Modeling Current-Energy-Converter Devices in the Tanana River, Alaska

Conceptual flowchart of the modeling methodology.

Using turbine and river data provided by the Alaska Hydrokinetic Energy Research Center, a steady-state flow model was constructed for varying river discharge levels. The wakes of University of Alaska at Fairbanks New Energy Systems vertical-axis, 5-kW turbine as well as commensurate changes to the steady-state flow field were simulated. Finally, an example optimization study was undertaken for turbines arranged in various arrays to demonstrate the effects of lateral and downstream interference, wake recovery, and overall momentum removal on the flow conditions and power generation.

Considering a distribution of flow conditions over a 10-year period for the Tanana River at Nenana, variations in number of CEC devices and array layout provided insights into power production and environmental effects. Specific quantities of interest included changes in velocity and bed shear stress, which each showed changes in proportion to the number of devices in the array. Using SNL-Delft3D- CEC-FM with calibrated turbulence constants allowed for a design that maximized CEC array power while remaining within constraints of minimally altered environmental conditions. That is, array layouts could be selected to optimize power generation while minimizing flow-field changes.

This work highlights the importance of investigating array performance at each site under consideration. These findings are helpful in optimizing turbine arrangements in the Tanana River at Nenana that maximize power production and minimizes undesirable/unintended changes to the river’s natural flow (flow depth, velocity, and bottom shear).