ENERGY USE ANALYSIS OF MAJOR MILKING CENTER COMPONENTS AT A DAIRY EXPERIMENT STATION

Abstract

Fourteen years of accumulated electrical energy use data related to milking operations at the 160-cow Universityof Tennessee Dairy Experiment Station in Lewisburg, Tennessee were analyzed to quantify relative effects ofproduction -related factors on energy use within the milking center. Energy use was measured for vacuum pumps, refrigerationcompressors, water heaters, and an air compressor. These energy use figures were then related to the recorded productionparameters: number of cows milked, the amount of milk sold, percent butterfat of the milk, the total pounds of fat correctedmilk, and high and low dry bulb temperature by means of multiple regression. Analyses were made on a monthly and yearlybasis. Total dairy energy use could not be computed due to numerous non-dairy load components in the Experiment Stationthat could not be subtracted. It followed logically that number of cows milked, milk production, and weather conditionsrepresented by dry bulb temperature were found to be the major factors affecting energy use. However, no parameter, orcombination of parameters, explained in a statistical sense more than 74% of the variability in the recorded energy use bythe equipment studied. Quantity, and not quality, of milk produced was the most significant factor affecting energy use, withthe number of cows milked and outside temperatures playing lesser roles. Regression results showing that cow numbers wasnot a factor related to energy use for milk cooling or vacuum pump operation, lead to some questions about the validity ofkWh/cow/yr as an energy use indicator.<br><br>For the 14 years of data available, average EUIs for the vacuum pumps for milking (1.10 kWh/cwt) and the refrigerationcompressors for milk cooling (1.02 kWh/cwt) were near the upper range of published reference values (0.4 to 1.19 kWh/cwtand 0.8 to 1.10 kWh/cwt, respectively), while average EUI for water heaters (0.65 kWh/cwt) were well below the publishedrange (0.95 to 1.40 kWh/cwt). The former two results confirm the validity of the published EUIs that were based only on afew years data. Interestingly, the results also indicate a general consistency in the year to year operation of similarly sizeddairy operations. The lower EUI for the water heater was due to the use of a preheater and also the every-other-day milkcollection at the dairy.