This case shows 22% potential energy savings by replacing the current irrigation pump with a more efficient unit, with estimated carbon savings of around 2.2t CO₂-e per year and a capital cost of $4,005. It further explores the connection between management practices, water, and the additional advantages that an energy and irrigation audit can provide.

The site currently draws water from a small DC pump located roughly 1km from the property. This pump is powered by two 5x75 watt solar panels that track the sunlight from a change in oil viscosity in a set of dampeners as the sun slowly increases their temperature. The water is pumped using a DC motor a kilometre from the creek through a 50mm main line to a holding tank controlled by a float valve. Two types of soil moisture probes are used on site including three G-Dots for visual clues, while two solar powered Davis probes are connected to a weather station console by Wi-Fi, which engages the irrigation decisions. 

The grape vines are then irrigated from water in a holding tank using a 5.5kW AC pump through a network of drippers. The site consumes 12,382kWh at a cost of $3,670 per annum. A 7.2kW solar system covers the site load including the house and part of the 5.5kW load from the irrigation pump located in the shed.  

A recent energy audit highlighted that efficiency gains in the pumping system could be achieved on top of the current systems in place, the recommendation included: 

• Replacement of the vine pump at a cost of $4,005 providing energy savings of 2,745kWh, $919 per annum and a payback period of 4.4 years. 

Table 1. Pre and Post audit metrics for the Vine Pump. 

After data logging with a flow meter and pressure gauge, the irrigation system efficiency was measured at 396 kilowatt hours per mega litre per metre of head (kWh/ML/m). The replacement pump, recommended based on the current measured flow (m3/hr) and Head (m) as tested, has the potential to reduce energy consumption by 22%. The suggested centrifugal volute pump has a higher efficiency class and would reduce this metric to 156.70 kWh/ML/m, a 60% reduction. 

 The site has been proactive and performed an irrigation audit which found some issues, these were rectified by: 

• The Vine pumps measured head and flow suggested a worn impeller; investigation discovered debris surrounding the impeller, reducing its performance, the debris was removed. 
• Replacing of all dripper and lateral lines was completed because the discharge variation of the emitters was very high at 76%;  
• Cyclic cleaning of the filtration system.  
• The DC motor has been replaced previously on occasion as a result of metal contraction caused by the extreme cold. Installing an insulated cover on the pump could fix further problems. 
• Flushing of the dripper lines and laterals annually to remove debris build up.  
• Implementing crop management practices including pruning the cordon arms to the first spur to reduce water transpiration from the vines, ultimately reducing pumping times and energy consumption. 

A more efficient pumping system will prevent over pumping to compensate for areas that require rectification. This also reduces crop water stress and improves yield uniformity. 

Moving forward further improvements were highlighted in the energy audit process. The solar panels that operate the creek pump are showing signs of age. The browning discolouration is associated with aging and from poor quality backing sheets. With the advances in solar and by replacing these there is potential to bypass the AC pump under optimal conditions and install batteries for night-time irrigation, should this prove feasible.  

With the help of a real–time energy meter, more HERE, the site is well informed to manually operate the pump when there is excessive solar generation to irrigate to field capacity. This requires monitoring of both the real time energy meter and the soil moisture probes onsite. These measures can further assist to lower both energy and water consumption onsite. 

Energy Audits for your Business 

An energy audit is a great way for a business to cut costs and boost productivity.  

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 in by the Queensland Farmers Federation with support and funding from the Queensland Department of Energy and Public Works.