How a Refrigerator Works and Uses Energy

How a Refrigerator Works and Uses Energy

Like all electronics, refrigerators use energy.  As we discussed in our Energy Action Month series, there are ways to save on energy by turning off electronics when we are not using them, unplugging them to prevent vampire power, and even setting back temperatures on thermostats during non-peak hours.  However, we do not have these luxuries with refrigerators; they have to be on and running 24 hours a day, 365 days a year to do their jobs properly.

While refrigeration accounts for 4 to 6 percent of all commercial buildings’ energy use, it plays a much larger role in the food service (16.4 percent) and the food sales (47.4 percent) segments.  But no matter the percentage of energy use, an inefficient refrigerator is wasting energy, and therefore money.

How does a refrigerator work?

Refrigerators are used to create a cold environment to keep food or other products viable and safe.  Sounds easy enough; pump some cold air into a box and you are good to go.  But that is not really how it works.  The refrigeration cycle is actually about removing heat from the environment rather than introducing cold air into it.  In the refrigeration cycle, refrigerant is evaporated and liquefied as it flows through tubes as a means to transfer heat.  Here’s how it works:

  1. Cold liquid refrigerant flows into the evaporator coils, which are inside the refrigerator.  An evaporator fan draws air from the refrigerator and blows it over the evaporator coils.  The liquid refrigerant absorbs heat from the air and the air blows back into the refrigerator at a lower temperature, cooling the refrigerator.  The liquid refrigerant starts to vaporize as it heats up and moves to the compressor.
  2. The compressor compresses the refrigerant, which raises the temperature of the gas.  The gas is then pumped through the condenser coils.
  3. In the condenser, a fan blows across the coils cooling the gas and releasing the heat out of the refrigerator to the outside.  As the heat is released, the refrigerant turns back into a liquid.
  4. The liquid then flows to an expansion device that regulates the flow of the refrigerant.  It reduces pressure which turns some of it to gas.  This release of extra heat makes the liquid even colder as it flows into the evaporator.  And here the cycle starts again, absorbing heat from inside the refrigerator.

How does a refrigerator use energy?

There are three components in the refrigerator that draw energy: the compressor, the condenser fan, and the evaporator fan.

  • The compressor uses electricity to pump the refrigerant through the refrigeration cycle.  The compressor can turn off when the refrigerator is at the correct temperature.  If the temperature starts to rise slightly, the compressor will kick back on and pump the refrigerant through the loop.
  • The condenser fan’s motor uses electricity to run and must be on whenever the compressor is running and pumping refrigerant through the condenser coils.  The condenser fan is responsible for cooling the refrigerant as it flows through the condenser coils, dispelling the heat picked up inside the box, and returning the refrigerant to a liquid.
  • The evaporator fan’s motor is always running, even if the compressor and condenser fan are off.  The evaporator fan is responsible for keeping a constant flow of air in the refrigerator box.  It must keep the air moving and flowing over the evaporator coils so the refrigerant can absorb the heat from the box.

The more time the refrigeration cycle is flowing, that is the more time the compressor is on, the more energy the refrigerator uses.  And what causes the compressor to turn on, HEAT.

So there are two main focuses to keeping refrigerator energy consumption down: reducing heat infiltration into your system and making sure all of your components are running efficiently.

Check out our related posts for tips to do just that through maintenance and retrofitting.

Categories: Energy Solutions, HVACR

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One response to “How a Refrigerator Works and Uses Energy”

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