Bangor officials will soon seek bids for the development of solar arrays on unused city property after a recent study estimated such a project could save the city $4 million on electricity costs over the next four decades. The study by Maine-based solar energy developer ReVision Energy, Inc. also helped identify a site at the corner of Maine Avenue and Godfrey Boulevard where the city could, with some work, place 17 rows of solar panels. On Monday night, Bangor Finance Director Deb Cyr presented some of ReVision’s findings during a meeting of the City Council’s finance committee.