The UAA School of Engineering has a number of active research programs in the area of renewable energy with a particular focus on hydrokinetic energy, hydropower, and wind power. In the area of hydrokinetic energy, UAA is conducting an Alaska-wide and a United States-wide assessment of the hydrokinetic energy potential (PI: Tom Ravens). The Alaska-wide project focuses on hydrokinetic energy available to rural villages located on the major rivers of Alaska. In the US-wide project, we are estimating the practically recoverable resource in the major US rivers in addition to the potential resource. In both projects, we are also addressing the impact of the deployment of hydrokinetic devices on the flow, water level, and sediment transport. In a third hydrokinetic project, we are working with a hydrokinetic energy company (Ocean Renewable Power Corporation) to test critical device components in a laboratory flume. In particular, we are examining the impact of suspended sediments on critical device components (e.g., bearings and seals). PI’s on the flume study include: Tom Ravens, Muhammad Ali, and Todd Petersen.
The School of Engineering (PI’s: Orson Smith, Jeffry Welker, and John Bean) is conducting active research in the area of small-scale hydropower. A major point of focus for this effort centers on the development of the "Girdwood Renewable Energy Research and Discovery Center". Related projects include: the California Creek hydropower feasibility study (with Alaska Green Energy, funded by Alaska Energy Authority); and hydropower feasibility studies at Crow, Alyeska, and Virgin Creeks (in partnership with Alyeska Resort, Sustainable Girdwood, Girdwood 2020, The Municipality of Anchorage, and local property owners).
Making Wind Work for Alaska
Dr. Matt Cullin, Dr. Todd Petersen, and student Chris Chance are currently working on a three year project installing ice-detection sensors on a wind turbine tower at the Banner Ridge wind farm in Nome, AK. Cold climate wind turbine operation presents a multitude of complex technical challenges.
This project performs a comprehensive analysis of wind turbine icing to determine the effect of blade icing on turbine efficiency and attempt to develop more reliable and easy to install sensors. An analysis of the foundation structure will also be performed in order to better quantify the unique requirements of cold climate construction and operation, and to optimize foundation designs as a way to reduce costs.
The presently available sensors have trouble reliably detecting ice which can end up being costly problem to turbine operators. These standards will help catalyze the development of cold weather specific turbines by providing manufacturers with definitive design specifications.
Assessment of the Hydrokinetic (Renewable) Energy Resource in the Continental US (2010-2012)
Tom Ravens and partners (Paul Jacobson, EPRI; Keith Cunningham, UAF; George Scott, NREL) are assessing the riverine hydrokinetic energy resource in the Continental US for the Dept. of Energy.The team has determined the theoretically available energy as well as the technically recoverable energy in river segments throughout the Continental US. For the "Lower 48", the theoretical resource (1146 Terawatt-hours/year) was estimated based on USGS's NHDPlus database. For Alaska, the theoretical resource (287 Terawatt-hours /year) was estimated based on Idaho National Lab's Hydro-Prospector. For reference, the total US demand for electricity is about 4000 Terawatt-hours /year. To estimate the technically recoverable resource, UAA did a number of case studies to estimate the fraction of the theoretical resource that would be available, given depth and velocity requirement, industry guidelines for device spacing, and "back effects". This fraction, referred to as the "Recovery Factor", depended on discharge and river slope and ranged from 0 to 0.26 for river segments representing the range of conditions throughout the US. The technical resource for the Continental US was estimated to be about 101 Terawatt-hours /year.Alaska's technical resource was estimated to be about 20 Terawatt-hours/year. The figure below indicates the distribution of the technically recoverable hydrokinetic resource (Terawatt-hours/year/km) in the Lower 48.
Statewide Assessment of the Hydrokinetic Energy resource in Alaska Rivers (2009-2012)
Tom Ravens and his research assistants have conducted a statewide assessment of the hydrokinetic energy resource at 30 village sites along the major rivers of Alaska including the Yukon, Kuskokwim, Copper, and Susitna Rivers. Funding was provided by the Alaska Energy Authority. The team visited each village site and measured velocity, depth, and water level along 6 to 10 cross-river transects.Based on these and other data, the team developed hydrologic and hydraulic models at the sites.Based on these models, the hydrokinetic power density (W/m2) was estimated. Figure 3a below indicates the state-wide distribution of in-river hydrokinetic energy based on the open water average velocity at these sites. Figure 3b provides an example fine-scale power density and velocity distribution at Red Devil (Kuskokwim River) for theflow rates at the time of the site visit, and for the 25, 50, and 75 percentile flow rates (flow statistics based on the open water period).
(a) Distribution of hydrokinetic power density (W/m2) at a number of village sites.(b) distribution of hydrokinetic power density and velocity at Red Devil for selected flow rates.
Hydraulic Impact of Hydrokinetic Energy extraction (2010-2012)
Tom Ravens and MS graduate student Maria Kartezhnikova have developed a technique to represent the hydraulic impact of HK devices using an enhanced Manning bottom roughness coefficient. The enhanced bottom roughness coefficient is a function of the Manning roughness of the natural channel bottom, the density of the HK device deployment, the efficiency of the devices, and the water depth. Figure 4 below shows the impact on velocity of a 20-device deployment in the Kuskokwim River by Red Devil. A technical paper entitled "Hydraulic Impacts of Hydrokinetic Devices" is in review in the Journal of Hydraulic Engineering.
Change in velocity distribution (m s-1) due to the deployment of HK devices.
Abrasion Testing of Critical Components of Hydrokinetic Devices (2010 - 2013)
Prof. Tom Ravens, Prof. Muhammad Ali, Prof. Todd Peterson, and their research assistants are working on a DOE-funded project to test critical components (bearings and seals) of hydrokinetic devices. The team has developed a lab flume (see figure) which simulates the hydrodynamic, thermal, and sedimentary environment of Cook Inlet. Preliminary testing on composite bearings has shown that these bearings wear faster at higher temperature. Future testing will examine wear rates for a range of bearing types. Testing will also examine wear rates with sedimented water.