Heating and cooling typically accounts for the highest percentage of energy consumption on a dairy farm. To cool the milk a dairy typically uses plate coolers for pre-cooling, which reduces the time taken when cooling milk once stored in the cooling vats. Guidelines suggest that the temperature difference between the cold fluid (water) in the system, and the hot fluid (milk) leaving the plate cooling system should be no more than 3°C when pre-cooling. When the temperature difference is greater than this, some inefficiency often exists in the sizing or operation of the system.
A recent Energy Savers audit identified the dairy farm could improve heating and cooling efficiency onsite by improving pre-cooling performance, improving vat cooling, reclaiming heat and reusing to heat water, improving the ratio of flow rates in the plate cooler, cleaning the plate cooler and various management measures.
Audit recommendations showing potential energy and cost savings
||Energy Saving (kWh)
||Cost Savings ($)
|Improve pre-cooling performance
|Improve vat cooling
|Reclaim heat and reuse to heat water
|Improve ratio of flow rates in plate cooler
|Plate cooler cleaning
Measurements taken onsite showed the plate cooler was performing below expectations with a flow rate of 1:1 and current production is close to exceeding the design capacity of the storage vat.
The common reasons for a temperature difference greater than 3°C within the system include:
- Plate cooler is incorrectly sized for volume and flow rate of the milk pump.
- Insufficient difference in flow rate between milk and water (typically a ratio of 3:1 for water to milk flow rate is required, depending on the design and sizing of the cooler.
- Plates require cleaning given fouling, debris or contaminants reducing the heat exchange between the plates.
With good management and practice change, low-cost options are also available for the dairy. The audit recommended the installation of pressure gauges on the water inlet and outlet of the plate cooler and record pressure measurements, as a drop in pressure usually indicates fouling or a blockage. While installing permanent temperature gauges and regularly checking the water coming into the plate cooler and milk exiting the plate cooler will provide an indication of potential issues within the system. Further, conducting regular cleaning of refrigeration condensers, insulating cold milk pipes and painting tanks with reflective colours could help to reduce heat gain and warming during the day.
Further measures to reduce energy consumption onsite include the installation of a heat recovery unit. This would utilise the current refrigeration system that operates on R22 gas providing good water heating characteristics. Installing a heat recovery unit could generate sufficient pre-heated water to offset most, if not all, the heating undertaken by the existing hot water services.
By installing the recommendations and undertaking management changes, energy consumption will be reduced by 38 per cent, and costs by 45 per cent. This will lower the kWh per unit of production, an important metric to increase profit for your business.
Pre and post audit metrics
|kWh/1000L of milk
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