AGRICULTURAL ENGINEERING SPECIALISTS REPTEC

Reducing the cost of your energy use in your dairy operation

Energy management is a key way dairy farmers and sharemilkers can cut costs and improve profits.
Key tips include:

  • Turn off lights, machines and equipment when not in use – preset timers can help
  • Use energy efficient light bulbs, natural light and fluorescent instead of incandescent lights.
  • Ensure cow comfort to reduce effluent discharge and reduce effluent clean up.
  • Insulate cold water pipes and your milk vat
  • Know what power tariffs you are on and be sure to take advantage of off-peak tarrif times.

Installing the right pump.

Larger pumps may consume up to 20% more energy than a smaller pump operation at a more efficient point on the pump curve. Ensure your pump is well maintained so leaks and inefficient use is avoided.
On many farms, irrigation pumps are run overnight in the off-peak period, with the additional benefit of reduced evaporation losses during application. During the summer months, however, irrigation may be required during daytime hours to apply sufficient water, and offsetting this peak demand with renewables may improve the cost-effectiveness of the investment. Talk to Reptec for assistance with pump parts and maintainance.

Hot Water Heating

Around 17% of your energy use is for hot water heating
Firstly minimise the volume of water used to wash the plant and vat. Then if you have not do so already install a water heater with capacity for all daily wash requirements so that all heating can occur on the offpeak tarrif. Install a hot water preheating device such as a heat recovery unit or solar hot water heater so that most of the heating can occur without using extra electricity.

Solar hot water systems

In many cases preheating hot water for the dairy using a solar hot water system is a great option financially and environmentally. Preheating water to 60–65 °C using solar and then boosting it to the required temperature with the dairy heater can save more.

Thermal heat recovery systems

A large amount of waste heat generated during milking can be harvested and used. Sources include plate coolers, refrigeration systems and some vacuum pumps. Heat recovery systems are available that capture the heat from the milk refrigeration system and use it to heat water (to 50 °C to 60 °C).
Further options may include CO2 Heat Pumps and Pellet Boilers.

Milk Cooling

Around 30% of your energy use is for milk cooling
Demand and farm diary operating costs can be reduced using different options that involve heat recovery from your cooling system.

Vat wraps

These are only utilised by 20% of dairy farms in New Zealand but can save around 15-25% of milk cooling costs. They insulate your milk from outside temperatures and weather, preventing it from heating up and reducing energy used by the refrigeration unit.

Plate coolers

Plate coolers are an extremely cost-effective way to cool milk, but in many cases are poorly utilised. There are several factors that impact on the effectiveness of plate coolers. Flow rates, surface area, plate compression, plate cleanliness, source water and plumbing.

Cooling towers

If you discover that the water entering your plate cooler is too warm, a cooling tower could be an option. They also allow for water from the plate cooler to be cooled so it can recirculate without jeopardising milk cooling. Cooling towers can be very effective at cooling water in areas of low humidity.
Other cooling options include ice banks, snap chillers and thermal stores.
Further references:
https://www.dairynz.co.nz/milking/the-milking-plant/milk-cooling/
https://www.dairynz.co.nz/milking/the-milking-plant/electricity-efficiency/
https://tools.genless.govt.nz/businesses/dairy-farm-energy-efficiency-tool/