The farm has two peak packing blocks, February to April and June to August, with the highest energy consumption, producing around 100,000 units per year.

The annual energy consumption for the site during the 2018-2019 period was 427,300 kWh at a cost of $127,540, with a 100kW solar PV system already implemented on the roof of the packing shed and two small 5kW systems connected to the irrigation pumps.

As the shed operates seasonally, there are six months of low usage in September–January and May, with shutdowns of packing operations. In this period, the inverter of the installed solar system is periodically switched off due to export restrictions by Ergon, given the size of the system and its operating voltage. This management practice reduces the performance of the system and the potential income from the energy generated, which is expected to change with the new regulations of the retailer to be able to export the remaining power to the grid.

The energy consumption on the farm consists mainly of:

• Packing shed: a sophisticated conveyer system connected to Variable Speed Drive (VSD) units for sorting and processing.
• Three large cold rooms and two small cold rooms: relying on refrigeration units, fans, and a vacuum, to keep the product at the right temperature for storage and dispatch.
• Irrigation pumps: solar-powered.
• Air compressor: used for stapling boxes, air cleaning of production lines and hydraulic jacks.
• Workshop and office areas.

A recent energy audit showed how improving the current systems can lead to energy and cost savings. The audit recommendations are:

• Change Tariff 62 on the Processing Shed NMI to large demand customer Tariff 50, saving around $12,094 per year. Additional savings of around $1,919 per year could be achieved by changing another NMI from Tariff 65 to Tariff 20.
• Install smart metering in the main switchboard of the Packing shed: including an energy management program to allow for more efficient operation and scheduling of processes.
• Maintenance and monitoring of existing 100kW solar PV system on the packing shed: annual maintenance is recommended to improve the system’s performance to the optimal level, with regular revisions. Otherwise, a reduction in solar output of 10% is expected. If possible, monitoring and alerts should also be incorporated in the current inverter communications system to flag errors and minimise system downtime.
• Install VSD on cold room fan motors: to reduce their speed and add variability depending on the different load requirements.
• Pressure reduction on air compressor: from 10bar to 9bar to control air leaks.
• Install strip curtains on smaller cold rooms: to assist with reductions to the air losses and infiltration through the doorway.

Table 1. Costs and savings from audit recommendations.

*Calculated considering current tariff 62.

The farmer installed VSD on cold room fan motors and a smart metering device in the main switchboard. The savings made with the VSD solution have been measured in a Measurement and Verification (M&V) process, as outlined in Table 2.

Table 2. Estimated and Actual energy and cost savings.

The lower energy and cost savings obtained from the M&V calculations compared to those estimated in the audit have been influenced by the lower total run hours of the cold room fans during the measured period, having used the fans at full capacity only 53% of the time considered for the estimation of the savings in the audit.

From implementing the recommendation in the audit, the farm has reduced total energy consumption by 2%, costs by 3%, and Carbon emission savings of 8.5 t/CO₂-e per year.

Table 3. Pre and post implementation energy consumption, costs and energy productivity improvements.

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.

The Energy Savers Plus Extension Program was delivered by the Queensland Farmers Federation with support and funding from the Queensland Department of Energy and Public Works.