Energy Estimator for Irrigation is the third of several tools from Natural Resources Conservation Service (NRCS) developed to increase energy awareness in agriculture. This NRCS energy consumption tool enables you to estimate energy cost of pumping water in the irrigation operations on your farm or ranch. NRCS technical specialists have developed these cost estimates based on irrigation methods for predominant crops in your State. This tool does not provide field-specific recommendations. It evaluates options based on user input. Steps to use the Energy Estimator: Irrigation Tool
Step 1: ZIP Code
To use this tool, begin by entering your ZIP code, then click Next:
Step 2: Hydraulic Factors and Your Irrigation System
There are several factors that affect the energy consumption and cost of irrigating your crops. The vertical elevation difference between water surface being pumped and pumping plant discharge point during pumping operations (i.e., for vertical turbine pump static water level plus draw down) referred to as lift, and system water pressure at pumping plant discharge point in pounds per square inch (PSI) are critical factors in determining energy consumption and operation cost. There are system modifications that you can perform that will improve the efficiency of your system that will lead to energy consumption and cost savings.
Enter the Well Lift in feet, System Pressure in PSI, and cost per unit of fuel/energy you use to power your irrigation system. Select "Yes" or "No" to the questions regarding the system modifications you have completed.
Step 3: Crops and Irrigation Volume
The crops available for selection are the most commonly irrigated crops in your State. These crops may not be the most common crops in your area, but they are significant crops in your State.
Instructions:
- Select a Crop.
- Enter the number of acres you irrigate for one Crop with the Irrigation System you selected. You may run this tool again to examine another Crop and/or Irrigation System.
- The Average Seasonal Application Depth for each Crop is the average gross seasonal water application depth (acre-inches/acre) for the selected Crop in your State based on the Irrigation System you selected. If you know your Seasonal Application Depth, you can enter that value and all computations will be based on the value you enter.
Step 4: Irrigation System Analysis
The table below indicates your irrigation system water use and cost estimates for your selected crop and compares it with our projected use and costs for your system after irrigation system modifications have been implemented to improve efficiency. The table also shows estimates of energy cost and potential cost savings if you were to implement recommendations of a pumping plant evaluation with the corresponding irrigation system modifications. Factors considered in the analysis include adding a flow meter, implementing irrigation scheduling and conducting system maintenance & upgrades. This tool does not provide field-specific recommendations. It evaluates alternatives based on your input. Changes in energy use and costs are reported as differences from your current system configuration based on your responses on the previous pages.
Assumptions
What is Well Lift?
The vertical distance, in feet, of the distance between the average level of water in the well during the irrigation season and ground level. If surface water is used, it is the vertical distance between the average level of the surface water and the pump. For the purpose of this program, the frictional loss of head due to the well drop pipe is assumed to be negligible.
Based on:
Static Suction Lift: The vertical distance in feet, when the source of supply is below the pump, from the surface of the liquid to the pump centerline. (Source: Cornell Pump)
Total Static Head: The potential energy due to the vertical distance between the pumping water level and the entrance to the distribution system. (Source MWPS-30)
What is System Operating Pressure?
The measured water pressure of the irrigation system. The iPAT tool will give the most accurate results if the water pressure is known close to the outlet of the pump.
Based on:
Pressure Head: The pressure energy necessary at the distribution system entrance to overcome losses and operate sprinklers at the design pressure. (Source MWPS-30)
Pressure ranges
Operating pressure will vary for each individual system based on initial conditions but a general range follows. The range includes friction loss from the pump to the point of application.
| Low pressure | 0 - 25 PSI | most surface and some drip/micro systems |
| Medium pressure | 26 - 59 PSI | some drip/micro and some sprinkler systems |
| High pressure | 60 + - PSI | some sprinkler systems |
What are Energy Units?
The energy units are as follows:
- Electric - dollars / kilowatt-hours $/kwh (The minimum is $0.001 and the maximum is $0.50.)
- Diesel - dollars / gallon $/gallon (The minimum is $1.00 and maximum is $9.99)
- Natural Gas - dollars / one thousand cubic feet $/MCF (The minimum is $1.00 and the maximum is $50.00)
- Propane - dollars / gallon $/gallon (The minimum is $1.00 and the maximum is $9.99)
- Gasoline - dollars / gallon $/gallon (The minimum is $1.00 and the maximum is $9.99)
Why these crops?
The crops available for selection are the most commonly irrigated crops in your State. These crops may not be the most common crops in your area, but they are significant crops in your State.
How were the Average Seasonal Application Depth values determined?
These values were obtained from the following USDA document:
USDA NASS 2008 Farm and Ranch Irrigation Survey, Table 28.
Estimated Quantity of Water Applied and Primary Method of Distribution by Selected Crops Harvested: 2008 and 2003. State average seasonal application quantities by crop found in the tables were converted to ac-in/ac and assumed to equal the average seasonal application depth in inches. Gravity system values were used for flood and furrow systems, sprinkler system values were used for sprinkler systems, and for microirrigation if values were not available for low flow irrigation. When values were available in the table for low flow irrigation, those values were used for microirrigation. How were estimates made?
The Energy Estimator uses national averages to estimate the energy savings for a particular farm.
A pumping efficiency is assumed for each different type of irrigation system.
The use of a flow meter, irrigation scheduling, and/or regular maintenance & upgrades typically reduces the amount of water pumped over the course of a growing season.
Pumping less water will result in some measurable energy savings.
In addition, conducting a Pumping Plant Evaluation and acting on the resulting recommendations has been shown to increase the efficiency of the pumping plant by 15%.
All of these figures are based on averages. Your own energy savings may vary from the estimate given.
What are the assumptions?
Estimated cost if a flow meter is used. Irrigation water must be measured if it is to be used efficiently. Measurement often results in a decision to use less water. Water must be measured to each field, and each set for optimum irrigation water management. A measurement at the diversion, lateral, or farm delivery point can be translated to each field if the water is not split and used on separate fields. Most water-measuring devices indicate the rate of flow and require a conversion to volume or depth applied. An irrigator needs to know how many acre-feet or acre-inches of water are being applied to a field of known area.
Estimated cost if Irrigation scheduling is used. Irrigation scheduling is deciding when and how much irrigation water to apply. The soil moisture deficit in the root zone must be measured (monitored) and irrigations scheduled in order to obtain good water management. Farmers use a number of irrigation scheduling methods that consider soil type, soil water storage capacity, crop growth stage, water availability and level of irrigator control. Scheduling generally involves monitoring plant available soil moisture, estimating current crop water use, and anticipating future crop water use during the scheduling period. Tools commonly used in scheduling include visual and or thermal measurement of crop condition, soil moisture sensing devices, rainfall monitoring, media Evapotranspiration (ET) reports, local crop ET networks, and commercial scheduling services.
Estimated cost if System Maintenance and/or an Upgrade is performed. A system must be maintained in order to be managed at its potential. Nozzles on sprinklers have to be replaced, drip emitters must be cleaned and replaced, fields need to be re-leveled, concrete ditches and structures for water control have to be replaced when they wear out or repaired when damaged. Replacement of old, worn-out, damaged, and obsolete systems is needed for efficient irrigation. The operator of a trickle or sprinkler system should use a pressure gage to periodically verify and regulate line pressure.
Estimates for Pumping Plant Evaluation. Well tests should be run to establish overall pumping plant efficiency. A comparison between measured values and attainable field pumping plant efficiencies would indicate the need for adjustments, repair, or system improvements, which could result in lower annual pumping cost. Want a more accurate estimation?
- If you need assistance running this tool, contact your local NRCS field staff.
Click to find your local NRCS office - For other sources of technical assistance and services you may want to contact the following:
- extension service
- irrigation or water districts
- Technical Service Providers
- pump or utility companies
- consultants
Definitions
Average Well Lift Distance in your State:
Average Seasonal Application Depth:
These values were obtained from the following USDA document:
USDA NASS 2008 Farm and Ranch Irrigation Survey, Table 28.
Estimated Quantity of Water Applied and Primary Method of Distribution by Selected Crops Harvested: 2008 and 2003. State average seasonal application quantities by crop found in the tables were converted to ac-in/ac and assumed to equal the average seasonal application depth in inches. Gravity system values were used for flood and furrow systems, sprinkler system values were used for sprinkler systems, and for microirrigation if values were not available for low flow irrigation. When values were available in the table for low flow irrigation, those values were used for microirrigation. Flow Meter:
An instrument used to measure the volume and/or rate of flow of water in a conduit or channel (Source: ASAE 526.2)
Irrigation Scheduling:
The process of determining when to irrigate and how much water to apply, based upon measurements or estimates of soil moisture or water used by the plant (Source: ASAE 526.2)
Pressure Ranges:
Pressure ranges
Operating pressure will vary for each individual system based on initial conditions but a general range follows. The range includes friction loss from the pump to the point of application.
| Low pressure | 0 - 25 PSI | most surface and some drip/micro systems |
| Medium pressure | 26 - 59 PSI | some drip/micro and some sprinkler systems |
| High pressure | 60 + - PSI | some sprinkler systems |
Pumping Plant Evaluation:
Pumping plant efficiency is the ratio of the amount of work done (output) by a pumping plant (pump and power unit) to the amount of energy required to do the work (input). Pumps and many engines and motors are designed to operate under a narrow range of conditions. They should be operated within this range for best efficiency. Pumps and power units are subject to wear, so close attention to maintenance is required to sustain desirable pumping efficiency.
An overall pumping plant evaluation can be conducted where "water or output horsepower" is calculated based on measured "total dynamic head" (pumping lift(ft) + discharge head (ft)), and flow rate. The fuel usage rate is measured while the pumping plant is in operation. The method used to measure fuel usage rate depends on the energy source. An overall pumping plant efficiency is determined and compared to the Nebraska Standard Pumping Plant Efficiency for the type of pumping plant evaluated. This comparison is usually expressed as a "Per Cent of Nebraska Standard Efficiency". Based on the results of the overall efficiency test, the producer can determine potential energy cost reductions that would be possible if the system was brought up to the standard. If the current system is at or above the standard efficiency, improvements may not be cost effective. A list of potential improvements is generally provided. Some of the potential problems may include
- Over loaded and under loaded engines and motors
- Natural gas pressure at carburetor too high, or too low
- Natural gas leaks
- Pumping plant valve problems
- Improper pipeline installations
- Electric motors improperly wired
- Damaged or improperly installed electric control panel
- Need for a change of spark plug, spark plug wires, cooling system service, or an engine overhaul
- Pump bearings or impellor needs replacing
- Irrigation system changes from a low pressure to a higher pressure system without changing or updating pump
Regular Irrigation Application System Maintenance and Upgrades:
Any of a variety of repairs or maintenance activities that reduce water loss during the irrigation season, or increase the efficiency of the irrigation applications.
Seasonal Seasonal Application Depth:
The Seasonal Application Depth of irrigation water in inches applied on the crop acres from the pumping plant during a growing season.
Based on:
Gross irrigation requirements: :The total irrigation requirement including net crop requirement plus any losses incurred in distributing and applying water and in operating the system. It is generally expressed as volume of water per unit area (acre-inches per acre; or inches). (Source: ASAE 526.2)
System Type:
Flood:
For the iPAT tool, this refers to any surface irrigation method that does not use furrows.
Based on:
Flood Irrigation, wild flooding: A surface irrigation system where water is applied to the soil surface without such flow controls as furrows, borders (including dikes) or corrugations.
(Source: ASAE 526.2)
Furrow:
Method of surface irrigation where the water is supplied to small ditches or furrows for guiding across the field.
(Source: ASAE 526.2)
MicroIrrigation:
The frequent application of small quantities of water as drops, tiny streams, or miniature spray through emitters or applicators placed along a water delivery line.
The microirrigation method encompasses a number of systems or concepts, such as bubbler, drip, trickle, line source, mist, or spray.
(Source: ASAE 526.2)
Sprinkler:
Method of irrigation in which the water is sprayed, or sprinkled, through the air to the ground surface.
(Source: ASAE 526.2)
Calculation Examples
Calculation definition
Reference document:
USDA, NRCS, National Engineering Handbook, Part 652
Chapter 12 - Energy Use and Conservation
|
Table 12-3 Nebraska performance criteria vs. overall efficiency 1/
| Energy type | Unit of
energy | wHp-h per
unit of energy | Performance
rating (%) | Overall
efficiency (%) | | Diesel | gal | 12.5 | 100 | 23 | | Propane | gal | 6.89 | 100 | 18 | | Natural Gas | mcf | 61.7 | 100 | 17 | | Electric | kWh | 0.885 | 100 | 66 2/ | | Gasoline | gal | 8.66 | 100 | 17 | |
1/ Efficiency given for electricity is wire to water efficiency, which is calculated at the pump site. Liquid or gas fuel is based on average Btu values.
2/ Overall efficiencies for electric motors vary from 55 percent for 5 horsepower to 67 percent for 100 horsepower. |
Energy Tool: Irrigation Calculation criteria
| Energy type | Overall Pumping Plant
efficiency (PPE 3/) | Unit Hp-h
(UHH) | | Diesel | 19.55% | 54.326 | | Propane | 15.3% | 38.33 | | Natural Gas | 14.45% | 362.647 | | Electric | 56.1% | 1.34 | | Gasoline | 14.45% | 50.735 | |
| 3/ Assumes that the existing pumping plant has a Nebraska Pumping Plant Performance rating of 85. |
Energy Tool: Irrigation Calculation formula
#1) SAF = SAI / 12
#2) CWU = AI * SAF
#3) CF = CvF * ((WL + (SP * SPF)) / PPE / UHH)
#4) TEC = UEC * (CWU * CF) |
Energy Tool: Irrigation Formula legend
| AI | Acres irrigated | | CF | Cost factors (Kwh per acre feet) | | CvF | Conversion factor = 1.3715 | | CWU | Current water use (in acre feet) | | PPE | Power Plant efficiency | | SAF | Seasonal application feet (in feet per acre) | | SAI | Seasonal application inches (in acre inches per acre) | | SP | System pressure | | SPF | System pressure (PSI) to feet conversion = 2.31 | | TEC | Total energy cost | | UEC | Unit energy cost | | UHH | Unit horsepower per hour | | WL | Well lift in feet | |
Calculation example: Flood, Electric
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Calculation example: Furrow, Natural Gas
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Calculation example: Sprinkler, Propane
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Calculation example: Microirrigation, Gasoline
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Calculation example: Sprinkler, Diesel
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