Tidal Power
Tidal power converts the kinetic energy within the mass of moving water into electricity, including underwater currents which tend to be tidal. This energy can be harnessed to generate electricity. Unlike electricity from wind power, tidal power is predictable and reliable. Electricity from these renewable resources has a low carbon output.
Tidal streams passing through the tidal stream generators use the kinetic energy in the water to operate turbines which generate the electricity.
tidal power is the result of the moon's gravitational effect on the mass of the oceans. There are other factors affecting tidal movements but the effect of the moon is the major one.
According to the Sustainable Development Commission (SDC), the UK's outstanding tidal resources could provide at least 10% of the country's electricity.
Tidal barrages
Tidal barrages are built across a channel in order to force the tidal waters to flow through the turbines as the tides ebb and flow. The presence of waves is not a factor in generating electricity from tidal movements - see wave energy for more information.
The role of tidal power schemes in the UK energy plans has suffered a severe blow with the abandonment by the current government of the Severn Barrage scheme and the potential barrages in the north west. These had the potential to have produced 17TWh of electricity which would have been 44.4% of the UK demand!
The feasibility study concluded that there was currently no 'strategic case' for investing public money in such a scheme. Proposed barrage schemes in Cardiff and Liverpool have also been shelved. The study did concede that barrage schemes could be reconsidered as a longer-term option in the future. (barrage schemes)
The one problem with developing this resource is the impact on the unique ecosystems and regional economies.
References
(barrage schemes) BBC accessed 18-Oct-2010
(SDC) The Sustainable Development Commission
(LIVERPOOL) North-west tidal barrages