(FORTUNE Magazine) – THE BACKGROUND Carbon dioxide makes up nearly 80% of all greenhouse gases. More than a quarter of that CO2 comes from electrical power plants. That's why replacing plants that run on fossil fuels like coal, oil, and natural gas with renewable power sources, even nukes, has emerged as a major plank in the campaign against global warming. The effort is heightened in Europe because the continent relies on fuel imports from Russia and the Middle East for 50% of its energy, and a recent projection shows that portion increasing to 70% by 2025.

THE SOLUTION Emission-free nuclear power is enjoying a renaissance in China and India, but worries about radioactive-waste storage and terrorist attacks have kept it in check elsewhere. That's helped open the door for wind power—which is gaining momentum thanks to recent breakthroughs in turbine and transmission technology and because it's 70% cheaper to generate than solar power. In May, Dublin-based Airtricity, the world's fastest-growing wind-power developer, announced plans for a European supergrid—a network of 2,000 offshore wind turbines in the North Atlantic. The grid would initially supply 10,000 megawatts to eight million homes. Ultimately, Airtricity envisions a wind grid stretching from Spain to Sweden, with an output equal to that of 30 nuclear reactors. The supergrid wouldn't eliminate the CO2 thrown off by Europe's power plants, but it would reduce it by 60 million tons a year—the equivalent of taking 15 million cars off the road.

THE PAYOFF Founded just seven years ago, Airtricity is on track to bring in $657 million in annual revenue by 2010. The company currently operates 16 wind farms in the U.S., Britain, and Ireland, and its five-year project timeline will ramp it up to a potential 7,000 megawatts in capacity, equal to the output of 14 U.S. coal plants. If any of its grid projects get to completion, even if Airtricity is only a minority partner, says Harvard Business School professor Richard Vietor, the company will be catapulted into the ranks of the world's top green-energy players. "There's a fortune to be made here," says Airtricity CEO Eddie O'Connor. Airtricity already has a team pushing plans for an even larger supergrid of one million megawatts to be based across the Great Plains states.

THE OPPORTUNITY Airtricity estimates that the first stage of the European supergrid will cost more than $25 billion over ten years, and the company is lobbying for government approvals. But there's no shortage of opportunity for hundreds of other wind producers to start banding together, since scale is what's needed most to lift wind out of the "alternative" market. European governments are discussing whether to pour additional tens of billions of dollars into building green-energy infrastructure. Says Bo Normark, vice president of transmission technology supplier ABB: "Whether they're Airtricity's or not, projects based on this concept will be built by someone and will likely be in operation by 2012."