VSDs lead irrigation efficiency measures for Gunnedah cropping enterprise

by Gerry Flores, David Hoffmann, Leigh Rostron and Phil Shorten, NSW Farmers

Working with the NSW Farmers’ Energy Team, the Kensal Green farm in Gunnedah identified significant energy saving opportunities over the short, medium and long term. Heading the list of opportunities was the use of variable speed drives (VSDs) on pumps, as well as proper ballasting of the farm’s new tractor.

Just south of Gunnedah is Kensal Green, an irrigated farming property that grows cotton, wheat and other grains. Owned by Tagmor Ag, and managed and operated by farmer Scott Morgan, the farm uses no-till planting and is located on a historic flood plain. 460ha of the 720ha property are irrigated.

During periods of flooding, or when there is sufficient moisture in the soil, the farm implements ‘double cropping’, meaning that after harvest, a crop is planted directly on top of the previous crop to take advantage of the latent soil moisture.

As in much of the country, water is a scarce resource at Kensal Green. To maximise his water allotment and minimise costs for water use, Scott uses moisture probes to prevent overwatering and has undertaken work to ensure low seepage from his dams and reservoirs.

Scott also uses as much water as possible from the free-flowing river adjacent to his property when this water is available. With a long-standing interest in energy efficiency, Scott retrofitted a VSD on his number 1 bore and installed two 10kW solar PV systems.

To drive further cost reduction opportunities, Scott contacted the NSW Farmers Energy Team to participate in the energy innovation program.

Working with Scott, the NSW Farmers’ team developed an energy profile of Kensal Green’s operations, then identified and prioritised efficiency opportunities and, finally, created a plan for implementing efficiency projects over time.

Energy profile insights

The property uses approximately 160,000kWh of electricity and 40,000 litres of diesel per year for tractors, other vehicles and pumps (used to run various bore, transfer, and storage and lift water pumps for irrigation) (Tables 1 and 2).

Table 1) Kensal Green’s energy breakdown by energy type

Fuel Type Consumption (p.a.) Units Conversion to GJ factor GJ Cost Cost per Unit Cost /GJ
Diesel 41,759.00 litres 0.0386 1,611.90 $62,220.91 $1.49 $38.60
Electricity 163,228.63 kWh 0.0036 587.62 $42,500.00 $0.26 $72.33
Total/Averages: Total: 2199.52 Total: $104,720.91 Average: $0.88 Average: $55.46

Tables 2) Kensal Green’s energy breakdown by end-use purpose

Fuel Type Purpose Energy Used (GJ)
Diesel Tractors & backhoe 1,021.086
Diesel Lateral irrigator 294.055
Diesel River, storage and transfer pumps 221.024
Diesel Farm utes 75.733
Electricity Bore and lift pumps 548.023
Electricity Homestead and other 39.600
Totals Total: 2,199.52

Scott assembled information on all of the farm’s energy-using equipment and estimated fuel/energy use per year (Table 3).

Table 3) Kensal Green’s register of energy-using equipment

Equipment Description Equipment Description Energy/Fuel Type Qty of Energy /Fuel use p.a.
JD 8130 235 hp (5 years old) Diesel 13,560.00 Litres
JD 8235R 235 hp (new) Diesel NA (not used yet)
JD 7800 120 hp (95 model) Diesel 3,744.00 Litres
JD Header 9500 120 hp (98 model) Diesel 2,921.00 Litres
JD Picker 9970 120 hp (98 model) Diesel 5,981.00 Litres
Sub bore pump electric motor #1 75kW (4 years old) Electricity 75,812.33 kWh
Sub bore pump electric motor #2 75kW (3 years old) Electricity 63,551.06 kWh
Re-lift pump China 16″ electric motor 37kW (8 years old) Electricity 12,865.24 kWh
Homestead and other (20 yrs +) Electricity 11,000.00 kWh
Storage pump 20″ axial flow Volvo a100 !00 hp (8 years old) Diesel 1,908.67 Litres
Storage pump 12″ china Deutz 60 hp (3 years old) Diesel 1,908.67 Litres
River pump 20″ china Volvo TD100 140 hp (8 years old) Diesel 1,908.67 Litres
580K BackHoe Diesel 247.00 Litres
Lateral irrigator (2 years old) Diesel 7,618.00 Litres
Farm utes (12 years old) Diesel 1,962.00 Litres

The farm has three John Deere tractors: a new 235hp, a five-year-old 235hp, and a 120hp from 1995. It slso uses six pumps. Two of these are bore pumps (both 75kW, both electric); two are used for storage (a 60hp and a 100hp, both diesel powered); and there is a 140hp diesel-powered river pump and a 37kW electric re-lift pump.

The diesel pump on the Mooki River pumps water into the channel leading to crops or to the lift pump for it to be stored in the reservoir.

Kensal Green has a roof-mounted PV system (on a barn) and uses conventional silicon cells, while another PV system is ground-mounted beside an irrigation channel and uses thin film amorphous silicon cells.

Identifying and prioritising cost-saving opportunities Scott referred to the fact sheets provided by the NSW Farmers Energy Team and, with assistance from energy consulting group Energetics, generated a list of potential cost-saving opportunities.

This list (Table 4) includes simple paybacks that were quantified using calculators available through the Energy Innovation Program.

Table 4) Identified efficiency opportunities and their expected savings/costs

Measure Energy savings Energy cost savings ($) Up-front cost ($) Payback (years)
QW: Adaptive driving 2,194 $3,272 $0 0
QW: Ballasting & tyre pressures 1,141 $1,701 $851 1
QW: Vehicle maintenance 1,316 $1,963 $982 1
Diesel to electric pump 10,087 $2,774 $0 0
VSD on pumps 33,289 $9,154 $22,886 3
Voltage optimisation 20,000 $5,500 $110,000 20
Power Factor Correction 0 $2,750 $6,875 3
Solar PV 13,820 $3,801 $25,080 7
Solar pumps 7,960 $11,871 $75,471 6
Wind 16,200 $4,455 $68,493 15

Although more than $40,000 in potential fuel and electricity savings were identified, it was unrealistic to expect Scott and his small team to be able to progress every opportunity. Therefore, a prioritised list of projects was developed using business criteria that reflected Scott’s farm plan.

The criteria included cost reductions, decreasing his use of diesel, and having a seven-year maximum payback period for any investments.

Variable speed drives (VSDs)

Prior to his involvement with the Energy Innovation Program, Scott Morgan retrofitted a VSD on one of his bore pumps in pursuit of energy savings. The energy consumption of this bore pump will be analysed regularly with a view to refining the specific savings it enables (compared to the previous operation).

However, expectations are that slowing the speed of the motors by 20 per cent has the potential to save Scott 50 per cent of his pumping costs. Extending the use of VSDs to two additional electric pumps, in addition to the one that Scott had already modernised and is using, was another opportunity for him to make energy savings on-farm.

Variable speed drives on electric 75kW bore pump and 37kW electric re-lift pump

VSDs reduce power draw at times when the pumps do not need to run at full power. The identified energy savings are outlined in Table 5.

Table 5) Expected savings and costs for VSD opportunity

Estimated upfront costs ~$1,000 (estimated costs of courses, labour, tyre pressure gauges and leasing tractor weigh pads)
Expected yearly savings $3,919.92
Simple ROI 2 months
Notes The ROI and savings figures are based on existing fuel prices and do not take into account future price fluctuations For more information on this measure, please see the NSW Farmers fact sheets on tyre pressures and ballasting for efficiency.

Tractor optimisation (ballast and tyres)

Scott also set up a new spray tank for his tractor. Given the driving practices of his operators, and management of tyre pressures and ballast points, it was estimated that savings in fuel consumption of approximately 10 per cent could be made to his fleet of tractors (Table 6).

Table 6) Expected savings and costs for ballast & tyre optimisation opportunity

Estimated upfront costs $22,886 (inclusive of purchase of new variable speed pump drives & labour and installation costs)
Expected yearly savings $6,963.81 (expected 35{87a03eb4327cd2ba79570dbcca4066c6d479b8f7279bafdb318e7183d82771cf} savings from current pumps’ operation)
Simple ROI 3.3 yrs
Notes The ROI and savings figures are based on existing electricity prices and do not take into account future price fluctuations or the opportunity for eventual electric generation from non-grid sources (wind, biogas, solar). For more information on this measure, please see the NSW Farmers fact sheet on variable speed drives on pumps.

Total potential savings

Scott’s team used the energy innovation templates provided by NSW Farmers and Energetics to develop an action plan to progress his priority projects.

Embedding energy efficiency into farming operations
The action plan Scott intended to implement at Kensal Green identified energy-efficiency opportunities and allocates projects over the short, medium and long term.

Incremental steps are the key to a workable action plan

In the short term (within 12 months), Scott pursued adaptive driving practices, ensuring that all the farm’s tractor tyres are inflated adequately and that the ballast set-up of tractors
is optimal for critical operations.

Like 50 per cent of farmers questioned under this program, Scott believed his operators could do more to apply adaptive driving practices, such as using ‘Gear-Up-Throttle-Down’, to maximise efficiency and engine RMP. He also began to log fuel use in order to understand better where and how fuel was
being used.

Training courses with a potential return of $2,200 (given Scott’s current tractor use) are available for less than $200. Other savings are available in proper ballast set-up and tyre pressure adjustments that would bring potential savings of $1,700.

This compares with a cost of around $800 in additional maintenance and ballast adjustments when switching implements (spraying to sowing, et cetera).

Medium-term opportunities (two to three years) included advanced water-monitoring controls to improve irrigation effectiveness, and blending natural gas into diesel-driven pumps and tractor engines to help them run more efficiently and on a lower-cost fuel mix.

VSDs in this case are considered medium-term as Scott prepared his budget for the next season. Voltage optimisation is also considered a medium-term opportunity, as investigation into the power rating of all equipment, especially motors, is necessary to ascertain potential savings.

Long-term opportunities (eight to ten years) included incorporating localised solar PV into power pumps, and examining the potential of powering pumps and engines using biogas or biofuels sourced from local on-farm waste or from nearby agricultural operations.

Case study courtesy of aginnovators.org.au. To read the full case study visit the website. Or for more information about energy and pumping in agriculture, visit http://www.aginnovators.org.au/project/solar-powered-pumping-initiative.


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