The farm is 32 ha and irrigated all year-round, predominantly overnight (off-peak period), producing around 111 units per ha per year.

The annual energy consumption for the entire site during the 2018-2019 period was 181,850 kWh at a cost of $40,047, with a 5kW solar PV system already implemented used by the miking system. The energy consumption on the farm consists mainly of:

• Milk Cooling: plate cooler, cooling tower, vat cooling system.
• Milk harvesting and stalling: vacuum pump.
• Water Heating.
• Irrigation system: centrifugal pump with a 37kW motor and a 12m suction pipe of 140mm HDPE.

The pump worked at an average 64% efficiency drawing less than 5kWh/ML/m, a bit lower than the industry standards. The motor was overloaded and the impeller was likely to be damaged, reducing the long-term efficiency of the pump and motor.

A recent energy audit showed how improving the current irrigation systems can lead to energy and cost savings. The irrigation audit recommendations are:

1. Review system design, re-jet the size and replace sprinklers: considering all the 450 sprinklers in the system, to limit the flow rate for each section so that the irrigation system has a duty point within the pump capability.
2. Review system design, replace sprinklers to obtain CU>80%: since the current CU is 72% given short nozzles on the sprays, the new sprinklers could deliver flow rate and pressure appropriate for the existing reticulation system.
3. Review system design, replace sprinklers to obtain CU>85%: since the current CU is 72% given short nozzles on the sprays, the new sprinklers could deliver flow rate and pressure appropriate for the existing reticulation system.
4. Replace pump and suction line with 100×65-250 pump with 37 kWE motor and 200mm HDPE suction line: reaching 77% efficiency to be more appropriate to the measured flow and head of the irrigation system, being more stable with less risk of failure or decline in performance.
5. Install in-line filter on discharge pipeline: to prevent the end sprinklers continually blocking up.
6. Install automation system: to enable 3×3 hours shifts per night rather than 2×5 hours shifts, being more efficient in water use. This solution can potentially increase production of 16 t DM/year as soil moisture is closer to an optimum level for longer, valued between $5,000 – 10,000 per year. Also, this solution allows reduced labour input to change valves in the middle of the night of around $2,880/year.

Table 1. Costs and savings from irrigation audit recommendations.

The farmer installed the automation system as recommended, and replaced sprinklers with a different design as recommended in the audit report. The savings made with the installation of the automation system have been measured in a Measurement and Verification (M&V) process, as outlined in Table 2.

Table 2. Estimated and Actual energy and cost savings from the automation system.

The greater energy and cost savings obtained from the M&V calculations compared to those estimated in the audit have been influenced by the lower energy draw by the automated system during the day time, allowing operating only at off-peak periods.

Additionally, the new sprinklers have allowed an improvement in the Distribution Uniformity (DU) from 58% to 80%, increasing pasture production. Typical production levels for irrigation with moderate DU are 8-10 tonnes of dry matter per hectare per year (t DM/ha/year). With the improved uniformity and with careful management, production is expected to increase over 12 t DM/ha/year, to around 32 t DM/year for the whole irrigated area, with a minimum estimated value of $10,000. This value has not been included in the cost savings. These improvements haven’t been translated into increases in milk production.

From the implementation of the automation recommendation in the audit, the farm has reduced total energy consumption by 6% and total costs by 25%, with Carbon emission savings of 8.1 t/CO₂-e per year.

Table 3. Pre and post implementation energy consumption and cost improvements.

This case study was developed as part of the Energy Savers Plus Extension Program, delivered by the Queensland Farmers Federation with support and funding from the Queensland Department of Energy and Public Works.