SUSTAINABILITY VICTORIA contracted Tallemenco to conduct a detailed pumping energy efficiency audit in Jan 2018 on a modern 350 head dairy farm in the Gippsland District.

An 8 yr old 1650’ long Center Pivot (CP) irrigated mixed pasture on the dairy farm. A 75 HP submersible pump on a VFD lifted 570 gpm, 66’from the underground aquifer and delivered it across level ground to the CP approx 2,130’ away via a 6” PVC pipe.

The audit measured pump efficiency plus friction losses across each major pipe and irrigation equipment sector. The pumped system had 380 AF/yr usage, approx $35,885/yr electricity cost at ave 20c/kWh and pumped head was 206.7’.

The residual pressure at the end of the CP was 10 psi.

The CP was also supplied from another pump 1 mile away.

Findings

The old and tired submersible well pump was down 10% on efficiency and running well to right of BEP, at 57% effy.

The 2,130 feet of 6” rising main from the bore/well had a H&W C Value of 112 and was undersized, resulting in 82’ friction to the CP.

Replacement of the 6” PVC pipe with 8” would result in only 13’ head loss, a saving of 69’ friction.

Optimizing the pipeline would result in saving $11,960 pa, whilst replacing the pump with a lower head pump operating at BEP would save an additional $6,850 pa.

Total savings would be 52% or $49.3/AF.

Ultimate pumping cost would be $44.7/AF.

To potentiate the savings, the pump needed to be changed out to a lower head pump with the same output 570 gpm, but with the correct BEP.

This was conveniently facilitated 12 months after the audit when the pump motor failed.

The pump was downsized from 75 to 50HP at 570 gpm, at the same time the pipeline was replaced with an 8” PVC.

ROI for the upgrade was 2.4 years, saving $18,800 pa energy costs.

In this case, a pump test only would have missed the extra $11,900 pa (33%) attributed to the optimization of the hydraulics.

Quantifying pumping energy efficiency in an irrigation system has long been understood to be made with a simple pump test. Ignored was the significant additional potential energy savings available in irrigation system pipelines due to poor hydraulics.

The WATER PUMPING INSTITUTE’s aim is to educate water engineers in the art and science of identifying hydraulic in-efficiencies in irrigation (and other water) systems. This is achieved through its training course “Pumping System Master Class (US)” with “Fit for Purpose” software which comes with the training course.

These case studies have been compiled as living proof of the feasibility and practicality of identifying (or incorporating into new systems) up to 50% hydraulic savings from pumping system energy audits. These case studies demonstrate the importance and savings advantages of quantifying hydraulic efficiencies when conducting pumping energy audits.