Biddeford’s Pepperell Mill Campus, a sprawling former mill complex that includes residential units, plans to install the largest privately-held solar energy project in Maine, according to a news advisory from ReVision Energy.

The large-scale solar array will produce enough electricity to more than meet the needs of the campus’s residential units, according to an announcement from U.S. Sen. Angus King’s office. King, a Maine independent, will be in Biddeford on Friday to tour the campus and formally unveil the project.

ReVision Energy is contracting to do the work for the Pepperell Mill Campus.

It was not known Thursday how many panels will be installed, when or at what cost. The array will be connected to the energy grid.

Pepperell Mill Campus officials declined to provide details of the project before Friday’s announcement.

Mill owner Doug Sanford and his company have invested $40 million to $50 million in the mills since 2004. The 16-acre campus, with 1 million square feet of interior space, is more than 65 percent complete and plans are in the works for more housing, a hotel and the expansion of light industrial space.

Doug Sanford in his apartment at the Pepperell Mill Complex in June 2015. He began buying the vacant mill properties in 2004 and has accumulated more than a million square feet of residential and commercial space since then.

The campus includes more than 115 businesses and 100 residential apartments. The apartments are a mix of studio, 1-bedroom, 2-bedroom and luxury loft units.

City leaders, who consider Sanford a pioneer for leading investment in the mill district, have said the Pepperell Mill Campus is drawing attention to the city’s revitalization, bringing new businesses and residents to the community and expanding Biddeford’s tax base.

This story has been edited for clarity on 7/29 at 10:40 a.m.