| Tidal power represents an excellent renewable energy resource for the United States, but its economics must be reassessed in such a way that it becomes cost competitive with fossil fuels. In order to reduce operating costs, Sunlight Photonics Inc., in conjunction with Rutgers University, has designed and tested a modified tidal current system which utilizes an underwater hydraulic energy transfer system instead of the current underwater turbine-generator assembly, a design which experiences high failure rates and is expensive to build and maintain. In the modified design, generators and all electrical components are relegated to on-land electrical stations, while the underwater system consists of a tidal turbine and hydraulic pump assembly; as the tidal turbine spins, a hydraulic pump attached to its drive shaft creates high pressure fluid. This high pressure fluid is sent to land, where it can produce electricity in a well-controlled environment.;The prototype was designed with knowledge gained from extensive research into centrifugal and positive displacement pumps, gearboxes, and hydraulic fluids. The prototype utilizes a radial piston pump engaged to a 20 horsepower motor via a 14.63:1 reduction helical gearbox to simulate the power potential of the tides. An axial piston motor linked to a 460 volt three-phase alternating current generator and resistive load bank helps to simulate the effects of an active power plant on the hydraulic circuit. Testing showed that a heavily loaded generator produces greater pressure differentials between the high and low pressure sides of the hydraulic circuit than an unloaded generator. System efficiency of 20%, which is lower than anticipated, is traced to an underperforming generator and improperly sized hydraulic circuit. Recommended design modifications include a resized axial piston motor and generator assembly to help increase system efficiency to competitive levels of 70% or greater. |
