Facilities with heavy water needs—such as farms, golf courses, and commercial green spaces—spend a large portion of their energy usage on irrigation, particularly for operating the pumps that their processes rely on. For example, pumping water can be as much as 30% of a farm’s total energy use.
Prioritize system maintenance At the beginning of each season, check your irrigation system to make sure it’s performing optimally. Keep your pumps serviced and well-tuned, and keep electric motors, switches, and control panels free of dirt, insects, and bird nests. Check connections for tightness and lubricate moving parts as needed. Check for correct motor impeller alignment, worn nozzles and shaft sleeves, leaking gaskets and drains, and dried-out pump packing and bearings. At season’s end, thoroughly clean and lubricate components to prevent deterioration during periods of dormancy.
Optimize pump operation You can find significant energy savings by optimizing the way your pumps and irrigation equipment work. We discuss all of these options and more in our Managing Energy Costs in Agriculture topic, but we’ve collected some of the most effective options here.
- Test your well pumps; aim for 60% efficiency
- Upgrade to premium-efficiency motors, particularly if repair costs would exceed 65% of replacement cost
- Install variable-frequency drives to reduce energy use when flow rates are low and allow the pump to start and stop more slowly
- Consider replacing aging pump components such as shaft sleeves, wear rings, packing, and impellers
- Ensure your system fittings are appropriate for system usage
- Take advantage of surface-water sources, and ensure that both suction and discharge systems are operating efficiently
What are the options?
Almost all irrigation runs on centrifugal pumps, which use impellers to spin the water in a housing, moving the water via centrifugal force. If a centrifugal pump has more than one impeller and casing setup, it’s referred to as a multistage pump, with pressure increasing each time the water passes through an impeller-casing pair. Centrifugal pumps cannot pull any air, only water, and must be primed by filling both the pipe and casing with water before starting the pump. Most centrifugal pumps can hold water via a valve so that you don’t need to prime the pump after the first time.
End-suction centrifugal pumps End-suction pumps are best suited for smaller volumes of water. These pumps are close-coupled to the electric motor, so that the pump itself is mounted on the motor’s drive shaft and the pump case is bolted on so that the pump and motor look like a single unit (Figure 1). This is why the terms “pump” and “motor” are often used interchangeably.
Almost all portable pumps are end-suction centrifugal pumps. This portability also results in them being great booster pumps for situations where the water pressure in an irrigation system is too low for sprinklers to operate.
Submersible pumps Submersible pumps operate completely underwater, with pump and motor making up a single unit (Figure 2). They can be a good choice if you have access to any sizable amount of standing or running water via wells, ponds, lakes, or streams.
Submersible pumps tend to be more efficient because they only push water, they don’t need to draw it in first. Because they are already underwater, they don’t need to be primed.
Turbine pumps A turbine pump is a centrifugal pump that’s mounted underwater and attached by a shaft to a motor mounted above the water (Figure 3). The shaft usually extends vertically down a large pipe. The water is pumped up this pipe and exits directly under the motor.
Turbine pumps are efficient, and they’re a good fit for larger pump applications, such as farming. Often they consist of multiple stages; each stage is essentially another pump stacked on top of the previous one to form a chain that increases operating pressure.
How to make the best choice
Selecting the best pumps can be difficult. If you’re inexperienced or unfamiliar with pump selection, it can be well worth the time and expense to hire a professional to suggest options. Alternatively, if you know your irrigation system’s operating pressure (in either “head,” which is measured in feet, or pounds per square inch) and volume flow rate (gallons per minute), you can also contact a pump dealer, and they’ll be able to provide suggestions. Make sure to know your water supply laws and limitations, and be mindful of whether your water source is intermittent or if objects or debris end up causing blockages, since operating pumps without any water can cause damage.
Once you know the pressure and flow requirements of your system, research the available pump models and select one that meets your requirements. Manufacturers should be able to provide you with a performance curve for a specific pump (Figure 4). When reading this curve, keep in mind that there is a trade-off between pressure and flow: higher pressure means lower flow, and lower pressure means higher flow.
What’s on the horizon?
Pumps mainly improve when motor efficiency does. Alternating current (AC) induction motors have long been the industry workhorse, and they’ve benefited from incremental efficiency gains over the years. As efficiency standards continue to tighten, “super premium efficiency” motors may become mandatory. AC induction motors are near their technological limit and cannot reach these new standards without adding high-cost materials, so industry personnel will be looking to different motor types—such as permanent magnet motors or induction motors—to make further efficiency gains.
Who are the manufacturers?
- Berkeley (a Pentair brand)
- Franklin Electric
- Gorman-Rupp Pumps
- Goulds Water Technology
- Rain Bird
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