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The Buckeye Project: Realizing the Potential of Low-Head Hydropower

Natel Energy installed its first commercial turbine system in an irrigation canal owned by the Buckeye Water Conservation and Drainage District in Arizona. The system works in waterways with as little as 5 feet of head.

By Ed Gerak, Joe Blankenship and Laila Winner

Natel Energy Inc. was founded in 2005 with the purpose of commercializing a new low-head hydropower technology, the hydroEngine™. Although the technology had been in various stages of design and initial field trials since the 1970s, it wasn't until the mid-2000s that the Natel team correctly assessed that the renewable energy market would welcome a renewed effort to develop environmentally friendly hydropower.

Natel's management team faced the challenges of any business attempting to introduce a disruptive technology: How to fund the path from design to manufacture and deployment of the product and how to convince a skeptical market that the product is reliable, low cost and efficient compared to long-established technologies.

Initial funding - sufficient to complete the design of the smallest model of a planned product family of five and to order parts for three machines - came from a small group of angel investors.

However, having a machine on the floor is not enough. The Natel team recognized that the only way to convince the market about new technology is to have a commercial-size unit running. That unit would provide sufficient operating data to demonstrate availability, reliability, and operating and maintenance costs. Perhaps most critically, it would demonstrate to constituents of the target market - irrigation and municipal water districts - that the technology could be installed in constructed waterways without interrupting their core business of providing water to customers.

Natel Energy installed its first commercial turbine system in December 2010 in an irrigation canal owned by the Buckeye Water Conservation and Drainage District in Arizona. The company's hydropower system works in waterways with as little as 5 feet of head.
Natel Energy installed its first commercial turbine system in December 2010 in an irrigation canal owned by the Buckeye Water Conservation and Drainage District in Arizona. The company's hydropower system works in waterways with as little as 5 feet of head.

Searching for a partner

In 2007, Natel was in discussion with a prospective licensee who identified irrigation canals and constructed waterways as a good first market for low-head hydro.

That prospective licensee broadened the discussion to include a consulting engineer whose business was assisting irrigation districts in the purchase and scheduling of electricity requirements. The engineer provided the introduction to the Buckeye Water Conservation and Drainage District as a prospective participant in demonstration of the Schneider Linear hydroEngine™ (SLH) technology.

With its allocation of power from the 2,078-MW Hoover project set to expire in 2017, the district had decided to reevaluate the potential for using its irrigation system to generate hydropower.

Convinced from previous field trials that the SLH technology would work, the district agreed to partner on a commercial demonstration of Natel's smallest model, the SLH10, rated to provide a capacity of 40 kW at 20 feet of head.

This installation was not intended to function as a source of revenue for the district, but rather to demonstrate a technology that could potentially provide 200 to 300 kW of generating capacity within the district's system by installation of other units at additional sites.

From Natel's perspective, this was a critical step toward achieving full commercialization of its technology. The hydroEngine is a scalable impulse turbine designed for heads as low as 5 feet in both streams and constructed waterways.

Unlike Francis and Kaplan turbines, which are characterized by complex geometries and high manufacturing cost, the hydroEngine features a simple, symmetrical blade design in which water flows across the curved blades mounted at the ends on a pair of parallel belts.

In operation, water enters a penstock, passes through the turbine and exits a draft tube at the velocity of the incoming water. The Natel package includes the engine, inlet throttle, penstock, draft tube, generator and PLC system, making installation as close to "plug-and-play" as practical.

The district's interest in partnering presented an opportunity for demonstrating the hydroEngine in a canal setting, particularly since the district had other prospective sites for installation of larger machines.

The canal setting also allowed the Natel team to experience preparing, filing and obtaining an exemption from Federal Energy Regulatory Commission licensing requirements, a necessary step in the process of installing hydro generation facilities in this market.

The South Extension Canal

The best site available for the SLH10 was on the district's South Extension Canal, at the last weir of the system before the water flows back into the Gila River. Before the project started, the South Extension drop featured a simple check structure not much changed since its construction 40 years earlier.

The weir consisted of 2-inch by 6-inch and 2-inch by 8-inch boards that were manually adjusted to affect the level of the upstream pool. This site was chosen because its 8 feet of head and 20 to 50 cfs of flow made it well-suited to an application of the SLH10 technology and because the district could easily adapt the installation to its then-current plans for updating the weir and lining the canal with shotcrete.

After the site had been selected, a partnership of the district, Natel, Stantec Inc. as the civil engineering designer and K.R. Saline and Associates as electrical consultant was crafted to design, build and operate the pilot SLH10 at the South Extension drop. The district committed to providing the site and undertaking modifications of the drop to accommodate the system.

Stantec committed to contributing the civil design. K.R. Saline agreed to contribute the permitting and electrical connection consulting necessary to obtain the FERC conduit exemption and formal interconnection agreement with the local utility, Arizona Public Service. Natel would provide the SLH10 system and its installation.

Once the full team was assembled and roles defined, several processes were set in motion, including the initial design to determine the housing of the unit, as well as the preparatory work of applying for the FERC exemption and filing an application for the interconnection.

Licensing, installation and interconnect

As a project in an existing canal drop structure, the SLH10 installation was eligible to apply for a "conduit exemption," a simpler process than obtaining a hydropower license from FERC. Natel prepared the bulk of the exemption application, with guidance from K.R. Saline.

With the FERC exemption process accomplished, work began on modifying the drop to effect the planned canal improvements. Preparation entailed re-moving the old boards that formed the upstream pool, preparing a foundation for an 11-foot by 17-foot pre-cast concrete vault to contain the bypass chute and turbine, and setting and sealing the vault against the concrete structure that was the previous weir.

Although other housing structures had been considered, a concrete vault was selected for reasons of safety and security, with the intention that all the components would be installed inside the vault, including the bypass and electrical boxes.

Installation of the SLH10 was scheduled after the FERC exemption had been granted in September 2009, to fit with the district's annual dry-up schedule.

On November 21, 2009, the Natel team arrived to install the upstream flow control gates and assemble the engine components. The draft tube was assembled in place and the team used a small crane to lower the SLH10, mounting frame and generator into the vault. The district was able to contribute critical manpower for the assembly and installation of the draft tube and security fence and participated in other "field fits" as the installation progressed.

In less than two weeks, the installation process was complete. In December 2010, Natel and the district filed for the interconnection agreement with Arizona Public Service.

In early April 2010, the interconnection process was complete, including the installation of the meter, a new pole and step-up transformers to convert the 480 V output of the plant to the 12.5 kV rating of the power line.

A learning experience

As the first hydropower project for the district and the first commercial installation of the hydroEngine for Natel, the Buckeye South Extension project presented a number of challenges.

Some field fits were necessary to match the mechanical parts to the structure and assembly. Installation of the draft tube took place in a driving rain. The district provided installation assistance throughout the process.

For the interconnection, the challenge was matching an already constructed control panel to designs provided by a newly retained electrical engineer. Finally, when the mechanical and civil part was in place, fencing and lights were added on top of the vault to maintain a high level of security.

Members of the Natel team agree the South Extension experience afforded valuable insights that will aid in streamlining the design and installation process for future projects. When asked what he would do differently next time, Natel Chief Technology Officer Abe Schneider, a mechanical engineer, commented on several aspects of the civil design.

"While the concept of using a pre-cast concrete vault is a good idea to help control costs, in the future we would recommend designing the flow bypass to go outside of the structure containing the power generation equipment," Schneider said. "We know now that passive bypass flow configurations are preferred. Additionally, we would configure the trash rack on an angle rather than perpendicular to the water flow so it can passively shed trash. Finally, as with all projects, clear and frequent communication between all parties is critical to ensure smooth execution of project tasks."

Natel Chief Executive Officer Gia Schneider observes that although there were a number of learning experiences in the project, there were also a number of things done well.

"In particular," she says, "the licensing process proceeded relatively well, due largely to the groundwork that K.R. Saline and Associates did with the relevant stakeholders ahead of filing the application. This ensured that all relevant stakeholders were aware of the details of the project prior to filing and that concerns were addressed in this pre-application phase."

As a demonstration project, the South Extension installation is fulfilling its purpose. Testing has validated hydraulic efficiency greater than 85%, and improved blade designs have already been installed.

The Buckeye project has received visitors representing numerous utilities, irrigation districts, and other owners of non-powered dams in the U.S., as well as interested parties from South Korea, Japan, Australia, Chile and Bangladesh. Lessons learned and knowledge confirmed during construction of the Buckeye project has enabled Natel to move forward with confidence with the development of larger, more economically significant projects, including a U.S. Department of Energy-funded project with North Unit Irrigation District in Madras, Ore. Finally, this project has given the district a new perspective on the possibilities of low-head hydropower.

Ed Gerak is general manager of the Buckeye Water Conservation and Drainage District. Joe Blankenship is director of sales and marketing and Laila Winner is a business analyst for Natel Energy.

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