Alaska Power Company’s goal for this project is the development and assessment of a hydrokinetic project in the Yukon River, near Eagle, Alaska. Originally, APC was working with UEK, a hydrokinetic turbine manufacturer, to develop site-appropriate technology. Recently APC has contracted with ABS Alaskan, Inc. who will, in a joint venture with New Energy Corp., provide the turbine equipment for the project. The New Energy Corp. technology is similar to the technology deployed at Ruby in 2008, but with a larger generation capacity. Due to the large potential and interest in hydrokinetic technology in Alaska, this project will seek to collect data on many vital questions for all hydrokinetic projects, including environmental interaction, performance and efficiency, deployment challenges, support design, debris avoidance, and economics.
The objectives of the Yukon Hydrokinetic project was the demonstration of technology that could be used produce electricity from moving water without the construction of large, expensive and potentially environmentally damaging dams.
Eagle, AK, is a rural interior city on the Yukon River. According to the 2010 census, the year round population of Eagle was 86. Eagle is accessible by Taylor Highway from the United States and the Top of the World Highway from Canada. However, during the winter months, these roads become inaccessible. The community is also accessible by air, with regular flights from Fairbanks and Tok into a nearby state-owned gravel airstrip which provides transportation all year.
Like most rural communities within the state, Eagle is reliant on diesel generators
for electricity production. The objective of the Yukon hydrokinetic project was the development and demonstration of a cost effective solution to expensive diesel generation. Remote communities like Eagle and Eagle Village suffer from high diesel costs when transportation options are limited. Alaska Power and Communication spearheaded this project as an investigation into the potential of hydrokinetic power for the purpose displacing diesel use in meeting Eagle’s electricity load demands, which range from 70kW to 150kW. Reducing diesel consumption, and replacing it with a renewable option, would lower electricity costs for residents.
In 2008, 2009, and 2010, a 5kW turbine using the same technology on a smaller scale to the Eagle project was installed on the Yukon river at Ruby Alaska. This project failed to generate significant power due to it’s proximity to the bank of the river was not able to access sufficient current for operation. The failure of this project taught valuable lessons for the implementation of a successful hydrokinetic project, there must be a clear understanding of the moving water as a resource. Ruby also suffered from debris issues. While the barge had a debris diversion device sub-surface debris proved devastating. In addition ice proved a significant challenge and the device was only usable during the summer months between breakup and refreezing. Transmission was yet another challenge faced during the Ruby project, there were various issues with the cable used for transmitting. The first cable used was simply laid across the river bed, and was worn through within a matter for days. A more durable cable was used in later trials, but proved unwieldy.
The Eagle project included a larger turbine (25kW) that was designed to provide power to Eagle and Eagle Village. During design, many of the lessons learned from the project at Ruby were taken into account.
steps in the project included:
- Resource and Site Characterization: After the issues with the project at Ruby, it was important for the successful deployment of the the turbine at Eagle to understand the resource and site fully. The site assessment generated a complete physical profile of the river site with a variety of survey methods. These methods examined river depth/bottom topography sediment movement current velocity and flow profiles for optimizing turbine electricity generation, and a sub-bottom profile and bottom sampling to determine the best anchor for the turbine placement.
- Understand debris, sediment load, ice formation and breakup, and turbulence: These can significantly affect the engineering of every part of the turbine and it’s infrastructure.
- Sediment is at it’s highest during the summer months when the turbine would be operational. Sediment can abrade key parts of the turbine.
- Ice formation Ice formation poses significant risks to the project. Ice can hit and damage the turbine. Ice dams and resulting floods pose risks physical risks to the turbine and it’s supporting infrastructure and the community. In addition the severe flooding events can change the hydrologic characteristics of the river.
- Debris can seriously damage the turbine as was learned in the Ruby project. For the eagle project, understanding, and mitigating debris impact was important. An upgraded version of the debris deflection device used in the Ruby project was designed for Eagle.
- Turbine Technology Selection: Initially the project planned to deploy a UEK turbine, however due to events outside project control, that turbine was not deliverable. A 25-kW turbine was selected to be installed on a double-pontoon barge that would allow the vertical-axis device to be adjusted to current velocities allowing for maximum power generation.
- Anchoring: The correct type of anchor was needed to secure the turbine and the barge to the river bottom that was appropriate for the river floor as determined by the bottom profiles done by Terrasond during site characterization. It was determined that a combination deadweight penetration anchor system was most appropriate. A 36,000 pound anchor was used.
- Transmission: Due to the issues with the cable used at Ruby, it was key to find a cable that would prove successful in conditions at Eagle. Several different solutions were investigated including a bore which was determined to be too expensive. A custom-made, armored power cable with protective metal bands reinforced the 3-phase conducting cables, which were encased within a PVC jacket. About 600 feet of this cable connected the turbine to the on-shore station.
- Permitting A host of permits were required for the installation of the turbine. Studies were required to ensure that the turbine would not negatively affect young salmon. In 2008, APT applied for a pilot project license from the Federal Energy Regulatory Commission which oversees all Federal and State Hydroelectric projects. This pilot project license applies to hydrokinetic applications which are:
- Less than 5MW
- Less than 5 years long and are removed before the end of the license term
- Located in an area approved as not “sensitive” by FERC review, also based on stakeholder comments
- Able to be removed or shut down quickly if necessary with full test site restoration
- Accompanied by the required information on environmental study, monitoring and/or analysis with proof of measures for “safeguarding the public and environmental resources”
The Electric Power Research Institute (EPRI) estimates that Alaska boasts up to 40% of the country’s total river hydrokinetic potential harnessing this potential would be highly beneficial to communities near these resources, however the technology is still in the development stage. Initial results of testing at the Eagle site showed flow levels at 2.5 meters per second, which lies in the ideal 5-7 knot range needed for hydrokinetic power production. After the contract with UEK was terminated, the use of a New Energy Corporation 25-kW vertical axis turbine. The turbine used was a Darrieus type turbine. These types of turbines look similar to an eggbeater, a vertical shaft descends into the water, four blades are connected to this shaft which can be lowered into water at various angles to utilize the current most efficiently. The shaft, turned by blades powers a generator on a pontoon barge. The barge also permitted maintenance to be performed on the turbine which allowed APT and ABS crews to remove debris from the turbine.
To learn more about hydrokinetic technology please visit the hydrokinetic page
Data and Analysis
The turbine began operating in mid-June 2010. Throughout the course of its operation it typically produced between 15-18kW. At this output, the single installed turbine would have been capable of fulfilling 20-25% of Eagle’s daytime and ~40% of the community’s nightly
electricity demand, offsetting some diesel use in the process. The ability of the turbine to produce electricity successfully demonstrated the integrity of the hydrokinetic principle. However there were some issues with the transmission and integration systems. These issues compromised the ability to successfully use this electricity, as an overheating transmission cable and the limited capability of the power conversion system contributed to frequent outages.
Along with the transmission issues mentioned above, which had easy solutions, there were significant challenges that were difficult to overcome. Working on the barge proved challenging, and at times, dangerous to maintenance workers, thus making some simple solutions like the those related to transmission and integration difficult to implement.
One of the most significant challenges that was faced by both Ruby and Eagle was debris management. Debris buildup proved so significant that in the course of one night, debris were gathered up in a significant enough amount to swamp the barge. A 12 man crew was required to work for a full day to clear debris. This was not an isolated event, both surface and subsurface debris damaged the turbine and barge on multiple occasions. Debris management is one of the main hindrances to the maturity of small in-river hydrokinetic technology.
The turbine was removed from the water in late September of 2010, after more damage was caused by debris and the Taylor highway was closed due to flood damage, limiting maintenance crew’s ability to reach the turbine and repair it.
Hydrokinetic technology has shown potential, however the challenges seen with these projects reflects that more research is needed especially in the area of debris management. The Alaska Hydrokinetic Energy Research Center (AHERC), located in Nenana is continuing to study hydrokinetics in Alaska.
This project is a Denali Commission EETG Program project. The funding goal of the EETG program is to develop emerging energy technology that has the potential of widespread deployment in Alaska and has the long-term goal of reducing energy costs for Alaskans.
Alaska Power and Telephone is recognized as one of the most progressive utilities in Alaska, the keys to AP&T's continued success lay primarily in its willingness to promote and develop long term reliable energy and communication solutions while capitalizing on the innovation and technical expertise of its skilled and dedicated employees
The Alaska Center for Energy and Power (ACEP), an energy research group housed under the Institute of Northern Engineering at the University of Alaska, Fairbanks, is serving as the program manager of the EETG solicitation. As the projects deal with emerging energy technology and by nature are high risk, high reward, ACEP’s technical knowledge and objective academic management of the projects, specifically for data collection, analysis, and reporting, is a vital component to the intent of the solicitation, i.e., providing lessons learned and recommendations.
New Energy Corporation
New Energy Corporation, based in Calgary Alberta, is a developer of in-stream power generation devices. They developed the turbine used in the Yukon hydrokinetic project.
ABS Alaskan is a renewable and remote power technology supplier.
TerraSond conducted hydrographic surveys of the river bottom for this project. They provide various geophysical services from various global locations, including Palmer, Alaska.
BioSonics offers a range of echosounder equipment for fish research.
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