district energy distribution systems–consisting of underground piping grids–provide efficient thermal arteries for the distribution of steam or hot water for heating and chilled water for cooling many buildings. this video, made in 2003, explains how enwave constructed a deep lake water cooling(r) system that provides the equivalent of 62,000 tons of air conditioning to cool hundreds of buildings in downtown toronto. the system literally cleared the air of pollutants by replacing the electrical demand of huge chillers from fossil-fired utilities with the much lower demand to run simple pumps that move cold water through a heat exchanger system.