Aroostook County’s iconic Maine Solar System Model is about to get even bigger.

The system’s four-hour lithium-ion battery array will store excess energy for use during peak demand. All 4,250 solar panels will be American made.

Launched in 2000, the solar system project began with students and community members building scaled models of the planets at a scale of 93 million to 1—and over the years, the project has grown ...