The world’s oceans hold a vast, largely untapped store of kinetic energy in their tides and waves. Tidal energy, driven by the gravitational pull of the Moon and Sun, and wave energy, generated by wind blowing across the ocean surface, together represent a predictable and abundant source of clean power. While still in relatively early stages of commercial deployment compared to wind and solar, marine energy technologies are advancing rapidly, with several nations investing heavily in harnessing the power of the sea.
Tidal Energy: Predictable and Reliable
Unlike wind and solar, tidal energy is almost perfectly predictable. The timing and magnitude of tides can be calculated with precision centuries in advance, making tidal power a uniquely reliable renewable energy source that can be integrated into electrical grids with minimal uncertainty.
Tidal energy can be captured through several technologies. Tidal barrages are dam-like structures built across estuaries that capture water during high tide and release it through turbines as the tide falls. The La Rance tidal barrage in France, operating since 1966, generates 240 megawatts and remains one of the largest tidal power installations in the world. However, barrages are expensive to build and can significantly impact estuarine ecosystems.
Tidal stream generators, essentially underwater wind turbines, are deployed in channels and straits where tidal currents flow rapidly. These devices extract kinetic energy from moving water, which is roughly 800 times denser than air, meaning that relatively small turbines can generate substantial power. Several commercial-scale tidal stream projects are operating in Scotland, Canada, and France.
The Bay of Fundy in Nova Scotia experiences the world’s highest tides, over 16 metres in range, and has been identified as one of the most promising sites for tidal energy development globally. The Fundy Ocean Research Center for Energy (FORCE) serves as a test site for tidal turbine technologies, and Canada is positioning itself as a leader in the emerging tidal energy industry.
Wave Energy: Harnessing Ocean Swells
Wave energy converters (WECs) capture the energy carried by ocean surface waves. Several distinct technologies are being developed. Point absorbers are floating buoys that move up and down with passing waves, driving a generator through their vertical motion. Oscillating water columns use wave action to push air through a turbine housed in a partially submerged chamber. Attenuator devices are long, articulated structures that flex as waves pass along their length, generating power at each joint.
The global theoretical wave energy resource is estimated at approximately 2 terawatts, comparable to current global electricity consumption. Practical extraction is limited by technology, economics, and environmental constraints, but even capturing a fraction of this resource could make a significant contribution to global clean energy supply.
Challenges and Progress
Marine energy faces significant engineering challenges. The ocean is a harsh environment, saltwater corrosion, biofouling, extreme wave loads during storms, and the difficulty of installing and maintaining equipment in deep water all increase costs and reduce reliability. As a result, marine energy currently costs significantly more per kilowatt-hour than onshore wind or solar.
However, the industry is following a similar learning curve to early wind energy. Costs are decreasing as technologies mature, manufacturing scales up, and operational experience accumulates. Standardisation of components, improved materials science, and better environmental monitoring are all contributing to progress.
Environmental considerations include potential impacts on marine mammals, fish migration, sediment transport, and seabed habitats. Ongoing monitoring at tidal and wave energy test sites has generally found impacts to be modest, but comprehensive long-term studies remain necessary as deployment scales up.
Future Outlook
The European Marine Energy Centre in Orkney, Scotland, serves as the world’s leading test facility for marine energy technologies. The UK, France, Canada, and several other nations have established dedicated funding programs for marine energy development. As climate targets require diversification of renewable energy sources beyond wind and solar, the predictable, high-density energy of the ocean is poised to play an increasingly important role in the global energy transition.
