Heat sources at District Energy's main plant include three coal/biomass/gas--fired boilers (132 MW) and three gas/oil-fired boilers (62 MW). A backup plant has four gas/oil-fired boilers (25 MW). A mobile boiler is also available for temporary or backup use (5 MW). The primary fuel is high-Btu, low-sulfur coal. Secondary fuels include natural gas, fuel oil, waste wood and purchased steam. The distributor system totals 77,400 feet of twin supply and return piping (up to 28 inches in diameter)1 circulating 710,000 gallons of hot water.
Cogeneration meant adding a single-stage turbine and connecting it to an 860-kilowatt synchronous generator.
Chilled water for the district cooling system is supplied by three 2,25O-ton electric chillers and two 500-ton, low-pressure steam absorption chillers.Two chillers (1,520 tons total) for peaking or backup use are located at a nearby satellite chiller plant. A 2.5-million-gallon chilled water storage system (33850 tons) stores chilled water produced at night using off-peak - electricity for daytime distribution to downtown district cooling customers. The distribution Systems totals 12,000 feet of twin supply and return piping (up to 30 inches in diameter), circulating 350,000 gallons of chilled water.
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