Case Study 4: Hay, NSW, Flood Irrigation

One of the submersible flood pumps audited for pumping energy efficiency.

The NSW Office of Water (NOW) contracted Tallemenco (via a third party) to conduct a detailed pumping energy efficiency audit in Aug 2010 on a large flood irrigation farm in the Riverina district of NSW.

A 250 HP submersible (motor=0.83% effy) flood pump lifted water from the Murrumbidgee River into an earth channel from where it gravitated a couple of miles to irrigation outlets.

The audit measured pump efficiency plus friction losses across the lift pipe to the channel. The system pumped 4,540 AF/yr, approx $23,000/yr electricity cost at ave 10c/kWh and TDH was 17.7’, with a lift of 16.7’.

Measuring flow at the flood irrigation site audit. A stream velocity meter was used to measure a water velocity profile, hence flowrate, since the station’s propeller actuated flowmeter was considered in-accurate.

Measuring static lift at pump site using survey equipment. Pump suction in background.

Findings

This table summarises the findings in terms of $$/AF attributed to deficiencies in the pumping system.

It was found that the pump efficiency was well down, in addition to running off BEP.

Once overhauled, this pump would operate with a $9,270pa electricity saving.

OFF BEP component has not been considered since that is not recoverable in this instance.

The hydraulic losses from the pump discharge to the discharge channel were approx 1.0ft head, or 0.4 psi. This is considered optimal.

Head loss in this system is critical, since every additional 1’ head loss results in $800pa, or 5.5% additional cost with an overhauled pump.

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.