Nation's First Solar District Energy System Heats Up with DOE Support

March 30, 2011

Photo of rows of solar collectors atop a large office building with an urban background.

The solar collectors atop St. Paul, Minnesota's downtown RiverCentre convention hall are providing hot water to the nation's largest solar district.
Credit: District Energy St. Paul

The first U.S. solar district—supported with $1 million in American Recovery and Reinvestment Act funding under DOE's Solar America Communities program—was officially launched on March 18. District Energy St. Paul provided matching funds and now operates the system, which heats water using 144 solar collectors atop St. Paul, Minnesota's downtown city convention center. The water heats the convention center and neighboring buildings in North America's largest hot-water district heating system, which covers 80% of downtown St. Paul. The city was selected because the Twin Cities of Minneapolis-St. Paul are among the 25 cities in the Solar America Cities program in Solar America Communities.

The rooftop project is designed to peak at 1 megawatt thermal capacity. While it will primary supply the city's downtown Saint Paul RiverCenter convention center with hot water and space heating, any excess solar-heated water will travel to the district's other customers. The collectors will heat the water up to 160°F for the building, but once the convention center's needs are met, the excess will be heated up to 195°F and fed into the district heating system. The solar water heating system is expected to reduce the center's carbon footprint by an estimated 900,000 pounds per year, equivalent to removing the emissions of about 90 vehicles per year. The Solar America Communities program is designed to increase the use and integration of solar energy in communities across the United States. See the St. Paul mayoral press release, the original District Energy St. Paul announcement, and the Solar America Communities website.