Energy Savers
South East Queensland

South East Queensland Dairy Farm

Proposed
38
Proposed Energy Savings
Industry
Dairy
Location
South East Queensland
Pumps
Centrifugal
Irrigation
Travelling Gun
Solution
Maintenance quick wins, install VSD and Solar PV, replace pump and mainline, install new centre pivot

Farm Profile

A 240ha Southeast Queensland 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.

Electricity Audit

An objective of the audit was to identify measures to keep energy consumption 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 at be 2 degrees or less.
  2. Vacuum milk pumps rationalisation, moving from two, to one pump with the use of 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 solar system.

 

Recommendation Estimated Energy Savings (kWh) Estimated Cost ($) Saving ($) Payback (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 $39,000 6,879 7.4
Total 65,170 $45,500 10,721

 

By implementing the changes, the farm has the potential to reduce the energy usage per litre of milk produced as shown above, as well as keeping the energy consumption below 100 MWh/year.

With solar, a 65 per cent reduction in the grid electricity required to produce 1000L could be achieved.

  Energy Use (kWh) kWh/1000L of Milk
Pre-Audit 99,636 76.6
Post Audit 80,965 62.3
Post Audit with Solar* 34,466 26.5

 

The addition of a 30kW solar system will reduce the grid electricity by approximately 46,500kWh.

With the above changes combined with the potential energy reductions from the irrigation systems, the farm could reduce the overall site consumption and costs on site across a few energy meters.

System Energy Use Pre- Audit (kWh) Energy Use Post- Audit (kWh)
Milking 99,636 34,466
Irrigation: Pumping and main line 57,387 32,282
Irrigation: New Irrigators (34ha) 48,433 12,917
Total 205,456 79,655

 

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 a total of 124 ha

Currently water is supplied to the irrigators from a dam using a 100x65x250 pump running at 42 per cent 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 which is 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 overall efficiency of the system.

Recommendation Cost ($) Energy Savings (kWh) Savings ($) Payback (Years)
Investigate inefficient pump and fix

(Keep existing suction line)

 

2,500 24,505 5,955 0.41
Investigate inefficient pump and fix

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 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.

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.

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 than 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 on site across a few energy meters.

 

System Energy Use Pre- Audit (kWh) Energy Use Post- Audit (kWh)
Milking 99,636 34,466
Pumping 57,387 32,282
Irrigators (34ha) 48,433 12,917
Total 205,456 79,655

 

The site has the potential to reduce overall energy consumption by 38%.

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.