The freshwater barramundi farm at Cowley Beach consists of 38 ponds with a combined total area of approximately 55 hectares. Annual production is 1,150 tonnes of whole fish.
The ponds are aerated with paddle aerators to provide the required oxygen levels, with water supplied by several submersible river pumps and centrifugal booster pumps. The farm has its own processing facility where the fish are prepared for transport.
The main electricity consumption loads are:
The total annual energy consumption of the farm is around 3,500,000kWh at a cost of over $850,000. The farm also has 4 diesel generators to support the pond’s supply, which operate in an alarm auto-start and consume 500L of diesel every 8 hours.
To reduce energy consumption and costs onsite, recommendations in the audit included;
Table 1. Audit recommendations and savings.
| Recommendation | Estimated Cost to Implement ($) | Payback Period (years) | Energy Savings (kWh) | Cost Savings ($) | Emission Savings (tCO2-e) |
| Restructure of tariff | — | — | — | 41,450 | — |
| Sensors in pond aerator control | 814,000 | 6.9 | 645,000 | 116,825 | 522 |
| Pump upgrade | 30,000 | 3.2 | 49,950 | 9,320 | 62 |
| 60kW solar PV | 108,000 | 4.8 | 110,000 | 27,655 | 88 |
| Combined supply for solar PV | 500,000 | — | 100,000 | — | |
|
Total |
1,452,000 | 5.5 | 805,000 | 295,000 | 672 |
The energy audit recommended installing real-time Dissolved Oxygen (DO) sensors to automatically control the paddle wheel operation and improve the pond aerator control system. The audit also recommended replacing the manual chemical test performed three times a day, reducing labour time and associated costs. The system provides real-time data every 4 minutes, including DO levels and water temperature, allowing identify reductions in DO levels throughout the day, avoiding stressing the fish, especially at night. The system also monitors current draws of the individual aerators, assisting in monitoring the biofouling of the paddles as well as the gearbox and motor conditions.
The solar PV system recommended was only viable if all supplies were combined at a single point, which implies installing a new distribution line across the farm to connect the current 7 supply points into the same line. Although this solution has associated capital and maintenance costs, it can save fixed metering charges, reduce energy unit rates, and bring additional tariff structure benefits. Since all power consumed onsite would be under the same tariff, it would be possible to reduce the nigh time loads by matching the energy consumption with solar generation.
Alternatively, the installation of small solar PV systems dispersed across multiple buildings was evaluated, with the advantage that they would be less affected by climatic conditions, given their distribution, and would have less interference with voltage fluctuations. However, implementing individual PV systems at each supply point requires greater management with associated costs and time. See more information HERE.
At current production levels, a 23% decrease in energy consumption could be realised by installing all the recommendations in the audit, with 35% cost reductions and carbon emissions of 672 tCO2-e avoided per year.
An energy audit is a good investment.
An energy audit is a great first step in moving a business towards a more efficient future by reducing energy use, costs and carbon emissions.
An energy auditor will review your past energy bills, your equipment and the way your business operates. They’ll show you where you’re using excess energy and explain what you can do about it. Find out about what’s involved in an energy audit HERE.
See our range of agricultural energy efficiency case studies 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.
