A New Solution for Sea Wave Energy Harvesting, the Proposal of an Ironless Linear Generator

Abstract

The paper investigates an innovative ironless linear generator, installable inside a wave energy converter, in order to produce electricity from sea waves. This energy source is considered strategic for the future, especially in small islands; however, this technology is still far from the commercial phase. Considering the wave energy potential of the Mediterranean Sea, a first prototype of the electrical linear generator was realized at the Department of Engineering of Palermo University. This machine can be run by a two-floating buoys system, able to produce a linear vertical motion. The main goal of this paper is the investigation of the advantages and the disadvantages of the utilization of steel materials to realize the stator of linear generators. Thus, starting from the prototype, the authors analyzed the effects produced by the replacement of steel in the stator with a non-magnetic material. For comparison, the authors evaluated the amplitude of no-load voltages, using a three-phase connection scheme, and the amplitude of the magnetic force produced by the interaction of magnets with the stator. Both aspects were evaluated through numerical simulations and mathematical models.

A Review of the Linear Generator Type of Wave Energy Converters’ Power Take-Off Systems

“…Usually, the linear PM generator consists of a translator which holds the permanent magnets (PMs) and the stator equipped with coil windings, or vice versa. The operating principle of the linear PM generator-based WEC has the translator connected to a floating or submerged buoy, and the stator is fixed, or vice versa [17]. With the hydrodynamic motion of the ocean waves, the translator goes up and down along with the buoy and produces the fluctuating magnetic field within the coil windings, generating electrical energy.…”

“…In addition to that, to get the maximum magnetic flux density Halbach, quasi-Halbach arrays have been used in linear PM generators for WECs [42]. The linear generators can be classified as transverse and longitudinal according to the location of windings relative to translator motion [17]. Using both transverse and longitudinal flux, a new hybrid transverse/longitudinal flux There are three possible ways to attach the permanent magnets: axially aligned-buried, radially aligned-buried and radially aligned-surface [40].…”

“…If the electromagnetic damping of the linear generator is defined by Equation ( 16), then the electromagnetic force can be calculated by Equation (17).…”

Research on Energy-Capture Characteristics of a Direct-Drive Wave-Energy Converter Based on Parallel Mechanism

“…Faraday's law of electromagnetic induction states that the induced electromotive force (EMF) in a closed loop is proportional to the change rate of magnetic flux across the loop over time. It is expressed by integrals as [26]:…”

Sea Wave Energy. A Review of the Current Technologies and Perspectives

“…Many authors claim that sea waves could play a significant role in the energy sector, especially in small islands [33][34][35]. Recent statistics indicate that the total theoretical wave-energy potential could achieve 30 × 10 6 GWh/year; however, this renewable source is irregularly distributed worldwide [36,37]. As shown in Figure 5, there are some hot spots (red-colored areas in the picture), i.e., regions with the highest values of wave-energy potential.…”