Hybrid Energy System at a Queensland Table Grape Farm

Overview

A Queensland farm producing table grapes and lychees sought to enhance its irrigation efficiency while reducing energy costs. The property relies on three key pump sites—Pump Site A, Pump Site C, and a transfer pump system between two storage dams—to irrigate its crops. With Pump Site C recently upgraded it is response for a majority of the irrigation tasks, while Pump Site A is predominately used as a support pump. Rising energy costs, looming Tariff changes and increased demand prompted farm to participate in the Large Customer Adjustment Program commissioning an Energy Management Opportunity Assessment, which identified practical and cost-effective solutions to improve operations and lower energy consumption.

Challenge

The farm’s irrigation system consumed 491,254.99 kWh during the 2017/18 financial year, with Pump Site A alone using 175,230.3 kWh. The transfer pump consumed 56,257.3 kWh, and the remaining 259,767.4kWh consumed by Pump Site C, all contributing to significant electricity costs. Each pump site exhibited unique inefficiencies:

Pump Site A: This site consists of three 110kW Everflow 300FHM axial flow pumps that provide support to irrigate the table grape vines and lychee orchards when Pump Site C doesn’t have the capacity to meet demand. The pump site will be utilised to irrigate green sites that will be developed soon. This will require the expertise of a Certified Irrigation Designer for optimisation.
Pump Site C: This site features two new Southern Cross 250x200-500 mixed flow pumps, with a third pump slanted for installation soon. This is the primary pump site used for irrigating table grapes and lychees, connected to a combination of drip irrigation and micro-sprinklers. The pump operates inefficiently due to water flow and pressure misalignment with the existing irrigation schedule causing excessive energy demands.
Transfer Pump: A 55kW Batescrew 17-24-8.5 axial flow pump transfers water from the between to the two adjacent on-farm storage dams. The assessment highlights the importance of operating the pump within the design specification. The static water level was high due to the low storage dam level on the suction side. It is not a common practice to operate with lower water levels but has been done on occasions. When the system experiences high static water levels, pump efficiency is reduced to 41% compared to 78% at the designed operating level.

Proposed Solution

The farm’s irrigation scheduling is based on the experience of farm management, with an application rate of 8ML/ha determined through historical practices. To optimise irrigation efficiency, it is recommended the farm installs soil moisture probes across 11 locations. Each location will have two probes—one at the middle and one at the bottom of the active root zone—providing insights into soil moisture availability. This approach will improve irrigation timing and reduce overwatering, minimising energy and water costs, while improving production and quality.

A hybrid system requires careful planning and engineering. The following was an outline for a potential project to optimise energy efficiency and reduce operational costs at the farm’s irrigation system A staged implementation of a hybrid energy system is recommended, to spread capital expenditure. The hybrid system integrates solar panels, batteries, biodiesel generators, and advanced control systems, tailored to the farm’s irrigation requirements and electricity pricing.

Stage 1: Solar Energy Integration

Stage 2: Expanding Solar and Introducing Biodiesel Generators

Stage 3: Scaling for Increased Irrigation Demand

Installation of an additional 100kW solar system for a third pump to accommodate future increases in irrigated hectares.
Total estimated capital expenditure: $697,000 for 300kW solar installation, biodiesel integration, battery bank and system controls.
Cost Savings: Operating two pumps on Tariff 50 has an estimated costs of $89,369 p.a. and biofuel $37,230 saving 58.3% on energy costs.

Conclusion

Implementing soil moisture monitoring and a hybrid energy system will provide significant operational benefits, including reduced energy and water usage, improved irrigation scheduling, and a foundation for future precision irrigation systems. These practical solutions align with the farm’s goals of optimising efficiency while reducing costs and environmental impact. By leveraging solar energy, biodiesel generators, advanced controls, and soil data, the farm can achieve substantial savings, ensure flexibility for future growth, and enhance sustainability. Saturn Engineering Group is committed to supporting farms in implementing tailored energy solutions to drive cost savings and environmental stewardship.

Key Takeaway

By tailoring energy solutions to the specific needs of each pump site, farms can achieve significant cost and energy savings. Saturn Engineering Group remains committed to delivering innovative, practical strategies to support agricultural businesses in their transition to sustainable operations.