Refrigeration

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The refrigerator, at roughly 40-140 kWh/month depending on the size and age of the model, is among the top six residential users of electricity. In the last 50 years, the design of refrigerator/freezers has changed considerably, with sizes increasing from 5-10 to 20-25 ft.3 today. At the same time, the energy input per unit increased up until the oil embargo, after which efforts were made that led to a steady decline in energy use per unit between the mid-1970s through today, despite increases in average refrigerator size. The net result is that current refrigerators use about as much energy as those half their size did 40 years ago.

Energy losses in refrigerators arise from a variety of sources. The largest losses are due to heat gains through the walls and door openings. Because much of the energy used by a refrigerator depends on its design, care should be used in selection. Look for Energy star models to maximize efficiency.

Purchase of a new, more efficient unit is not a viable option for many individuals who have a serviceable unit and do not wish to replace it. In this case, the energy management challenge is to obtain the most effective operation of the existing equipment.

More efficient operation of refrigeration equipment can be achieved by:

• Better insulation (although this is not generally a user option for refrigerators)

• Disconnecting or reducing operation of automatic defrost and anti-sweat heaters

• Providing a cool location for the refrigerator coils (or reduce room temperature); also clean coils frequently

• Reducing the number of door openings

• Increasing temperature settings

• Precooling foods before refrigerating

Commercial refrigeration systems are found in supermarkets, liquor stores, restaurants, hospitals, hotels, schools, and other institutions—about one-fifth of all commercial facilities. Systems include walk-in dairy cases, open refrigerated cases, and freezer cases. In a typical supermarket, lighting, HVAC, and miscellaneous uses account for half the electricity use, while refrigerated display cases, compressors, and condenser fans account for the other half. Thus commercial refrigeration can be an important element of electric energy efficiency.

It is common practice in some types of units to have the compressor and heat exchange equipment located remotely from the refrigerator compartment. In such systems, a cool location should be selected, rater than locating the compressor next to other equipment which gives off heat. Many of the newer commercial refrigerators now come equipped with heat recovery systems, which recover compressor heat for space conditioning or water heating.

Walk-in freezers and refrigerators lose energy though door openings; refrigerated display cases have direct transfer of heat. Covers, strip curtains, air curtains, glass doors, or other thermal barriers can help mitigate these problems. The most efficient light sources should be used in large refrigerators and freezers; every 1 W eliminated saves 3 W. Elimination of 1 W of electricity to produce light also eliminates an additional 2 W required to extract the heat. Other improvements can reduce energy use, including high-efficiency motors, variable speed drives, more efficient compressors, and improved refrigeration cycles and controls.

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