Design of a micro-hydrokinetic electric power generation system

Abstract

The objective of this thesis project is to design a Micro-Hydrokinetic Power Generating (MHPG) system to generate electricity from sustainable and distributed hydrokinetic resources. The system is developed from a patent held by one of our team members, Robert Kallenberg. The MHPG does not require a dam or diversion, thus avoiding the negative environmental impacts associated with dams. The project could also help some communities to make use of their locally available hydrokinetic resources and significantly reduce their electricity costs. Reviewing of the literature in hydrokinetic electric power generation technology shows that hydrokinetic projects developed to date have largely made use of hydro turbine systems. These hydro turbines have a strong potential to cause fish mortality, while by design, the MHPG has little chance of causing mortality due to its gentle motion. On the other hand, the build-up of debris on a conventional hydro turbine can easily disable or even destroy the turbine, while the hydro foil in our device is generally oriented with the angle of attack less than 30 degree from the current, keeping debris build up at a minimum. The state of the art software COMSOL Multiphysics has been used as our numerical analysis tool. The interaction of water and the designed foil in a straight rectangular turbulent channel is modeled, explicitly, using two conservation laws: conservation of momentum and conservation of mass. The incompressible Navier-Stokes application mode in COMSOL Multiphysics has been used in this simulation to solve the distribution of the pressure and the velocity filed. Results show that the oscillating hydro foil has the potential to surpass the efficiency of a conventional turbine, and is deployable in relatively low velocity streams. Future project development suggestions will be presented focusing on further improvements electric machinery design and system integration. Finally, the prototype of the device has been fabricated and tested in natural rivers. The first test in Chena River, AK, verified the design by showing that the prototype can move in an oscillating manner. The second test in San Gabriel River, CA, shown that the designed Scotch Yoke, which was used to convert linear motion into rotational motion, could be efficiently integrated with the motion generation system. Future test work including permanent magnetic generator coupling and energy efficiency measurement need to be carefully studied concerning the system efficiency and maintenance.