The farm consists of 60 ha which are irrigated all-year-round producing 480 units per ha per year. Variability in energy consumption occurs within seasons, being highest in summer. The annual energy consumption for the site during the 2018-2019 period, in the two NMIs audited, was 50,541 kWh at a cost of $10,104.

Current energy consumption on the farm consists of:

• Irrigation system: 30 kW suction centrifugal pump and a pressure pump.
• Workshop shed with machinery.
• Packing shed: includes 2 cold rooms with air compressors, 3 dehydrators, 6 drying cabinets, a commercial dishwasher and a water heater.
• Other minor uses, including a house.

The farm also has a 5kW solar system installed on the suction irrigation pump.

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

• A 15.6kW Roof-Mounted Solar PV: to offset 50% of electricity consumption from the grid in the packing shed.
• Install a food temperature probe in the main cold room: to improve the efficiency of the system.

The audit identified some immediate no cost or low-cost operational adjustments as follows:

• Perform 6 monthly cleanings of the solar panels using water only to remove any build-up of dust and bird droppings as well as checking of the panels for any discolour or browning.
• Perform an irrigation audit on the sprinklers by taking random discharge samples. A target discharge variation should be 10% across the farm. A higher variation indicates a poor condition of the emitters and/or blockages in the laterals. Is recommended to replace all sprinkler lines if the variance is higher than 30%.
• Flush the sprinkler lines and laterals annually to remove debris build-up.
• Perform cyclic cleaning of the filtration system.
• Spread out load in the cold room to allow for better air circulation; aim for cold rooms to be filled to at least 60% capacity.
• Replace worn and damaged seals, identify areas of damage from trolleys and other equipment.
• Re-align doors and ensure they functioning to prevent unnecessary loss of cold air.

Table 1. Costs and savings from audit recommendations.

After consultation with the solar electrician, the grower proceeded with the implementation of a Roof-Mounted Grid-Connected 19.8 kW Solar PV with a 15kW connected to the main switchboard in the packing shed. The savings made 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.

*Extrapolated from 5 months of measured data and considering the seasonality of solar generation based on the audit calculations.

The greater savings obtained from the M&V calculations compared to those estimated in the audit have probably been influenced by the larger system implemented and the limited 5 months of measured data that was used to calculate the solar generation for a whole year. This period corresponds to the summer season and is likely to be lower in winter given the lower irradiation. To facilitate future monitoring of electricity consumption the auditor recommended installing adequate metering equipment with manually or remotely adjustable internal clocks.

The lower cost savings achieved have been influenced by changes in solar energy use. Only 13,375 kWh or 42% of total solar energy generated are being used onsite valued at $2,910 and around 18,623 kWh are being exported to the grid with a revenue of $1,464. Considering that 24,263 kWh – 65% of the total energy use onsite – are being imported from the grid at a cost of $5,279, there are significant potential savings from shifting consumption into the solar generation period. The total power balance of the farm, including solar exports and the energy cost distribution, are shown in the following figures.

The next step for the farm is to adjust energy usage to offset as much energy consumption as possible from the grid, which would lead to further cost savings. The revenue from feeding into the grid is lower than the cost savings from using the energy onsite: for every dollar of energy exported, around $3 could be saved if the energy were consumed onsite. If the farm were to shift 18,623kWh of energy consumption per year to coincide with solar generation times, they would save an extra $2,588 per year.

From the implementation of recommendations in the audit, the farm has reduced energy consumption by 63% and costs by 43%, including feed-in revenue, with Carbon emission savings of 25.9 t/CO₂-e per year.

Table 3. Pre and post implementation energy and costs 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 onsite.

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.