The UK’s largest proposed scheme, a huge concrete barrage (similar to a dam) stretching across the Severn Estuary was recently given the nod by the Sustainable Development Commission. If built, however, it would cause extensive damage to wetland ecosystems and disrupt the tidal range further up the estuary. Studies in 1989 concluded that at least three important bird species would be driven away from the South West as a result, fish mortality would increase, and the impact upon the 65,000 birds that winter on the estuary is uncertain.
In place of the barrage, Friends of the Earth supports the building of tidal ‘lagoons’ – circular impoundment structures built in sections of the estuary which trap water inside their boundaries at high tide and let it flow through turbines built into their walls at low tide to generate huge amounts of power.
The lagoons, proposed by British/US company Tidal Electric, would not only have minimal impact upon the tidal range and ecology of the estuary, but could in fact generate up to 14 TWh more power than the barrage each year.
Lagoons can also help match the availability of electricity with demand. When consumers are using less electricity than is being produced on the grid, water can be pumped up into the lagoon. This can then be released to generate energy at times of high demand.
Tidal stream technology, which uses turbines placed in fast-flowing water to generate electricity, could also play a significant role in generating regular, predictable amounts of power. Pilot projects are already underway.
To read the fulll investigation click here
This article first appeared in the Ecologist November 2007