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 $3,500.
- A change in strategy to day-time pumping using energy produced from solar on-site, with a change to Tariff 20.
||Energy Savings T62 (kWh)
||Energy Savings T20 (kWh)
|Cost Savings T62 ($)
||Cost Savings T20 ($)
||Payback period T62 (Years)
||Payback Period T20 (Years)
|40kW Solar PV
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.
|Energy Savings including exports (kWh)
|Cost Savings including exports revenue ($)
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 revenue, with Carbon emission savings of 57.6 tCO2-e per year.
Table 3. Pre and post implementation energy, costs, and energy productivity improvements.
|Energy Consumption (kWh)
|Energy Productivity (kWh/ton)
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
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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.