Wave and Tidal

Wave energy captures the movement in the waves and transforms it into electricity through variants of Oscillating Water Column or Point Absorber technology. The power output increases with the size of the waves. Tidal power uses the energy of currents created by the rise and fall of tides to drive turbines located in passages of water such as estuaries, which in turn drive a generator to produce electricity. Alternatively the high tide fills a reservoir with sea water which is later released through turbines when the tide is low.

Types

• Wave systems: floating or fixed to the seabed or shore
• Tidal: barrages, lagoons, fixed turbines

Other components

• Electricity transmission lines
• Grid connection that allows electricity export to grid and back-up electricity supply
• Battery if not grid-connected

Typical saving

Zero carbon renewable energy source. Savings depend entirely on the local resource and size of system. Small scale systems are not yet available. A single large system (~1MW) could meet the annual equivalent electricity requirements of 500 homes.

Indicative cost

Marine energy technology is still developing so cost estimates are very difficult. Most projects currently depend on grants but are expected to be commercially viable in near future. So far most systems are only profitable in remote coastal areas where alternative power production is limited or expensive.

Main issues affecting feasibility

• Availability of local resource close to source of electricity demand
• Variation in output over time: requires back-up supply or storage
• Other uses of location: shipping lanes, fisheries etc.
• Ecological impacts: in particular marine life and birds
• Noise and visual impact of surface systems