From Wikipedia - "They are fitted with environmental technologies that mimic the ecological function of trees – photovoltaic cells that harness solar energy which can be used for some of the functions of the Supertrees, such as lighting, just like how trees photosynthesize; and collection of rainwater for use in irrigation and fountain displays, exactly like how trees absorb rainwater for growth. The Supertrees also serve air intake and exhaust functions as part of the conservatories' cooling systems."