Nenana Hydrokinetic Turbine - An Emerging Energy Technology Grant Project
There is much interest in hydrokinetic technology in Alaska given the high cost of energy for communities located along rivers throughout the state. Hydrokinetics, however, is a pre-commercial technology seeking to address barriers to deployment (including debris mitigation, anchoring, deployment and operation, and environmental interaction) through technology development, demonstration, and research. This project sought the development and demonstration of an in-river hydrokinetic system by ORPC Alaska, LLC.
Hydrokinetic technology generates electricity directly from the natural flow of water. In contrast, hydroelectric technology produces electricity using the gravitational force of falling or flowing water. Traditional hydroelectric projects require damming or diverting water, while hydrokinetic projects are simply deployed into the resource. Potential hydrokinetic resources include ocean currents, tidal flows, and rivers.
Rural Alaskans pay some of the highest energy prices in the United States. In most rural Alaska communities, electricity is produced with diesel electric generators, which rely on expensive diesel fuel shipped to the community, often only once or twice a year. Alternative and renewable sources of energy are being explored around the state in an effort to stabilize costs, localize energy production, and create viable long-term communities. Alaska is estimated to contain about 40% of the total U.S. river energy resource. In Interior and Western Alaska, many communities are situated alongside large rivers with tremendous energy potential. While implementing a hydroelectric project is usually impractical for environmental and economic reasons, a hydrokinetics project may be viable.
Generating electricity using hydrokinetics holds great promise; however, the technology is still maturing. Testing in the villages of Eagle and Ruby has highlighted the challenges that this technology faces and the barriers that must be overcome before it is commercialized on a wider scale.
ORPC was awarded an EETG grant by the Denali Commission in 2009 to support research and development of its RivGen™ hydrokinetic turbine and to help the technology advance through the demonstration phase to a point where its use in communities around Alaska could be explored further. The original ORPC proposal called for the design, construction, and testing of the RivGen™ Power System along with support work to be conducted at Nenana (e.g., resource and debris characterization) to gain a Federal Energy Regulatory Commission (FERC) pilot project license.
The initial ORPC proposal was subsequently amended to address a variety of concerns, primarily the availability of funding and preliminary findings at the proposed test site. In addition, preliminary project work and resource characterization at Nenana emphasized high silt loads, high risk of damage from river debris, and the challenges of working in a river as large and powerful as the Tanana River. These site concerns were further emphasized by the experiences of both the Ruby and Eagle deployments.
Because of these concerns it was decided that the RivGen™ Power System would be built and constructed at ORPC facilities in Maine (already equipped for ORPC TidGen® Power System construction and testing, which would allow for significant cost savings) and the successfully tested system would be brought to Nenana for field demonstration and deployment after the EETG project expired. The pontoon support structure and anchoring would still be constructed and tested at Nenana, and ORPC would still pursue a FERC pilot license for the site for the anticipated future RivGen™ deployment at Nenana.
The completed project tasks and timelines were as follows:
- ORPC environmental and site characterization data collection for project design and FERC draft license application, to be performed by October 1, 2010
- Foundation and debris diversion literature surveys, data collection, and final reporting to be completed by December 31, 2010
- Prototype pontoon support structure and debris system fabricated, deployed, tested, and retrieved at theNenana site, to be performed July through September 2011
- Additional field work and final pilot license application to be completed by October 31, 2011
- FERC final license application to be submitted by December 31, 2011
- RivGen™ TGU built and tested at Eastport, Maine, test site by December 31, 2011
- Final report on Nenana site characterization work and foundation system and debris diversion system performance to be submitted to ACEP by December 31, 2011
- Final performance report on RivGen™ test to be completed by February 15, 2012
The chassis, foils, TGU, and driveline of the RivGen™ Power System were successfully constructed, integrated, and deployed in the Bay of Fundy for performance testing. The RivGen™ Power System was successful in converting moving water to AC power. Performance testing indicated that the RivGen™ turbine reached a maximum efficiency of 17%; the projected design efficiency, however, was between 25% and 27%. Although bearing friction has been identified as a significant contributing factor to system underperformance, ORPC is currently investigating a number of other factors, including, control system efficiency, generator efficiency, and turbine foil performance. In addition, ORPC is working on refining the control system to increase performance. Further demonstration of the technology will need to incorporate a fully integrated system (RivGen™ TGU, pontoon support structure, and anchors), address key differences between marine and riverine environments, and validate a deployment strategy for the system in remote riverine conditions with the use of locally available equipment and infrastructure.
As a result of the lessons learned from this project, ORPC intends to use a tiered approach for future in-river hydrokinetic development in Alaska. The first tier will be further demonstration and refinement of their technology in a marine environment, such as at Nikiski or the Bay of Fundy, utilizing available infrastructure (roads, testing barges, heavy equipment, etc.) and slack tides to optimize deployment strategies. The second tier will be deployment and demonstration in the Kvichak River at Igiugig, which provides ideal riverine conditions (clear water, low river sediment content, limited debris, etc.) for further testing and refinement of deployment and operations strategies. The third tier will include deployment and demonstration at the Nenana hydrokinetic testing facility, which provides a challenging river profile (high sedimentation and debris, etc.) common to many of the potential hydrokinetic sites around Alaska, but which also has available infrastructure to support further testing and refinement of deployment and operations strategies. The final tier will be the commercialization of the technology for wider deployment around the state.
ORPC has received funding through the EETF program to continue the demonstration activities initiated under this project with this approach. The goal of the EETF project is to deploy and demonstrate a fully integrated system (RivGen™ TGU, pontoon support structure, and anchors) in the Kivchak River at Igiugig.
Photo 1: ORPC Testing Barge, Energy TIde 2, Anchored in the Bay of Fundy. Courtesy Jason Meyer, ACEP.
Photo 2: ORPC Rivgen™ TGU (blue) and Chassis (yellow). Courtesy Jason Meyer, ACEP.
Photo 3: ORPC Rivgen™ Hydrokinetic Device. Courtesy Jason Meyer, ACEP.