The addition of hydroelectric generating capabilities could benefit irrigation districts, municipalities and other waterway operators. Recognizing this untapped potential, Oregon’s North Unit Irrigation District in the U.S. installed a 3.24-MW system on its Main Canal.
By Jessica Andrews and Mike Britton
The installation of small in-conduit hydropower projects on existing infrastructure offers a significant untapped potential that is being recognized at both the state and federal level in the U.S. Working with Oregon’s North Unit Irrigation District, Natel Energy has identified additional potential for low-head hydropower on NUID’s Main Canal, harnessing a generating resource that would have otherwise been wasted.
Setting the stage
In 2007, the Oregon legislature voted to set standards for electric utilities and retail electricity suppliers to support portfolios of renewable energy facilities through a renewable portfolio standard (RPS), contributing to a greener Oregon.
In 2016, Oregon Senate Bill 1547 raised the state’s RPS target to 50% renewable energy by 2040, an increase of 48% from what was originally adopted in 2007 . With support from state agencies such as the Energy Trust of Oregon, renewable energy project portfolios are now receiving financial support to realize the greater RPS goal.
Oregon has a diverse set of renewable projects already under development, including hydro, wind, solar, and pumped storage. In central Oregon, in-conduit hydropower has grown in importance as a way to develop low-impact and cost-effective hydropower at existing infrastructure. Irrigation districts across the U.S. have installed power plants at diversion points and in-canal drops, which are traditionally used for flow measurement, to stabilize upstream heads and to dissipate energy where there is significant elevation change throughout the canal system.
|Buckets attached to the end of slats capture the kinetic force of the water, causing them to move between two fixed poles like a tank tread.|
Points of diversion pass water entering the canal and may have high head, which has meant that many of these sites were developed with Francis and Kaplan turbines. Because many remaining sites are lower head, less hydro has been developed, but these drops are where distributed generation can make a big impact. These distributed sites are often located in close proximity to transmission lines and consumers and impose minimal environmental impact, as power is generated at existing infrastructure and the flow is now used for two purposes: hydropower and irrigation or water conveyance.
Central Oregon is a focal area of agriculture so there are over 8 irrigation districts, many with seasonal flows and developable drops. Water conservation is a priority in the state and districts are completing irrigation modernization assessments by Farmers Conservation Alliance (FCA) for water conservation and energy generation potential. The results from the assessments are helping plan where hydropower can benefit ratepayers, Oregon’s RPS goals and the environment.
Based in Madras, Ore., NUID supplies irrigation water to about 59,000 acres of farmland in Jefferson County, drawing water from the Deschutes and Crooked Rivers. The district operates 65 miles of canals and 235 miles of laterals and 2 reservoirs Wickiup and Haystack.
Natel and NUID were introduced through a piping company who had been working with various other districts on hydropower and water conservation projects. Blackrock Consulting, the engineering firm who in 2009 completed a feasibility study for NUID identifying five potential hydropower sites, was brought into the development discussion as they were already designing a hydroelectric project in a neighboring district. NUID elected to work with Natel Energy starting in 2011 to develop one of those five sites as an in-conduit project on its Main Canal.
The Main Canal diverts water from the Deschutes River at Bend, Ore., and once water is in the canal it flows in a northerly direction before terminating just north of Madras. The canal was built for a maximum capacity of 1,000 cfs and is gravity fed, eliminating pumping expenses.
In cooperation with NUID, Natel Energy, located in Alameda, Calif., installed a 250kW hydroEngine at a drop in NUID’s main canal in 2015. The Monroe Hydro project, purchased by Apple, is located in Madras, was constructed by JAL Construction Company. They completed the work between December 2014 and June 2015 when water was not running in the canal. TOMCO completed the electrical design and installation. The hydroEngine itself was installed and commissioned by Natel engineers who also continue to monitor the system remotely and a NUID ditchrider has been trained to assist with onsite maintenance.
In 2016, NUID worked with FCA to complete a district wide irrigation modernization assessment that outlined the potential for gravity-fed and pressurized hydropower, water savings and environmental improvement opportunities within the canal system.
The report supported the installation of hydropower at low-head sites in the main canal. Natel Energy performed its own assessment of the district’s Main Canal to locate sites that meet the criteria for the hydroEngine.
Site selection accounts for head, flow, proximity to distribution lines and land ownership and a significant factor was whether or not they would require the installation of costly grid-connection infrastructure. Several sites identified can be designed with co-located solar for additional annual generation, while seasonal irrigation canal flows produce hydropower during peak agriculture energy consumption.
The linear pelton hydroEngine
Natel’s proprietary “linear pelton” (LP) units are a pure impulse, single-stage Pelton turbine that employ a unique drivetrain (see Figure 1 at left). This drivetrain features two parallel shafts, with carbon fiber belts linked between the shafts to form a horizontal loop. Buckets are attached to the ends of each of the segments that, when hit with water, cause the assembly to roll much like a conveyor belt. This motion in turn provides the kinetic energy used by the generator to produce electricity.
The low-head operating range of the LP makes it ideal for installation within the Main Canal (see Figure 2). The units are made to operate with head ranges between 10 feet and 65 feet, while the sites have heads ranging from 11 feet to 64 feet.
Meanwhile, the units can pass up to 450 cubic feet per second of water. So, with up to 700 cfs flowing through some parts of the canal, some sites could have two hydroEngines installed.
The infrastructure of each site fall under two umbrella categories: naturally lined (rocks or shot concrete) and engineered (poured concrete). The modular hydroEngine package reduces installation costs by having a base design that requires minimal site customization.
By using the same construction and electrical companies, the installation goes smoothly as the crews are familiar with the design and process for installation. Compared to one-off conventionally designed sites, installations can be more efficient.
In addition to having a smooth installation process, there are cost benefits beyond the design phase such as economy of scale in purchasing prefabricated sections of the design and also on maintenance. The installations are cost competitive for renewables, targeting less than 5 cents per kWh.
Installing the hydroEngine
The construction and installation schedule from Monroe Hydro provided guidance on construction timeline for site with hydropower potential within NUID. For Monroe, project construction began Jan. 5, 2015, after excavation was completed in December. The penstock and draft tube were delivered midJanuary and the steel building erected in February.
The powerhouse included a three-axis bridge crane used both at installation, and also to maintain the turbine and eliminate the need to bring in specialized equipment for every removal or insertion of the cassette or servicing the powertrain offtake.
The powerhouse electrical work was completed in early March, and the hydroEngine installation completed by the middle of June. The first penstock fill was completed without operation soon after, and on June 22, the hydroEngine was run with water — but without the generator being energized — up to full speed for the first time.
The initial sync and generation tests began on July 7, with the hydroEngine becoming grid connected for the first time. Commissioning tests took place mid-September.
Low-head distributed hydropower can provide renewable, clean energy generation using existing infrastructure. Natel is assessing the hydropower potential in the district for future projects that can provide benefits to the community.
“The district has long recognized the untapped potential its conveyance system could provide,” NUID General Manager Mike Britton said. “The district also realized that conventional hydro development projects were beyond the district’s capabilities, and, as such, has developed a model that works well for the district and partners like Natel.”
Power generated from the portfolio interconnects to PacifiCorp’s distribution lines, contributing to their Oregon RPS portfolio. The fully developed project will assist in meeting Oregon’s RPS goal, be a source of income for the district with an annual lease payment, and demonstrate distributed low-head hydro at scale.
Irrigation districts are an ideal location for low head hydropower if there is sufficient flow, 1 to 200 cms, and 3 to 20 m of head, as they are historically a single use water system.
By adding hydropower, the district leverages its resources, adding value for the ratepayers by being able to offset expenses. Natel’s hydroEngine is designed for a large representation of the hydropower potential that has not yet been developed. The company expects the installation timeline to be shortened to about 4 months due to further improvements on civil works and protective building reductions.
Jessica Andrews is a project development coordinator for Natel Energy. Mike Britton is the general manager at the North Unit Irrigation District.