The city’s first green school at Site 2B in the south end of Battery Park City will feature 10,000 square feet of play space on the roof and a weather station for outdoor experiments. At the top of the building, a photovoltaic array will perform the double duty of hiding mechanical equipment and providing up to half the energy needed for the building’s lights. Daniel Heuberger, principal at Dattner Architects, presented these details to Community Board 1 last week at a public hearing. Construction on the school, which may opens in September 2010, will begin this summer.