# Modeling and Simulation of a Wave Energy Converter _Nwave_
## 5 Characteristics of the _Inwave_ Device  
Commonly, a point absorber is installed in an area deeper than 20 m of water. CETO [20] and the Lysekil project [21] pick the center of the buoy as the single point mooring and connect it to PTO because these locations have high enough energy density to concentrate mainly on the heavy motions. As water depths become shallower, the wave moves more in the direction of the surge than heave. As such, the _INWAVE_ device focuses on the surge and pitch motion and is installed nearer to the coast. Waves in shallow water are affected by sea-bed topography, resulting in irregular motions. To overcome this, the _INWAVE_ device is connected via three ropes that are on the bottom of the buoy. It is designed to respond to all motions within six degrees of freedom. The three ropes that are connected to the buoy are also connected to the counterweight on land via underwater pulleys. The ropes also spin the rope drum. Each rope drum transmits the torque to the electrical generator through the ratchet mechanism. While all three ropes move back and forth irregularly according to the movement of the buoy, they do not move in phase with each other. Accordingly, the time point in which each rope drum sends power to the generator is different. This reduces the effect of the inhomogeneity of electricity, which is one of disadvantages of wave power energy.  
Ropes are preferentially considered when designing the device. Due to the tension that is always in action between the buoy and the counterweight, ropes must have toughness to endure stress, the ability to endure salinity and sunlight, as well as the friction created as it winds up on the underwater pulley and the rope drums. While this paper's analysis was done with the assumption that power is supplied to the generator only when the buoy pulls on the rope and the counterweight rises, in reality, torque can be supplied to the generator when the counterweight is descending, as well. For this to occur, the ratchet mechanism needs to be designed in such a way that it allows for the generator to spin in one direction, regardless of the direction of the counterweight's movement. Currently, both ratchet mechanisms are undergoing field tests. In terms of smoothing of the created electricity, the best method would be to send all of the power created by two-way directional spin. However, to do so, we must carefully consider the relationship between the mass of the counterweight and the maximum wave height. The greatest function of the counterweight is providing the buoy with restorability. While heave and pitch motion gets restorability from buoyancy, surge motion gets its restorability from the tensions supplied from the rope by the counterweight. If the counterweight sends force to the generator on its way down, the tension supplied to the buoy will inevitably be smaller. If the tension supplied becomes zero, the rope will become loose. The moment the counterweight rises, it will put sudden shock on the rope, causing the rope to potentially break, or breakaway from the rope drum. This would not be a problem if the mass of the counterweight is sufficient. However, this would require the rope to be tougher, so that it can endure higher tension. Thus, we did not simulate this kind of situation because it would require more complex hardware. However, in future works, we plan to compare and analyze the data given by the prototypes.