Thousands of megawatts of cheap, clean hydroelectricity from Canada are continuously rushing into the New York Power Authority's sprawling substation in Marcy, NY-enough juice to light up 40 World Trade Centers. For almost a half-century, the Marcy facility, located just a few miles from the remote Adirondack National Park in upstate New York, has transformed this torrent of electricity from a blistering 765,000 volts to the slightly more manageable 345,000 volts used by the overhead transmission cables that feed power-hungry Manhattan 300 kilometers to the southeast.

But the real action at Marcy these days takes place in a nondescript metal building, easily overlooked amidst the 40-meter-high towers supporting the mass of transmission cables. Here, European engineering giant Siemens has just installed the world's most sophisticated high-power switch. If things get really hot this summer, the ability of the specialized chips inside the device to route electricity exactly where it's needed just might save New York City's cool.