Glycol systems freeze water by circulating ethylene or propylene glycol through storage tanks. The glycol ice storage system is very simple. Few accessories are needed, and conventional water chillers are used. Instead of water, a glycol solution (in this case, 25% ethylene glycol) is - pumped through the chiller, coils and ice storage tanks in the chilled water loop. The 22 to 24°F ethylene glycol produced by the packaged chiller freezes the water contained inside the ice storage tanks.