Energy Savers
Atherton Tablelands

Mareeba Irrigation Farm

Implemented
113
Energy Savings
57.6
Savings
9,800
Industry
Grains and Fodder
Product
Hay
Irrigation
Centre Pivot
Pumps
Centrifugal
Technology
Solar pumping, Variable Speed Control, Tariffs
Capital Cost
$43,500

Farm Profile

The farm produces around 7,000 tonnes of hay per annum with an irrigation system consisting of one centrifugal pump, pumping water from a reticulation system to a centre pivot. 95% of the electricity consumption on site is due to pumping. The farm is currently using the obsolete Tariff 62, pumping at night during off-peak times.

The farm produces around 7,000t of hay over 41 hectares, with most of the energy used for irrigation.  The annual energy consumption for the site during the 2018-2019 period was 63,642kWh at a cost of $14,052. 

The energy audit identified several opportunities to reduce energy consumption and cut costs including:

  • Installing a 40kW solar system with a 30kW inverter to cover base load power with possible export.
  • Installing an automated control system with an SMS alert in the pump station, with a capital cost of $3,500.
  • A change in strategy to day-time pumping using energy produced from solar on-site, with a change to Tariff 20.
Recommendation  System Cost  Energy Savings T62 (kWh)  Energy Savings T20 (kWh) 

 

Cost Savings T62 ($)  Cost Savings T20 ($)  Payback period T62 (Years)  Payback Period T20 (Years) 
40kW Solar PV 40,000      3,999  46,656  1,851  12,539  21  3.2 

After talks between the auditor, electrician, and the farmer, the best efficiency and production outcomes for the site were determined. The solar system has been designed to cover the load expected by the pump with any allowable export to the grid.

The 39.6 kW Solar array with 30kW inverter capacity has been arranged in an East-West configuration. As the irrigators run for long periods, the panels facing East will get to maximum capacity earlier in the morning with the panels facing West producing maximum power in the afternoon providing constant supply through the day.

As the inverter capacity is no larger than 30kW, the system was treated as a micro embedded generating unit keeping the connection process simple and meaning the farm is still able to export during times of no irrigation. Maintaining grid connection allows the irrigator to draw grid power when required.

The auditor recommended the farm move to a flat rate Tariff 20 and shift pumping to daylight hours while the solar PV System is producing enough energy. Implementation of solar PV will absorb the increased tariff rate and any potential price increases in the future reducing the overall energy costs and consumption.

The Farmer has implemented the Solar PV system and a Variable Speed Drive to reduce the speed of the motors due to high pressure delivered by the pump causing leakages in the pivot system. Further, ‘time’ efficiency measures have been achieved using automation on the centre pivot. With the main farmhouse around 10 minutes from the irrigator, regular drives are required to start and stop its operation. Additionally, the automation will reduce fuel usage and allow time to be better spent on the crop. Should the centre pivot stop working, an SMS is sent to a mobile device alerting the operator.

The savings made have been measured in a Measurement and Verification (M&V) process, as outlined in Table 2. 

Table 2. Estimated and Actual annual energy and cost savings. 

Metric  Audit estimation  M&V calculation  Variation (%) 
Energy Savings including exports (kWh)   46,656  72,260 55
Cost Savings including exports revenue ($)  12,539 9,815 -22

 

The lower cost savings measured compared to the estimated have been affected by the high amount of energy exported to the grid and the low 2020 feed-in tariff. From the annual solar generation, only 29,756 kWh are being used onsite valued at $6,474 and 42,504 kWh valued at $3,341 are being exported to the grid. However, if the farm was able to adjust energy usage to offset all the energy consumption from the grid, it would lead to further cost savings as the revenue from feeding into the grid is lower than the cost of using energy from the grid.  

By implementing the recommendations in the audit, the farm has reduced energy consumption by 113%, including the energy exported to the grid, and costs by 70%, including feed-in revenuewith Carbon emission savings of 57.6 tCO2-e per year. 

Table 3. Pre and post implementation energy, costs, and energy productivity improvements. 

Metric  Pre-implementation  Post-implementation  Reduction (%) 
Energy Consumption (kWh) 63,642 -8,618 113
Cost ($)  14,052 4,237 70
Energy Productivity (kWh/ton)  9.1 -1.2 113

 

The accuracy of the recommendations in the audit coupled with the specialist electrician’s advice provided the best possible outcome for the farm. Energy consumption from the grid could be further reduced by matching pump use with solar generation.

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.

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