Fighter jets scream over Columbus Air Force Base, a sprawling military facility in eastern Mississippi that is especially busy these days training aviators for the war on terror. But for all the high tech aeronautics on display overhead, the bustling Air Force base often relies on an old-fashioned diesel generator to keep radar and communications humming and the jets from colliding. That's because the region's antiquated, overloaded power grid dishes out 25 blackouts a year, as well as another hundred or so voltage fluctuations that crash sophisticated flight simulators.

The solution-the world's largest battery-is under construction nearby. Two cavernous steel tanks, each one 10 meters tall and 20 meters in diameter, will soon hold nearly four million liters of concentrated salt solutions, electrolytes that will be charged and discharged by 24,000 fuel cells in an adjacent building. At night this installation, known as a flow cell battery, will suck electricity from the grid and store the energy, which it will discharge during the day when power lines are strained. When blackouts strike-common in this tornado-prone region-the huge battery will keep the base humming for up to 24 hours.