Using High Frequency Pump Monitoring to Reduce Energy Consumption
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In California, the financial cost of pumping irrigation water has seen significant increase in recent years. This is due to in large part to the long-term drought, which has forced a shift in water sourcing from surface water to groundwater aquifers. Groundwater is generally more expensive to produce, due to the high energy cost of pumping water from underground and amortization costs of constructing wells. Agricultural users have responded to price pressure in several ways: reducing water consumption with improvements in irrigation technique and equipment, improvements in pumping equipment, higher levels of monitoring of pump equipment condition, and shifting energy consumption to take advantage of time-of-use (TOU) rate structures. In regards to energy efficiency, there has been a significant shift to utilize variable-frequency drives (VFDs) to control irrigation pumps, many of which have been subsidized by a wide range of state and utility grant programs. Many users also utilize pump efficiency tests more often, which are often subsidized or provided free of charge by local utilities. While VFDs and efficiency tests certainly aid in reducing energy consumption and improving pump efficiency, they may offer misleading results for many systems. In particular, operations where the irrigation load varies significantly, and/or where there are multiple pumps connected to a single pressurized distribution system can see significant deviations from the nominal efficiency indicated by standard efficiency tests. Our approach seeks to use high-resolution monitoring of pump operational parameters (water flow, water pressure, energy consumption, pumping depth, VFD parameters) to more accurately assess true pump efficiency and pumping cost. More accurate information enables pump operators to better optimize their irrigation systems to reduce energy consumption (by optimizing which pumps to run and at what speed) based on segmented irrigation loads. Providing easy visibility to pricing information may encourage shifting irrigation operations to off-peak energy hours. Presently, this information is invisible to operators except in the form of long-term energy and water flow comparisons. To date, we have installed monitoring systems on three large-scale irrigation systems in California. Preliminary results indicate that real pump efficiency varies significantly from nominal tested values. Pumping costs often change by 20% with common variations in irrigation load. Future observations will show if providing this information to operators can impact irrigation practices and improve energy efficiency and/or lower average water pumping costs.