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National Geographic : 1972 Nov
Contents
The struggle to convert natural energy to electrical energy AS THE NATION HUNGERS for more and more electricity, scientists grapple with a wide variety of power sources (column at far left) and ways to harness them. Many techniques still rely on the turbine gener ator powered by steam (blue lines), while others convert natural forces directly to electricity (red lines). * FOSSIL FUELS: Lifeblood of the power in dustry, oil, gas, and coal will retain their pre eminence for years, perhaps decades. Burned today in steam power plants, they may someday fuel more efficient systems, such as magnetohydrodynamics (page 673) or a remarkable but still experimental home unit, the fuel cell. Involving no moving parts and creating little pollution, this device will use hydrogen from natural gas to generate electricity chemically. * NUCLEAR FISSION: Despite a slow start, nuclear plants are taking hold. Next will come the amazing breeder reactor (page 672), which produces more fuel than it consumes. * NUCLEAR FUSION: Man's ultimate power source may lie in harnessing the energy process of the stars. If and when the dream becomes reality, fuel for fusion will be ex tracted inexpensively from seawater. * TIDAL POWER: The tides' restless energy already spins turbines in France's Rance River estuary. Engineers look longingly at Passamaquoddy Bay, between Maine and Canada, but few sites in the United States lend themselves to capture of tidal power. * HYDROELECTRIC ENERGY: With prime sites already harnessed, the United States nears full utilization of this clean resource. * WIND: Free and abundant, energy from the wind involves a serious flaw-unrelia bility. Man cannot yet store massive amounts of electricity for use during calms. * SOLAR POWER: The sun's stupendous en ergy could drive civilization forever, if only man could harness it. The "solar farm" (pages 676-7) offers a possible approach, as does the orbiting solar collector. * GEOTHERMAL ENERGY: Intriguing new techniques for tapping the heat in earth's crust (pages 674-5) make this one of the most appealing of potential power sources. by a strange twist of logic, we switched to Scylla. Later, as the experiment evolved, we added the 'c' to signify 'Scylla closed.'" Scyllac looks almost as monstrous as its name suggests. Its heart is an aluminum-and quartz doughnut called a torus, which will eventually be 50 feet around. At the moment it operates with only a third of the circle. This tube is all but hidden by a tangled web of thick electrical cables, some 70 miles in all, flowing from a three-story bank of capacitors where enormous electrical charges are stored (pages 670-671). When released, the charges flow into heavy magnets surrounding the torus. As the current charges the magnets, an intense magnetic field (60,000 times that of earth's) squeezes the plasma to the center of the tube, away from the containing wall. At the same time it heats the gas to the enor mous temperatures required for fusion. Strange as it seems, there is no problem of melting the walls of the tube, even if the magnetic field releases the plasma. True, the individual particles in the gas are at high temperatures because they are moving at ex treme velocities. But because the gas is so very thin, the heat in the plasma in this experiment would seem less than that in a cup of hot coffee. If you could stick your finger in it, it would put the fire out immedi ately. Thus the plasma must be kept away from the tube walls so as not to cool it down! Scyllac Fires With a Bang High up in a glassed-in observation room, I watched Scyllac go through its paces. Dr. Warren Quinn directed the experiment from a control panel behind me, speaking by walkie-talkie to technicians below. First a charge of deuterium gas was fed into the evacuated tube. The correct amount of deu terium represented about 1/10,000th the den sity of the air we breathe. Then I saw a bright pink glow as an electrical charge was released into this gas, tearing electrons from the deu terium atoms and thus ionizing them. Now Dr. Quinn watched his gauges closely. Five red needles showed the buildup of kilo volts in the capacitors. As the needles moved slowly, the scientist called out "Twenty... thirty... forty...." All the lights on the board turned yellow. A bell rang, signifying that the charge was ready to be triggered. A second later a loud bang echoed through the building, and a bright blue glow suffused the room. (Continued on page 673) 667
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