National Geographic : 2010 Jul
dangerous---but it's also what allows power to be transmitted hundreds of miles without exces- sive loss. AC won out over DC largely because it can easily be stepped up with transformers, transmitted, then stepped down again to a safer household voltage of 110 or 220. By the 1890s AC lines were running from the new Niagara Falls generating station to Buffalo, some 20 miles away. ese days, ironically, high-voltage DC is sometimes preferred for very long dis- tances; it's harder to produce than AC, but it loses even less power. It took decades for electricity to expand from factories and mansions into the homes of the middle class. In 1920 electricity still accounted for less than 10 percent of the U.S. energy sup- ply. But inexorably it in ltrated everyday life. Unlike coal, oil, or gas, electricity is clean at the point of use. ere is no noise, except perhaps a faint hum, no odor, and no soot on the walls. When you switch on an electric lamp, you don't think of the huge, sprawling power plant that's generating the electricity (noisily, odorifer- ously, sootily) many miles away. Refrigerators replaced iceboxes, air conditioners replaced heat prostration, and in 1956 the electric can opener completed our emergence from the dark ages. Today about 40 percent of the energy we use goes into making electricity. At rst, utilities were local operations that ran the generating plant and the distribution. A patchwork of mini-grids formed across the U.S. In time the utilities realized they could improve reliability and achieve economies of scale by linking their transmission networks. A er the massive Northeast blackout of 1965, much of the control of the grid shi ed to regional oper- ators spanning many states. Yet today there is still no single grid in the U.S.; there are three nearly independent ones---the Eastern, West- ern, and Texas Interconnections. ey function with antiquated technology. e parts of the grid you come into contact with are symptomatic. How does the power company measure your electricity usage? With a meter reader---a human being who goes to your home or business and reads the dials on a meter. How does the power company learn that you've lost power? When you call on the phone. In gen- eral, utilities don't have enough instantaneous ROOM. THE OPERATORS THOUGHT: 9/11.