False Pass Ocean Energy Project
KUCB story July 29, 2013
Here's a story on the False Pass project, which first aired on KUCB July 29, 2013.
http://kucb.org/news/article/false-pass-inches-closer-to-ocean-energy/
Phase II: False Pass Tidal Energy Project (July 2013)
During the summer 2013 Benthic GeoScience Inc. (Benthic) will be working on the site characterization and hazard evaluation at the False Pass Tidal Power Project.
Benthic will be responsible for mobilization to site, execution of the geophysical survey, processing the data, interpretation, and reporting the conclusions.
Figure 1. Idealized survey polygon for the False Pass Tidal Power Project. The shoreline boundaries will terminate at or near the 5m contour referenced to MLLW.
Project Team Members:
Alaska Energy Authority (funder)
Aleutian Pribilof Community Development Association (APICDA)
Aleutian Pribilof Island Association (APIA)
Benthic GeoScience Inc. (Benthic)
Ocean Renewable Power Company (ORPC)
University of Alaska, Anchorage (UAA)
The Phase II goal is to inform the project team about the nature of the seafloor, the surficial geology, and submarine obstructions. The deliverables will be used to plan future marine operations, avoid dangers to navigation, validate permits for the project, included in various modeling efforts, and, ultimately, to construct infrastructure on the seafloor. The products generated through this effort are expected to persist in usefulness and remain meaningful, in the form of a legacy baseline measurement, should persistent measurements of the project area be important after construction of the False Pass Tidal Power Project.
Isanotski Strait has not been surveyed for nautical charting purposes since during the 1923-1925 field seasons. Mean Lower Low Water (MLLW) is the national standard datum for nautical charting and is a good method for classifying Danger to Navigation (DtoN) obstructions. There is no requirement for founding the vertical datum upon MLLW, however, as the national standard; it is often the preferred method for permitting purposes and merging information with the federal agency information. The Department of Commerce, National Ocean & Atmospheric Administration (NOAA) and Department of Defense, US Army Corps of Engineers (USACE) both reference MLLW for nautical projects and charting.
The lack of modern historical information for this project requires geodetic space to be well defined prior to, or coincident with, the Site Character Survey. To our knowledge, Isanotski Strait and the surrounding area do not have survey monumentation correlated to Mean Lower Low Water (MLLW).
For the purpose of this geophysical survey, Benthic recommends measuring local MLLW and correlating it in association with local terrestrial survey monumentation. All field measurements will be made in WGS84, while utilizing broadcast Real-Time Kinematic (RTK) corrections from a GPS base station. The horizontal datum selected for all final products will match national nautical charting methodology. The horizontal datum will be NAD83, and the vertical datum will be MLLW. All units used in this project will be metric.
The local Geodetic Network to be established by Benthic early in the field effort is especially important for the False Pass Tidal Power Project. No broad navigation beacons are available within Isanotski Strait. Both Wide Area Augmentation System (WAAS) and Coast Guard Beacon Differential Global Positioning System (DGPS) were not receivable during ORPC’s Resource Reconnaissance Measurements in October 2012.
Upon arrival, Benthic will establish a maximum of three new geodetic monuments within Isanotski Strait. Any new monuments established will be for the specific purpose of positioning the geophysical hydrographic survey. For the purposes of connectivity with historic terrestrial survey and plat information, Benthic will attempt to utilize existing survey monuments that are referenced by the local power grid maps.
Due to the position of False Pass and the geomorphologic orientation of Isanotski Strait, Benthic believes that survey operations may need to include an RTK radio repeater at the most southern portion of the survey area.
The northern boundary is defined by early versions of the current modeling accomplished by UAA. Project Members are looking forward to identifying the best candidate site for power production. One of the variables that will help define the suitability for site development will be transmission distance. Future UAA models of Isanotski Strait may identify near field candidate sites currently unmeasured with Doppler Current Profilers.
Areas in the vicinity of the large dock structures will need to be surveyed to a more shoal depth then the 5 m contour. In an attempt to mitigate risk of dangers to navigation (DtoN) for safe vessel traffic, barge traffic, and other envisioned infrastructure (submarine turbine and turbine framework) which may transit the project area from the township of False Pass to the final deployment site, Benthic has been asked to survey in the area of the dock structures to a more shoal depth. This area will be measured to the most shoal depth judged safe at the time of survey in the proximity of one Project Team Member determined dock structure.
The southern boundary of the survey polygon is defined by the constricted geomorphology of Isanotski Strait. The polygon presented in this document is an idealized boundary, and actual in situ landmarks will likely be used for final determination of project boundary.
The shoreline boundaries of the survey polygon are idealized for the purposes of the graphic. The shoreline survey polygon boundary will actually be determined by the 5m (~15ft) depth contour as measured within Isanotski Strait. In some areas, Benthic will survey to a more shoal depth based upon sea conditions, time constraints, and in the interest of geologic continuity or understanding. For the purposes of commitments in the Scope of work, Benthic will not be responsible for depths more shoal than 5m. The acquisition of shoreline and other shoal areas are restricted to high tide events and therefore will have limited opportunity to be accomplished.
In addition to the survey area delineated by the survey polygon, Benthic is prepared to approach shore in two locations for the purpose of identifying possible cable corridors. Benthic will seek prioritization from Project Team Members for a minimum of three locations where it is believed that the submarine power infrastructure can merge with the power grid. Project Team Members will predetermine corridors prior to mobilization.
If possible, the ideal geodetic network will straddle the survey area. However, actual monument locations will be selected upon quality of persistent geology, land ownership, and line of sight communication.
The ideal monument for the most northern area would be a pre-existing survey monument in False Pass Township that is referenced by the existing power infrastructure and has easy access to the shoreline for water elevations measurements. Perhaps in the vicinity of the ferry dock or some power infrastructure.
Benthic will be responsible for mobilization to site, execution of the geophysical survey, processing the data, interpretation, and reporting the conclusions.
Figure 1. Idealized survey polygon for the False Pass Tidal Power Project. The shoreline boundaries will terminate at or near the 5m contour referenced to MLLW.
Project Team Members:
Alaska Energy Authority (funder)
Aleutian Pribilof Community Development Association (APICDA)
Aleutian Pribilof Island Association (APIA)
Benthic GeoScience Inc. (Benthic)
Ocean Renewable Power Company (ORPC)
University of Alaska, Anchorage (UAA)
The Phase II goal is to inform the project team about the nature of the seafloor, the surficial geology, and submarine obstructions. The deliverables will be used to plan future marine operations, avoid dangers to navigation, validate permits for the project, included in various modeling efforts, and, ultimately, to construct infrastructure on the seafloor. The products generated through this effort are expected to persist in usefulness and remain meaningful, in the form of a legacy baseline measurement, should persistent measurements of the project area be important after construction of the False Pass Tidal Power Project.
Isanotski Strait has not been surveyed for nautical charting purposes since during the 1923-1925 field seasons. Mean Lower Low Water (MLLW) is the national standard datum for nautical charting and is a good method for classifying Danger to Navigation (DtoN) obstructions. There is no requirement for founding the vertical datum upon MLLW, however, as the national standard; it is often the preferred method for permitting purposes and merging information with the federal agency information. The Department of Commerce, National Ocean & Atmospheric Administration (NOAA) and Department of Defense, US Army Corps of Engineers (USACE) both reference MLLW for nautical projects and charting.
The lack of modern historical information for this project requires geodetic space to be well defined prior to, or coincident with, the Site Character Survey. To our knowledge, Isanotski Strait and the surrounding area do not have survey monumentation correlated to Mean Lower Low Water (MLLW).
For the purpose of this geophysical survey, Benthic recommends measuring local MLLW and correlating it in association with local terrestrial survey monumentation. All field measurements will be made in WGS84, while utilizing broadcast Real-Time Kinematic (RTK) corrections from a GPS base station. The horizontal datum selected for all final products will match national nautical charting methodology. The horizontal datum will be NAD83, and the vertical datum will be MLLW. All units used in this project will be metric.
The local Geodetic Network to be established by Benthic early in the field effort is especially important for the False Pass Tidal Power Project. No broad navigation beacons are available within Isanotski Strait. Both Wide Area Augmentation System (WAAS) and Coast Guard Beacon Differential Global Positioning System (DGPS) were not receivable during ORPC’s Resource Reconnaissance Measurements in October 2012.
Upon arrival, Benthic will establish a maximum of three new geodetic monuments within Isanotski Strait. Any new monuments established will be for the specific purpose of positioning the geophysical hydrographic survey. For the purposes of connectivity with historic terrestrial survey and plat information, Benthic will attempt to utilize existing survey monuments that are referenced by the local power grid maps.
Due to the position of False Pass and the geomorphologic orientation of Isanotski Strait, Benthic believes that survey operations may need to include an RTK radio repeater at the most southern portion of the survey area.
The northern boundary is defined by early versions of the current modeling accomplished by UAA. Project Members are looking forward to identifying the best candidate site for power production. One of the variables that will help define the suitability for site development will be transmission distance. Future UAA models of Isanotski Strait may identify near field candidate sites currently unmeasured with Doppler Current Profilers.
Areas in the vicinity of the large dock structures will need to be surveyed to a more shoal depth then the 5 m contour. In an attempt to mitigate risk of dangers to navigation (DtoN) for safe vessel traffic, barge traffic, and other envisioned infrastructure (submarine turbine and turbine framework) which may transit the project area from the township of False Pass to the final deployment site, Benthic has been asked to survey in the area of the dock structures to a more shoal depth. This area will be measured to the most shoal depth judged safe at the time of survey in the proximity of one Project Team Member determined dock structure.
The southern boundary of the survey polygon is defined by the constricted geomorphology of Isanotski Strait. The polygon presented in this document is an idealized boundary, and actual in situ landmarks will likely be used for final determination of project boundary.
The shoreline boundaries of the survey polygon are idealized for the purposes of the graphic. The shoreline survey polygon boundary will actually be determined by the 5m (~15ft) depth contour as measured within Isanotski Strait. In some areas, Benthic will survey to a more shoal depth based upon sea conditions, time constraints, and in the interest of geologic continuity or understanding. For the purposes of commitments in the Scope of work, Benthic will not be responsible for depths more shoal than 5m. The acquisition of shoreline and other shoal areas are restricted to high tide events and therefore will have limited opportunity to be accomplished.
In addition to the survey area delineated by the survey polygon, Benthic is prepared to approach shore in two locations for the purpose of identifying possible cable corridors. Benthic will seek prioritization from Project Team Members for a minimum of three locations where it is believed that the submarine power infrastructure can merge with the power grid. Project Team Members will predetermine corridors prior to mobilization.
If possible, the ideal geodetic network will straddle the survey area. However, actual monument locations will be selected upon quality of persistent geology, land ownership, and line of sight communication.
The ideal monument for the most northern area would be a pre-existing survey monument in False Pass Township that is referenced by the existing power infrastructure and has easy access to the shoreline for water elevations measurements. Perhaps in the vicinity of the ferry dock or some power infrastructure.
The second monument is expected to be established near mid-polygon area at a location which provides line of sight communication between the most northern and the most southern monuments. As viewed on charts and maps of the area, this is currently idealized to be on the eastern shore of Isanotski Strait; however, all monuments are subject to land ownership permitting. Additionally, locating persistent monument infrastructure may prove difficult on the eastern shoreline. However, the structure of Stonewall may be suitable for persistent monumentation. Benthic will pursue permitting for the second monument with the owner of Stonewall.
Figure 2. Idealized location for two terrestrial monuments during establishment for Geodetic Network
The third monument is expected to be established near the most southern portion of the survey area. The site is currently idealized to be located on the western shore, however, satellite availability in the narrow channel is expected to present communication reception issues. Identification of land ownership and communication reception remain outstanding variables for final locating of monument position.
MLLW datum will be measured for the local area. This will be accomplished by deploying a pressure sensor in the vicinity of one of the monuments. The water level will be measured in relation to that monument several times throughout the field operation period.
After the Geodetic Network has been determined, Benthic will establish a survey vessel from a vessel of opportunity at the False Pass harbor. The vessel identified for this effort is MV Pogo, a stable 30ft aluminum vessel owned by APICDA, and ideal for survey operations. Benthic will measure and mount various computers, monitors, navigation equipment, and both sonar (pole mounted and towed) systems during this process.
All navigation will be accomplished using GPS while receiving RTK corrections. The vessel pilot will navigate the vessel by Electronic Navigation Chart with preplanned survey lines (where available) while presented with seafloor bathymetric information as acquitted in real-time.
Benthic will accomplish a contiguous high-density bathymetric survey of the seafloor utilizing one (single or dual head) multibeam echosounder (MBES). The MBES will be pole mounted on MV Pogo for stability. The data recorded with this instrument will produce a high-density point cloud file. The target survey density for this area will be a minimum of three pings per square meter of seafloor. The target obstruction size for all depths < 20m depth will be 1m3. There are often areas of the seafloor where this level of detail are not possible, and the Isanotski Strait seafloor may present with difficult zones as well. Where possible, areas of the seafloor not surveyed to level of detail desired will be interpolated. No DtoN information will be available for interpolated areas.
The data will be minimally In-Field Processed daily for quality, continuity, and identification of significant errors.
Benthic will mobilize, deploy, and record a cable towed Side Scan Sonar which will acquire acoustic backscatter for all areas deeper than 15m of depth within the project survey polygon.
In addition, Benthic will record the backscatter from the MBES system during the bathymetry survey.
The two datasets together will comprise a fully ensonified seafloor, which will be processed to produce the acoustic intensity mosaic utilized during obstruction classification and geologic interpretation.
The data will be minimally In-Field Processed daily for quality, continuity, and identification of significant errors.
Both bathymetric and backscatter data will be checked for quality, continuity, and other significant error while in the field to ensure meaningful production for deliverables. Of primary concern, holidays and gaps between survey lines will be identified and noted for final acquisition at the end of the field effort.
Once Benthic returns from the field, official processing of the data set products will begin. The depth of precision and computations associated with this effort generate significant data. Although maintained for comparison, the In-Field Processing will be abandoned, and the more methodic Processing Center effort will begin.
The geodetic monument positions will be computed, refined, and ultimately narrowed down to a final location. Although working iterations will be used in the meantime, final positioning typically requires a 2-4 week period for final ephemeris to be published by the National Geodetic Service.
The bathymetric data will be processed in quality processing software on strong processing computers. The data size for a project of this size is expected to reach 70-90 Gb depending upon the product requirements. Shoal points of significant obstructions will be retained during final surface production.
The backscatter data will be processed in quality processing software on strong processing computers. The data size for a project of this size is expected to reach 70-90 Gb depending upon the product requirements. Shoal points of significant obstructions will be retained during final surface production.
The data will be exported into analytical software for computed or interpreted surfaces such as slope analysis, geologic interpretation, hazard evaluation, and cable route corridor opportunities.
All deliverables will be positioned in NAD83 UTM Zone 3 meters.
Final deliverables from this project
1. Table of Monument Positions
2. MLLW Bathymetric Surface, CUBE Computed, 1m grid, .XYZ & .ASC File
3. MLW Bathymetric Surface, CUBE Computed, 10m grid, .XYZ File
4. MLW Roughness Surface, .XYZ & .ASC File
5. Acoustic Intensity Mosaic, georeferenced TIFF & .ASC File
6. Geologic Interpretation, georeferenced TIFF & .SHP File
7. Hazard Evaluation, georeferenced TIFF & .SHP File
8. Table of Danger to Navigation (DtoN) Positions & .SHP File
9. Slope Analysis, georeferenced TIFF & .ASC File
All processed products will be imported into QPS Fledermaus for compilation of a comprehensive 3D Digital Presentation. This product will be viewable (with a free downloadable software) by each of the Project Members. All processed products will be imported into ESRI ArcGIS Electronic Nautical Chart (ENC) software and delivered as an ArcGIS Project or a comprehensive ENC. Paper charts can be produced upon request, however, as of yet, no paper chart production has been cost into the project.
One of the next steps is to use the new data to produce the generation of circulation model. The high-density bathymetry will be used to feed a finer scale 3D circulation model of Isanotski Strait. The model will compute hind cast values during the time period of the resource reconnaissance (October 2012) to validate the accuracy of this improved model with the existing ADCP data. The model output will then be analyzed to inform selection of optimal locations for tidal energy extraction based on the hydrokinetic energy available within the project area. The locations identified will be utilized in the subsequent phase of the project (not included in this scope and budget) to inform a second ADCP data collection effort (The Resource Assessment) that will provide real world validation of the model and finer scale selection of optimal locations for tidal turbine placement, allowing the project layout and design to be completed.
Benthic will mobilize personnel and equipment to False Pass, certifying MV Pogo as a precision survey vessel, establishing a geodetic network, accomplishing the geophysical surveys, processing, and interpreting the data during this project effort. Benthic will be deploying several expensive sonar and navigation kits during the field operations. In order for our project to be successful, we will need well-planned timeline events and to work closely with the Project Team Members.
Due the coordination of personnel, vessels, and onsite vehicles provided by APICDA, Benthic will be seeking to lock down our operation opportunities for field work as soon as possible. We will correlate rental equipment opportunities with the APICDA timeline and reserve equipment packages as best possible.
APICDA has generously contributed many fundamental and necessary components for the In-Field operations, which has significantly reduced the actual cost request for this project.
Figure 2. Idealized location for two terrestrial monuments during establishment for Geodetic Network
The third monument is expected to be established near the most southern portion of the survey area. The site is currently idealized to be located on the western shore, however, satellite availability in the narrow channel is expected to present communication reception issues. Identification of land ownership and communication reception remain outstanding variables for final locating of monument position.
MLLW datum will be measured for the local area. This will be accomplished by deploying a pressure sensor in the vicinity of one of the monuments. The water level will be measured in relation to that monument several times throughout the field operation period.
After the Geodetic Network has been determined, Benthic will establish a survey vessel from a vessel of opportunity at the False Pass harbor. The vessel identified for this effort is MV Pogo, a stable 30ft aluminum vessel owned by APICDA, and ideal for survey operations. Benthic will measure and mount various computers, monitors, navigation equipment, and both sonar (pole mounted and towed) systems during this process.
All navigation will be accomplished using GPS while receiving RTK corrections. The vessel pilot will navigate the vessel by Electronic Navigation Chart with preplanned survey lines (where available) while presented with seafloor bathymetric information as acquitted in real-time.
Benthic will accomplish a contiguous high-density bathymetric survey of the seafloor utilizing one (single or dual head) multibeam echosounder (MBES). The MBES will be pole mounted on MV Pogo for stability. The data recorded with this instrument will produce a high-density point cloud file. The target survey density for this area will be a minimum of three pings per square meter of seafloor. The target obstruction size for all depths < 20m depth will be 1m3. There are often areas of the seafloor where this level of detail are not possible, and the Isanotski Strait seafloor may present with difficult zones as well. Where possible, areas of the seafloor not surveyed to level of detail desired will be interpolated. No DtoN information will be available for interpolated areas.
The data will be minimally In-Field Processed daily for quality, continuity, and identification of significant errors.
Benthic will mobilize, deploy, and record a cable towed Side Scan Sonar which will acquire acoustic backscatter for all areas deeper than 15m of depth within the project survey polygon.
In addition, Benthic will record the backscatter from the MBES system during the bathymetry survey.
The two datasets together will comprise a fully ensonified seafloor, which will be processed to produce the acoustic intensity mosaic utilized during obstruction classification and geologic interpretation.
The data will be minimally In-Field Processed daily for quality, continuity, and identification of significant errors.
Both bathymetric and backscatter data will be checked for quality, continuity, and other significant error while in the field to ensure meaningful production for deliverables. Of primary concern, holidays and gaps between survey lines will be identified and noted for final acquisition at the end of the field effort.
Once Benthic returns from the field, official processing of the data set products will begin. The depth of precision and computations associated with this effort generate significant data. Although maintained for comparison, the In-Field Processing will be abandoned, and the more methodic Processing Center effort will begin.
The geodetic monument positions will be computed, refined, and ultimately narrowed down to a final location. Although working iterations will be used in the meantime, final positioning typically requires a 2-4 week period for final ephemeris to be published by the National Geodetic Service.
The bathymetric data will be processed in quality processing software on strong processing computers. The data size for a project of this size is expected to reach 70-90 Gb depending upon the product requirements. Shoal points of significant obstructions will be retained during final surface production.
The backscatter data will be processed in quality processing software on strong processing computers. The data size for a project of this size is expected to reach 70-90 Gb depending upon the product requirements. Shoal points of significant obstructions will be retained during final surface production.
The data will be exported into analytical software for computed or interpreted surfaces such as slope analysis, geologic interpretation, hazard evaluation, and cable route corridor opportunities.
All deliverables will be positioned in NAD83 UTM Zone 3 meters.
Final deliverables from this project
1. Table of Monument Positions
2. MLLW Bathymetric Surface, CUBE Computed, 1m grid, .XYZ & .ASC File
3. MLW Bathymetric Surface, CUBE Computed, 10m grid, .XYZ File
4. MLW Roughness Surface, .XYZ & .ASC File
5. Acoustic Intensity Mosaic, georeferenced TIFF & .ASC File
6. Geologic Interpretation, georeferenced TIFF & .SHP File
7. Hazard Evaluation, georeferenced TIFF & .SHP File
8. Table of Danger to Navigation (DtoN) Positions & .SHP File
9. Slope Analysis, georeferenced TIFF & .ASC File
All processed products will be imported into QPS Fledermaus for compilation of a comprehensive 3D Digital Presentation. This product will be viewable (with a free downloadable software) by each of the Project Members. All processed products will be imported into ESRI ArcGIS Electronic Nautical Chart (ENC) software and delivered as an ArcGIS Project or a comprehensive ENC. Paper charts can be produced upon request, however, as of yet, no paper chart production has been cost into the project.
One of the next steps is to use the new data to produce the generation of circulation model. The high-density bathymetry will be used to feed a finer scale 3D circulation model of Isanotski Strait. The model will compute hind cast values during the time period of the resource reconnaissance (October 2012) to validate the accuracy of this improved model with the existing ADCP data. The model output will then be analyzed to inform selection of optimal locations for tidal energy extraction based on the hydrokinetic energy available within the project area. The locations identified will be utilized in the subsequent phase of the project (not included in this scope and budget) to inform a second ADCP data collection effort (The Resource Assessment) that will provide real world validation of the model and finer scale selection of optimal locations for tidal turbine placement, allowing the project layout and design to be completed.
Benthic will mobilize personnel and equipment to False Pass, certifying MV Pogo as a precision survey vessel, establishing a geodetic network, accomplishing the geophysical surveys, processing, and interpreting the data during this project effort. Benthic will be deploying several expensive sonar and navigation kits during the field operations. In order for our project to be successful, we will need well-planned timeline events and to work closely with the Project Team Members.
Due the coordination of personnel, vessels, and onsite vehicles provided by APICDA, Benthic will be seeking to lock down our operation opportunities for field work as soon as possible. We will correlate rental equipment opportunities with the APICDA timeline and reserve equipment packages as best possible.
APICDA has generously contributed many fundamental and necessary components for the In-Field operations, which has significantly reduced the actual cost request for this project.
Phase I: False Pass Tidal Energy Project (June 2013)
Summary:
Ocean Renewable Power Company, LLC performed a reconnaissance tidal current survey to obtain a preliminary assessment of the potential for a tidal energy project as an energy alternative for the community of False Pass, Alaska under contract with Aleutian Pribilof Island Association (APIA). ORPC successfully collected acoustic doppler current profiler (ADCP) current velocity data from two sites in Isanotski Strait in the vicinity of False Pass over the course of a lunar cycle (one month) during the period from September to November 2012. The collected data was normalized through a quality control and data analysis process to allow for a comparison of the available tidal energy resource between the two sites. The survey analysis shows that site “N2” in the near vicinity of False Pass has a marginal tidal energy resource, while site “S2” in the narrowest portion of the Isanotski Strait is an extremely robust tidal energy resource for tidal energy extraction utilizing currently existing hydrokinetic technologies. Based on the results of the survey, the tidal energy resource in the vicinity of False Pass has sufficient energy for a viable tidal energy project. The results justify further investigation of the site characteristics, project development considerations, and project economics to determine the ultimate feasibility of a tidal energy project in the False Pass area.
Project Team Members:
Aleutian Pribilof Community Development Association (APICDA)
Aleutian Pribilof Island Association (APIA)
Benthic GeoScience Inc. (Benthic)
Marsh Creek, LLC
Ocean Renewable Power Company (ORPC)
University of Alaska, Anchorage (UAA)
U.S. Department of Energy, Tribal Energy Program (funder)
Description:
The University of Alaska Anchorage (UAA) developed a numerical circulation model to determine the spatial and temporal distribution of velocity within False Pass based on existing bathymetric, tidal and ocean current data and numerical modeling. The model’s resolution of about 50 m, has a domain extending north to the Bering Sea and south to the Pacific Ocean. The model is “forced” at its boundaries by the results of a coarse grid circulation model (e.g., BESTMAS, Univ. of Washington). The BESTMAS model provides monthly-averaged water level and velocity on a 10 km grid from 1970 to 2010. This data was augmented using tidal constituent data (e.g., from Oregon State University). Bathymetry was obtained from NOAA. The Delft3D model generated hourly velocity and water level data throughout the False Pass area for selected time periods. After performing initial modeling, UAA consulted with ORPC to provide detailed data on areas considered for further investigations. This model functions as a base to incorporate more detailed data as the project develops, including updated bathymetry and tidal stage data, and will be verified by in field current velocity measurements to determine its accuracy.
ORPC collected a lunar cycle (29.5 days) of current velocity data at two sites near False Pass that was used to make a preliminary determination of the potential for a tidal energy project. ORPC had agreed to provide data from at least one site, but was able to collect data at two sites as the National Renewable Energy Laboratory (NREL) supplied one additional ADCP for the project period. This enabled two sites to be measured at the same time, allowing a comparison of the energy resource of the two sites during the same time period.
The field work and data collection was performed as described below:
September 28, 2012
ORPC deployed a team to False Pass to perform this tidal/ocean current resource reconnaissance under contract to APIA. Team members Monty Worthington, ORPC, David Oliver, Benthic GeoScience, and Levi Kilcher, NREL, mobilized to False Pass and met with Shane Hoblet contracted by the Aleutian Pribilof Island Community Development Association (APICDA) to skipper the Nightrider, a vessel of opportunity for the equipment deployment operations. The goal of this expedition was to deploy two ADCPs to measure current velocities at sites likely to have viable resources over a full lunar cycle (29.5 days), and to deploy two HOBO water level sensors to validate the UAA’s modeling efforts.
Ocean Renewable Power Company, LLC performed a reconnaissance tidal current survey to obtain a preliminary assessment of the potential for a tidal energy project as an energy alternative for the community of False Pass, Alaska under contract with Aleutian Pribilof Island Association (APIA). ORPC successfully collected acoustic doppler current profiler (ADCP) current velocity data from two sites in Isanotski Strait in the vicinity of False Pass over the course of a lunar cycle (one month) during the period from September to November 2012. The collected data was normalized through a quality control and data analysis process to allow for a comparison of the available tidal energy resource between the two sites. The survey analysis shows that site “N2” in the near vicinity of False Pass has a marginal tidal energy resource, while site “S2” in the narrowest portion of the Isanotski Strait is an extremely robust tidal energy resource for tidal energy extraction utilizing currently existing hydrokinetic technologies. Based on the results of the survey, the tidal energy resource in the vicinity of False Pass has sufficient energy for a viable tidal energy project. The results justify further investigation of the site characteristics, project development considerations, and project economics to determine the ultimate feasibility of a tidal energy project in the False Pass area.
Project Team Members:
Aleutian Pribilof Community Development Association (APICDA)
Aleutian Pribilof Island Association (APIA)
Benthic GeoScience Inc. (Benthic)
Marsh Creek, LLC
Ocean Renewable Power Company (ORPC)
University of Alaska, Anchorage (UAA)
U.S. Department of Energy, Tribal Energy Program (funder)
Description:
The University of Alaska Anchorage (UAA) developed a numerical circulation model to determine the spatial and temporal distribution of velocity within False Pass based on existing bathymetric, tidal and ocean current data and numerical modeling. The model’s resolution of about 50 m, has a domain extending north to the Bering Sea and south to the Pacific Ocean. The model is “forced” at its boundaries by the results of a coarse grid circulation model (e.g., BESTMAS, Univ. of Washington). The BESTMAS model provides monthly-averaged water level and velocity on a 10 km grid from 1970 to 2010. This data was augmented using tidal constituent data (e.g., from Oregon State University). Bathymetry was obtained from NOAA. The Delft3D model generated hourly velocity and water level data throughout the False Pass area for selected time periods. After performing initial modeling, UAA consulted with ORPC to provide detailed data on areas considered for further investigations. This model functions as a base to incorporate more detailed data as the project develops, including updated bathymetry and tidal stage data, and will be verified by in field current velocity measurements to determine its accuracy.
ORPC collected a lunar cycle (29.5 days) of current velocity data at two sites near False Pass that was used to make a preliminary determination of the potential for a tidal energy project. ORPC had agreed to provide data from at least one site, but was able to collect data at two sites as the National Renewable Energy Laboratory (NREL) supplied one additional ADCP for the project period. This enabled two sites to be measured at the same time, allowing a comparison of the energy resource of the two sites during the same time period.
The field work and data collection was performed as described below:
September 28, 2012
ORPC deployed a team to False Pass to perform this tidal/ocean current resource reconnaissance under contract to APIA. Team members Monty Worthington, ORPC, David Oliver, Benthic GeoScience, and Levi Kilcher, NREL, mobilized to False Pass and met with Shane Hoblet contracted by the Aleutian Pribilof Island Community Development Association (APICDA) to skipper the Nightrider, a vessel of opportunity for the equipment deployment operations. The goal of this expedition was to deploy two ADCPs to measure current velocities at sites likely to have viable resources over a full lunar cycle (29.5 days), and to deploy two HOBO water level sensors to validate the UAA’s modeling efforts.
September 29-30, 2013
ORPC investigated ADCP deployment sites, selected on the basis of UAA modeling efforts, local knowledge, and known bathymetry with a SeaKing Tritech Scanning Sonar. Seven sites were assessed for hazards to ADCP deployments in the vicinity of two prospective ADCP locations, and ultimately two sites “N2” in the vicinity of False Pass and “S2” approximately two miles south of the town of False Pass near Whirl Point were selected for deployment.
September 30, 2012
At 19:50 AKDT a 600 kHz Nortek Acoustic Wave and Current (AWAC) profiler provided by NREL was deployed and began collecting data at N2 (lat -163.3870W long 54.8515N).
October 2, 2012
At 19:59 AKDT a 300 kHz RDI ADCP was deployed and began collecting data at S2 (lat -163.3676W long 54.8174N). The HOBO water level sensors were also deployed approximately 7 nm North and South of False Pass.
October 29, 2012
Monty Worthington, ORPC, mobilized back to False Pass for ADCP recovery operations where he met Calvin Kashevarof under contract to APICDA to skipper the Nightrider for these efforts.
October 30, 2012
At 12:44 AKDT the AWAC ADCP was recovered and completed its data collection, logging 29.7 days of data.
November 3, 2012
The HOBO deployed north of False Pass was recovered at 12:30 AKDT.
November 4, 2012
The RDI ADCP deployed at S2 was recovered at 17:45 AKDT. This ADCP had stopped recording data on October 3, 2012 at 3:57 AKDT due to premature battery depletion, logging 28.35 days of data.
March 25, 2012
The HOBO deployed south of False Pass was recovered by Shane Hoblet and his crew while commercial fishing. It had washed up on the beach near its deployment site and was returned to UAA for data analysis.
ORPC investigated ADCP deployment sites, selected on the basis of UAA modeling efforts, local knowledge, and known bathymetry with a SeaKing Tritech Scanning Sonar. Seven sites were assessed for hazards to ADCP deployments in the vicinity of two prospective ADCP locations, and ultimately two sites “N2” in the vicinity of False Pass and “S2” approximately two miles south of the town of False Pass near Whirl Point were selected for deployment.
September 30, 2012
At 19:50 AKDT a 600 kHz Nortek Acoustic Wave and Current (AWAC) profiler provided by NREL was deployed and began collecting data at N2 (lat -163.3870W long 54.8515N).
October 2, 2012
At 19:59 AKDT a 300 kHz RDI ADCP was deployed and began collecting data at S2 (lat -163.3676W long 54.8174N). The HOBO water level sensors were also deployed approximately 7 nm North and South of False Pass.
October 29, 2012
Monty Worthington, ORPC, mobilized back to False Pass for ADCP recovery operations where he met Calvin Kashevarof under contract to APICDA to skipper the Nightrider for these efforts.
October 30, 2012
At 12:44 AKDT the AWAC ADCP was recovered and completed its data collection, logging 29.7 days of data.
November 3, 2012
The HOBO deployed north of False Pass was recovered at 12:30 AKDT.
November 4, 2012
The RDI ADCP deployed at S2 was recovered at 17:45 AKDT. This ADCP had stopped recording data on October 3, 2012 at 3:57 AKDT due to premature battery depletion, logging 28.35 days of data.
March 25, 2012
The HOBO deployed south of False Pass was recovered by Shane Hoblet and his crew while commercial fishing. It had washed up on the beach near its deployment site and was returned to UAA for data analysis.
ADCP Configuration:
Both the RDI AWAC and Nortek ADCP were configured in the field and calibrated for each of the sites, including calibration of the magnetic compass on each device, setting of the deployment depth, and configuring the data acquisition parameters. Each device passed the configuration checks performed under the guidance of NREL and Benthic Geoscience personnel. Differences in the two devices necessitated programming each device to sample and store data at different intervals while optimizing for the maximum rate of data collection, storage and battery life. This programming allowed the data to be utilized to the maximum extent for analysis of the strength of the resource, direction of the currents, and potential analysis of turbulence. Each device also had a slightly different “blanking distance.” This is the distance between the device and the first bin of data. This resulted in a 0.2 meter difference in the height above the seafloor of nearest data bins between the two devices.
Data Quality Control:
The data from the AWAC and RDI ADCPs was downloaded from the devices, and data quality and accuracy was verified independently by NREL and ORPC. Data analysis was focused approximately 10.7 meters above the bottom for the RDI ADCP and 10.5 meters above the bottom for the AWAC ADCP—the anticipated height of ORPC’s TidGen™ device and a likely hub height for medium sized tidal turbines. Data was also analyzed throughout the water column for comparison purposes. The strongest near surface current velocities and highest energy densities were also identified. As the RDI had a pressure sensor, it also collected data on the water level and identified the surface of the water. The AWAC did not have a pressure sensor, so water surface and “false” data bins from above the water surface were identified by unrealistic trends in the data. At site N2, the deployment depth was 26 meters (85 feet) and at least 22 bins of quality data were collected above. The data, however, appeared unreliable due either to surface reflection or possibly interference from the submerged buoy used in the deployment. At site S2 the deployment depth was 35 meters (114 feet), and 32 bins of quality data were collected.
One challenge encountered in performing a comparative analysis of the sites was due to the fact that the RDI ADCP, deployed at site S2, had stopped logging data before the end of the synodic full lunar cycle (28.35 days of data instead of 29.53 days). This was likely due to premature battery depletion. The ADCP had been programmed to use 90% of its battery over a 29.5 day deployment which should have left reserve capacity; but this was not the case. Because of this, it was necessary to determine how to normalize the data for comparison purposes between the two sites because a full lunar cycle of data was not collected at S2. ORPC analyzed the difference between the data collected by first comparing the data from a full lunar cycle which was collected at N2 to the data from site N2 during the 27.5 days during which concurrent data was collected at site S2. Mean velocities at the selected depth (10.5 meters above the seafloor) were 1.24 m/s for the flood tide for both durations, while for the ebb tide, the mean velocity was slightly higher for the full lunar cycle at 1.25 m/s (as opposed to 1.24 m/s for the 27.5 day cycle, a difference of less than 1%). The average energy density also differed slightly between 1.57 kW/m^2 for the full lunar cycle as compared to 1.54 kW/m^2 for the period of concurrent data collection. This represents a 1.9% difference in energy density; a larger difference than the current velocity as it varies as a cube of current velocity. This difference is within the acceptable range for extrapolating annual energy output as natural variations between concurrent lunar cycles may exhibit similar differences. It was therefore deemed a correct approach to focus on the 27.5 day time period of concurrent data collection for comparison of energy at the two sites and for extrapolation of annual energy production. The data presented in this report was analyzed over the 27.5 day time period of concurrent deployment.
Current velocity, energy density and flow symmetry comparison:
At 10.5 meters above the seafloor, the N2 site had a maximum velocity of 2.51 m/s and average velocity of 1.24 m/s and an average energy density of 1.54 kW/m^2. By comparison, at 10.7 meters above the seafloor the S2 site had a maximum current of 3.68 m/s an average velocity of 1.62 m/s and an average energy density of 3.68 kW/m^2—over twice the available energy of site N2. At both sites, the strongest currents occurred during the ebb (southerly) flows. Peak current velocities and energy densities occurred near the surface of each site, but, here again, energy density at site S2 was more than double that of N2.
Both the RDI AWAC and Nortek ADCP were configured in the field and calibrated for each of the sites, including calibration of the magnetic compass on each device, setting of the deployment depth, and configuring the data acquisition parameters. Each device passed the configuration checks performed under the guidance of NREL and Benthic Geoscience personnel. Differences in the two devices necessitated programming each device to sample and store data at different intervals while optimizing for the maximum rate of data collection, storage and battery life. This programming allowed the data to be utilized to the maximum extent for analysis of the strength of the resource, direction of the currents, and potential analysis of turbulence. Each device also had a slightly different “blanking distance.” This is the distance between the device and the first bin of data. This resulted in a 0.2 meter difference in the height above the seafloor of nearest data bins between the two devices.
Data Quality Control:
The data from the AWAC and RDI ADCPs was downloaded from the devices, and data quality and accuracy was verified independently by NREL and ORPC. Data analysis was focused approximately 10.7 meters above the bottom for the RDI ADCP and 10.5 meters above the bottom for the AWAC ADCP—the anticipated height of ORPC’s TidGen™ device and a likely hub height for medium sized tidal turbines. Data was also analyzed throughout the water column for comparison purposes. The strongest near surface current velocities and highest energy densities were also identified. As the RDI had a pressure sensor, it also collected data on the water level and identified the surface of the water. The AWAC did not have a pressure sensor, so water surface and “false” data bins from above the water surface were identified by unrealistic trends in the data. At site N2, the deployment depth was 26 meters (85 feet) and at least 22 bins of quality data were collected above. The data, however, appeared unreliable due either to surface reflection or possibly interference from the submerged buoy used in the deployment. At site S2 the deployment depth was 35 meters (114 feet), and 32 bins of quality data were collected.
One challenge encountered in performing a comparative analysis of the sites was due to the fact that the RDI ADCP, deployed at site S2, had stopped logging data before the end of the synodic full lunar cycle (28.35 days of data instead of 29.53 days). This was likely due to premature battery depletion. The ADCP had been programmed to use 90% of its battery over a 29.5 day deployment which should have left reserve capacity; but this was not the case. Because of this, it was necessary to determine how to normalize the data for comparison purposes between the two sites because a full lunar cycle of data was not collected at S2. ORPC analyzed the difference between the data collected by first comparing the data from a full lunar cycle which was collected at N2 to the data from site N2 during the 27.5 days during which concurrent data was collected at site S2. Mean velocities at the selected depth (10.5 meters above the seafloor) were 1.24 m/s for the flood tide for both durations, while for the ebb tide, the mean velocity was slightly higher for the full lunar cycle at 1.25 m/s (as opposed to 1.24 m/s for the 27.5 day cycle, a difference of less than 1%). The average energy density also differed slightly between 1.57 kW/m^2 for the full lunar cycle as compared to 1.54 kW/m^2 for the period of concurrent data collection. This represents a 1.9% difference in energy density; a larger difference than the current velocity as it varies as a cube of current velocity. This difference is within the acceptable range for extrapolating annual energy output as natural variations between concurrent lunar cycles may exhibit similar differences. It was therefore deemed a correct approach to focus on the 27.5 day time period of concurrent data collection for comparison of energy at the two sites and for extrapolation of annual energy production. The data presented in this report was analyzed over the 27.5 day time period of concurrent deployment.
Current velocity, energy density and flow symmetry comparison:
At 10.5 meters above the seafloor, the N2 site had a maximum velocity of 2.51 m/s and average velocity of 1.24 m/s and an average energy density of 1.54 kW/m^2. By comparison, at 10.7 meters above the seafloor the S2 site had a maximum current of 3.68 m/s an average velocity of 1.62 m/s and an average energy density of 3.68 kW/m^2—over twice the available energy of site N2. At both sites, the strongest currents occurred during the ebb (southerly) flows. Peak current velocities and energy densities occurred near the surface of each site, but, here again, energy density at site S2 was more than double that of N2.
The flow direction and its symmetry between flood and ebb events at tidal sites can be highly variable, and this can have adverse effects on energy capture using tidal turbines. It is important to analyze this aspect of tidal currents as asymmetric currents can have adverse effects on total recoverable energy. In addition to analysis of the mean direction and standard deviation of the currents direction, ORPC generated a “tidal rose” for each site at the tidal turbines hub height to graphically depict current direction, symmetry, and magnitude. These tidal roses reveal that the flow is highly symmetric (near to180 degrees opposed) at sites S2 and N2 and those viable current velocities for energy production occur most of the time. However, current velocities and overall energy at N2 are significantly lower as noted above.
Data Analysis over the entire water column
The following figures illustrate the data of the site inclusive of the entire water column to provide a perspective on how the resource varies as a function of depth and time. The figures show the temporal and spatial variation of current velocity magnitude and direction at site S2.
This figure shows the spatial and temporal variation of the “residual” current velocity correspondingly at sites S2 and N2. This residual current is the net flow of water over the deployment period with the tidally influenced flows extracted. These residual currents are only at a single column in the cross section of the channel and can be explained by circulation patterns where ebb currents are enhanced in one portion of a channel and flood currents are enhanced in another area while the net current is essential zero. Fresh water input at one end of an estuary can also lead to residual currents being stronger in one direction than another. These currents are not generally of large consequence for tidal energy extraction, but the information is included here to provide differentiation of tidal versus ocean currents at False Pass as the influence of each was not well understood at the onset of this study. During initial desktop investigation into the False Pass project site, it was suspected that the northwesterly flowing Alaska ocean current (Alaska Coastal Current) might have an influence in creating a stronger northerly flood current while diminishing the southerly ebb current. As these residual current velocity charts suggest, larger tidal variations resulted in a stronger residual southerly ebb current at both sites and overall energy was higher on the ebb tide over the course of the month. Smaller tidal variations corresponded to a stronger residual northerly flood current though overall flood energy was lower at both sites.
The following figures illustrate the data of the site inclusive of the entire water column to provide a perspective on how the resource varies as a function of depth and time. The figures show the temporal and spatial variation of current velocity magnitude and direction at site S2.
This figure shows the spatial and temporal variation of the “residual” current velocity correspondingly at sites S2 and N2. This residual current is the net flow of water over the deployment period with the tidally influenced flows extracted. These residual currents are only at a single column in the cross section of the channel and can be explained by circulation patterns where ebb currents are enhanced in one portion of a channel and flood currents are enhanced in another area while the net current is essential zero. Fresh water input at one end of an estuary can also lead to residual currents being stronger in one direction than another. These currents are not generally of large consequence for tidal energy extraction, but the information is included here to provide differentiation of tidal versus ocean currents at False Pass as the influence of each was not well understood at the onset of this study. During initial desktop investigation into the False Pass project site, it was suspected that the northwesterly flowing Alaska ocean current (Alaska Coastal Current) might have an influence in creating a stronger northerly flood current while diminishing the southerly ebb current. As these residual current velocity charts suggest, larger tidal variations resulted in a stronger residual southerly ebb current at both sites and overall energy was higher on the ebb tide over the course of the month. Smaller tidal variations corresponded to a stronger residual northerly flood current though overall flood energy was lower at both sites.
Figure showing AWAC data from N2 of residual current velocity over deployment duration. A positive current is indicative of the northerly flood current while a negative current velocity is indicative of a southerly ebb residual current. The velocity data in the lower image represents the tidal velocity 10.5 meters above the seafloor.
Recoverable Energy
For a tidal energy device such as ORPC’s TidGen™ turbine generator unit (TGU), deployed with a hub height 10.5 meters above the bottom, a swept area of 59 m^2 and an efficiency of 32.3%, the annual energy delivery from site N2 would be 284,490 kWh, resulting in a capacity factor of 21.6%. By comparison the same device deployed 10.5 meters above the bottom at S2 would have an annual generation of 577,655 kWh and a 43.9% capacity factor. For higher efficiency (36%) turbines with the same swept area, such as future versions of ORPC power systems, the annual energy delivered would increase to 318,972 kWh and 24% capacity factor at N2 and 624,941 kWh and 47.5 % capacity factor at S2. By comparison to other sites which ORPC has studied in Alaska and Maine, site S2 represents a robust and very attractive tidal energy resource, while site N2 is a marginal resource for energy production using a device analogous to ORPC’s TidGen™ TGU.
Conclusions
Based on the results of the reconnaissance tidal current survey performed in the False Pass area, it is clear that, from strictly a resource perspective, site S2 has great potential and site N2 is marginal at best. However, many other factors come into play when evaluating the feasibility of a site for a tidal energy project. These factors include bathymetric and geotechnical considerations, access to the site, proximity to the interconnection point with the local grid, etc.
The evaluation of the feasibility of a tidal energy project at a marginal resource site such as N2 is highly dependent on the costs associated with the development and construction of the project and the value of the power that is delivered. While the energy density found at site N2 is much lower than that encountered at S2, the short transmission distance from site N2 to the interconnect locations in False Pass (approximately ½ mile) and the relative easy access to the site could reduce associated construction costs significantly and make a project in its vicinity economically viable. It is also entirely possible that better tidal current velocities exist in the near vicinity of site N2 that could increase the site’s energy density to a point where development of a project is more attractive.
We believe it would be worthwhile to enhance circulation modeling efforts in the vicinity of N2 to determine if local variations in the velocity profile would lead to identification of one or more specific sites with higher energy density. This could tip the scales in favor of a tidal energy project in the vicinity of site N2, and if so, make it desirable to follow up with an ADCP survey at the location(s) of interest.
The robust tidal energy resource at site S2 will provide exceptional output from a tidal energy project with impressive capacity factors in the range of 40-50% of rated capacity. Site S2 is, however, more remote than site N2, and construction costs will likely be higher, especially for the associated power transmission line which would be at least 2 miles long. Further investigation of project development considerations and constructability of a tidal energy project at site S2 are warranted to assess the economics of installing a tidal energy project at this site. Of key importance in this assessment will be a bathymetric survey (Phase II) covering the area of potential device locations and submarine power cable routes, and analysis of technical and cost considerations for a power cable line to connect the project to False Pass.
Recoverable Energy
For a tidal energy device such as ORPC’s TidGen™ turbine generator unit (TGU), deployed with a hub height 10.5 meters above the bottom, a swept area of 59 m^2 and an efficiency of 32.3%, the annual energy delivery from site N2 would be 284,490 kWh, resulting in a capacity factor of 21.6%. By comparison the same device deployed 10.5 meters above the bottom at S2 would have an annual generation of 577,655 kWh and a 43.9% capacity factor. For higher efficiency (36%) turbines with the same swept area, such as future versions of ORPC power systems, the annual energy delivered would increase to 318,972 kWh and 24% capacity factor at N2 and 624,941 kWh and 47.5 % capacity factor at S2. By comparison to other sites which ORPC has studied in Alaska and Maine, site S2 represents a robust and very attractive tidal energy resource, while site N2 is a marginal resource for energy production using a device analogous to ORPC’s TidGen™ TGU.
Conclusions
Based on the results of the reconnaissance tidal current survey performed in the False Pass area, it is clear that, from strictly a resource perspective, site S2 has great potential and site N2 is marginal at best. However, many other factors come into play when evaluating the feasibility of a site for a tidal energy project. These factors include bathymetric and geotechnical considerations, access to the site, proximity to the interconnection point with the local grid, etc.
The evaluation of the feasibility of a tidal energy project at a marginal resource site such as N2 is highly dependent on the costs associated with the development and construction of the project and the value of the power that is delivered. While the energy density found at site N2 is much lower than that encountered at S2, the short transmission distance from site N2 to the interconnect locations in False Pass (approximately ½ mile) and the relative easy access to the site could reduce associated construction costs significantly and make a project in its vicinity economically viable. It is also entirely possible that better tidal current velocities exist in the near vicinity of site N2 that could increase the site’s energy density to a point where development of a project is more attractive.
We believe it would be worthwhile to enhance circulation modeling efforts in the vicinity of N2 to determine if local variations in the velocity profile would lead to identification of one or more specific sites with higher energy density. This could tip the scales in favor of a tidal energy project in the vicinity of site N2, and if so, make it desirable to follow up with an ADCP survey at the location(s) of interest.
The robust tidal energy resource at site S2 will provide exceptional output from a tidal energy project with impressive capacity factors in the range of 40-50% of rated capacity. Site S2 is, however, more remote than site N2, and construction costs will likely be higher, especially for the associated power transmission line which would be at least 2 miles long. Further investigation of project development considerations and constructability of a tidal energy project at site S2 are warranted to assess the economics of installing a tidal energy project at this site. Of key importance in this assessment will be a bathymetric survey (Phase II) covering the area of potential device locations and submarine power cable routes, and analysis of technical and cost considerations for a power cable line to connect the project to False Pass.
False Pass Tidal Feasibility Study Objectives (March 2012)
The False Pass ocean current - tidal energy project feasibility study objectives are:
1) Collect existing bathymetric, tidal, and ocean current data at the site to develop a basic model of current circulation at False Pass.
2) Measure current velocities at a site of interest for a full lunar cycle to establish the viability of the current resource.
3) Collect data on transmission infrastructure, electrical loads, and electrical generation at False Pass.
4) Perform economic analysis based on current costs of energy and amount of energy anticipated from and costs associated with tidal energy project conceptual design.
5) Consult with agencies and perform literature review to scope permitting process and identify key environmental issues. Compile a report for project partners.
The data collected indicates False Pass has the country's best tidal energy resource measured so far. A verbal report will be presented at Ocean and River Power session of the Rural Energy Conference in Anchorage Tuesday, Apr 30th from 1:30pm-3:30pm
see also: http://alaskadispatch.com/article/20130505/tidal-energy-potential-aleutians-blows-expectations-out-water
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Tidal power research underway at False Pass
October 5th 2:11 pm | Hannah Heimbuch
As energy companies race to reap the benefits of Arctic oil, other parts of the state are charging into new energy technologies.
In False Pass, researchers have initiated a project that explores the potential power of ocean currents. Much like wind turbines harness the massive moving energy of air currents, underwater turbines lasso the energy created by water currents.
Alaska is lacking in neither natural phenomenon, said scientist Bruce Wright.
Wright is the senior scientist for the Aleutian Pribilof Islands Association, an Aleut tribal non-profit organization. They recently received a $200,000 Department of Energy grant to explore tidal energies, and are focusing their attention at the narrow saltwater chute of Isanotski Strait at False Pass, at the end of the Alaska Peninsula.
It is the first pass that Pacific waters come to as the Alaska Coastal Current pushes them toward the Arctic Ocean, Wright said.
Alaska possesses 90 percent of the United State's total tidal power potential, according to the Ocean Renewable Power Company, the company contracted to conduct the research at False Pass.
ORPC is also conducting similar research in Cook Inlet, as well as other locations around the country.
Last week, two acoustic current Doppler profilers were placed in the waters of False Pass, and will remain there for about five weeks, Wright said, collecting data on the volume and speed of water moving through.
There are two forces at work in coastal waters, Wright said, the Alaska Coastal Current and the daily tides.
"There's a correalus effect which is caused by the spinning of the earth on its axis," Wright said.
The earth's rotation naturally pumps water out between Canada and Greenland and down into the northern Atlantic Ocean.
"To make up for that vacuum that's created in the Arctic Ocean, water from the Pacific fills that, coming up along the Alaska coast. The Alaska Coastal Current starts along the coast around British Columbia, and propagates up."
The velocity with which that massive current moves is in part determined by how much fresh water is streaming out of Alaska's coastal range and into the ocean. That outflow is about 1.2 times the size of the Mississippi River's.
What Wright and the Ocean Renewable Power Company want to know is, how much force is generated as this current pushes past land formations, like at False Pass, and how well can it be harnessed by underwater turbines.
A speed of about seven knots is prime, Wright said, and not terribly uncommon along coastal Alaska.
Their research will include several elements, Wright said. First, they will examine the power grid at False Pass to determine how much power the community uses, and how equipped it is to handle power efficiently.
The next part, which began last week when the profilers went underwater, is to determine exactly what kind of power output could be available by harnessing the local waters.
The University of Alaska Anchorage engineering department helped by establishing optimum spots to put the profilers, using historical tidal and current data.
"When I proposed this project I wanted to capture that Alaska coastal current," Wright said. "(Find out) if it was strong enough to drive a turbine. In addition to the ocean current going through False Pass there is also a tidal influence, caused by the gravity of the moon and the sun."
They want to know how much this tidal influence affects the power of the current. This is one of the reasons they are conducting at least a full month of data collection, to observe an entire lunar cycle of tides.
"So there's a question then, how strong is the Alaska coastal current and how does it correspond, dovetail, counteract or relate to the tidal current."
Should they find a viable amount of power, a number of things will need to happen before False Pass can be plugged in.
They will need to explore the permitting process, Wright said, as well as conduct environmental work to ensure their project and product are environmentally safe.
However, that's one of the things Wright likes about this project's potential, its low impact in many environmental aspects.
"What is appealing to me is that they're geared to run at low speed," Wright said.
Wind turbines have to run at very high speeds to generate power, but water, being 200 times denser, allows turbines to rotate more slowly.
"Animals moving through the water can avoid these things or even swim through them," Wright said, adding that tests for the equipment they are using now verify that.
"We're also real excited about deploying during October," he said. "The period between late September and early December is when you have your big fall tides."
After their data collection period is done, Wright and his team will spend the winter analyzing data and coming up with the next step.
"I'm pretty excited about the project because of the potential it means for Alaska, especially these remote communities," Wright said. "If we can provide half of the electricity and half of the heat for False Pass, why can't we do that in all of our coastal communities?"
Or for that matter, Wright said, for larger cities as well.
Publication that describe Gulf of Alaska ocean currents:
Wright, B.A., J. W. Short, T. J. Weingartner, P. J. Anderson. 2000. The Gulf of Alaska. In: Seas at the Millennium: An Environmental Evaluation. Ed. C. Sheppard. Elsevier Science Ltd.
1) Collect existing bathymetric, tidal, and ocean current data at the site to develop a basic model of current circulation at False Pass.
2) Measure current velocities at a site of interest for a full lunar cycle to establish the viability of the current resource.
3) Collect data on transmission infrastructure, electrical loads, and electrical generation at False Pass.
4) Perform economic analysis based on current costs of energy and amount of energy anticipated from and costs associated with tidal energy project conceptual design.
5) Consult with agencies and perform literature review to scope permitting process and identify key environmental issues. Compile a report for project partners.
The data collected indicates False Pass has the country's best tidal energy resource measured so far. A verbal report will be presented at Ocean and River Power session of the Rural Energy Conference in Anchorage Tuesday, Apr 30th from 1:30pm-3:30pm
see also: http://alaskadispatch.com/article/20130505/tidal-energy-potential-aleutians-blows-expectations-out-water
------------------------------------------------------------------------------------------------------------------------------------------------------
Tidal power research underway at False Pass
October 5th 2:11 pm | Hannah Heimbuch
As energy companies race to reap the benefits of Arctic oil, other parts of the state are charging into new energy technologies.
In False Pass, researchers have initiated a project that explores the potential power of ocean currents. Much like wind turbines harness the massive moving energy of air currents, underwater turbines lasso the energy created by water currents.
Alaska is lacking in neither natural phenomenon, said scientist Bruce Wright.
Wright is the senior scientist for the Aleutian Pribilof Islands Association, an Aleut tribal non-profit organization. They recently received a $200,000 Department of Energy grant to explore tidal energies, and are focusing their attention at the narrow saltwater chute of Isanotski Strait at False Pass, at the end of the Alaska Peninsula.
It is the first pass that Pacific waters come to as the Alaska Coastal Current pushes them toward the Arctic Ocean, Wright said.
Alaska possesses 90 percent of the United State's total tidal power potential, according to the Ocean Renewable Power Company, the company contracted to conduct the research at False Pass.
ORPC is also conducting similar research in Cook Inlet, as well as other locations around the country.
Last week, two acoustic current Doppler profilers were placed in the waters of False Pass, and will remain there for about five weeks, Wright said, collecting data on the volume and speed of water moving through.
There are two forces at work in coastal waters, Wright said, the Alaska Coastal Current and the daily tides.
"There's a correalus effect which is caused by the spinning of the earth on its axis," Wright said.
The earth's rotation naturally pumps water out between Canada and Greenland and down into the northern Atlantic Ocean.
"To make up for that vacuum that's created in the Arctic Ocean, water from the Pacific fills that, coming up along the Alaska coast. The Alaska Coastal Current starts along the coast around British Columbia, and propagates up."
The velocity with which that massive current moves is in part determined by how much fresh water is streaming out of Alaska's coastal range and into the ocean. That outflow is about 1.2 times the size of the Mississippi River's.
What Wright and the Ocean Renewable Power Company want to know is, how much force is generated as this current pushes past land formations, like at False Pass, and how well can it be harnessed by underwater turbines.
A speed of about seven knots is prime, Wright said, and not terribly uncommon along coastal Alaska.
Their research will include several elements, Wright said. First, they will examine the power grid at False Pass to determine how much power the community uses, and how equipped it is to handle power efficiently.
The next part, which began last week when the profilers went underwater, is to determine exactly what kind of power output could be available by harnessing the local waters.
The University of Alaska Anchorage engineering department helped by establishing optimum spots to put the profilers, using historical tidal and current data.
"When I proposed this project I wanted to capture that Alaska coastal current," Wright said. "(Find out) if it was strong enough to drive a turbine. In addition to the ocean current going through False Pass there is also a tidal influence, caused by the gravity of the moon and the sun."
They want to know how much this tidal influence affects the power of the current. This is one of the reasons they are conducting at least a full month of data collection, to observe an entire lunar cycle of tides.
"So there's a question then, how strong is the Alaska coastal current and how does it correspond, dovetail, counteract or relate to the tidal current."
Should they find a viable amount of power, a number of things will need to happen before False Pass can be plugged in.
They will need to explore the permitting process, Wright said, as well as conduct environmental work to ensure their project and product are environmentally safe.
However, that's one of the things Wright likes about this project's potential, its low impact in many environmental aspects.
"What is appealing to me is that they're geared to run at low speed," Wright said.
Wind turbines have to run at very high speeds to generate power, but water, being 200 times denser, allows turbines to rotate more slowly.
"Animals moving through the water can avoid these things or even swim through them," Wright said, adding that tests for the equipment they are using now verify that.
"We're also real excited about deploying during October," he said. "The period between late September and early December is when you have your big fall tides."
After their data collection period is done, Wright and his team will spend the winter analyzing data and coming up with the next step.
"I'm pretty excited about the project because of the potential it means for Alaska, especially these remote communities," Wright said. "If we can provide half of the electricity and half of the heat for False Pass, why can't we do that in all of our coastal communities?"
Or for that matter, Wright said, for larger cities as well.
Publication that describe Gulf of Alaska ocean currents:
Wright, B.A., J. W. Short, T. J. Weingartner, P. J. Anderson. 2000. The Gulf of Alaska. In: Seas at the Millennium: An Environmental Evaluation. Ed. C. Sheppard. Elsevier Science Ltd.