Near-shore vs. off-shore

Near-shore wave energy levels compared with off-shore and on-shoreThe high-level review of global wave energy resources indicates the areas of the globe where wave energy converters can exploit most of this clean energy resource. However, a more detailed analysis of wave climate characteristics indicates that there is also a clear distinction in conditions present in off-shore compared to near-shore waves. Taking into account technical and economic constraints, near-shore areas offer far more attractive opportunities for exploitation than other ocean areas. Near-shore locations provide only slightly fewer exploitable resources, but with far less extreme conditions, easier access and significantly easier design criterions, which results in far lower investment requirement per MW of generating capacity.

Filtering the highest waves. The extreme waves created during storms do not reach near-shore areas as they break in more shallow water. Wave energy converters installed in deeper waters than WaveRoller have to weather these extreme conditions. Ensuring sustainability in this setting is very challenging not only from the technology viewpoint, but also from the cost perspective.

Narrower directional spread. Waves in deep water can travel in almost any direction, making energy extraction more difficult. However, as deep-water waves come closer to the shore they make contact with the sea bed and it is this "friction" that causes them to turn towards the shore. Consequently, WaveRoller devices located in near-shore areas encounter waves that almost always comes from the same direction, greatly improving the quantity of energy captured.

Highly exploitable wave power. The maximum wave height observed in near-shore areas is much closer to the average wave height. This narrower distribution of wave heights means that wave energy converters located in near-shore areas encounter more stable sea states that are closer to their normal operating conditions. This provides highly exploitable wave energy resources. On the contrary, off-shore locations are characterised by high gross wave power, but a much lower level of exploitable resources, due to extreme conditions.

Lower power transmission losses. Naturally, near-shore areas are closer to the shoreline than off-shore sites. A shorter distance to land means that electricity can be delivered to the grid with lower power losses. Although WaveRoller farms are not constrained by the distance to the beach, proximity to the shore significantly reduces the infrastructure costs.

WaveRoller operates in near-shore wave climate- milder than offshoreAmplification of back-and-forth movement of water due to shoaling. Water particles in deep-water waves move in a circular motion. This movement is however distorted in the near-shore region due to seabed interaction. The water moves back and forth in this area, which is exactly the phenomenon used by WaveRoller (See more on surge phenomenon). Although the circular motion in deep water would be sufficient to put the device into motion, the forces are amplified in the near-shore area, providing the optimal location for WaveRoller.