September 12, 2008

With irrigation season ending, it's a good time to analyze the performance of your pumping plant during the past season. Identifying and correcting pumping plant inefficiencies can save thousands of dollars per year in energy costs. If you determine your pumping plant is below par yet this fall, you will have plenty of time to consider your options and schedule a well driller to repair it or replace worn or mismatched components before the next irrigation season.

Poor pump performance can be caused by several things, including:

• poor pump design for the current pumping conditions,
• a pump with excessive wear or one that's not properly adjusted, and
• inefficient power units.

Online Assessment Tool

I developed an Excel worksheet, Long_Term_Pump.xls, which is available free on the Web, to analyze a pumping plant’s efficiency. Access it on the UNL Extension Lancaster County Web site for irrigation at http://lancaster.unl.edu/ag/crops/irrigate.shtml. It's under the heading What Can Be Done About Irrigation Energy Bill. The user can run the worksheet online in most Internet browsers or save it to a computer and open it with MS Excel.

To use it, you'll need to know

• the type of energy used for pumping,
• the price per unit of energy,
• the type of water meter installed,
• the beginning and ending water meter readings,
• the average pumping water level,
• the average system pressure, and
• the total energy consumed over the test period.

If there is no water meter, the user selects "no meter" and estimates the acres irrigated and the gross inches of water applied.

The worksheet does all of the calculations necessary to analyze the performance of the pumping plant and reports the:

• acre-inches pumped over the test period,
• total Water Horsepower-hours for the test period,
• performance of the pumping plant, expressed as WHP-hours per unit of energy,
• performance rating, percentage of the Nebraska Pumping Plant Performance Criteria (NPPPC),
• potential energy savings if this pumping plant were operating at 100% of the NPPPC.

With high energy prices, it is vitally important for irrigators to identify pumping plants with low efficiencies so any problems can be corrected before the 2009 irrigation season. This handy performance calculator makes it easy to spot pumping plants that may require some attention.

Tom Dorn
Extension Educator, Lancaster County