Wind and solar, two renewable energy sources with a promising future, nevertheless face a bottleneck of sorts in the United States: the electric power grid. The existing grid can not handle the new demands, The New York Times reported Wednesday, forcing renewable wind and solar sites to shut down, even when conditions are right to generate and sell power.

An infrastructure-challenged U.S.

Economist Glen Langan says there's a theme that keeps popping up in the U.S. economy in the early 21st century: inadequate infrastructure. "We're a nation of inadequate infrastructures: the power grid, air travel/air traffic control, railways, highways... pick an infrastructure and you'll see a network that can't handle present demands, let alone an expanded national economy in 2020 or 2030," Langan said.

The power grid bottleneck is particularly frustrating and damaging because both wind and solar power generation systems are mushrooming, and could, with an adequate grid, account for more than 20% of the nation's power needs, Langan said, adding that some economic models put renewable energy's potential contribution even higher, at 25% or more.

"Imagine T. Boone Pickens building his massive, multi-billion dollar wind mill farm and having it sit idle because the grid cannot tolerate and transmit the increased power? Pretty sad," Langan said.