Chilled water is used to cool the campus, and can also be used as an energy reserve.
Electricity is used at night to chill water. The cold water is stored and then used during the day for air conditioning and research equipment such as lasers, CAT-Scan equipment, electron microscopes and computer facilities. This allows the university to purchase electricity when it is least expensive and avoid using power when it is most expensive and the electric grid is most stressed.
A ton of cooling is equivalent to the amount of heat (removal) associated with melting 2000 pounds of ice over a 24 hour period.
By centralizing heating and cooling operations in the co-generation plant and creating a “district energy system”, energy life-cycle costs and carbon footprint for Princeton’s campus is greatly reduced.