District Energy: The Basics

District Energy: District energy is the production and supply of thermal energy. Hot water and chilled water are produced at central plants and distributed to surrounding buildings via a closed-loop underground distribution system known as a thermal grid. The thermal energy delivered to the buildings is used for space heating, domestic hot water heating and air conditioning. Buildings connected to the thermal grid do not need their own boiler or furnaces, chillers or air conditioners. Commercial buildings, condominiums, hotels, sports facilities, universities, and government complexes are all examples of buildings commonly connected to a thermal grid.

District energy is not a new concept. Its origins stem from the hot water-heated baths and greenhouses of ancient Rome. Today, it is an internationally accepted method of heating, cooling and powering communities. In some European countries, such as Denmark, district energy is mandated. In Canada, a number of communities have operated district energy systems for many decades. The oldest system is in London, Ontario dating back to 1880. In Ontario, district energy systems are currently operating in Toronto, Ottawa, London, Markham, Hamilton, Sudbury, Cornwall, and Windsor.

Combined Heat and Power (CHP): Once a thermal grid is established, a common next step is to connect small power generation plants. Known as cogeneration or combined heat and power, the generation plants recover waste heat to be used in the thermal grid and deliver electricity to the local power grid.