Tides are formed as a result of gravitation force from the sun and the moon, Tidal barrage are dams constructed across an estuary to hold water during high tides and then utilise the potential energy from the high water levels during low tide to generate electricity using turbines, the largest tidal barrage is the Rance tidal plant in France that produces 240 mega watts.
Wave are formed when a strong wind passes over sea water, when wave energy is captured it is used to generate electricity, the height of waves depend on the speed of wind, depth of water and duration of wind. According to Jason Margolis(2007) the Pelamis system is on of the widely used method to produce electricity, the Pelamis is a large snake like device that floats and is anchored to the seabed, the device has three power generating sections and waves enable the device to make snake like movements that push hydraulic fluids used in generating electricity,
Jason Margolis (2007) states that the system is expensive compared to other sources of energy and at the same time relatively inefficient, these devices are placed parallel to each other forming a wave farm, one of the operational Pelamis system was installed in Portugal in 2008 producing 2.25 megawatts.
Offshore Wind farms:
Wind power is utilised by turbines which that produce electric energy, according to Jason Margolis (2007) wind energy costs have reduced by 80% over the years due to advancement in technology. A wind farm is a number of wind turbines in the same location. Wind farms are either onshore farm, near shore or offshore. Offshore wind farms are located some kilometres into the sea, wind speed in the sea is considered to have higher speed compared to the wind on the land, however offshore wind firms are more expensive than other wind farms.
According to Jason Szep (2009) the US plans to install an offshore wind firm at a cost of 1 billion dollars, the project is expected to have 130 turbines which will produce approximately 170 megawatts in the Cape Cod region and the power generated will be in a position to provide power to over 400,000 residents.
Ocean thermal energy conversion:
This is a form of energy source that involves utilising temperature differences in sea water, large temperature differences produce more power, the thermal system used in producing electricity is approximately 3%, system used in utilising this form of energy are very expensive and the power produced is relatively low and depends on the location.
According to Reuters (2008) the US government has plans of spending over 1.4 billion to enable innovations of Ocean thermal energy conversion, for this reason therefore there have been efforts to improve Ocean thermal energy conversion.
Political, economic and environmental implications:
The European Union according to this report is planning to over 20% of energy using renewable source and therefore it is likely that the renewable energy will be alternative in the future to produce electric energy. However Critics exist is that the some forms of energy sources will hinder economic growth, example the proposed wind farm in the US is expected to hinder commercial fishing in