Minnesota Power said Tuesday it will build its first large solar generation project at Camp Ripley in Little Falls, Minn.

Under a deal to be signed Wednesday, the Duluth-based utility will build a $25 million, 10-megawatt solar power array on 100 acres of land on the military base in 2015 or 2016. A megawatt is 1 million watts.

The solar array is part of Minnesota Power’s larger planned investment at the base that also will include new generators powered by diesel or natural gas engines as well as “smart grid” technology. The combination would allow Camp Ripley to operate off the power grid during an emergency, using the new, on-site generating units.

“This is a first of a kind for us and a first of its kind for the state of Minnesota,” Al Rudeck, vice president for strategy and planning at Minnesota Power, said in an interview Tuesday.

Rudeck said the project is not strictly for the National Guard. The solar power will flow onto the electrical grid, benefiting the utility’s 144,000 customers in central and northern Minnesota. The diesel or natural gas generation also will be tied to the grid, and fired up to meet customers’ peak demand.

Maj. Gen. Rick Nash said the Minnesota National Guard has been looking for ways to increase its environmental stewardship. “This signing marks a milestone along our path to making that vision a reality,” Nash, the state Guard’s adjutant general, said in a statement.

Under the agreement between the utility and the Guard, Minnesota Power also will help find ways to cut the base’s energy use by 30 percent from 2003 levels.

The solar array will help Minnesota Power comply with the state’s new solar mandate. It represents about one-third of the solar power that Minnesota Power needs to add by 2020 under a new law requiring investor-owned electric utilities to get 1.5 percent of their energy from the sun, Rudeck said.

Minnesota Power said it also plans to build another 19 megawatts of large, utility-scale solar projects elsewhere on its system, along with some smaller projects, but the details have not been announced. Rudeck said Minnesota Power is considering offering its customers the option to invest in community solar gardens, which are large solar arrays whose output is shared by customers.

The utility offered no immediate estimate of the cost of the Camp Ripley backup generation and smart grid. All of the projects would be put out for competitive bid, Rudeck added.

The Camp Ripley solar array will be the largest solar installation on any National Guard base in the country, and will be among the largest in the state. Minnesota’s largest current solar array, in Slayton, Minn., has a 2-megawatt output, but new solar projects up to 50 megawatts are planned by energy developers.