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Cutting energy costs for irrigation.

Cutting Energy Costs for Irrigation

A computer program cut power consumption by irrigation pumps up to 20 percent--a savings that translates into more efficient food production and significant energy conservation.

Where irrigators use a pipe network to move water from multiple pumps to several center pivot sprinklers, cutting energy costs can be difficult and very laborious. Many combinations of pumps are possible to maintain the minimum flow and pressure as various pivots are turned on or off, depending on crop needs, but only one pump combination is the most energy efficient.

"The program we wrote calculates how much pressure is required from pumps to move water to center pivot sprinklers that the irrigator needs. If irrigators don't know the minimum pressure they need, it's often the case that they will use too much and drive up their energy costs," says ARS' Dale F. Heermann, an agricultural engineer stationed at Fort Collins, Colorado.

Electricity costs for large users can total thousands of dollars a month. Bills are based, as for private homes, on how much was used during the month. Like individual consumers, large users, including factories and farm irrigators, are billed according to peak demand for the billing period. The larger the peak demand, the more electricity costs.

"The computer knows the individual performance characteristics of each pump in the system and keeps track of the peak electrical demand of each pump station during the billing period," says agricultural engineer Gerald W. Buchleiter, also at Fort Collins. "The computer recommends the pump combination that can supply the minimum pressure needed for the operating pivots and at the least cost for that billing period."

Mercer Ranches near Paterson, Washington, has used the program since its release about 5 years ago. That operation lifts water about 450 feet from the Columbia River to irrigate 3,500 acres of potatoes, carrots, sweet corn, and asparagus. Six pumps at the main pump station, ranging in size from 600 to 1,500 horsepower, plus two pumps at a booster station, deliver water through nearly 15 miles of underground pipeline to 33 pivots.

"The program is especially valuable for regulating our variable-speed pumps to just barely meet minimum water pressure requirements of the system. However, implementing the recommendations under changing conditions was difficult because of the time it took to drive nearly 7 miles to make the necessary changes at the main pump station," says Dick Beightol, vice president of plant operations.

Last summer he purchased a radio telemetry system to control the pumps and to monitor a critical center pivot where it is difficult to maintain the correct pressure.

As Beightol makes irrigation changes from his pickup truck, he also keys in information about the pivots into a portable, battery-powered computer. The computer program recommends the least-cost pump combination and Beightol sends the appropriate commands to the main pump station via radio signal.

"The ARS program also offers help in designing new irrigation systems and improving old ones. By plugging in different pump designs and delivery paths, irrigators and engineers can learn the least expensive way to deliver water from a well or river to fields," says Heermann.

Dale F. Heermann and Gerald W. Buchleiter are at the USDA-ARS Agricultural Engineering Research Center, Colorado State University, Fort Collins, CO 80523. Phone (303) 491-8229.

PHOTO : Above: Each center-pivot sprinkler irrigates about 128 acres. (K-3015-3)

PHOTO : Right: Over 100 center-pivot sprinklers, controlled by a central computer, irrigate wheat, alfalfa, potatoes, and melons along the Columbia River near Hermiston, Oregon. (K-3016-8)
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Title Annotation:by using a computer program
Author:Senft, Dennis
Publication:Agricultural Research
Date:May 1, 1991
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