Experimental and Numerical Studies of the Wave Energy Hyberbaric Device for Electricity Production

Abstract

Small scale experiments and numerical simulations have been performed to evaluate a new concept of converter to produce electricity from wave energy. The models, tested in scale 1:10, have been submitted to different regular waves, with height and period representatives of the Brazilian coast, to evaluate the power generation and efficiency. The tests were carried out in a wave basin able to simulate in scale the wave conditions. Software especially written for the simulation of the converter behavior under regular waves has been initially correlated with the experimental results and, later on, it will be employed in parametric studies to estimate the best parameters of the system, in particular the prescribed pressure to be set for the best performance in terms of electricity production.

Hierarchical control and emulation of a wave energy hyperbaric converter

“…Figure 13 shows the average hydraulic power absorbed by one pumping module as a function of the IMP position reference of the HSS control, for sea states with T av of 6 s and different values of H s from 0.7 to 1 m. The hydraulic power is proportional to the HSS input flow and the pressure p 1 . As the theoretical power per meter of incident wavefront is proportional to the square of the significant wave heights, that is P w ≈ 0.5H 2 s T av , curves with higher plateaus are observed for significant waves heights of 0.9 and 1.0 m. It can be observed that each power curve presents a maximum point of power conversion, which corresponds to the IMP position as calculated by (20). For example, when H s = 0.7 m, the maximum power point is reached at 𝛿 ref = 0 m. Then, the HSS pressure stabilizes at values close to its optimum value of 2 × 10 6 N∕m 2 and the average hydraulic power transferred to the HSS is about 0.08 p.u.…”

“…Two stages are defined according to the body motion: (a) the high-pressure stage occurs during the downward motion of the body, when water is injected into the accumulator; (b) the low-pressure stage occurs during the upward motion FIGURE 2 Schematic of the accumulator and variables of the HSS model of the body, when the pump is filled with water. Thus, the PTO force is defined as [20]…”

“…Thus, the control scheme that integrates both the HSS and DFIG controllers plays an important role in the overall performance of the system. If, for instance, the IMP position is different than the desired value (20), the FIGURE 15 Typical power curve of a Pelton turbine overall efficiency can drop up to 17% for the studied cases, assuming the same conditions for the electromechanical system.…”

“…Other studies related to the hyperbaric WEC have focused on small-scale model studies [20], dynamic wave-to-wire modelling [21], optimizing the wave energy absorption [22], verifying the impact of the storage system on the quality of the generated power for different configurations of the SCU [21] [23], and distributed generation applications [24]. In contrast to [23], where the DFIG is controlled by the mechanical speed, this work presents a different control strategy for the DFIG, which is controlled by the active power.…”

Numerical Model of Constrained Wave Energy Hyperbaric Converter under Full-Scale Sea Wave Conditions

“…A wave energy hyperbaric converter (WEHC) is a top-mounted pitching point wave energy converter (WEC) device, which mainly consists of three different sub-systems: floater, lever arm and a complex hydraulic power take-off (PTO) system [1,2]. The floater is connected by a lever arm to a hinge in the support platform where the rotational motion of the lever arm is damped by a PTO system to absorb power in operational conditions.…”