From the energy audit and discussions with the local pump shop, and electrician, the best efficiency and production outcomes for the site included:
- Installing a smaller Pump and motor, and adding a Variable Speed Drive (VSD) with remote pressure sensors
- Adding a 40kW solar system with a 30kW inverter to cover pump load power with possible export
- A small solar system for the Farm shed
- Retrofit existing lighting with LEDs
- A change in strategy to day-time pumping using energy produced from solar on-site, with a change to Tariff 20.
Table 1. Audit recommendations comparing savings between tariffs.
||Energy Savings T62 (kWh)
|Energy Savings T20 (kWh)
|Cost Savings T62 ($)
||Cost Savings T20 ($)
||Payback period T62 (Years)
||Payback Period T20 (Years)
|40kW Solar System
|Pump replacement and VSD
|7.5 kW Solar System
|Retrofit lighting with LEDs
A 55kW pump was removed and downsized to 45kW. The pump, which supplies a small centre pivot and a large traveling irrigator was positioned lower to the water reducing suction lift and improving efficiency. To overcome the slope as the irrigator moves across the paddock a Variable Speed Drive (VSD) was installed on the electric motor. This controls the motor speed to improve the irrigation system efficiency.
The solar system will cover most of the load required by the new pump. A 39.6 kW solar array with 30kW inverter capacity has been installed and 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.
As the invertor capacity is no larger than 30kW the installation 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.
A new radio link has been established between the lateral irrigator, centre pivot, and the pump. This measures the pressure available at the irrigator or pivot sending the data back to the VSD, ensuring the correct water pressure is maintained. The pump will run slower using less power at the bottom of the paddock increasing up the slopes maintaining perfect pressure and even water distribution. Further, the radio link will allow remote starting and should pump stop or there is a fault with the pivot or irrigator than the pump will not operate.
By reducing consumption and generating power from solar PV, the farm is likely to reduce their consumption below 100,000kWh per annum and can access the small business tariffs, removing any possible demand charges.
With requirements to move off obsolete tariff 62 by June 2021, a move to tariff 20 will provide quicker paybacks from changes made to the pumping system. The solar and pump changes represent the highest cost savings. With the farm implementing the larger pumping recommendations they will move to the small business tariffs, once consumption has been reduced below the threshold.
The change of tariff will extend the payback period on the smaller solar system. In the future should the farm implement changes at the shed the savings from the irrigation changes will cover any potential difference.
The savings will be updated once measurement and verification has taken place onsite
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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.