BY MATTHEW L. WALD
NEW YORK

When the builders of the Maple Ridge Wind farm spent $320 million to put nearly 200 wind turbines in upstate New York, the idea was to get paid for producing electricity.

But at times, regional electric lines have been so congested that Maple Ridge has been forced to shut down even with a brisk wind blowing.

That is a symptom of a broad national problem. Expansive dreams about renewable energy, like Al Gore's hope of replacing all fossil fuels in a decade, are bumping up against the reality of a power grid that cannot handle the new demands.