Heating and cooling public spaces for people to assemble for work, entertainment and home life has been a challenge for the human race since the beginning of time. District heating was developed in ancient Rome to deliver hot water or steam heat to its structures. In the nineteenth century, the technology was perfected in Europe to meet the heating needs of countries with varying weather climates. Today in St. Paul, Minn., and cities all over the world, district energy systems provide heating and cooling to public spaces such as commercial buildings, condominiums, hotels, sports facilities, universities, and government complexes.

District energy systems produce hot water, steam or chilled water at a central plant and then distribute the energy through underground pipes to buildings connected to the system. Individual buildings do not need boilers, chillers or cooling towers. Customers use the hot and chilled water to meet their space heating, water heating, processing and air-conditioning needs. Once used in customer buildings, the water is returned to the central plant to be reheated and rechilled and then recirculated through the closed-loop piping system.

District Energy St. Paul uses wood chips (biomass), natural gas, oil or clean-burning coal to fuel its district heating and cooling systems. With the April 2003 startup of an adjacent wood-waste-fired combined heat and power facility, managed by an affiliate, the company reduced its reliance on coal and oil by 80 percent. This produces signficant environmental benefits and helps the community solve a local wood waste disposal problem. Our customers benefit from reduced costs, yet another fuel source, and the knowledge that they are using an environmentally sustainable source of "green energy" to heat and cool their buildings.

District energy systems offer many environmental benefits. They increase energy efficiency; reduce air pollution; decrease emissions of ozone-depleting refrigerants; combat global warming; enhance fuel flexibility; facilitate the use of renewable energy; and help manage the demand for electricity.