Chicago ? A nagging issue wound its way through the chatter at what was an otherwise celebratory event for the nation’s wind industry in Chicago.

The U.S. has become the world’s biggest wind-power generator and of the electricity production added in the country last year, 42 percent came from wind turbines. But as more megawatts come on line, the problem of getting power from wind-swept Plains to other places becomes more urgent.

“In some ways we’re reaching the glass ceiling,” said Rob Gramlich, vice president of policy at the American Wind Energy Association. It was the organization’s biggest annual conference to date, drawing 1,200 exhibitors and more than 20,000 people.

The country’s grid is aging, often overloaded and, in the case of wide-open states like Wyoming and North Dakota — some of the best places to erect wind turbines — not nearly extensive enough to move electricity to major markets where customers wait.

The wind industry group says it needs 19,000 miles of new high-voltage lines — at a cost of about $100 billion — for wind-farm developers to keep building.

That barrier, Gramlich said, could imperil President Barack Obama’s goal for the country of generating 25 percent of its electric supply through renewable energy by 2025.

On Tuesday, Siemens AG said it was building a wind turbine plant in Kansas where it would employ 400 workers. The 30,000-square foot facility will begin production next year.