Energy Savers
South East

Lockyer Valley Dairy Farm

Implemented
26
Energy Savings
43.3
Savings
7,508
Industry
Dairy
Irrigation
Travelling Gun
Pumps
Centrifugal
Technology
Solar Photovoltaic
Capital Cost
$37,000

Summary

A 240ha Lockyer Valley dairy farm milks 250 cows to produce around 1,300,000L of milk per year and produces much of its own feed onsite. The farm irrigates the feed growing areas with a travelling gun and has an annual energy use of nearly 100,000kWh at a cost of over $22,000 for the milking shed.

The farmer has implemented the 30kW roof-mounted solar system recommended.

Electricity Audit

An objective of the audit was to identify measures to keep energy consumption from the milking meter below 100,000 kWh per year (or 100 MWh) so that the farm can remain a Small User and remain on small business tariffs.

The preliminary analysis identified potential energy savings for the milking shed, including:

  1. The difference between the incoming coolant and the outgoing milk was 3 degrees, higher than expected for the type of plate cooler, which should be 2 degrees or less.
  2. Vacuum milk pumps rationalisation, moving from two to one pump using an isolator.
  3. Installing a Variable Speed Drive (VSD) on the vacuum pump.
  4. A more detailed investigation of chiller systems.
  5. Installing of a 30kW roof-mounted solar PV system.

Table 1. Energy and cost savings from audit recommendations.

Recommendation Annual Energy Savings (kWh) Capital Cost ($) Annual Cost Savings ($) Payback Period (years)
Plate cooler maintenance 654 0 126 Immediate
Milking vacuum pumps 14,413 Up to 1,000 2,973 Immediate
Install a Variable Speed Drive (VSD) on the vacuum pump 3,603 Up to 5,500 743 5.7
Installation of a 30kW solar system 46,500 37,000 6,880 7.4
Total 65,170 43,500 10,721  3.3

 

The grower has proceeded with the implementation of the 30kW solar PV system. The savings 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 Solar PV. 

Metric  Audit estimation  M&V calculation  Variation (%) 
Energy Savings including exports (kWh)  46,500 53,400  15
Cost Savings including exports revenue ($)  6,880 7,506 9

 

Higher energy savings have been achieved, given the greater efficiency of the solar system. The higher solar generation has allowed offsetting the increase in energy consumption given the greater production of the farm, thus keeping the energy consumption of the milking meter below 100,000 kWh per year.

The cost savings from solar exports have been estimated using a conservative feed-in tariff as the farm has no export revenue at the moment since it is on demand tariff 44. The business aims to move to a consumption tariff in the short term.

From the solar generation, 15,695 kWh or 30% are being used onsite valued at $4,550, and around 37,705 kWh are being exported to the grid with expected revenue of $2,956. Considering that 98,915 kWh – 86% of the total energy used onsite – are being imported from the grid at a cost of $28,685, there are significant potential savings from shifting consumption into the solar generation period. The total power balance of the farm, including solar exports and the energy cost distribution, are shown in the following figures.

Energy ES064

Cost ES064

 

The next step for the farm is to adjust energy usage to offset as much energy consumption as possible from the grid, which would lead to further cost savings. The revenue from feeding into the grid is lower than the cost savings from using the energy onsite: for every dollar of energy exported, more than $4 could be saved if the energy were consumed onsite. If the farm were to shift 37,705kWh of energy consumption per year to coincide with solar generation times, they would save an extra $7,978 per year.

Solar optimisation ES064

By implementing the solar PV system, the farm has reduced energy consumption by 26% and costs by 14% based on pre-audit values, with carbon emission savings of 43.3 tCO2-e per year. The solar system also allows the farm to keep the energy consumption in the milking meter below 100 MWh/year despite the increase in consumption post-audit.

Table 3. Pre and post implementation energy and cost savings.

Metric Pre-Implementation Post-Implementation Reduction (%) 
TOTAL farm energy consumption (kWh) 205,456  152,056  26
TOTAL farm energy costs ($)
52,000 44,494 14

Irrigation Audit

The dairy farm produces feed onsite using the following irrigation infrastructure:

  • 40ha part circle, 470m span centre pivot.
  • A total of 84ha irrigated by several soft hose travelling irrigators.
  • A network of 150mm and 100mm PVC underground pipelines linking several pump sites and dams to irrigate 124 ha.

Currently, water is supplied to the irrigators from a dam using a 100x65x250 pump running at 42% efficiency and connected to a 37kW motor with a VSD. With an average annual energy use of 57,387kWh, it currently delivers 7.3kWh/ML/m, above a typical benchmark for energy used at 5kWh/ML/m.

The recommendations in the audit explored different options to replace current infrastructure, reduce costs and improve the system’s overall efficiency.

Table 1. Energy and cost savings from audit recommendations.

Recommendation Capital Cost ($) Annual Energy Savings (kWh) Annual Cost Savings ($) Payback Period (years)
Investigate inefficient pump and fix (keep existing suction line) 2,500 24,505 5,955 0.41
Investigate inefficient pump to fix it and install new 200mm HDPE suction line  5,000 24,505 5,955 0.83
Replace pump (keep existing suction line) 8,000 24,505 5,955 1.34
Replace pump and install new 200mm HDPE suction line 10,500 24,505 5,955 1.76
New centre pivot (34ha) 

(savings include labour, production, and scheduling)

220,000 35,516 35,031 6.28
New centre pivot (16ha) 

(savings include labour, production, and scheduling)

140,000 16,245 16,907 8.28

 

Travelling irrigators typically have a low distribution and co-efficient of uniformity, leading to over and under watering in the paddocks. Installed on a separate meter, energy use is currently 48,433kWh per annum.

There are considerable costs involved when moving to a centre pivot, and it is important to determine the highest returns for your business. As centre pivots operate at lower water pressure than travelling guns, they can offer energy efficiency gains, reduced costs, and improved production. Further, the reduced labour required in running the pivot can lead to significant additional savings.

With large variability in Australia’s rainfall, water is stored in dams with the energy required to move water around the farm, often involving double-pumping, that is pumping to harvest water into storage then irrigation pumping. If water can be saved, then energy can be saved as well.

Table 2. Efficiency of irrigation improvements recommended.

Irrigation System Distribution of Uniformity (%) Scheduling Coefficient Energy Savings (kWh)
Travelling Gun 41 2.5 N/A
Centre Pivot (34ha) 90 1.11 12,918
Centre Pivot (16ha) 90 1.11 6,547

 

The lower scheduling coefficient results in reduced run times leading to energy savings. The centre pivot will consume the same volume of water (or more), though with improved uniformity an increase in production-per ML of water can result. With an estimated increase of 2t of dry matter (DM) per hectare, the farm could expect an increase in production value.

Table 3. Productivity of irrigation improvements recommended.

Recommendation Production (DM/ha/Year) Production Increase (t/DM) Production Value ($)
Travelling Gun 6-8 N/A N/A
Centre Pivot (34ha) 8-12 68 Up to 40,000
Centre Pivot (16ha) 8-12 32 Up to 20,000

 

With a quicker payback, the audit recommended installing a new centre pivot over 34ha. The suction line should be replaced, and the pump investigated for potential issues. If repair of the pump is not cost-effective, then it is recommended to replace it.

From the above and combined with the potential energy reductions on the milking enterprise, the farm could reduce the overall site consumption and costs onsite across a few energy meters.

An energy audit is a good investment 

An energy audit is a great way for a business to cut costs and boost productivity. Find out about what’s involved in an energy audit HERE and subscribe to our bi-monthly energy e-news HERE.

If you have any energy efficiency related questions for the team, get in touch at energysavers@qff.org.au.


The Energy Savers Plus Extension Program is delivered by the Queensland Farmers Federation with support and funding from the Queensland Department of Energy and Public Works.

Captureqdo