The 27 ha farm irrigates all year round using groundwater producing roughly 5,000 units per ha per year. Energy consumption varies around the harvesting and packing seasons. As there are three varieties of crops produced, there are also three main harvesting seasons. Site operations during these harvesting periods follow a similar process of cooling, sorting, packing then storing.

The farm already had a 30kW solar system installed on the large workshop roof. The annual energy consumption for the site during the 2018-2019 period was 102,000kWh, with 32,000kWh generated by the solar system and 70,000kWh supplied by the grid at a cost of $16,000.

The current energy consumption on the farm consists of:

• Refrigeration system: includes 4 cold rooms.
• Irrigation: a centrifugal pump already fitted with a Variable Speed Drive (VSD).
• Other minor uses: including lighting, processing line and compressed air systems.

The energy audit showed how improving the current systems can lead to energy and cost savings. The audit recommendations summarised in Table 1 are:

• Insulation: repair and maintain door seals on 3 cold rooms, improving temperature control.
• Cold Room Maintenance: external the condenser and evaporator coil to maintain the optimal efficiency of the cooling system.
• LED Upgrade: improving the processing room lighting system thus allowing the doors to be closed during operations to reduce cooling losses and refrigeration energy consumption.
• Roof on Cold Rooms: install a roof on cold rooms 3 & 4 to reduce thermal gains.
• Pump Upgrade: upgrade the main irrigation pump with a 12 – 17.5 kW VSD to improve system efficiency and provide greater flow rates to parts of the farm.
• LED Lighting Upgrade: light fittings upgrade in 57 lights in 4 areas.

Likewise, within the analysis immediate no cost or low-cost maintenance measures were identified, as follows:

• Annual cleaning and maintenance schedule for on-site solar PV array to improve system efficiency, lifespan and total energy savings.
• Continue annual maintenance and cleaning of cold room coils.
• Repair damage to cold room roof to reduce moisture ingress within cold room panels.
• Identify and fix a small leak in the air compressor.
• Review irrigation leakage and blockages prior to the upgrade of the main pump.

Table 1. Costs and savings from audit recommendations.

The grower has proceeded with all the recommendations, which have been measured in a Measurement and Verification (M&V) process, as outlined in Table 2. This case study focuses on the pump upgrade.

Irrigation system energy consumption has been reduced from 4.36 kWh/ML/m head to approximately 3 kWh/ML/m head, an improvement of 33% in pumping efficiency.

The increase in flow rate for parts of the farm is delivering improved production estimated between 10-20% and $8,000 of additional revenue per year. This will result in 17,500 kWh/year of additional energy consumption at an extra energy cost of around $4,000.

Table 2. Estimated and Actual annual energy and costs savings.

Since the energy savings measured for refrigeration and lighting upgrades are the same as those estimated, it seems that the lower cost savings have been influenced by a lower energy tariff during the monitoring period. The pump upgrade has generated almost 4 times more cost savings than expected given the productivity gains, having outweighed the net increase in energy use.

A real-time energy meter was also installed on the pumping circuits, the workshop, packing shed and the solar PV system. The device will allow the business to monitor and understand their energy consumption, aiming to find further demand reductions onsite. Read more about that HERE.

The establishment of SMS and email alerts for if the Solar PV system shuts down has also been recommended in the audit. This will allow controlling the system in real-time, assisting in achieving maximum performance.

Following implementation, the farm has reduced energy consumption by 9% and costs by 53%, including productivity gains, with Carbon emission savings of 8.7 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 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.