District heating and cooling (DHC) has a good side with regard to the environment, as one system replaces many individual boilers and furnaces that together would emit a larger amount of uncontrolled, environmentally damaging substances than the DHC power plant. However, the more controlled emissions from the power plant are more visible and concentrated and are carried on by winds to longer distances. The Clean Air Act Amendments of 1990 set definite goals for reducing harmful emissions, and the power plants must gradually improve their plants and operations to follow these new guidelines. Similarly, the National Energy Strategy calls for adherence to the purposes of the Clean Air Act, but at the same time it provides some trade-offs in order to allow more time for the construction and installation of more effective equipment. As the use of electricity has increased tenfold in the United States during the past 40 years and the electricity-producing power plants are usually only about 30% fuel-efficient, the emissions from the fuel that is used to burn and generate electricity - with two-thirds of it wasted - have multiplied enormously. To harness the wasted energy by utilising district heating and cooling could greatly improve environmental conditions and conserve large amounts of energy.

KEYWORDS: district heating, district cooling, air pollution, outdoor, environment, USA, power stations, efficiency, energy conservation