Marine in brief
Marine energy harnesses the movement of the oceans: the rise and fall of the tides, the flow of tidal currents and the energy in waves.
Tides are entirely predictable decades ahead, which makes tidal power attractive for a grid with lots of wind and solar. The industry is still early, with a few large tidal-range plants and growing tidal-stream arrays.
How it works
- Tides move huge volumes of water. The Moon's and Sun's gravity drive regular rises, falls and currents.
- Turbines or barrages capture it. Underwater turbines sit in fast currents; barrages and lagoons hold back the tide.
- Wave devices ride the swell. Floating or seabed devices convert the motion of waves.
- Subsea cables bring power ashore. As with offshore wind, export cables connect to the grid.
Main technologies
- Tidal stream: Underwater turbines in fast tidal currents.
- Tidal range: Barrages and lagoons using the height of the tide.
- Wave energy: Devices capturing the energy of ocean swell.
Strengths
- Predictable years in advance
- High energy density of water
- Complements wind and solar
Challenges
- High costs at today's small scale
- Harsh marine environment
- Few suitable high-flow sites
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