Variable frequency drives can be a game-changer for your agricultural customers.
By David Stover
With a growing focus on maximizing energy savings while improving pump performance, advancements in motor technology and controls are transforming the agricultural market and resulting in the smarter, more efficient delivery of water.
While hydronic systems have a long history of automation in commercial environments, the big change lately has been the adoption of energy-efficient technology and smart devices for irrigation systems.
One proven method to significantly increase energy savings in agricultural pumping operations is the use of variable frequency drives. VFDs are electronic devices that vary the pump speed to enable the performance to be adjusted to better match the operating conditions of the irrigation well. When used in agricultural settings, VFDs offer many benefits, including:
Reduced energy consumption
By controlling the speed of the electric motor, farmers can control the speed of the pump motor to deliver only what their operation needs to function at optimal efficiency. Preventing over-pumping and over-pressurizing of irrigation systems can dramatically boost energy savings. VFDs also conserve electricity by allowing for slow or soft starts, resulting in lower electric costs.
Often applied to existing systems to increase overall system effectiveness, VFDs help pumps work more efficiently, thereby extending their product life and reducing energy consumption.
Elimination of mechanical drive components
Installing a VFD on an irrigation pump eliminates the need for expensive and inefficient mechanical drive components such as pressure-reducing valves and flow-control valves. Because a VFD can operate with an infinite variable speed, it can deliver the high or low speed required by the load without a speed-increasing or reduction device between the motor and load. This ultimately helps reduce maintenance costs.
Optimized system performance
Soft-start capabilities that gradually ramp up a motor’s operating speed greatly reduces the stress on the motor and related components so the pump system can last longer. The soft-start and stop function of VFDs also are beneficial in reducing water hammer. Especially with older irrigation systems, minimizing water hammer will prevent damage to the pump, piping, valves and other components, and reduce the potential for leaks and failures.
VFDs also enable farmers tocontrol the water conditions in an irrigation well. When combined with well depth monitoring and computer software, VFDs can be used to slow down pumps when wells near their water level limits, in this way preventing them from sucking air and cavitating.
Installing a VFD on a single pump serving multiple irrigation lines provides the flexibility to change pressures for different pumping requirements. For example, if one field is using a drip irrigation line and another field is using a sprinkler irrigation line, the VFD enables the pump to vary the flow of water while maintaining a constant operating pressure.
In other words, when cutting back on the flow, the pump will reduce in speed and the flow will reduce, but still keep as close as possible to the best efficiency point on the pump curve. As the system calls for a larger volume of water, the pump will supply more but still keep constant pressure.
Because a VFD maintains a constant discharge pressure regardless of the irrigation demand, the device enables the operation of one, some, or all irrigation lines depending on irrigation needs or pump capacity.
The remote monitoring capabilities associated with VFDs provide another means of managing water consumption and maximizing energy efficiency. A wireless monitoring and control system enables farmers to monitor operations remotely and control different aspects of the irrigation system from the convenience of a laptop, tablet, or smartphone.
With remote monitoring, farmers also have the capability to shut down irrigation pumps even when they’re not onsite, eliminating unnecessary pumping time. And when alerted to abnormal operating conditions, farmers can make immediate adjustments to ensure the system is functioning properly.
With government agencies continuing to offer incentives to farmers who implement more efficient equipment and practices, the use of VFDs for irrigation is gaining wider acceptance throughout the country. In many states, farmers are receiving rebates for using VFDs in agriculture and irrigation settings, and some electric utilities even offer farmers credits if they adopt VFD technology.
As saving energy and reducing operating costs are priorities for farmers, integrated drives and controls are proving to be game-changers in the agricultural market, giving farmers an entirely new level of control over system design and performance.
David Stover is the market development manager for turbine products for Xylem Inc. He has 16 years of expertise in the field of vertical turbine products and 40 years of industry experience. Stover is based in Atlanta and can be contacted at email@example.com.