Research suggests energy use on dairy farms is associated with cooling milk, the milking processes and lighting.
Installing variable speed milk and vacuum pumps, and heat recovery systems offer the greatest potential energy savings – farmers report energy savings of over 60%.
Heat exchangers and variable speed pumps help cool milk to the necessary temperature and reduce energy costs. For example heat exchangers will transfer the heat from freshly extracted milk to another liquid before entry in the bulk tank – this process can save 60% of energy costs. Variable speed milk pumps cool the liquid by an extra 15-20 degrees.
Low rate irrigation rather than tractors can be used for dirty water, which will save considerable amounts of energy.
Energy, noise and maintenance costs are all reduced by using variable speed vacuum pumps. These operate at different levels in response to capacity requirements, not at a constant rate as with conventional pumps, therefore reducing wear and tear and energy used.
Read more in the Dairy Co factsheet on energy efficiency for dairy farms
Areas to consider
Variable speed motors
Can have a range of applications, most commonly as vacuum pumps, but can also be applied to milk pumps, irrigation and ventilation systems.
Variable speed vacuum pumps
Current vacuum pumps operate at a constant speed to provide the vacuum requirements for milking. Variable speed vacuum pumps are designed to meet capacity required when it is needed. The addition of a variable speed driver pump eliminates the need for a conventional regulator because less energy is delivered to the motor and operating speeds are reduced.
By maintaining a constant vacuum level and only producing necessary amounts of air flow, energy cost savings of up to 60% can be made. The noise level is also greatly reduced allowing for a gentler parlour environment. There are also reduced maintenance costs and less wear, leading to an extended life compared with a conventional oil vane pump.
Milk cooling
Cooling milk accounts for the highest energy cost associated with the milking process. Milk needs to be cooled from its harvested temperature of 35 – 37 degrees, to three degrees to maintain high milk quality and low bacterial counts. There are various options to help cool the milk, including heat exchangers and variable speed milk pumps.
Heat exchangers
Used for pre cooling raw milk, transferring the heat from the milk to an intermediary cooling fluid (usually water). Installing a heat exchanger to pre-cool the milk prior to entry to the bulk tank can reduce energy consumption by 60%.
Variable speed milk pumps
The use of a variable speed milk pump allows the milk to be pumped through the plate cooler at a more consistent speed, allowing the plate coolers to operate more efficiently and resulting in greater milk cooling. It also allows more heat to be extracted by the plate cooler, and reduces the energy demand on the bulk tank. Milk can be cooled by an extra 15-20 degrees by installing a variable speed milk pump.
Heat recovery units
During the process of cooling milk, heat is rejected from the condenser coil of the refrigeration system. It is possible to recover this by passing the hot refrigeration gas through a heat exchange system which is immersed in water. A water temperature of over 50 degrees C can be achieved by using this technique. The water heating system needs to be carefully configured so that the heat recovery can deliver the maximum benefit without compromising the operation of the milk cooling system. Depending on the number of cows being milked, the water storage tank should be sized to provide enough hot water for one milking.
Tips for saving energy on dairy farms
- Record usage at various intervals
- Switch to a better tariff
- Use cheaper night time electricity where possible, especially for water heating
- Insulate water heaters and pipework to minimise losing heat you are paying for
- Consider investing in energy saving devices
- Switch off equipment and lights where appropriate
- Make staff aware of energy saving aspirations
- Replace old equipment with energy efficiency model
For more information, why not check out this great factsheet from SRUC’s Farming for a Better Climate project?
