District Energy Solar Thermal System

District Energy St. Paul set out to expand its city‑wide heating system without increasing fuel consumption, pursuing one of the first large‑scale solar thermal integrations in the United States and the largest in the Midwest. Partnering with Danish engineering firm Ramboll, TKDA designed and supported the construction of a 1 MW rooftop solar thermal array atop the River Centre convention center. The system includes 144 commercial‑grade panels mounted on a structural exoskeleton, with a glycol loop circulating to heat exchangers and a dual‑pipe connection that allows excess solar heat to be exported by reversing water flow. With optimized collector layout, reinforced roof structure, and balance‑of‑system safeguards, the project reduces CO₂ emissions by nearly 900,000 pounds annually and stands as a national model for integrating solar thermal technology into district heating networks.

CLIENT: District Energy St. Paul
LOCATION: Saint Paul, Minnesota
AWARDS: ACEC/MN Engineering Excellence Grand Award, IREC Innovation Award