The energy absorbing unit of the INWave WEC, responsible for recovering wave energy, is separated from the main power generating block. Not only does this set-up increase the power generating efficiency by collecting more energy of the wave, it also protects the power generators from wear and improves the overall durability, safety and economics.
INGINE’s unique ‘Multi-DOF Power Take Off’ technology and power control approach enables power generation in shallow coastal waters. This means that this can also be utilized in distributed power generation at target niche market such as islands and remote coastal areas otherwise inaccessible to existing technologies.
The buoy, designed to be sensitive to wave motions, moves up and down, left to right, and rotate along with waves. Each time the buoy moves, at least one of the ropes connecting power generating unit on land to the buoy is caused to pull and deliver the force (energy) of the waves.
The buoy is maintained in a natural mooring state by attached ropes, specially designed to withstand the underwater environment, and pulleys installed on the seabed. Required tension of ropes is ensured by the buoy’s buoyancy on one end and the counterweight load of the power generating unit on the other end.
The underwater pulleys employ the seawater lubricant bearings to ensure that the guiding ropes work in unison with movements of the buoy, which results in reduction of the power loss during transmission.
The wave energy recovered by the Energy Absorbing Unit (EAU) is transferred to the Power Generating Unit (PGU) through reciprocating motion of the guiding ropes, which is further converted into a one directional rotary motion imparting motive power to the generator. PGU controls the generated power and its further supply to the grid. By controlling the load of the generator, it becomes possible to control the tension of the rope to maximize the power generation and to prevent the rope from tear and rupture.
The following describes the process wherein a reciprocating linear motion of rope is converted into a one directional rotary motion.
The opposite end of the rope connecting the buoy with the power converter is attached to the drum. The linear reciprocating motion is converted into a rotary motion through the process of winding or unwinding the rope on the drum. A one-way clutch installed inside the drum ensures that the shaft connected to the generator always rotates in one direction.
An equalizer (counterweight) interlocked with the drum maintains the tension of the rope and ensures that the buoy stays in its designated position. In this case the number of drum rotations is relatively low considering the high torque; therefore, the speed of rotation is increased by the accelerator to drive the permanent magnet synchronous generator (PMSG). The Power Conditioning System (PCS), responsible for MPPT (Maximum Power Point Tracking), controls the input load corresponding to the rotating speed of the generator in order to determine an optimum generating point. Following the smoothing the produced electricity becomes compatible with applicable grid quality requirements for offtake.
Subject to location and site conditions, it is then decided whether to deploy a fixed or floating type of INWave WECs, suitable for shallow waters and deep sea respectively.
INWave Onshore, INGINE’s first WEC product model, is probably the most economical WEC available at this time since it does not require capital intensive infrastructure of laying underwater transmission cables. INWave Nearshore, currently under development, is a floating type WEC, having power generating units mounted on top of the buoy, which makes it less constrained by location.