Machine Design
Refrigerator Goes Green (…and we’re not talking produce)

Refrigerator Goes Green (…and we’re not talking produce)

To save energy, room, and reduce noise and oil use, Whirlpool Corp. and the U.S. Department of Energy at Oak Ridge National Laboratory have joined forces to design a green refrigerator. The fridge will use a Wisemotion linear compressor developed by Embraco, along with other energy-saving components to produce a more efficient and effective cooling system.

To drive the piston for refrigerant compression, early compressors from the 1970s and improved models from the 90s translate rotational motion to linear motion. In those 1970s models, a mere one-speed motor powers the rotational axis, turning on and off to regulate the refrigerator’s temperature. This model could use up to 5 kWh per day.

Redesigned compressors from the 1990s employ variable-capacity motors to rotate the axis at variable speeds for refrigerant pumping regulation, instead of powering on and off. This method reduces noise, better regulates cooling, and decreases the energy cost of switching on and off to approximately 1 kWh per day. Both eras’ compressors require oil to lubricate the axial moving parts.

Now, with Embraco’s Wisemotion compressors, the new refrigerator’s energy consumption will fall below 1 kWh per day. Created in the early 2000s, Wisemotion compressors don’t require translation from rotational to linear motion to move the piston. Rather, motor-powered linear spring displacement directly drives the piston.

Removal of the rotating parts lowers noise and eliminates the need for oil lubrication—moving parts instead use the refrigerant gas for lubrication. To save power as well as keep food fresher for longer, Wisemotion maintains a minimum piston stroke displacement, keeping the fridge above a minimum temperature setting and lengthening stroke for a higher refrigerant pump rate.

The new fridge is expected to cut electricity bills by $26 for the average consumer. If the green fridge were to replace every refrigerator in the U.S., estimates show that it would save 0.56 quads per year—equivalent to 100 million barrels of oil, according to Ed Vineyard, director of ORNL’s Building Technologies Research & Integration Center.

The team expects to come up with new designs for more efficient heat transfer, insulation, and new refrigerants. It’s hoped that within three years, the new design will change refrigerators for the better overall, and that these new technologies will likely affect other HVAC applications.

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