Obama administration's renewed focus on how to power the country without overloading the atmosphere with greenhouse gases.

http://www.scientificamerican.com/article.cfm?id=plan-b-for-energy-8-ideas

Plan B for Energy: 8 Revolutionary Energy Sources

Editor's Note: We are posting this feature from our September 2006 issue in light of the Obama administration's renewed focus on how to power the country without overloading the atmosphere with greenhouse gases.

To keep this world tolerable for life as we like it, humanity must complete a marathon of technological change whose finish line lies far over the horizon. Robert H. Socolow and Stephen W. Pacala of Princeton University have compared the feat to a multigenerational relay race. They outline a strategy to win the first 50-year leg by reining back carbon dioxide emissions from a century of unbridled acceleration. Existing technologies, applied both wisely and promptly, should carry us to this first milestone without trampling the global economy. That is a sound plan A.

The plan is far from foolproof, however. It depends on societies ramping up an array of carbon-reducing practices to form seven “wedges,” each of which keeps 25 billion tons of carbon in the ground and out of the air. Any slow starts or early plateaus will pull us off track. And some scientists worry that stabilizing greenhouse gas emissions will require up to 18 wedges by 2056, not the seven that Socolow and Pacala forecast in their most widely cited model.

It is a mistake to assume that carbon releases will rise more slowly than will economic output and energy use, argues Martin I. Hoffert, a physicist at New York University. As oil and gas prices rise, he notes, the energy industry is “recarbonizing” by turning back to coal. “About 850 coal-fired power plants are slated to be built by the U.S., China and India—none of which signed the Kyoto Protocol,” Hoffert says. “By 2012 the emissions of those plants will overwhelm Kyoto reductions by a factor of five.”

Even if plan A works and the teenagers of today complete the first leg of the relay by the time they retire, the race will be but half won. The baton will then pass in 2056 to a new generation for the next and possibly harder part of the marathon: cutting the rate of CO2 emissions in half by 2106.

Sooner or later the world is thus going to need a plan B: one or more fundamentally new technologies that together can supply 10 to 30 terawatts without belching a single ton of carbon dioxide. Energy buffs have been kicking around many such wild ideas since the 1960s. It is time to get serious about them. “If we don’t start now building the infrastructure for a revolutionary change in the energy system,” Hoffert warns, “we’ll never be able to do it in time.”

But what to build? The survey that follows sizes up some of the most promising options, as well as a couple that are popular yet implausible. None of them is a sure thing. But from one of these ideas might emerge a new engine of human civilization.

* Reality factors represent estimated technical feasibility from 1 (implausible) to 5 (ready for market)

1. Nuclear Fusion -- Reality Factor: 3*
Starry-eyed physicists point to the promise of unlimited fuel and minimal waste. But politicians blanch at fusion’s price tag and worry about getting burned

Fusion reactors—which make nuclear power by joining atoms rather than splitting them—top almost everyone’s list of ultimate energy technologies for humanity. By harnessing the same strong thermonuclear force that fires the sun, a fusion plant could extract a gigawatt of electricity from just a few kilograms of fuel a day. Its hydrogen-isotope fuel would come from seawater and lithium, a common metal. The reactor would produce no greenhouse gases and relatively small amounts of low-level radioactive waste, which would become harmless within a century. “Even if the plant were flattened [by an accident or attack], the radiation level one kilometer outside the fence would be so small that evacuation would not be necessary,” says Farrokh Najmabadi, a fusion expert who directs the Center for Energy Research at the University of California, San Diego.