Gov. Rendell is expected to announce Monday that a Greek solar-panel manufacturing company intends to build a production facility at the Philadelphia Navy Yard, a development that local officials hailed yesterday as an important step in positioning the city to be a key player in the emerging clean-energy economy.

The plant is expected to create 400 to 500 jobs.

The project, in the works at least three to six months, has been so hush-hush that those involved have used the code name "Project Helios" to refer to it. Helios was the personification of the sun in ancient Greek mythology.

The company's name is Heliosphera. It has been in business since 1998, according to its Web site.

"It's a very significant new project," said Peter S. Longstreth, president of the Philadelphia Industrial Development Corp., which owns and manages the Navy Yard on behalf of the city.

Longstreth credited the governor and Mayor Nutter with pulling the deal together.

The governor's office has said Rendell is reserving comment until a news conference set for 1 p.m. Monday in the lobby of One Crescent Drive at the Navy Yard. Nutter was unavailable yesterday as a result of his father's death Wednesday.

Jobs at the Heliosphera plant would be "advanced manufacturing" involving "a significant amount of technology," Longstreth said.

The facility would be from 400,000 to 500,000 square feet on 40 acres in the middle of the 1,000-acre Navy Yard. It will take "a couple of years to materialize" and would represent an investment of "several hundred million" dollars, Longstreth said.

How much state and local financial incentives will be involved is still under negotiation, he said. The land is a designated Keystone Opportunity Zone, which qualifies companies there for state and local corporate and real estate tax abatements.

In terms of size, the solar manufacturing plant would fall between two other prominent occupants of the Navy Yard: the just-completed 350,000-square-foot Tasty Baking Co. bakery and distribution complex and the 800,000-square-foot Aker shipyard operation.

It will build upon the master plan for the Navy Yard released in 2005, said John Grady, a senior vice president for the Philadelphia Industrial Development Corp. That redevelopment plan, which projected 15 million square feet of capacity on site, includes a "clean-energy campus initiative."

Currently, the Navy Yard has 5.5 million square feet of new and redeveloped buildings and 7,000 employees. When built out, the total workforce there is expected to reach 20,000 to 30,000.

"If we can provide the land and the labor force and the support necessary, Philadelphia can compete as a location for these valuable jobs," Grady said.

Among those enthusiastic about the prospects of solar panels being made in the region was Kira Costanza, whose family runs Sunpower Builders, a solar-installation business in Collegeville.

"At a time when so many manufacturers are moving out of the U.S. to take advantage of cheap labor in China, this is an inspiring commitment to U.S.-made product, quality control, and sustainable, homegrown green jobs," Costanza said. "There is a fantastic opportunity for this new facility to take advantage of the growing commitment by installers and consumers to U.S.-made product, particularly on the East Coast."

Labor leaders were pleased, too - even though it was unclear what portion of any jobs that would be created might be union jobs.

"It's wonderful," said Patrick B. Gillespie, business manager of the Building & Construction Trades Council.

"Anything that's going to generate some commerce," he said, "is great for the building trades unions."