Energy Savers
Mackay, Isaac and Whitsunday

Mackay Sugar Cane Farm

Proposed
48
Energy Savings
48.7
Savings
13,239
Industry
Cane
Irrigation
Flood
Pumps
Centrifugal, Diesel pump
Technology
Variable Speed Control, Solar Photovoltaic, Diesel Pumping
Capital Cost
$22,100

Farm Profile

A recent energy audit in the Mackay region on a 275ha Sugarcane farm split into three sites could reduce energy consumption and costs and improve on important energy and water cost indicators. On talks with the farmer, the major focus of the energy audit was to improve efficiencies, lower costs and improve profitability, rather than increasing productivity.

To tie in with the farmers discussion recommendations covered in the audit included: 

  • Replacing the star delta starters on three pumps with Variable Speed Drives (VSD) 
  • Replace the diesel winch pump 
  • Install 10kW Solar PV system 

Table 1 Audit recommendations, energy and cost savings. 

Recommendation  Cost to Implement ($)  Energy Savings (kWh)  Cost Savings ($)  Payback Period
(years)
Emission Savings
(tCO2-e) 
Replace star delta starter with 30kW VSD  3,500 4,420  2,939  1.2  4.1 
Replace star delta starter with 45kW VSD  5,300 8,060  1,996  2.7  7.4 
Replace star delta starter 37kW VSD  4,500 12,400  3,039  1.5  11.4 
Replace winch pump (Diesel)  3,800 8,000  2,912  1.3  7.4 
Install 10kW Solar  5,000 20,000  2,353  2.1  18.4 
Total  22,100 52,880  13,239  1.7  48.7 

 

Currently, all three pumps are being throttled back leading to a reduction in operating efficiency. Replacing the star-delta starters with new Variable Speed Drives (VSD) will eliminate this requirement with the pump now operating at the correct pressure, reducing energy consumption by 24,880kWh. Star delta starters are often used to limit start-up current. The motor will start winding up in a star wiring configuration and once ready move to delta at the required operating speed. It is an “older” style of load reduction control whereas the new technology found in VSD can lead to greater efficiency gains. Varying the frequency allows the motor to spin at the required operating speed which varies greatly when moving water through irrigation systems. They can also help limit irrigation pipes bursting, as water pressure ramps up slowly and can stop pump operation should one occur. This goes beyond a purely energy efficiency gains as time spent fixing irrigation lines can be better spent managing the farm. 

A tariff review also showed that post 2020 cost savings of $2,297 per annum could be achieved by changing tariffs, additional to the total energy efficiency savings of $13,329 per annum. Cost of the improvements is $22,100 with a payback periods for all five projects at 1.7 years. Further savings include approximately 8,000kWh per annum from replacement of the diesel winch pump and generating approximately 20,000 kWh of solar power to operate a bore pump, with potential export to the grid. 

 Energy and Productivity 

Energy is one part of the complex link involved in farming and natural systems. Often energy, water, production and climate are linked. A comprehensive energy audit will consider these factors and more in order to reduce costs and consumption onsite while maximising profit. 

With no limitations to inputs of water, sugarcane production in the Mackay region and the tonnes of cane produced across 3 major soil types can be dependent on the type of irrigation system. Further, the regions rainfall events are spiking mid-season and early growing and late maturing phases in the crop cycle are experiencing reduced rainfall leading to reduced yields.  

With water availability low, at an average of 1.4ML/ha, the focus from a productivity and economics position is to focus on reducing the cost of applying water and ensuring that water is not applied on later ratoons, where the cost of application may produce negative returns.  

The savings applied from recommendations, tariff changes and practice change of taking the crop from the 6th ratoon and reducing to the 5th ratoon will increase net returns from $379 to $440/ha. From installation of all the recommendations in the audit, the sites overall annual energy consumption can be reduced by 48% to 56,982kWh per annum, and its emissions can be reduced by 48.7t CO2-e. The cost of applying water at sites one and two could be reduced from $155/ML to $105/ML, while site three is $82/ML.  

 An energy audit is a good investment 

An energy audit is a great first step in moving a business towards a more efficient future by reducing energy use, costs, and Carbon emissions onsite.  

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. 

See our range of agricultural energy efficiency case studies HERE and Subscribe to our bi-monthly energy e-news HEREIf 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 in by the Queensland Farmers Federation with support and funding from the Queensland Department of Energy and Public Works.

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