April 13 , 2011 Jerome B Johnson, Energy From Moving Water: Tidal and River Current Hydrokinetic Energy , Institute of Northern Engineering, UAF

Energy From Moving Water: Tidal and River Current Hydrokinetic Energy

Jerome B Johnson, Institute of Northern Engineering, UAF

Turbines placed directly in river, ocean, or tidal currents generate hydrokinetic power from the kinetic energy of moving water. The available hydrokinetic power is a function of the density of the water and the speed of the current cubed. The minimum current required to operate a hydrokinetic device is typically 2–4 knots (1–2 m/s), but optimal currents are in the 5–7 knot (1.5–3.5 m/s) range. River and marine hydrokinetic technology is an emerging technology at a similar stage as wind power generation technology was 15 to 20 years ago. The Alaska region contains about 40% of the total U.S. river energy resource, 90% of the total U.S. tidal energy resource, and 40% of the U.S. continental shelf wave energy resource. Hydrokinetic turbines have frequently been discussed as an option for generating power in communities located along Alaska’s major river systems, and for tidal energy applications in Cook Inlet and coastal Southeast Alaska. Challenges to developing a commercial hydrokinetic industry in Alaska include determining the technological, operational, and economic viability of hydrokinetic turbines, meeting permitting requirements, and gaining stakeholder acceptance. Hydrokinetic technology can be affected by debris, sediment, frazil, and surface ice; river dynamics (turbulence, current velocity, channel stability); and the interaction of turbine operations with fish and marine mammals and their habitat. The question of turbine operation impacts on the aquatic environment is one of the major issues that will determine stakeholder and permitting agency views toward this new technology. The 2010 hydrokinetic turbine demonstrations conducted at Ruby and Eagle had major problems with floating and neutrally buoyant debris. These experiences indicate that developing technology to mitigate debris problems will need to be a high priority for practical hydrokinetic power production.