Huge masses of water are moved every second by wind, high and low tide and currents. Electricity can be generated from these natural movements as oceans and rivers have an almost inexhaustible amount of available energy. Nevertheless, waves and currents are hardly ever used; South Korea ranks 1 with a total capacity of 512MW, followed by France (246MW) and the UK (139MW) (Numbers from 2016). Considering that the worlds largest hydroelectric dam, the Three Gorges Dam in China, produces up to 22,500MW alone, the figures for wave and tidal power is not really impressive. Consequently – and despite estimations that waves and tidal power have the potential to supply 10% of the total world’s energy needs – this type of renewables accounts for less than 1% of the world energy mix.
Most of the plants realized so far are prototypes that are still in the test phase and not yet ready for the mass market. The most important plants currently capable of generating energy from the sea are tidal power plants, current power plants and wave power plants – with tidal power plants accounting for by far the largest share of generated electricity from the sea.
- No CO2 nor any other environmentally harmful emissions are released. Therefore, the generation of electricity from the sea is renewable and environmentally friendly.
- Electricity from the sea can be generated independently of the time of day or season and is therefore a reliable source of energy. Hence,
- Electricity from the sea is more predictable than wind and solar energy.
- Since the electricity is mostly generated in plants at sea, there are no adverse effects on land masses and residents enjoy an unspoiled view.
- Many large cities are located by the sea and could therefore be supplied with renewable electricity due to their geographical proximity. But:
- There is only a limited choice of location, as such plants can only be built in certain regions.
- The marine ecosystem can be disturbed by large installations.
- The maintenance costs for the plants are very high. Wear and corrosion of the turbines due to aggressive salt water, waves and wind are a major problem.
- The biggest obstacle, though, is the high investment costs – especially compared to other renewable energy sources – which deter many investors.