Modeling and Measuring the Interaction between Hydrokinetic Devices and the Hydraulic and Sedimentary Environment of the Tanana River, Alaska

Abstract:

In this paper, we report on our efforts to model and measure the interaction between hydrokinetic (HK) devices and the hydraulic and sedimentary environment of the Tanana River, by Nenana Alaska. The Tanana River, by Nenana Alaska, has an open-water median flow rate of about 1325 m³/s, a width of about 200 m, a maximum depth of about 9 m, peak flow velocities of about 2.5 m/s, and suspended sediment concentrations as high as 2 g/L. Preliminary modeling of the hydraulic impact of a 45 KW cross-flow-style HK turbine using SNL-EFDC software found that the device raised water levels upstream of the device by about 0.5 cm. It also led to reductions in velocity of about 0.05 m and enhancements of about 0.01 m/s. In this paper, we will report on ongoing efforts to model the corresponding sedimentary impacts of HK devices at this location. In late August of 2014, a 15 KW open-center-style hydrokinetic turbine (manufactured by Oceana Energy Corporation) was deployed for a three week period at the Tanana River site. Device performance (e.g., power generation and angular frequency (rpm’s)) were monitored along with environmental parameters including: velocity as a function of depth upstream and downstream of the device, turbulence at “hub elevation” upstream and downstream of the device, suspended sediment concentration upstream and downstream of the device, and sediment bed elevation before and after testing. In this paper, we will report on all of these data as well as data on the abrasion of device components. Further, we will present data on the dependence of device coefficient of performance and turbulence intensity. Finally, we will compare modeled and measured hydraulic and sedimentary impacts of the HK device.