13 Jul Water Footprint in Ice Machines
If you order any cold drink at any restaurant or café most likely it will contain ice cubes or be made with crushed ice. Ice is an important ingredient in any food service kitchen. Historically, ice was produced in central facilities and delivered to restaurants as blocks or crushed ice. With developments in refrigeration technologies, however, commercial ice-makers became popular and today many foodservice operators use their own ice-makers to produce ice.
Ice-makers produce ice in much the same way air conditioners produce cold air. A compressed refrigerant is pumped through a closed loop. As the refrigerant expands to become a gas, it absorbs heat from the water and the water freezes to form ice. The gas then ejects heat to the environment to condense it back to liquid, and the cycle continues.
There are three main types of ice-makers depending on the type of ice they produce: 1) cube ice, which is hard, clear ice cubes that melt slowly, 2) flake ice, which is a soft, crushed form of ice used in food displays and salad bars, and 3) nugget ice, which is shaped like small “nuggets” and is chewable and popular in soft drink fountains. Flake and nugget ice machines are inherently more water-efficient than cube ice machines since the production of cube ice requires frequent purging cycles.
Ice-machines are also classified based on the cooling method. There are water-cooled and air-cooled ice makers. Water-cooled ice machines use potable water connected directly to the machine to absorb heat from the refrigerant. Water-cooled ice machines typically use once-through cooling, where cold water passes only once through the ice maker’s heat exchanger and is discharged to the sewers. Air-cooled ice makers, on the other hand, are similar to house refrigerators in that heat is rejected to the surrounding air, and no water is required to absorb the rejected heat.
Energy and water consumption of ice-makers vary depending on their model, cooling method, and type of ice produced. In general, energy usage per pound of ice produced decreases with increasing machine capacity. However, there is a significant difference in energy and water consumption between air-cooled and water-cooled ice machines. Water-cooled ice machines consume significant quantities of water, which translates to high utility costs for foodservice operators.
Water-cooled machines consume anywhere between 187 and 193 gallons of water per 100 pounds of ice produced. In contrast, most air-cooled ice machines consume less than 20 gallons per 100 pounds of ice produced. The impact of water savings may not be apparent until one considers the actual cost of water and sewer discharge over the lifetime of the machine.
The average lifespan of a commercial ice-maker is 8.5 years. Consider a typical water-cooled ice-maker rated for 800 pounds of ice per day versus a highly-efficient air-cooled model of a similar capacity. Over the 8.5 year period, the total utility costs to operate the water-cooled machine would be $41,800. In contrast, operating a similar air-cooled model would cost as little as $16,800 (based on a study by Koeller & Company, 2008).
The use of water to cool ice-machines may appear to have little consequences on utility costs and the environment. However, a closer look reveals significant wastage of water and energy resources. In fact, water-cooled ice machines do not qualify for Energy Star certification.
If you are planning on replacing your water-cooled ice machine, consider an air-cooled oversized model. Large ice machines are more efficient than smaller ones and cost little to operate per pound of ice produced. In addition, the capital cost difference between models is not significant and you could even get twice the ice capacity at half the energy cost per pound of ice.
If you operate an air-cooled ice machine, there are some practical tips that can be implemented to reduce energy consumption and utility costs even further:
- Use a timer on the ice machine to shift production to nighttime during off-peak hours. That way you reduce demand on the electrical grid and use a lower energy rate.
- Keep the ice storage bin covers closed all the time to trap cold air inside and prevent leaking air into the surrounding environment. This will reduce the demand on the ice machine to keep running.
- Clean the coils on a regular basis to maintain high heat transfer efficiency and reduced energy consumption. This applies to refrigerators and freezers as well.