In an effort to cut power consumption and adopt a more green profile, some New York City office towers are making use of a somewhat archaic air conditioning system: blowing air over giant blocks of ice. WNBC reports that financial firm Credit Suisse is using such a system to cool its offices in the Met Life tower off Madison Square. The basement of the building houses three main cooling rooms with "chilling machines and 64 tanks that hold 800 gallons of water each."

At night, when energy demands are off-peak, the refrigeration system uses electricity to freeze the water in the tanks. During the day, the blocks of ice accumulated overnight are used to absorb heat from the building's air much like standard air conditioning. The melted ice is then refrozen each night.

Ice cooling systems are apparently all the rage with financial firms. Air conditioning manufacturer Trane built such a system for Morgan Stanley's offices in Westchester County and just finished another in that company's 5th Ave. building. Goldman Sachs' new headquarters downtown will incorporate ice cooling as part of its HVAC system. Credit Suisse is investigating installing ice cooling into all of its facilities worldwide. Don't expect a return of ice wagons to city streets, however. The considerable cost of system designs and installation and space requirements mean that ice cooling is best suited for large corporations with significant energy demands to make the investment economical.