Hydraulic power transfer for hydrokinetic turbine systems

Hydrokinetic power is attractive due to its abundance, particularly near population centers. It is estimated that 370 TWh/yr of hydrokinetic power is available from rivers and tidal currents in the United States, which equates to 9.25% of the total annual U.S. energy demand. The conventional hydrokinetic turbine farm consists of multiple devices, each operating independently to convert hydrokinetic power to electrical power; in a farm consisting of dozens of turbines, costly maintenance and downtime are expected (due to saltwater leakage into submerged electronics, gearbox failure due to mechanical overload, and fatigue failure due to turbulent unsteady blade loads).

We have developed an extremely efficient hydraulic pump and corresponding hydraulic motor that will be an enabling technology for the hydrokinetic power industry. Our concept is to use hydraulic power transfer to an on-shore electricity generating station. In this architecture, the individual devices would consist of a conventional turbine rotor that now drives a hydraulic pump (completely eliminating the gearbox and submerged electronics in the nacelle). A high-pressure hydraulic line transmits the power to shore, while a low-pressure return line completes the hydraulic circuit. On-shore, one or more hydraulic motors directly drive an electric generator apiece. By modulating the transmission ratio, we can maintain a constant optimal generator rotation speed for varying turbine rotor speeds. In addition, we can take advantage of economies of scale and use a small number of large, efficient, cost-effective electric generators. Current projects include design, fabrication, and proof-of-concept testing of a scale model system, as well as systems engineering and economic analysis.

Faculty contact: Brenden Epps