A thermal storage tank is basically a large battery or thermos for hot or cold water. Hot or cold water provides thermal energy and can be generated by a boiler or chiller and then stored in the tank until it is needed by energy customers. When that energy is needed it is sent through underground pipes which make up the district energy system. Thermal energy storage helps the local district energy system generate energy when it is most cost-effective and lowers demand on the local electric grid. It also helps avoid extreme weather situations, when it may be hard to generate cold water because of high humidity or heat.
For District Cooling St. Paul most of the chilled water is produced at night using off-peak electricity and stored in 2 large thermal storage tanks, located at the West Kellogg Boulevard plant (2.5 million gallons of capacity) and across town from the EcoDistrict on 10th Street (4.2 million gallons of capacity). Chilled water stored in these tanks is dispatched to customers as needed, particularly to meet higher cooling demand, such as high humidity and high temperature conditions.
Where can I find thermal storage?
There are two storage tanks in downtown that store energy for the district energy cooling system. Within the EcoDistrict is a 2.5 million gallon tank along Kellogg Boulevard between the District Energy plant and the Science Museum of Minnesota.