AgEnergy

Dairy

Milk Cooling - There are three technologies that will save electrical energy used for cooling milk: Scroll type refrigeration compressors, well water cooled precoolers (heat exchanger) and refrigeration heat recovery units.

• Refrigeration heat recovery (RHR) units will make a refrigeration system more efficient along with pre-heating water because in increases the heat exchanger surface area where the reject heat can be dumped to and the heat transfer rate between the refrigerant and water is higher than to air. However, RHR units are not purchased to increase the refrigeration system efficiency but it is a side benefit if purchase to capture the reject heat to pre-heat water. Refer to UW Extension bulletin A3784-4: "Energy Conservation in Agriculture: Refrigeration Systems".

• Scroll compressors are a newer type compressor unit that is 15 to 20% more efficient than the traditional reciprocation compressor yet has fewer moving parts and is only slightly more expensive than a reciprocating compressor. Scroll compressors have been used in the dairy industry for about 10 years with good results. If you are purchasing a new bulk tank, you should specify that the compressors be a scroll type. If you have a reciprocating compressor fail on an existing refrigeration system, it can be replaced by a scroll compressor for about 3 to $500 more than replacing if with a reciprocating compressor. This is a modest cost for the improvement in efficiency. Refer to UW Extension bulletin A3784-4: "Energy Conservation in Agriculture: Refrigeration Systems".

• Well water precoolers are heat exchangers that use well water to cool the milk before it reaches the bulk tank. If they are sized properly they can reduce milk cooling costs by up to 60% assuming 55°F well water. Undersized water lines and water system capacity are the two largest reasons that precooler do not perform up to their potential. If a refrigeration heat recovery unit is being used on the dairy, an energy audit should be done to assure that adding a precooler with not increase energy requirements as precoolers and refrigeration heat recovery units are competing technologies. If the milk is cooled with a precooler, then there is less heat available to pre-heat water in RHR unit. If an electric water heater is being used, it is usually more cost effective to maximize water heating with a RHR. Refer to UW Extension bulletin A3784-3: "Energy Conservation in Agriculture: Well Water Precoolers".

If you have information you think would be useful to this site please contact Scott Sanford, Senior Outreach Specialist, University of Wisconsin, sasanford@wisc.edu.