System Operation

Using “ice battery” technology, Enwave Chicago produces chilled water at five strategically located downtown Chicago plants. The plants have 101,000 tons of chilled-water capacity, including 315,000 ton-hr ice thermal energy storage. The plants pump chilled water through 8 trench miles of underground piping to energy transfer stations in customer buildings. Our customers use the chilled water for air conditioning.

Chilled-water plants. Enwave Chicago operates five interconnected plants in the Loop, West Loop, South Loop and River North. (See map below.) The sustainable cooling plants meet the needs of nearly 120 customers, producing 34 degree F chilled water during the peak cooling season.

Overnight ice production makes Enwave Chicago’s chilled-water system an “ice battery.” Enwave Chicago primarily produces ice at night during off-peak electricity hours. We then store the ice before allowing it to melt slowly the next day to meet chilled-water demand. This not only reduces stress on the electricity grid, but also lowers our carbon footprint.

Baltimore Aircoil, which provided instrumental system technology, explains the ice-storage thermal energy process in this video.


Diverse technologies. While ice storage is used at four of our five plants, we also employ ammonia chillers, river water chillers and traditional-type chillers. This diverse approach allows us to economically dispatch the most cost-effective cooling sources possible at any given time.

Customer use. Customers use heat exchangers to extract heat from their buildings and send it back to our central plants.



Quiz Yourself

How many gallons of fresh water can a 100,000-sq-ft building save annually by using district cooling instead of chillers?