The Farm

The Southern Downs dairy milks around 320 dairy cows in two daily milkings using an automated rotary milking system.

The site used 500,000kWh of electricity in the year prior to the audit at a cost of $170,000. The site uses 93 kWh/kL of milk which was above national average industry benchmark of 48kWh/kL.

Solar Commitment

Prior to the audit, the farm had paid a deposit for a 200kW Solar PV system at a cost of $330,000 which the solar company estimated would provide energy cost savings of around $59,000 per year, with a payback period of 4.8 years.

The audit

A comprehensive type 2 energy audit was conducted at the dairy, which used 19 run-time counters on most motors, thermal imaging cameras and temperature loggers. The data from these sensors in combination with the analysis of interval electricity meter data for the site meant that a comprehensive picture of energy consumption at the site was developed. For example, time of use profiles were developed showing when main loads were being used.

Energy Efficiency Recommendations

The audit recommended a number of low-cost energy efficiency measures.

Adjusting the Roof above the Milk Chillers: Thermal cameras and temperature loggers showed that the low lean-to roof over the milk chiller condenser units showed that hot air was being trapped close to the condensers, increasing their ambient temperature by up to 10 degrees. The audit recommended raising the roof to maintain shading and increase air flow.

Adjust the areas controlled by groups of fans in the barn: The auditor recommended that rewiring the groups of ventilation fans into zones would allow smaller groups of fans to be used, along with timers.

Other low cost measures included repairing leaks to reduce pump use and insulating hot water pipes.

Several actions were recommended with a higher cost to reduce energy consumption and other operational costs including:

• LED lighting upgrades
• Heat recovery system upgrade.
• Milk tank hot water system upgrade (heat pump)

Solar PV System

The auditor made an analysis to determine the most suitable size of Solar PV system for the site. The assessment found that the most suitable sized system would be 100kW, installed after the energy efficiency upgrades.

It was estimated that a 100kW system implemented after the energy efficiency upgrades would save around $22,700 per year with a payback period of 6.6 years, compared to a 200kW system before energy efficiency upgrades, which would save $31,000 per year with a payback period of 9.5 years.

Note that there is a significant difference in estimated payback period for the 200kW Solar System between the detailed energy audit and the estimate from the solar installer.

The farm has been able to renegotiate the contract with the installer to implement a 100kW system at the site.

Summary

The estimated costs and savings of the audit recommendations are summarised in the table below:

Implementing the above actions would reduce the dairy energy consumption to 48kWh/kL of milk, much closer to the industry benchmark of 43kWh/kL of milk.

The audit also considered a number of other opportunities but which were not recommended at this stage:

• Thermal energy storage
• 200 kW solar system
• Effluent pump upgrade
• Plate cooler upgrade.

The farm had a Type 2 energy audit as a participant in the QBEST Ag program. The program is being delivered by the Queensland Farmers’ Federation and is funded by the Queensland Government.

For more information about Choosing Solar Systems, see the Ag Energy Hub Solar Article HERE.

The program was delivered by the Queensland Farmers’ Federation and funded by the Queensland Government.