After several delays, the town’s first solar panel field is up and running on Brook Street, providing revenue to the town and saving the school department in nearby Plymouth between $400,000 and $500,000 a year in energy costs, according to a Borrego Solar representative. Plympton Town Coordinator Dale Pleau said the 23,000 solar panels on 30 acres, owned by Plympton Sand and Gravel and leased to Borrego, also will provide the town with $65,000 annually for 20 years in lieu of taxes. Jared Connell, a project developer with Borrego Solar, said the savings to the Plymouth schools will come through net metering credits created by the solar site, an arrangement that’s possible because Plympton and Plymouth are both in NStar’s service territory. The solar panel field, which has been fully operational for about two weeks, was ready to open sooner, but could not operate until NStar completed construction of a local substation. A ribbon-cutting ceremony is scheduled for Tuesday morning.