The RiverBend clean energy hub in South Buffalo - the centerpiece of Gov. Andrew M. Cuomo's Buffalo Billion economic development initiative - will likely feature a few large buildings to accommodate a giant solar panel factory rather than seven smaller buildings as originally envisioned.

The changes are being designed by EYP Architecture & Engineering of Albany after solar giant SolarCity agreed to buy California-based Silevo, the company originally slated to move into the site, and ramped up plans.

EYP, the biggest architecture firm in Albany and one of the 300 largest in the country, moved its headquarters to the campus of SUNY College of Nanoscale Science and Engineering three years ago. It has worked on some of the Albany complex's high-profile projects, including a $365 million facility that is the home for the Global 450 mm Consortium, a new state-backed venture aimed at producing next-generation computer chip technology on larger, 450 mm silicon wafers.

"They're a pretty well-renowned firm," said Christopher Beitel, Silevo's executive vice president.

Work on the RiverBend site has progressed slowly as the SolarCity acquisition required a major revamp of the site's plans, and the closing of the $2.5 million sale of the 88-acre site off South Park Avenue only took place Tuesday.

EYP, which has 385 employees at a dozen offices across the country, has done extensive work for colleges and government agencies across the globe. The company has worked on more than 80 U.S. embassies around the world and more than 50 college academic buildings across the country. Among its more prominent projects, the firm designed the $69 million renovation of the Birch Bayh Federal Building and U.S. Courthouse in Indianapolis, a nearly three-year effort that greatly improved the energy efficiency of the century-old building.

Earlier this year, EYP was picked to design a new classroom building on the Virginia Tech campus and to plan the renovation of the historic Steidle Building on the Penn State campus.

Kelly Donohue, an EYP spokeswoman, declined to comment on the RiverBend project.

The RiverBend complex is based on the same model the state used to create a bustling semiconductor industry in Albany, centered around the nanoscience college. The state plans to build the facilities in the RiverBend complex and equip them with state-of-the-art machinery that will be owned by the state, which then will contract with tenants like SolarCity to use them.

With the property sale now closed, workers from the project's developer, LPCiminelli, have started some small-scale excavation work at the site. Before the closing, most of the site work had been limited to environmental studies and early-stage testing, as well as some technical work to better understand the property's geology.

When city and state officials reached an agreement in early May on the $2.5 million deal for the Buffalo Urban Development Corp. to sell the site to the state, city officials expected the sale to be completed by the end of May. But the closing took longer because of the complex nature of the deal, which involves an environmentally contaminated site once home to the sprawling Republic Steel plant. Other delays centered around the creation of a property owners association, structured much like the homeowners association in a condominium complex, to oversee the costs involved with future environmental monitoring and operations at the site, as well as normal property maintenance work there.

Exactly what shape the RiverBend complex will take still is being determined. The preliminary design for the complex, which envisioned as many as seven rectangular-shaped buildings along a road through the center of the site, was rendered moot when SolarCity said it wanted to vastly increase the scope of the Buffalo factory.

"The initial idea is growing," said Brendan R. Mehaffy, executive director of the City of Buffalo's Office of Strategic Planning.

Silevo executives have said the plans for the RiverBend complex are being revamped to include fewer buildings than were originally planned, but bigger.

The state has had serious discussions with company executives about the project since the mid-June announcement that SolarCity was acquiring Silevo, Cuomo has said.

Under the original plan, the state pledged to invest $225 million to develop the RiverBend complex. Silevo had planned to occupy most of the first 275,000-square-foot building in the complex, but SolarCity, the nation's biggest residential solar energy system installer, now says it wants the Buffalo factory to have five times the capacity.

Under SolarCity's plan, the Buffalo factory would have the annual capacity to make enough solar panels to produce 200 megawatts of electricity a year to 1 gigawatt, or 1,000 megawatts, up from the 200-megawatt capacity in Silevo's original plan. The Buffalo factory would be one of the largest solar panel production facilities in the world.

With the expansion, the Buffalo factory now is expected to provide well over 1,000 jobs, rather than the 475 initially forecast. Another California-based company, LED manufacturer Soraa, also is slated to move into the RiverBend complex.