The solar thermal collectors capture solar heat to generate hot water. The collectors absorb energy from the sun into a heat transfer fluid (glycol) which is piped to a mechanical room. In the mechanical room the fluid travels through heat exchangers to transfer the heat into the building’s water loop where it can utilized by the building or exported to the District Energy St. Paul network.
District Energy was the first in the United States to integrate solar thermal into a district energy system. The 23,000 square foot system is comprised of 144 flat-plate collectors that can reach temperatures over 200°F. This allows the system to reach thermal peaks above 1.2 Megawatt and generate approximately 1000 Megawatt-hours of heat each year.
The heat generated is utilized primarily by the host building, the Saint Paul RiverCentre. Due to fluctuations in the building’s need for space heating and hot water, the solar heat collected can be exported to District Energy’s thermal grid when excess heat is available. This feature allows the Saint Paul RiverCentre and other District Energy customers to share the solar energy produced by the system and maximize the distribution of energy collected.