Erik Segergren

Converting kinetic energy in small watercourses using direct drive generators

Tidal currents, ocean currents and unregulated watercourses are all large sources of energy that can be converted into electricity. Several technical and economical solutions within this research area have been demonstrated. In literature there exists two different turbine types, horizontal and vertical axis. The present paper focuses on the design of a permanent magnetized generator directly coupled to a vertical axis turbine. The proposed theoretical concept is adapted to data measurements regarding water current velocities and flow profiles from a Swedish watercourse. A high electromagnetic efficiency of 90% is obtained.Copyright

Permanent Magnetized Generator for Marine Current Power Conversion: Proposed Experimental Setup

In order to verify the theoretical work considering very low speed permanent magnetized generators for marine current power conversion, an experimental setup is under construction. Earlier 2-dimensional Finite Element Method (FEM) simulations have been performed and in this paper focus is on the practical considerations regarding the rotor construction of the generator as well as the total system configuration with motor, frequency transformer and generator. A rotor configuration with milled grooves for magnet fixation along with a power feedback option with a resistive load is chosen for the first experimental setup.Copyright

Frequency optimization for direct drive synchronous current power generator

The objective of this paper is to theoretically demonstrate how the operational frequency affects the efficiency of a low-speed generator. Due to the varying nature of underwater currents, the voltage from a current power converter has to be rectified first and then digitally reconverted into a stable alternating current. When designing a direct drive generator for water current power conversion, the operational frequency is, thus, a free design parameter and not a fixed value determined by the grid. Finite element method was used to determine the efficiency and weight. A higher frequency means larger frequency-dependent losses, but also a lighter machine. Even at the highest frequency in this study, the frequency-dependent losses were not high enough to overcome the gain of a lighter machine. If a large generator diameter can be allowed, the water current power converter should be designed with as high operational frequency as possible.