Refrigeration systems work hard, 24 hours a day, 365 days a year, to keep food chilled or frozen. But most conventional refrigerated-space sensors do not sense the food temperature to know when to switch the refrigeration system on and off. Instead, they sense the circulating air temperature, even though the air temperature changes far more quickly than the food temperature. As a result, refrigeration systems usually work much harder than necessary to maintain stored food at the correct temperature, leading to excessive electricity use and undue wear on the refrigeration equipment.
Modern sensor technology resolves this problem by changing the way temperature is monitored and controlled. Some of the newest devices contain instruments that simulate the temperature of an average food. When fitted to an existing refrigerated-space thermostat sensor, these devices cause the refrigeration system to react to rises in food temperature rather than the air temperature. As a result, refrigeration starts are reduced by 60 percent or more while precise food temperature is maintained.
This reduction in starts can significantly lower electricity consumption. Independent trials conducted by a United Kingdom-based research association, Campden & Chorleywood Food Research Association (CCFRA), have shown that sensor technology that controls starts based on food temperature can reduce energy consumption by 16 to 34 percent while maintaining food temperatures within the recommended food-safety guidelines. Installations at food-processing facilities in the United States have shown similar results. Besides being good for the environment, such reductions can translate directly into bottom-line savings for food-processing operations.
Testing has confirmed the following benefits in refrigeration systems.
- Changing to a food-temperature-based sensor results in an
efficient system with a reduced number of refrigeration cycles. The compressor
experiences longer on and off cycles and fewer startups.
- Longer compressor on cycles result in a colder food-storage area.
Refrigeration plants that use the food-temperature-based sensor technology
typically run 4 to 5˚F (2 to 3˚C) colder than plants with air-temperature-based
sensors. Adjusting the thermostat to account for this difference can further
reduce electricity consumption (a 3.5 percent reduction in energy can be
achieved for every 1˚F [0.6˚C] adjusted), without compromising food safety or
- Longer on and off cycles reduce wear on the refrigeration equipment,
leading to lower maintenance costs and longer equipment life.
- Longer on and off cycles reduce noise pollution, which is a particularly important consideration for plants with compressors housed outdoors.
Case in Point: Goldy's FarmGoldy’s Farm Shops in Dorset, United Kingdom, grows food - much of which is organic - and runs its own in-house food manufacturing operation. The team bakes, prepares and sources a range of traditional Dorset dishes, including meat, regionally grown fruits and vegetables, drinks, breads and cakes. The company makes and markets its own ice cream, supplies other local business with prepared dishes, and sells directly to the public. The company strives to be energy efficient and environmentally friendly in all aspects of its operations. Besides benefiting the environment, these goals keep Goldy’s operating costs significantly lower than those of many other food-processing companies.
Goldy’s recently converted a 19th-century barn into its latest food manufacturing and retail outlet. The company incorporated food-temperature-based sensor technology in the new facility as part of a range of energy-saving measures, which also included wind turbines, solar panels, and heat and condensate water reclamation from the refrigeration system.
By using food-temperature-based sensors to control food-storage temperatures, Goldy’s achieved a more efficient refrigeration cycle. With the air-temperature-based sensors in its previous manufacturing facility, the compressors typically switched on and off 12 times per hour, and each on cycle averaged 3 min. With the food-temperature-based sensors, the compressors only cycle three to four times per hour, with an average on time of 10 min. This change has allowed Goldy’s to reduce its energy consumption by 16 to 22 percent while also cooling the food more quickly, leading to enhanced food safety.
Due Diligence, Preventive MaintenanceIn addition to its energy-saving capabilities, the food-temperature-based sensors can be used with remote-sensor monitoring equipment to record food-temperature trends over time. These data can be used for due-diligence reporting and also can assist with preventive-maintenance efforts by warning of an impending refrigeration breakdown before it occurs. Goldy’s is in the process of installing a system based on the food-temperature-based sensor technology that will provide an accurate record for the UK’s Institute of Environmental Health and also will monitor all of its refrigeration systems to ensure that they are working at their optimum level.
In the food processing, accurate temperature measurement is paramount to ensuring food safety. Food-temperature-based sensors can help companies achieve this goal while also minimizing energy and maintenance costs. PC
Minimizing Frost Buildup
- In chillers, frost restricts airflow
through evaporator surfaces and also inhibits good heat transfer. Systems that
rely on a conventional heat-induced defrost at six-hour intervals often must
run with a frosted coil (evaporator), which reduces efficiency.
- Food-temperature-based sensors boost chiller efficiency by inducing a natural off-cycle defrost (-1 to 1°C and 1 to 5°C) that prevents frost from building up on evaporation surfaces.