Tidal energy
Tidal energy uses the regular rise, fall, and flow of ocean tides to generate useful power. It is predictable, renewable, and site-specific, with engineering and environmental tradeoffs that shape where it can work.
What tidal energy is
Tidal energy is a form of marine renewable energy that converts the movement of seawater into power. It can use the height difference between high and low tide, the speed of tidal currents, or both. Unlike waves, which are shaped strongly by wind and storms, tides follow astronomical cycles that can be forecast far in advance.
Why tides move
Tides form because the moon and sun pull on Earth's oceans while Earth rotates. Coastlines, bays, seafloor shape, and narrow passages can amplify that movement. A site with a large tidal range stores potential energy between high and low water, while a constricted channel can turn the same tidal cycle into fast-moving currents.
Main technology types
Tidal barrages work like dams across an estuary or bay, using gates and turbines as water fills or leaves a basin. Tidal turbines sit in strong currents and work more like underwater wind turbines. Tidal fences place turbines in rows across a channel. Proposed tidal lagoons would partly enclose an area of coast, but large commercial examples remain limited.
Where it works best
Tidal energy is not equally practical on every coast. Good projects need strong, regular water movement, access to transmission or local users, seabed conditions that can hold equipment, and enough clearance for navigation, fishing, wildlife, and recreation. That is why many promising sites are in straits, inlets, estuaries, and high-range bays rather than open beaches.
Predictable but difficult
The predictability of tides is a major strength, but the ocean is a hard place to build. Saltwater corrosion, biofouling, storms, sediment movement, underwater maintenance, grid connection, and permitting can raise costs. Turbines must also be robust because seawater is far denser than air and pushes much harder on blades and supports.
Environmental tradeoffs
Tidal projects can produce electricity without burning fuel, but they still affect local environments. Barrages may change water levels, sediment movement, turbidity, fish passage, wetlands, and estuary ecology. In-stream turbines usually have a smaller physical footprint, yet they still require careful study of marine mammals, fish, seabed habitats, sound, and navigation risk.
Why it matters
Tidal energy will not replace every other renewable source, but it can fill a useful niche. Predictable coastal power can support island communities, ports, aquaculture, sensors, desalination, and electricity grids that already rely on variable solar and wind. Its future depends on proving durable devices, reducing costs, and choosing sites where benefits outweigh local impacts.