The City Council agreed 5 to 1 Monday to authorize Mayor Elinor C. Carbone to negotiate a lease agreement with Walden Renewables of Portland, Maine to lease six acres at the landfill. In the initial six-year development period, the company will pay $5,000 a year while it looks into permitting and connecting the facility with Eversource. After that, it will enter a 40-year lease at $6,000 per acre with a 2% increase per year. The facility, which would potentially hold between 100 and 150 megawatts of renewable energy, would be connected to the Eversource power grid and serve as a backup for power “to save for a rainy day when we have a capacity event,” Dale Knapp of Walden Renewables of Portland, Maine told the City Council last month during a presentation on the project. If the solar array and energy storage facility are built, there will still be about 55 undeveloped acres left at the landfill, he said.