Wave Energy is energy contained in the motion of ocean surface waves and can be converted into useful mechanical or electrical energy through specialised marine technologies. Ocean waves form primarily when wind transfers energy to the water surface through aerodynamic interaction. Once generated, waves can travel considerable distances while carrying energy, with wave characteristics influenced by wind speed, duration, fetch, water depth and atmospheric conditions.
Wave energy devices attempt to capture oscillatory movement, pressure changes or water displacement and convert those motions into electricity. Technologies include oscillating water columns, point absorbers, attenuators, overtopping devices and other concepts. Wave Energy Science combines fluid mechanics, oceanography, hydrodynamics, mechanical engineering, materials science, marine structures, power electronics and environmental assessment.
Waves are characterised by parameters such as height, period, wavelength, frequency and direction. Wave energy depends strongly on wave height and period, with the energy flux of deep water waves increasing substantially as wave height rises and also depending on wave period. Regular waves are useful for theoretical analysis, but real oceans contain irregular wave spectra produced by multiple wind systems and swell conditions.
Significant wave height is commonly used to describe an irregular sea state and represents a statistical measure rather than the height of every individual wave. Spectral analysis separates wave energy across frequencies and directions, helping engineers determine which frequencies a device should respond to efficiently. Near shore, waves interact with the seabed and undergo shoaling, refraction, diffraction, breaking and energy dissipation. Wave energy systems must therefore be designed around local hydrodynamic conditions.
Oscillating water columns use a chamber in which rising and falling water compresses and expands air. The changing air pressure drives a turbine, often a specialised turbine capable of operating with bidirectional airflow. Point absorbers are floating or submerged structures that respond to wave induced motion, with relative movement between components driving a mechanical or hydraulic power take off system. Attenuators are elongated devices oriented approximately parallel to incoming waves and generate power from flexing or relative movement between sections.
Overtopping devices collect wave water above the surrounding sea level and then release it through turbines. Each design uses a different physical mechanism and has different requirements for anchoring, survivability, maintenance and energy conversion. There is no single wave energy technology that is universally suitable for all marine environments.
The ocean is an extremely harsh engineering environment. Wave energy devices experience repeated cyclic loading, extreme storms, corrosion, biofouling, mooring forces and complex interactions between structural and hydrodynamic behaviour. A device must capture energy during ordinary operating conditions while surviving much larger extreme waves. This creates a fundamental design tension because structures must be robust enough to survive rare severe events without becoming excessively expensive or inefficient during normal operation. Mooring systems must maintain position while allowing appropriate movement.
Electrical cables must accommodate motion where devices are floating. Maintenance can be difficult because weather windows for marine operations may be limited. Reliability is therefore one of the major determinants of practical wave energy performance, and laboratory demonstrations do not automatically establish long term commercial viability.
Wave energy is renewable because ocean waves are continually regenerated by atmospheric wind systems, although the immediate resource varies with weather and geographical conditions. Unlike tidal currents, wave production is not governed primarily by astronomical cycles and is therefore less predictable far in advance. However, wave forecasts can provide useful information over operational timescales. Wave resources can also show geographical persistence because ocean swells may travel long distances.
Offshore locations can offer stronger wave resources, while near shore locations may simplify some aspects of infrastructure but experience altered wave conditions. Wave energy devices are therefore selected according to the local wave climate, water depth, seabed characteristics, accessibility and electrical connection requirements. Resource assessment commonly combines buoy measurements, satellite observations, numerical wave models and long term statistical analysis.
Environmental effects of wave energy can arise from device structures, moorings, electromagnetic fields from cables, underwater noise and changes in local wave energy. A large array may alter wave propagation and sediment transport, although the magnitude and significance depend on device design, spacing and site characteristics. Devices can create new surfaces that become colonised by marine organisms and may alter local habitat. Moorings and anchors can disturb seabed areas during installation.
Wildlife interactions must be assessed according to species and location. At the same time, wave energy devices do not require combustion and may have relatively limited direct atmospheric emissions during operation. Environmental assessment therefore requires comparison between infrastructure effects and the potential benefits of generating electricity without direct fossil fuel combustion.
The history of wave energy includes numerous concepts proposed during the development of modern electrical engineering, followed by periods of intense research and experimentation. Early ideas often struggled with poor survivability, high costs and inefficient power conversion. Later development benefited from improved computational fluid dynamics, numerical wave modelling, composite materials, hydraulic systems, permanent magnet generators, advanced control systems and marine engineering. Researchers now use numerical and physical tank experiments to investigate device behaviour before sea deployment.
Full scale demonstration remains important because real ocean conditions include irregular waves and extreme events that are difficult to reproduce completely in laboratories. The field therefore illustrates the importance of testing energy technologies under realistic environmental loads rather than evaluating only nominal energy conversion efficiency.
Wave Energy should be distinguished from tidal energy, offshore wind energy and general ocean energy. Wave energy extracts energy from surface wave motion, whereas tidal systems exploit gravitationally driven water level or current changes. Offshore wind turbines extract energy from atmospheric air movement above the sea rather than from the waves themselves. Wave devices can also be combined with offshore infrastructure, but shared infrastructure introduces additional design considerations.
Advantages include a large theoretical ocean resource and the possibility of producing electricity near coastal demand centres. Limitations include severe marine operating conditions, variable resource availability, difficult maintenance, relatively high engineering complexity and the need for reliable power take off systems. Wave Energy remains a technically demanding field in which survivability, reliability and cost are as important as theoretical resource magnitude.
