The long-promised potential of offshore wind development along American coastlines took a step toward fruition on Wednesday as the Department of Energy pledged up to $47 million each to three projects it previously supported.

The grants are intended to help the projects, off the coasts of New Jersey, Oregon and Virginia, begin delivering electricity by 2017.

“Offshore wind offers a large, untapped energy resource for the United States that can create thousands of manufacturing, construction and supply chain jobs across the country and drive billions of dollars in local economic investment,” Ernest J. Moniz, the energy secretary, said in a statement.

The announcement represents the next phase of an Energy Department push to invigorate the industry by promoting innovation to help bring the cost of offshore wind power into line with that of conventional electricity production.