Karin Thorburn

Catch the wave to electricity

The ocean are largely an untapped source of energy. However, compared to other energies, power fluctuations for ocean waves are small over longer periods of time. This paper present a grid-oriented approach to electricity production from ocean waves, utilizing a minimal amount of mechanical components.

A direct drive wave energy converter : Simulations and experiments

A novel wave energy converter concept is developed at Uppsala University, Department of Engineering Science. The concept is based on a synchronous permanent magnet linear generator, placed on the seabed. The piston of the generator is directly connected to a surface-floating buoy with a rope. The tension in the rope is maintained with springs that pull the piston downward. The three-phase current induced in the stator coil has a varying amplitude and frequency and a conversion is therefore necessary. Research has been carried out in three main areas: generator design, dynamic behavior and grid connection. The generator is modeled by full physics numeric simulations, based on a 2-dimensional finite element formulation of the time dependent electromagnetic field. A first set up is built to experimentally verify the simulated results. The impact of different parameters are estimated with mathematical models and verified by experiments. This paper includes both simulated and experimental results.Copyright

Dynamics of a Linear Generator for Wave Energy Conversion

A concept is presented where the piston of a seabed based linear generator is directly driven by a buoy on the water surface. A spring is connected to the other end of the piston. Thereby the buoy absorbs energy in two ways. A large number of poles are used as an “electromagnetic gearbox” which gives a high rate of flux change in the stator despite the slow piston motion. The damping force is a function of the velocity and the electric output power. In the studied concept the power from the generator is rectified with a diode bridge. The results of theoretical studies of output power and its interaction with the dynamics of the equation of motion are presented. It is shown that the DC voltage can be tuned to optimize the power production for each wave climate.Copyright