Modelling of an on-farm direct expansion bulk milk cooler to establish baseline energy consumption without milk pre-cooling: A case of Fort Hare Dairy Trust, South Africa

Storage of milk at a low temperature of 4°C inhibits bacterial growth. As such bulk milk coolers (BMC) are used for cooling and storage of milk on dairy farms. This paper presents performance monitoring of a direct expansion bulk milk cooler to establish its baseline energy consumption without milk pre-cooling through mathematical modelling. A data acquisition system comprising a power meter, a data logger, temperature sensors and relative humidity and ambient temperature sensors was constructed to capture the energy consumption of the BMC, room temperature and ambient conditions. On-farm milk records were used to determine milk production per milking session. Two milking times were considered, that is for the morning and the late afternoon periods. The average daily electrical energy consumption of the BMC for the two milking times was 48.31 kWh and 43.23 kWh, respectively. Mathematical models represented as multiple linear regression models were built and developed using the experimental data. The developed mathematical models gave good agreement with the experimental results as evidenced by correlation coefficients of 0.922 and 0.8995. ReliefF algorithm revealed that volume of milk is the principal contributor to the energy consumption of the BMC for both the AM and PM milking.