Hydrokinetic turbine systems for remote river applications in cold climates
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Date
2017
Authors
Woods, John
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Abstract
In-situ testing of hydrokinetic river turbines demonstrates the feasibility of installing these turbines in cold climates and at remote communities without significant infrastructure requirements. Complete water-to-wire systems are deployed, tested in winter conditions and retrieved with major aspects of the technology investigated. A robust river-bottom anchoring system is developed and tested suitable for remote communities with minimal infrastructure. Vertical-axis 5-kW and 25-kW hydrokinetic turbines are deployed and tested in the Winnipeg River, under various climatic and flow conditions: -36ºC to 30ºC and 2.0 m/s to 2.6 m/s. Winter testing reveals that frazil ice accumulates on devices near the water surface, ice forms at the air-water interface, and ice sheets flowing with the stream can impact near-surface components. These factors lead to the conclusion that for low-maintenance and reliable year-round deployment in cold climates, systems must be fully submerged and removed if major ice floes occur. Hydrokinetic turbine generated power is delivered to a utility 12.47-kV overhead distribution line through pole-top transformers and bi-directional electricity meters, establishing a remote community water-to-wire system for the first time. Commercially available rectifier/inverters, developed for use in wind and solar energy capture, are successfully integrated into the power conversion system for the 5-kW and 25-kW units, reducing costs. A power conversion design is developed and tested. Concurrent measurement of river flow and turbulence with electrical power output from the permanent magnet generator are obtained in-situ. This data is used to investigate power production fluctuations resulting from turbulence in the flow. Turbulence is evaluated in detail, using time domain and frequency domain analysis. Calculated turbulence length scales varied from 0.7 m to 1.2 m, which are in the order of magnitude for the physical rotor elements. The results show that power extraction is maintained in the presence of moderate to high levels of turbulence in the range of 4% to 5% and that such level can improve energy capture. These studies indicate that hydrokinetic turbine systems can provide reliable power for both micro-grids and base-load applications in remote communities located in cold climates if placed below the water surface and not impacted by river ice floes.
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Keywords
hydrokinetic turbine, renewable energy, distributed generation, river energy capture, turbulence, acoustic Doppler velocimetry, frazil ice, winter operation, three-dimensional velocity measurement, grid-connection, rectifier, inverter, rock anchoring system, hydrokinetic turbine deployment, site selection, river velocity profile, autocorrelation, power spectral density, turbulence length scale, remote community