Pump Efficiency for a Queensland Sugarcane Farm

Overview

A sugarcane farm in the Mackay region sought to optimise its irrigation systems to reduce energy costs and improve efficiency. The farm operates five pumps supplying irrigation water to centre pivots and lateral move systems. A Type 3 Energy Audit conducted by Saturn Engineering Group focused on two key pumps—the 110kW KSB pump and the 90kW TKL pump. These pumps irrigate fields through two centre pivots, either individually or simultaneously, depending on crop demand requirements.

Challenge

The farm consumed 69,400kWh of electricity during the 2022/23 financial year under SAC Large Tariff 44. However, in the 2023 calendar year, consumption surged to 188,300kWh due to increased irrigation demands during dry periods. This seasonal variability often pushed the farm’s electricity usage beyond the 100MWh annual threshold, which triggers a transition to SAC Large Business Tariffs, that imposes higher network and demand costs. The farm required strategies to manage energy use efficiently while maintaining its irrigation capacity. The energy audit identified water losses in the pipe network, ranging from 15.7% to 34.1%. Additionally, a pressure surge was observed during the shutdown process of KSB pump, caused by the valve prematurely closing before the pump had time to reduce speed. The KSB pump had an oversized motor for the required task, causing a low load situation.

Proposed Solutions

Water flow measurements taken at the pump and again at the centre pivots, indicated significant losses across the pipe network, with losses as high as 34.1%. It was recommended to repair leaks to minimise inefficiencies and improve overall irrigation performance

The shutdown process of the KSB pump caused a pressure surge due to premature valve closure. Implementing a gradual pump shutdown process, controlled at the pump, with open pipes would eliminate the surge, protecting the infrastructure and maintaining system integrity.

Replacing the existing 110kW motor on the KSB pump with a more efficient 90kW motor was evaluated. The load on the current 110kW motor was not low enough to cause a significant drp in motor efficiency. Replacing the motor would marginally improve efficiency, saving 552.8 kWh annually, the $18,000 capital expenditure resulted in a 59.7-year payback period and a 2.2% ROI. Given the minimal savings, this replacement was not recommended until the current motor reaches the end of its operational life.

Installing a 100kW solar system with 386.6kWh of battery storage was assessed to reduce grid electricity consumption by 71,792.8 kWh annually (based on 2023 consumption), saving $13,768.49. However, the $454,818.50 capital expenditure resulted in a 33-year payback period and a 3.0% ROI, making it financially impractical under current conditions.

Results

The audit revealed that both pumps were performing efficiently, achieving energy usage rates between 3.44 and 3.57 kWh/ML/m head—well within acceptable standards. By addressing pipe leaks and optimising the pump shutdown process, the farm could enhance system performance without significant capital investment.

Conclusion

The energy audit highlighted the farm’s strong operational efficiency while identifying targeted improvements to reduce energy costs and protect infrastructure. Repairing pipe leaks and refining operational practices offered immediate, cost-effective benefits. However, larger capital investments, such as motor replacement or solar installation, were deemed unnecessary at this stage.