Using Ice as Air Conditioning

By Deane Barker on July 25, 2007

Ice keeps New York office towers cool: New cooling units in some skyscrapers are using big blocks of ice to supplement or replace their air conditioning. Essentially they’re generating cold air at night, “saving it up,” then using it during the heat of the day when it’s needed.

Because electricity is needed to make the ice, water is frozen in large silver tanks at night when power demands are low. The cool air emanating from the ice blocks is then piped through the building. At night the water is frozen again and the cycle repeated.

[…] Ice storage at Credit Suisse lowers the facility’s peak energy use by 900 kilowatts, and reduces overall electric usage by 2.15 million kilowatt-hours annually — enough to power about 200 homes, officials said.

Great quote here on the reliability of the system.

“When you make something mechanical, it can break, but a big block of ice … isn’t going to do anything but melt,” […]

Everything old is new again.



  1. Energy saving my ass. How much power does it take to freeze and store the water? How about the gas the trucks use to deliver it? Sure the buildings that use the ice system have lower electric bills but how much are the spending on the new systems and the ice?

  2. Well, the water is frozen on-site, so there’s no delivery.

    I don’t think the system is being touted as “energy saving.” I think it’s meant to “time-shift” energy usage, meaning the energy used to power the system is expended at off-peak times.

    The power to run it comes in the middle of the night when the water is frozen. During the middle of the day, when everyone is competing for energy resources, you just melt the ice.

  3. I’m sorry for not having specifics but there was a brief mention of this technique on one of the History or Discovery channel shows. It is a cost saving measure thanks to energy prices being much lower at night than during the day. It is much cheaper, especially in a big city, to freeze water at night than it is to cool the air 20-30 degrees in the day by traditional methods. It does “save” energy consumption in that they are using what already exists but is under utilized at night. Which is exactly what the price difference is supposed to do.

  4. The system saves energy by having a more efficient chilling system. Air conditioners running in the heat of day work less effectively than they do running when the outside air is cooler.

  5. Credit Suisse uses an ice conditioning system to keep its New York City offices cool. It makes large blocks of ice at night, when energy prices are lower, then uses cool air from the melting blocks during the day to maintain the offices at 74 degrees during.

    William Beck, the head of critical engineering systems for Credit Suisse, estimates that the system saves the company about $1 million a year in energy costs. It’s initial cost was around $3 millions.

  6. Actually, they do not need to use electricity to produce the ice. They could use an ammonia refridgeration/cooling unit which uses heat from burning NG, which is cheaper in the summer than during the winter, to make the ammonia expand which in turn during the heating/cooling cycle produces a temperature differential that allows the water to be frozen. As far as them using differentially priced electricity that is one means of reducing overall costs, and may actually reduce power plant daytime emissions. However, it will increase overnight emissions.

  7. I am a Staionary Engineer by trade that was trained by the U S Military. I served in the Pursian Gulf War. I can speek from Experiance when I say I have seen this stile system work in the desert first hand. It does reduce consumtion of energy which reduces the bottom line. End of Story.

  8. This might actually save energy. At night when the requirements are low the power may be coming from the Niagara falls power station instead of coal and naturalgas plants that get activated during peak times.

  9. I work in NYC as an operating engineer. Yes the intitial cost is expensive, but the savings over the long run are incredible. In NYC Con-Ed charges a Peak and off-Peak rate, as well as a demand and a usage charge. Demand charge being the highest usage over any 15 minute interval during peak hours. For example, if you use 15 kw from 8 am to 8:15 am, your demand rate will be 15 kw. These high demand rates could be avoided by not having to start as much air conditioning equipment during peak hours (especially in a central plant). For this reason an ice plant is a great way to both conserve energy and reduce operating cost.

  10. If the ice block is inside the insulated shell of the building, there is no loss.
    Any ice that melts in the tank, cools the building. It store the “cooling” at night when efficiency is higher and electrical cost is lower and then uses it during the day. The short term cooling capacity can be several times the compressor rating until the ice is gone. In the 70s the DOE and a University built a house in Beaumont Texas cooled like this. The cooling costs were much lower than the avarage.

  11. Using Ice to save energy or spend less money is more than it seems to be …Some users of this blog sholud read more about air conditioning before giving opinions to public… It´s about equipment efficiency and energy reducing cost due to reduced price at night. Increased Efficiency in AA equipment is determined by the outside temperature and improved at night. In a sunny day the capacity of cooling is lower due to the higher temperature

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