Due to the recent energy problems that have arisen, considerable interest has been given to converting the kinetic energy of fluid flows occurring in nature into electrical power, e.g., using wind flows in wind power generation systems (e.g., that are sometimes called wind energy conversion systems) and water current flows in kinetic hydropower generation systems. For example, wind energy conversion systems involve directing wind through a turbine that rotates an electrical generator, causing the electrical generator to produce electrical power, whereas kinetic hydropower generation systems typically involve submerging a turbine under water and directing flowing water current through the turbine, causing the turbine to rotate an electrical generator for producing electrical power.
Such turbines are complex machines with several sub-machines that convert the kinetic energy of the moving fluid to electrical power. That is, these machines have a large number of moving parts that are subject to failure and that require considerable maintenance, resulting in high maintenance costs.
In particular, the power generation depends on the length of the turbine blades, e.g., the longer each turbine blade, the higher the power generation. However, long blades are costly, can be subjected to defects and failure, take up a large amount of space, and generate excessive noise and vibration. Longer propellers increase not only the cost of material and installation, but also the cost of maintenance. As such, current wind energy conversion systems and kinetic hydropower generation systems typically suffer from low efficiency, high capital cost, unpredictable failures, excessively high noise and vibration, and/or high maintenance.
Many of these turbines operate at relatively low rotational speeds (e.g., typically 20 rpm for wind turbines) and require gears to increase the rotational speed up to rotational speeds that are useful for the generator (e.g., typically 1500 rpm for a 1.5 MW generator). This involves high levels of torque and accompanying high gear-mesh forces that can cause the gears to fail, thus meaning considerable maintenance to reduce the amount of failures. Because of the low speed of the turbine, the various gearbox components are usually supported by rolling element bearings. These bearings are subject to significant radial loads that can cause the bearings to fail prematurely, thus meaning considerable maintenance to reduce the amount of failures.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternatives to existing fluid power generation systems, such as wind energy conversion systems and kinetic hydropower generation systems.