Cut Energy Consumption with Adaptive Refrigeration Controls

Denis Livchak
Grocery Refrigeration

Commercial refrigeration equipment consumes significant energy in supermarkets, restaurants and other food service establishments because it must keep perishable foods cold 24 hours a day and 365 days a year. According to the U.S. Department of Energy, a large commercial refrigerator used in a grocery store can consume up to 17,000 kilowatt-hours (kWh) of power a year, while a large commercial freezer can use up to 38,000 kWh a year.1 That amounts to an average of 43% of a supermarket's annual electricity usage.2

Owners and managers of supermarkets and food service businesses may not be able to limit the amount of time that refrigeration equipment must be turned on, or the internal temperature, but they can reduce the amount of energy it uses. Significant energy savings can be gained not only from proper operation and regular refrigeration maintenance, but also through component retrofit of walk-ins and cost-effective replacements of older refrigeration equipment.

Food service businesses that are planning a refrigeration retrofit should consider upgrading it with adaptive refrigeration controls. Also referred to as "smart refrigeration," adaptive refrigeration controls employ technology that continuously monitors conditions, such as air temperature, evaporator coil temperature, refrigerant temperature and pressure at different points inside the units that turn components on and off to maintain the required temperature.

Unlike legacy refrigeration controls that monitor temperature with a thermostat and turn the compressor on or off as the temperature goes up and down, adaptive refrigeration controls reduce the overall energy usage of refrigerator and freezer units by applying multiple data points, collected through various sensors, to an algorithm that controls the refrigeration components in a more effective manner. Overall, effective implementation of a control strategy reduces the compressor run time and reduces costs while maintaining desired temperature conditions within the units. While many different controls exist, it is not possible to reduce energy usage without affecting average internal temperature unless at least two sensors are utilized.

While there are many components on the market that offer energy savings over older products, not all of them are easy or practical to install. Two major adaptive refrigeration controls that are simple to install and offer immediate savings are smart defrost controller kits and evaporator fan motor controllers. Upgrading evaporator fan motors to electronically commutated motor (ECM) technology saves energy, and can be used in conjunction with the fan motor controllers. These retrofits mostly apply to walk-in coolers and freezers; however, more new reach-in units are starting to utilize the same technology.

Smart defrost controller kits
In refrigeration, it is an inevitable fact of life that the evaporator coils that lower the temperature in the unit eventually get covered with frost. This is due to the coil being significantly lower in temperature than its surroundings, where moisture in the air from the outside or from the refrigerated product itself condenses on the coil and freezes. The most common defrost control in traditional commercial and residential refrigeration is a mechanical defrost timer, which is a motorized device that turns on a heater to melt accumulated frost on the evaporator coils at set intervals, regardless of the frost accumulation level on the coil.

Today, many vendors offer smart defrost controller kits, also known as adaptive defrost controls. Smart defrost controller kits optimize the duration and number of daily defrost cycles for walk-in freezers. So instead of the heater coming on every eight hours, whether it needs to or not, it may be 24 hours, 18 hours, 10 hours—it depends on how many times employees have opened the doors, or how much warm food has been placed in the compartment. This is often done by comparing the walk-in box temperature to the evaporator coil temperature to determine the frost thickness on the coil. Smart defrost controllers can save hundreds of dollars each year, depending on the size of the freezer. Another advantage of defrost control is reduction of frost accumulation on the interior of the walk-in box.

ECM evaporator fan motors and controllers
Evaporator units are integral components of commercial walk-in refrigerators and freezers. The small fans housed within these units continuously move air across evaporator coils and circulate it throughout the cooled space. Most come equipped with fans that are driven by relatively low efficiency, shaded-pole or permanent split capacitor induction-type electric fan motors. Electronically commutated evaporator fan motors use about one-third the energy of the typical evaporator fan motors in walk-in coolers.

Individually, these small induction-type fan motors may not seem to consume a great deal of energy, but the energy consumption and operating cost of multiple evaporator fans that are running continuously can add up fast. This is mostly due to the fact that these fans operate 24/7/365 unless they are operated by a fan controller. Rather than having fans run continuously, ECM controllers manage fan speed based on need. The need is dictated by the compressor, which does not operate continuously. Fan controls can also be coupled with a door sensor that would turn off the fans once the door is open, reducing the amount of cold air that escapes the refrigerated cavity. This reduces the amount of energy required to keep walk-in coolers and freezers at the appropriate temperature. This upgrade can pay off within one year, depending on electricity rates.3

In a study conducted by PG&E's Food Service Technology Center, when fans with shaded-pole motors were replaced with ECMs, the fans used 67% less energy and yielded a projected annual operating cost savings of $104 per fan.4

Other adaptive controls
In addition to the defrost kits and ECM evaporator fan motors, there are many other smart refrigeration devices available that can save food service businesses energy and money. Here's a brief overview of some of the products that businesses should consider when planning a retrofit.

Anti-sweat Heater Controls: These components are used with display refrigerator doors and are equipped with humidity-sensing controls that reduce the amount of power supplied to the heaters in periods of low humidity. Humidity is often introduced into the refrigerated space through door openings and by placing warm humid product inside. Reducing anti-sweat heater energy also cuts down the compressor duty cycle by lessening the internal heat load, which saves energy on refrigeration.

Auto-closers for Walk-in Cooler or Freezer Doors: While this is not a controller, these passive mechanical devices are attached to the main insulated door of a walk-in and firmly close the door when it is within one inch of full closure, reducing the chance of infiltration.

Strip Curtains: These soft plastic curtains or swinging doors are installed in doorways of spaces that are refrigerated to a temperature under 50 degrees Fahrenheit to minimize infiltration.

Refrigeration Display Cases (High Efficiency, Low Temperature): These high-efficiency reach-in cases are equipped with T8 lamps with electronic ballasts, ECM fan motors and low/no anti-sweat glass double-paned glass doors.

Vending Machine Controllers: These devices have passive infrared occupancy sensors that turn off fluorescent lights and sometimes lower the holding temperature set-point by reducing compressor run time and energy when the surrounding area is unoccupied for 15 minutes or longer.

To learn other ways your business can cut energy waste, download the HVAC infographic, "Where's the Waste? The inside story on your HVAC system." This infographic will share best practices to reduce your HVAC energy costs today.

Referenced in article:

  1. U.S. Department of Energy
  3. Pacific Gas and Electric Company
  4. Food Service Technology Center