Advanced pump controls

While many in the irrigation industry may perceive that agricultural pumping systems are less sophisticated than their golf and landscape counterparts, in many ways the ag market has led the development of new control technologies for irrigation pumping systems. This, in turn, has helped growers better manage their pump systems and improve irrigation efficiency, while also saving on pumping energy costs.

In the ag pivot market, for example, manufacturers are utilizing cloud telemetry to control and coordinate pivots, pumping equipment, canal gates, flowmeters and crop sensors. There are many features of cloud telemetry that provide real value for irrigation managers. Having the information in a cloud database allows sophisticated algorithms to mine the data to generate reports, create advanced control logic and construct dashboards that can be viewed from any web-enabled device. A user’s password automatically determines which dashboard data is presented and in what language and local time. There are numerous advancements resulting from the integration of pump stations and pivot controls.

There are numerous advancements resulting from the integration of pump stations and pivot controls.

Eliminate pressure overload

Pump selection, regardless of the market, usually factors in a worst-case scenario of the irrigation system’s hydraulic requirements. This includes the maximum head loss due to elevation and the maximum friction loss based on the highest anticipated flow. In reality, the irrigation system only operates in this worst-case scenario for a fraction of its running time.

If the pump station is set to a single regulate setpoint based on this worst-case scenario, tremendous energy is wasted because the station is providing more pressure to the irrigation system than is needed. Advanced pumping systems can be programmed to adjust the pump output to compensate for these varying requirements.

For example, in deep well pump systems, the depth to water can vary greatly due to pumping drawdown and seasonal variations in the aquifer level. This maximum anticipated depth to water must be factored into the pump total dynamic head required even though the depth to water may be less for much of the watering cycle. By utilizing a variable frequency drive on the pump with a pressure transducer at the surface, the control system will be able to adjust the pump speed to precisely meet the irrigation system pressure requirements and reduce energy consumption. The controls can also monitor motor current and limit the pump rpm to avoid overload and prevent the pump from running too far out on its curve.

Manage system demands

In many scenarios, the land irrigated by pivots has significant elevation changes. Locating a pressure transducer at the end of the pivot allows the VFD-controlled pump to modulate its output to maintain the desired pressure at the pivot regardless of its location in the field. This eliminates the wasted energy that would result when there is over-pressurization in the low elevation areas of the field.

In larger systems where a centrally located pump station supplies water to multiple pivots with varying pressure requirements, determining the pressure required from the pump station is a more complicated task. Through today’s technology, it is possible to monitor which pivots are running and the pressure at each running pivot. Based on that cloud data, a control algorithm calculates the pressure regulate setpoint required and relays it to the pump station to ensure that the pressure supplied to the irrigation system exactly meets the requirements of the running pivots.

Measured energy savings of 25%-30% have been realized by this closed loop control method.

While this concept originated in the agricultural market, it is proving to be equally effective in the golf and landscape markets. These systems utilize transducers mounted on nodes in the piping system, and through coordination with the irrigation controls, the pump station’s pressure setpoint is adjusted to maintain the minimum desired pressure in the piping nodes where irrigation is occurring.

As irrigation equipment manufacturers in all markets add pressure sensors to their sprinkler offerings there will be more opportunities to refine dynamic pressure controls.

Managing multiple locations

Cloud telemetry enables water managers to aggregate data from hundreds of pumping stations to eliminate wasted time driving to locations to check on equipment. The data collected can be used to generate reports on water and energy usage, create alerts when there are problems with equipment and provide a histogram of the station’s operating conditions to help them troubleshoot issues (see fig. 1).

The California Department of Transportation wanted to monitor the operation and water usage of nearly 300 pumping stations along the freeway interchanges near Bakersfield and Fresno, California. Typically, the department would deploy crews to drive to the various locations to record flowmeter readings and check for any fault conditions on the equipment. This was a time-consuming and labor-intensive operation. In 2016 they engaged with a manufacturer to install new cloud telemetry systems on their existing and newly purchased pumping equipment. Now a single manager can view hundreds of pump stations around the city in a single satellite view and quickly scan for any pump stations that have alarms. He can then drill into the individual station views to see precisely what is happening at each location. Working with the manufacturer they configured a rules-based logic and alarming system so when a pump station has an issue, an alert can be sent to the appropriate managers. That manager can quickly access the station from any web-connected device to determine the problem and either reset the alarm or dispatch a service crew to the site.

Pathways to the cloud

For CalTrans, their desired way to connect to the equipment was through a wireless Ethernet backbone they created to monitor the freeways, so an Ethernet RTU was utilized to connect the pump stations to the cloud. In most single pump monitoring applications a cellular RTU is collecting the data and transmitting it to the cloud through a cellular network. Large agricultural customers may prefer to have a radio network for their farms, so oftentimes radio RTUs are utilized to collect pump station data, which is aggregated at a bridge device to provide an Ethernet or cellular pathway to the cloud. This eliminates multiple cellular connection charges.

Rules-based logic for AI

With the vast amount of pumping equipment data collected in the cloud, there are opportunities to mine that data to create more intelligent systems and controls. Rules-based logic within the cloud environment allows sophisticated algorithms to watch for undesirable conditions like excessive pump cycling, vibration, pressure and level fluctuation, or excessive power consumption to create alerts and determine predictive maintenance requirements on connected equipment. Identifying problems like bearing vibration or motor over-temperature early allows the issue to be resolved before costly catastrophic failures occur.

Sharing the data

Collecting the data in the cloud allows for near-real-time collaboration and sharing with other cloud platforms. The pump station data collected can be shared, using an API protocol, with cloud-based irrigation scheduling controllers to allow more intelligent interactions. For example, if the pump station loses part of its pumping capacity due to a pump failure, that partial loss of capacity is shared with the irrigation scheduling, which responds by reducing the flow rate or prioritizing the schedule to ensure that critical areas are watered. Data collected on water usage and depth to water in wells can be shared with irrigation districts to better manage seasonal water resources. Energy usage can be monitored and shared with power utilities to help shed load when power outages are imminent.

Improving efficiency

A common phrase is “You can’t improve what you can’t measure.” This is particularly true for irrigation schedulers. Clearly there are constraints that determine irrigation schedules, but there is little feedback regarding the efficiency of one schedule versus another. By collecting energy usage and determining the kilowatts per acre feet or kilowatts per gallon pumped, the schedulers can compare the efficiency of each irrigation cycle and make refinements to maximize efficiency (see fig. 2).

Control in the palm of your hand

One of the many benefits of cloud telemetry is the ability to have instant access to equipment in the field from any web-enabled device. No matter where the operator is in the world, if there is an internet connection, they will be able to monitor and control the operation of their pumping stations from the cell phone they carry.

Rick Reinders and Chip Carlson are business partners and co-chief executive officers of Watertronics LLC.