PJM’s focus on security has expanded to address the possibility of sophisticated Internet-based attacks on the transmission system.
But as complex as the work at PJM can be, there’s one display that’s simple and it’s Bryson’s favorite.
“It’s what I call the control panel," he says. "The idea is to keep that little green ball in the middle. Keep it in the blue. If it goes into the red, you want to steer it back in. We do that by raising and lowering generation. If we had a joystick to move it, it would be a lot easier.”
Yet every evening as the street lights blink on again in Chicago, Washington, D.C. and all the towns in between, it’s a reminder that - even without a joystick - PJM’s operators have the region’s power grid well in hand.