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District EnergyEver-Green Energy affiliate, District Energy St. Paul, operates the largest, most successful, hot water district heating system in North America. |
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Ever-Green Energy affiliate, District Energy St. Paul, operates the largest, most successful, hot water district heating system in North America. The non-profit company, located in downtown Saint Paul, Minnesota, was founded in 1979. Service to its first district heating customers began in fall 1983. Ever-Green Energy manages the operations of District Energy. How it WorksDistrict Energy's heating system delivers hot water to customers year-round via a system of super-insulated underground pipes that extends through the downtown Saint Paul area. The heat from these pipes is used to keep buildings warm and to heat water in those buildings. The heating system distributes hot water (190°-250°F) at a pressure of 160-180 pounds per square inch throughout the downtown area in a closed loop. The water is used for space heating, domestic hot water and light industrial process use. The system currently consists of 211,800 feet of underground supply and return piping (up to 28 inches in diameter), circulating 910,000 gallons of hot water. The system's main distribution pumps can circulate up to one million gallons of water per hour. The hot water distribution piping has an estimated life of 50 to 100 years. Customer BaseDistrict Energy currently serves more than 185 downtown area buildings and 300 individual residences. The customer base includes multi-family, commercial, industrial and large institutional structures. The total building area served exceeds 31 million square feet, or about 80 percent of downtown Saint Paul and adjacent areas. Major district heating customers include the Minnesota State Capitol Complex, the four major downtown hospitals, the Warren Burger Federal Building, the City of Saint Paul, Ramsey County, the Eugene J. McCarthy Post Office, the Science Museum of Minnesota, Wells Fargo Place, Xcel Energy Center, and the world headquarters of Ecolab, Travelers and Securian. PerformanceThe district heating system has operated reliably for 25 years, with a reliability rating exceeding 99.99 percent over the past five years based on customer hours served. System efficiency has doubled over the course of its development. District Energy now serves twice as much building area as the former steam system it replaced while consuming the same amount of fuel. Distribution losses are 5-7 percent. District heating rates are stable with increases averaging just 2.5 percent per year since service began. A combined heat and power (CHP) plant adjacent to the District Energy facility is fueled by clean wood waste, a viable, renewable resource that was previously sent to landfills or disposed of in other ways. The CHP plant uses renewable fuel that is helping District Energy reduce its reliance on fossil fuels by more than 60 percent and significantly reduce carbon dioxide, sulfur dioxide and particulate emissions. The CHP plant also helps the community solve a waste disposal problem. |
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