The concept of using ice for cooling goes back to the Egyptians use of evaporative cooling to form ice at night in clay casks covered in wet cloths.  Ice has long been used for space comfort conditioning.  In the early nineteenth century, ice was placed in air ducts in theaters to cool and dehumidify warm air blown by fans or melted and used as in air washing/cooling systems in movie studios.  Many such systems are still in use at the Paramount Studios in Hollywood, CA. after more than 65 years of service.

Today mechanical refrigeration is used to make ice, often at night when electric rates are lower. This ice is stored, and when cooling is needed in the daytime water is circulated through the ice storage media and then distributed at about 34F (1.7C) to provide space cooling, although lower temperatures can be used with appropriate fluids.

Ice thermal storage has two potential advantages. In addition to the use of off-peak ice making, an ice storage system can reduce chilled water flow requirements by half. A traditional chilled water system using 44F (6.7C) supply and 54F (12.2C) return will require 2.4 gallons per minute (gpm) of chilled water for each ton-hour of refrigeration. An ice storage system can supply chilled water at 34F (1.7C),  by reducing the chilled water flow to 1.2 gpm. This significantly reduces pumping and distribution fan horsepower and associated energy costs.

At a time when we talk more and more about the environment and rationalization of energy use, thermal energy storage represents a highly viable technical solution adapted to air conditioning and industrial cooling systems.

Office building cooling loads often peak at a level two or more times higher than the daily 24-h average load. Some industrial processes also have load peaks or "spikes"; that rise much higher than the average load.  In addition, many electric utilities impose demand charges based on the customer’s highest power demand during on-peak hours and/or during the entire billing cycle. In some cases it is ratcheted rates may apply making any peak the rate for the balance that must be paid for the next year.  Thermal storage is an ideal and efficient solution for these applications.

Traditional refrigeration systems are designed to satisfy the maximum peak cooling demand, which occurs only a few hours per year, and thus spend their operational life working at reduced capacity and low efficiency.  Thermal Storage, is suitable for any air-conditioning system or refrigeration plant, allowing installed chiller capacity (and size of other components) to be significantly reduced – typically between 40 and 60%.  The thermal energy storage system provides the shortfall of the energy when demand is higher than the chiller capacity.  Thus chiller operation is continuous and its efficiency is at a maximum. This is the most effective way to reduce operating costs of process refrigeration and building air-conditioning and to take advantage of lower cost off-peak electricity and to reduce the demand charge by reducing the required electrical supply. Thermal Storage allows real management of the cooling energy according to the demand.

The profile below is of an actual processing plant operating in a daily summer profile taking electrical service at transmission level power (110kv+).  Combining thermal storage with cogeneration the clients annual savings will exceed $1,200,000 annually.