Agricultural producers use a variety of refrigeration systems to extend the shelf life of perishable materials. Cooling not only reduces the potential for spoiling due to bacterial growth but also reduces humidity levels for some products. Refrigeration may also be used during sorting, processing, packaging, and storage.
Fruit and vegetable farmers must cool many of their products quickly after harvest; removal of field heat is important to maintaining produce quality and shelf life.
Fruit and vegetable farm refrigeration systems are operated most intensively during the warmest months of the year, often when electrical costs are at their highest levels. Improving energy efficiency of refrigeration systems can therefore lead to significant savings. This can be accomplished by:
- Precooling produce with cold water before putting it into refrigerated areas.
- Improving insulation of the refrigerated cold storage area.
- Reducing infiltration of warm air through the doors, cracks, and other openings.
- Regular maintenance and servicing of refrigeration equipment.
- Utilizing energy-efficient compressors, heat exchangers, and refrigerants.
- Taking steps to prevent and detect refrigerant leakage.
Dairy farmers also rely heavily on refrigeration equipment, but on a daily rather than seasonal basis. Dairy farming is one of the most energy-intensive agricultural operations, using electrical power to operate vacuum pumps and to pump water, ventilate structures (heat and cool), provide lighting, heat water, and, most importantly, refrigerate milk.
Refrigeration systems with scroll compressors are 15% to 20% more efficient than traditional reciprocating compressor systems. These compressors can be used for cooling milk or for space conditioning, such as a walk-in cooler. In addition to high-technology refrigeration equipment, a variety of supplemental refrigeration technologies are available to reduce energy costs. Well water-cooled plate heat exchangers can be used to precool the milk before it enters the bulk tank.
Heat-recovery units can scavenge the discharge heat from refrigeration equipment to supplement water-heating needs while increasing the efficiency of the refrigeration system slightly. A refrigeration heat recovery (RHR) unit consists of a water storage tank and a heat exchanger. The heat exchanger can be separate from the water tank or jacketed to the outside of the storage tank and covered with insulation and a protective shell.
Jacketed storage tanks are commonly available in 50-, 80-, and 120-gallon size tanks. The refrigerant inside the jacket is cooled while the water in the tank is heated. Depending on ambient conditions, the incoming refrigerant gas to the RHR heat exchanger can reach more than 200°F and then — before exiting the tank — drop to 115° to 125°F as the heat transfers to the water.
Innovative systems and equipment can help agricultural producers increase energy efficiency and reduce energy costs. Energy-efficient refrigeration equipment and technologies can lower energy expenses and improve productivity. Maximum profitability from refrigerated agricultural products is only possible if the equipment is reliable and operating efficiently.
Agricultural producers should invest in an energy audit to determine whether an investment in more energy-efficient refrigeration equipment or other energy-saving technology offers an acceptable economic payback.
For Additional Information
- Energy Conservation on the Farm: Refrigeration Systems, University of Wisconsin Extension.
- Dairy Farm Milk Cooling Chapter 2 in: Dairy Farm Energy Management Guide, Southern California Edison.
- Precooling and Storage Facilities by James F. Thompson, Department of Biological & Agricultural Engineering, University of California, Davis, CA.
- Design of Room Cooling Facilities: Structural & Energy Requirements, North Carolina Cooperative Extension Service.
- Precooling Produce by Karen L.B. Gast and Rolando A. Flores, Kansas State University Cooperative Extension Service.
- Low-Cost Cold Storage Room for Market Growers, by John Wilhoit, University of Kentucky, AEN-96. Plans for an 8′ x 10′ cold room, constructed from locally available building materials and cooled by a room air conditioner and a CoolBot control unit.
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