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2016

Reports

  • Yakutat Area Wave Resource Assessment
  • Tschetter, T., J. Kasper, and P. Duvoy. "Yakutat Area Wave Resource Assessment"
  • Alaska Center for Energy and Power, Alaska Hydrokinetic Energy Research Center, 2016. Funding was provided by the Alaska Energy Authority and the City and Borough of Yakutat.

Yakutat is a community along the northeast coast of the Gulf of Alaska that is currently considering utilizing renewable, wave based electricity generation in order to lessen their reliance on diesel fuel for electricity generation. As part of this effort the University of Alaska Fairbanks carried out a study to assess the wave energy resource off of Yakutat’s Cannon Beach. Funding for the assessment was provided by the Alaska Energy Authority and the City and Borough of Yakutat. The study described herein utilized a combination of in situ observations and numerical modeling. The mean annual available wave energy at the mooring site is approximately 19.2 kW/m. While on an annual basis, this is less than sites off of Oregon or Hawaii (e.g. Kilcher, 2015), there is a large interannual variability in the Yakutat resource due to the frequent passage of storms over the Northern Gulf of Alaska. Winter values of the monthly mean available wave kinetic energy exceed 35 kW/m. Thus the resource is more than enough to satisfy Yakutat’s relatively modest electrical demand (e.g. Previsic and Bedard, 2009).

2015

Peer-reviewed Articles

Installation of hydrokinetic power-generating devices is currently being considered for the Yukon and Tanana rivers, two large and glacially turbid rivers in Alaska. We sampled downstream-migrating fish along the margins of both rivers, a middle island in the Yukon River, and mid-channel in the Tanana River in order to assess the temporal and spatial patterns of movement by resident and anadromous fishes and hence the potential for fish interactions with hydrokinetic devices. Results suggest that (1) river margins in the Yukon and Tanana rivers are primarily utilized by resident freshwater species, (2) the mid-channel is utilized by Pacific salmon Oncorhynchus spp. smolts, and (3) only Chum Salmon O. keta smolts utilize both river margin and mid-channel areas. Some species exhibited distinct peaks and trends in downstream migration timing, including Longnose Suckers Catostomus catostomus, whitefishes (Coregoninae), Arctic Grayling Thymallus arcticus, Lake Chub Couesius plumbeus, Chinook Salmon O. tshawytscha, Coho Salmon O. kisutch, and Chum Salmon. Due to their downstream migration behavior, Pacific salmon smolts out-migrating in May–July will have the greatest potential for interactions with hydrokinetic devices installed in mid-channel surface waters of the Yukon and Tanana rivers.

Reports

  • A Review of Debris Detection Methods
  • Kasper, J.L., J.B. Johnson, P.X. Duvoy, N. Konefal, and J. Schmid. "A Review of Debris Detection Methods."
  • Northwest National Marine Renewable Energy Center, 2015. Funded by Department of Energy, Final Report, Project "Advanced Laboratory and Field Arrays for Marine Energy.

Debris in rivers and along coastlines occurs frequently. However very little quantitative information is available on the size, location, dynamics and most importantly the risk debris poses to river and marine energy converters. This report reviews techniques and instruments for quantifying debris, its potential for damaging marine hydrokinetic infrastructure and technologies that may be suitable for quantifying debris at prospective hydrokinetic energy sites. The different detection options discussed include mechanical, video and sonar technologies.

The research debris diversion platform (RDDP) has proven a robust platform for protecting surface-mounted river energy converters (RECs) from floating debris. With funding from the Alaska Energy Authority (AEA) the design of the RDDP, as well as our ability to detect and understand its use with RECs, was significantly improved. In addition, the support of the AEA has enabled the development of new analysis techniques and technologies for describing and quantifying debris and its effect on RECs in Alaska’s environments. Though beyond the scope of the original project, an existing discrete element method (DEM) model, COUPi, was tested for simulating the interaction of debris with hydrokinetic infrastructure.

Brochures

Alaska has over 200 communities located on or near rivers and the ocean coastlines. Tapping into the rivers that flow past these communities to produce power has been a dream for many years. That dream is closer to becoming a reality, in large part thanks to pioneering work made possible by the success of the Tanana River Hydrokinetic Test Site and the products being tested there.

Conference Proceedings

During summer 2014, the Alaska Hydrokinetic Energy Research Center (AHERC) and OCEANA Energy Company (OCEANA) conducted performance tests on OCEANA’s river energy converter (REC) at the Tanana River Test Site (TRTS). OCEANA’s REC was deployed from AHERC’s test barge moored immediately downstream from AHERC’s research debris diversion platform (RDDP), which was moored to a midstream buoy attached to an embedment anchor. RECs operating on large uncontrolled rivers can be subject to impacts from woody debris that can cause damage, result in unsustainable operating and maintenance costs and create safety hazards. To reduce the risk of debris impacts on RECs deployed from floating platforms the AHERC developed the RDDP and demonstrated its effectiveness at the TRTS in Nenana, Alaska. A concern of placing a REC downstream from the RDDP is that turbulence generated by flow around and under the RDDP might adversely affect the power performance of the REC. To examine the influence of RDDP generated turbulence on OCEANA turbine performance the power output of the turbine was determined at 14.5, 50m and 100m downstream from the RDDP. The 14.5 m downstream distance was the default position of the turbine during most of the performance testing.

2014

Reports

In spring 2010, Alaska Power and Telephone (AP&T) deployed a 25 kW New Energy Corporation EnCurrent hydrokinetic turbine in the Yukon River at Eagle, Alaska, to determine the feasibility of using river in-stream energy conversion (RISEC) devices to supply power to remote communities. The company found that extensive debris problems on the Yukon at Eagle posed a severe challenge to operating the turbine and created significant safety hazards for their personnel. As a result, plans for deploying the turbine in 2011 were cancelled, and AP&T initiated a project with the Alaska Hydrokinetic Research Center (AHERC) to examine ways to reduce the hazard of surface debris for RISEC devices deployed from floating platforms. The focus of AHERC’s study was on the characteristics of river debris and strategies for reducing the impact of debris on RISEC infrastructure. This information was used to develop statistics on the occurrence of debris at AHERC’s Tanana River Test Site located in Nenana, Alaska, and to design a research debris diversion platform (RDDP). The RDDP consists of two steel pontoons joined in a wedge with its apex facing upstream. A vertical-axis freely rotating cylinder (1.1 m diameter) was placed at the leading edge of the wedge. The rotating cylinder initially employed an array of hinged vanes that would exploit the river current to promote rotation, but later was covered with plastic to reduce surface friction. The angle between the two pontoons of the RDDP is adjustable, from 25 to 77 degrees. The RDDP system can provide effective protection from river surface debris for RISEC devices deployed from a floating platform. The RDDP is not designed to divert subsurface debris that is moving in the river. Further work is needed in understanding the prevalence of subsurface debris to determine the probability of subsurface debris impact on a RISEC device and to guide concepts for protecting RISIC devices from subsurface debris.

2013

Reports

The Tanana River hydrokinetic characterization study started in 2009 when little was known about how Alaskan river environments would affect hydrokinetic power generating devices or how hydrokinetic devices might affect river environments. Few hydrokinetic devices were beyond the concept/design stage and attempts to demonstrate a hydrokinetic device at Ruby, AK, had just concluded its first year. The primary focus of previous paper studies of Alaskan hydrokinetic power generation was to determine the locations of the highest average river currents and hydrokinetic power densities without regard to other aspects of river environments. This project took a broader approach to examine a range of river conditions that included sediment transport and riverbed conditions, river current velocity and turbulence and their seasonal variation, woody debris, fish stocks and wintertime flow. As the project progressed it became apparent that many of the river environmental factors identified in our study had the potential to significantly affect the deployment and operation of hydrokinetic power generating devices. For example, both the Ruby demonstration project and another demonstration at Eagle, Alaska, were ended due to problems with debris. To adequately characterize the most important river environmental factors, it was necessary to go beyond the project’s original scope of work to include river hydrodynamic modeling, more extensive fisheries measurements, and an expanded study of woody debris and its mitigation. The results from this expanded scope of work provides a solid basis for moving to the next stage of hydrokinetic technology development and testing needed to allow for successful long-term deployment and operation of hydrokinetic devices in Alaskan rivers.

2012

Reports

One of the challenges of generating electrical energy with a hydrokinetic turbine in Alaska rivers is the detrimental effect of woody debris in the water column. In order to mitigate this problem the questions of describing what types of debris might be encountered, the frequency of occurrence, the force of impact, and location in the water column need to be answered. The University of Alaska Fairbanks (UAF) Alaska Hydrokinetic Energy Research Center (AHERC) designed, constructed, and tested a mechanical debris detection device (MDDD) for Ocean Renewable Power Company (ORPC). The MDDD was intended to be deployed in the Tanana River at Nenana, Alaska, to assess the debris conditions at the location and depth at which ORPC was planning to deploy a hydrokinetic turbine demonstration project. The MDD was mounted on ORPC’s anchoring system that was designed to hold their turbine support structure in place during turbine operations. Due to difficulties in trying to deploy the anchoring system the MDDD was not deployed during the project period. This report summarizes the design, testing and operating instructions for the MDDD. Technical specifications and information are contained in the appendices.

This report reviews the Nenana, Alaska Hydrokinetic RivGen™ Power System Project – the development and demonstration of an in-river hydrokinetic system by ORPC Alaska, LLC (a wholly-owned subsidiary of Ocean Renewable Power Company, collectively ORPC). 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 report identifies the project participants and their roles and documents the development of the project and demonstration of the power system turbine and foundation. The report also presents findings based on the experience of the demonstration, makes recommendations for future deployments of the RivGen™ Power System, and presents broader recommendations for other hydrokinetic development efforts in Alaska.

Additional Reports:

2011

Peer-reviewed Articles

Hydrokinetic devices generate electricity by capturing kinetic energy from flowing water as it moves across or through a rotor, without impounding or diverting the water source. The Tanana River in Alaska, a turbid glacial system, has been selected as a pilot location to evaluate the effects of such a device on fish communities that are highly valued by subsistence, sport, and commercial users. The basic ecology and habitat use of fishes in turbid glacial systems are poorly understood; therefore it is necessary to study the species composition of the fish community and the spatial and temporal patterns of mainstem river use by these fishes to evaluate impacts of a hydrokinetic device. In this document, we provide an overview of existing knowledge of fish ecology in the Tanana River and impacts of hydrokinetic devices on fishes in other river systems. Seventeen fish species are known to inhabit the Tanana River and several may utilize the deepest and fastest section of the channel, the probable deployment location for the hydrokinetic device, as a seasonal migration corridor. Previous studies in clearwater river systems indicate that mortality and injury rates from turbine passage are low. However, the results from these studies may not apply to the Tanana River because of its distinctive physical properties. To rectify this shortcoming, a conceptual framework for a comprehensive fish ecology study is recommended to determine the impacts of hydrokinetic devices on fishes in turbid, glacial rivers.

A new tool for hydrokinetic energy potential assessment in rivers—HYDROKAL, which stands for a “hydrokinetic calculator”—is presented. This tool was developed in the Fortran 90 programming language as an external module for the CCHE2D application, an existing two-dimensional hydrodynamic numerical model developed at the National Center for Computational Hydroscience and Engineering, University of Mississippi. Velocity outputs generated by the CCHE2D model are used by HYDROKAL to compute the instantaneous power density, an essential element in calculating the hydrokinetic power of a river reach. The tool includes a user-defined efficiency factor to account for turbine efficiency, which is fundamental for estimating the energy that could be harvested from the river. For each river cross section along the computational domain, maximum velocity and specific discharge are identified to assist in estimating the stability of the river reach and, thus, the feasibility of installing an in-stream turbine. A Python script was also developed to export the results from HYDROKAL to CCHE2D. HYDROKAL is applied to a reach of the Tanana River at Nenana, Alaska, USA.

  • The Alaskan Way
  • Johnson, J. B., H. Toniolo, and A. C. Seitz. “The Alaskan Way.”
  • International Water Power & Dam Construction, July 2011.

Alaska is proving to be an ideal place to develop a hydrokinetic power industry. Innovative technology ideas, strong interest from utilities and local communities, plus high energy costs are some of the reasons that look set to pave the way for Alaskan power development.

The site selection for the installation of hydrokinetic devices along a river reach is an issue of fundamental importance. While it is acknowledged that multiple factors such as accessibility, navigation, safety, and hydraulics, among many others, must be considered in the final decision, this article focuses on the influence of river morphology on turbulence flow parameters. Specifically, continuous high-resolution velocity measurements from a hydrokinetic resource assessment on the Tanana River near Nenana in the interior of Alaska are analysed to estimate, kinetic energy (KE), turbulent kinetic energy (TKE) as well as KE partition at particular locations. To accomplish these tasks, two different methods used to rotate the coordinate systems into the main flow direction are correlated and compared in order to extract the turbulent parameters from the main flow. The coordinate system methods include the streamline coordinate rotation and the extraction of statistical fluctuations from the average flow. The streamline coordinate rotation method is chosen to extract the TKE in temporal series. The calculated TKE was up to 30 per cent of the total flow KE in measurements located in pools and dissipated downstream, beyond the highly turbulent locations of bathymetric depressions and river bends. The overall KE increased over a bed free of major macro-obstacles and reduced depth, where the TKE fraction accounted for only 2 per cent of the total KE. The visualizations of the KE and TKE are compared with the river morphology, leading to identification of helical flow, flow separation, and turbulent flow structures along the river bend and in pools to help the decision-making process in hydrokinetic planning.

Reports

Perhaps the greatest obstacle that confronts the implementation of commercial-scale hydrokinetic devices in rivers is debris. Until recently, this problem has been largely avoided by installing devices in areas where debris is not a factor. This practice significantly limits the possible locations for deployment, however, so new techniques must be developed. Although there is little precedent for large hydrokinetic devices and the issue of debris, there are examples of efforts to protect other engineered riverine structures. In addition to presenting these examples, we discuss the mechanisms for how debris enters the flow and is transported downstream, as this information can provide important insight in the development of debris mitigation strategies.

2010

Peer-reviewed Articles

A comprehensive methodology to assess the hydrokinetic potential of a reach of the Tanana river near Nenana, Alaska, is developed to help determine the suitability of the reach for installing and operating hydrokinetic electric turbines. The methodology utilizes field measurements and two-dimensional model simulations to define the discharge, velocity, power density, turbulence, and Froude number throughout the river reach. Thalweg stability is assessed using the maximum cross-sectional velocity, specific discharge, and turbulence. The thalweg was determined to be stable, for the current river condition, from the upstream end of the reach to about 800 m downstream. From 800 m to the end of the reach, at 1100 m, river hydrodynamics indicate an unstable thalweg shifting towards the right bank. The thalweg instability is associated with the transition between upstream and downstream river bends, which may migrate with river stage, bed load, existing bed conditions, and other factors. The flow is subcritical with an average Froude number of 0.30 along the thalweg. Averaged measured velocities along the thalweg are about 1.5 m/s. The average value for instantaneous power density is approximately 4500 W/m2 at the period of measurement (late August). Study results indicate that hydraulic conditions in the river reach may be suitable for turbine operations above the 800 m location with the exception of a possible eddy located around the 400 m location.

Reports

This report outlines the status of hydrokinetic power generation technology, the expected trajectory of improvement over the next five years, and recommended actions the state can take to accelerate this technology field. The report is based on numerous sources as well as data collected by ACEP over the past year at a hydrokinetic research site in Nenana, Alaska.