Baseline Description: Conventional center pivot irrigation not utilizing SIS practices.
Baseline Energy Use: 1209 kWh per year per Acre

A 1500-foot long center pivot will cover 162 acres.  Water use depends on crop type and electrical energy use is dependent upon water use, pumping lift, and pump efficiency.  Navigant’s “Northwest Agricultural Irrigation Market Characterization and Baseline Study” indicates a median regional irrigation water energy intensity of 403 kWh/acre-foot when taking various well lifts and pumping system total dynamic head into account (Navigant, 2013).  (Energy intensity goes down when surface water is used.  Median energy intensity of water consumption is 434 kWh/acre-foot in Idaho; 343 kWh/acre-foot in Oregon; and 289 kWh/acre-foot in Washington).  Assuming an application of 3 acre-feet/acre, the water energy use is about 403 kWh/acre-foot x 3 acre-feet = 1,209 kWh/acre-year.  

The 2013 USDA Census of Agriculture indicates that the majority of irrigators in the Northwest do not use SIS so instead rely on condition of crop, feel of soil, or personal calendars to schedule their water applications.  Some begin to water their crops when their neighbors begin irrigating.  A minority of farmers use soil moisture-sensing devices or rely upon schedules by water delivery organizations (USDA, 2013 Pg Table 22, Methods Used in Deciding When to Irrigate). 

There are no manufacturers of SIS systems.  Commercial services vendors across the region gather weather data, offer soil moisture monitoring services, and use evapotranspiration software tools (to determine water applications), and report preparation that meet specifications for energy savings claims. 

"Typical" Savings: 17%

Comments:

A 10% reduction in water and pumping energy use translates to roughly 121 kWh/acre for the example cited.  A water use reduction of 16.5% is taken to achieve the typical energy savings of 199 kWh/acre per year determined by Navigant.  Energy savings vary widely based upon pumping lift and pump efficiency; crop type, soil type, rainfall, and water application equipment efficiency.  Energy savings claims are based upon use of an RTF specified protocol and calculator.

According to the 2008 Farm and Ranch Irrigation Survey put out by the National Agricultural Statistics Service (NASS) there are 3.2 million acres under center pivots in the Pacific Northwest Water Resource Region.   Assume that about 50% of the acreage is managed by SIS, so the potential number of units replaced is thus 1.6 million acres.

Installed first cost per: Acre

Comments:

Growers typically pay agricultural consultants to provide SIS services as well as other services that support their successful operation, including pest management, fertilization, etc.  It is therefore difficult to isolate the cost of the SIS services.  With an incentive payment of $4.85 per acre, it has been demonstrated that growers are willing to adopt SIS practices.  A typical utility-sponsored SIS program consists of payment of an annual incentive to service providers to assist growers to implement SIS management practices.  With a typical annual incentive payment being $4.85/acre, full subscription in a program of this type would require an annual regional cost of $7.76 million per year.  (Note: this does not include additional utility incentives that may be required for recruitment of growers, utility administrative costs, marketing costs, programmatic costs and report preparation costs). 

Cost Effectiveness:

Simple payback, new construction (years): N/A

Simple payback, retrofit (years): N/A

The measure life for SIS is considered to be one year, as it is not cost-effective for all end users and many would discontinue the practice absent the BPA incentive.  Consider a typical Washington state 900 gallons/minute mid-level application pivot (with a 20-psig pressure regulator) that is supplied by water from a well that is 100 feet to water.  The pivot operates 2000 hours per year.  Assuming wire-to-water pump efficiency of 60%, the annual energy consumption for this scenario is 103,774 kWh with the existing pivot package.  A 10% reduction in pumping energy use is equivalent to 10,377 kWh/year, valued at $622 at an electrical rate of $0.06/kWh.  As a typical pivot serves 162 acres, the cost for the irrigation water management services is roughly $786, which exceeds the value of the energy savings to the end user.  Therefore, in this example, without an incentive, the annual costs of an SIS service will exceed the energy savings achieved by SIS.  The incentive required to compensate growers for this lack of cost effectiveness would be $164 per pivot.  However, utilities have found that an incentive of $4.85 per acre, which translates to roughly $786 per pivot, is what is required to get a reasonable fraction of growers to be willing to participate in the programs. 

Energy savings, and the cost-effectiveness of SIS are greater for wells with greater pumping lifts, so in these cases cost effectiveness for the grower may be achieved.   Note: with an incentive of $786 per pivot and energy savings of 10,377 kWh, the cost to the region for the conserved energy in this example is $0.075/kWh (without taking transmission and distribution benefits into account).   Given a regional average savings of 199 kWh/acre, the cost to the region for energy conserved decreases to only $0.024/kWh.  This is a technology that is cost-effective for the region even though it is not always cost effective for an end user.