National Geographic : 2010 Jul
• information on the flow of current through their lines---many of those lines don't carry any data---and people and slow mechanical switches are too involved in controlling that ow. "The electrical grid is still basically 1960s technology," says physicist Phillip F. Schewe, author of e Grid. " e Internet has passed it by. The meter on the side of your house is 1920s technology." Sometimes that quaintness becomes a problem. On the grid these days, things can go bad very fast. WHEN YOU FLIP A LIGHT SWITCH, the electricity that zips into the bulb was created just a fraction of a second earlier, many miles away. Where it was made, you can't know, because hundreds of power plants spread over many states are all pour- ing their output into the same communal grid. Electricity can't be stored on a large scale with today's technology; it has to be used instantly. At each instant there has to be a precise balance between generation and demand over the whole grid. In control rooms around the grid, engineers constantly monitor the ow of electricity, try- ing to keep voltage and frequency steady and to avoid surges that could damage both their cus- tomers' equipment and their own. When I ip a switch at my house in Wash- ington, D.C., I'm dipping into a giant pool of electricity called the PJM Interconnection. PJM is one of several regional operators that make up the Eastern grid; it covers the District of Columbia and 13 states, from the Mississippi River east to New Jersey and all the way down to the Outer Banks of North Carolina. It's an elec- tricity market that keeps supply and demand almost perfectly matched---every day, every minute, every fraction of a second---among hundreds of producers and distributors and 51 million people, via 56,350 miles of high-voltage transmission lines. One of PJM's new control centers is an hour north of Philadelphia. Last February I went to visit it with Ray E. Dotter, a company spokes- man. Along the way Dotter identi ed the power lines we passed under. There was a pair of 500-kilovolt lines linking the Limerick nuclear plant with the Whitpain substation. Then a 230-kilovolt line. Then another. Burying the ungainly lines is prohibitively expensive except THE ELECTRICITY FLOWING IN YOUR LIGHTBULB Southern California Edison's fleet of elec- tric vehicles, almost 300 strong, has logged 18.3 million tailpipe- emission-free miles. Its test center evaluates how cycles of charging and discharging affect vehicle batteries--- which one day may not only draw energy from the grid but also return some at moments of peak demand.