Energy Savers
South East Queensland

South East Queensland Dairy Farm

Proposed
35
Proposed Energy Savings
Industry
Dairy
Location
South East Queensland
Irrigation
Centre Pivot
Pumps
Bore
Solution
Maintain the milk cooling system, and utilise solar generation for thermal storage.

Farm Profile

A 160-hectare South East Queensland dairy farm producing milk, milk solids and some milling of grain could benefit from a recent Energy Savers Audit. This farm is considered a large energy user consuming 155,000 kWh/year.

This case study looks at ways to decrease energy use below 100,000kWh per annum to reduce demand charges using recommendations in the audit. The audit showed additional opportunities with energy management using pressure and temperature monitoring, and low-cost maintenance of general equipment onsite.

General recommendations in the audit included;

  • Fixing a leak in the air compressor saving 1,600kWh and $297p.a. and,
  • Install electronic expansion valve on the refrigeration system saving 4,860kWh and $751p.a.

The main contributor to energy usage onsite is milk cooling. Cooling milk requires the use of the initial water plate cooler, a secondary glycerol plate cooler and finally, storage in a large cooled milk vat. The general standard for milking is to cool the milk down below 5°C within less than 3.5 hours of milk extraction.

Cooling Element Energy Use (kWh) Site Energy Use (%)
Plate Cooler 1 3,900 3
Glycerol Plate Cooler 15,000 10
Milk Vat 17,400 12
Cooling Tower 1,800 1
Total 38,100 26

 

Generally, milking occurs outside peak solar generation periods. The audit recommended shifting the load across the middle of the day achieving a best-case scenario, increasing the solar utilisation by 29%. This could be achieved using a new chilled water system utilising the existing glycol refrigeration loop to chill water to be stored in an insulated tank. This chilled water would be used to cool the milk vat and pre-cool milk via the secondary plate cooler (replacing the glycol circulation in this plate cooler). This operation is a form of thermal storage and would need to occur in the hours between milking to maximise the energy offset from the solar system.

AS

Figure: Current and proposed solar utilisation from practice change.

The energy, cost savings, and payback period for works on the cooling system are summarised and tabled below.

Recommendation Energy Savings Cost Savings Payback Period
Solar and chilled water installation 50,271 12,678 7.9
Shade/insulate outdoor storage tanks 2,322 359 7.6
Permanent data logging of key areas 1,500 1,232 1.2
Management opportunities 1,000 404 3.5
Total 55,093 14,673 N/A

 

The management and monitoring changes shown in the table included:

  • Cleaning of the plates on the plate coolers
  • Installing pressure gauges on plate coolers an increase in pressure could indicate a blockage and requires cleaning
  • Managing temperature probes
  • Insulating cold water and milk pipes
  • Cleaning solar panels
  • Cleaning and maintaining motors including bearing and impellor replacement

Implementation of the project and on shifting an annual pump using 30,000kWh off the dairy NIMI would bring consumption below the 100,000kWh threshold. This would allow adoption of a small user tariff 20 providing a payback of 7.9 years.

The national average energy use on dairy farms in Australia was found to be 48 kWh/kL of milk, with the site using slightly above this average. From implementation of the cooling measures listed in the audit the site can reduce the current kWh/kL of milk by 17.5% bringing this below the national average.

 

Metric Pre-Audit Post Audit
Energy Consumption 155,000 99,907
kWh/kL of milk 55.7 38.2

 

An energy audit is a great way for a business to cut costs and boost productivity.

An energy auditor will review your past energy bills, your equipment and the way your business operates. They’ll show you where you’re using excess energy and explain what you can do about it.

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.