Renew On Line (UK) 55

Extracts from NATTA's journal
Renew, issue 155 May-June2005

4.‘Tidal lagoons OK’

In a new report on tidal lagoons, as proposed by the company Tidal Electric Ltd. (see Renew 151, 152), independent consultants WS Atkins Engineering have confirmed that the generation of electricity by this means is viable. The report also confirms that a proposed 60MW lagoon scheme in Swansea Bay could generate electricity competitively- estimated at 3.4 pence/kWhour from a 2 square mile impoundment in an 8 meter tidal range. 

Tidal Electric Ltd Chairman Peter Ullman said,“Tidal lagoons are ready to contribute to meeting 2010 targets for emissions reduction by producing commercial amounts of predictable renewable power. Atkins confirms that tidal lagoons use conventional power generation equipment and marine construction techniques and pose no unusual challenges. We hope that electricity providers, the National grid, and government will be cheered by this news that another reliable renewable technology is now ready for deployment thereby adding to the mix of immediately available renewable technologies.”

As we have noted before, the DTI has been rather dismissive of this concept, in the belief that it would be expensive. Friends of the Earth Executive Director, Tony Juniper said, “The Atkins studies indicate that Tidal Electric has been giving a straight story on its costs all along. The lack of DTI recognition of the tidal lagoon concept has resulted in several years of delay when the UK could have been world leaders of this innovative idea. The DTI must move tidal lagoons forward in its priorities and support this technology now, where environmentally acceptable, alongside wind, solar, wave and biomass energy sources, rather than keeping lagoons in the 2020 basket of far-off experimental technologies.”

Friends of the Earth Cymru says that the Welsh Assembly ‘should now support Tidal Electric Ltd in the company’s vision to generate electricity from the large tidal energy resources of the Severn Estuary’.  The group say that potential investors in the proposed lagoon scheme in Swansea Bay will be looking to the Assembly and WDA for their view of the technology. They add that if the Assembly and the Agency are unsupportive then that cannot help investor confidence. Unfortunately,  the Welsh Assembly has so far been non committal in part it seems since it has been briefed by the DTI and WDA that Tidal Electric Ltd have underestimated the costs of their technology.   FoE Cymru claim that the DTI and WDA briefings have missed the point that the cost of electricity generated by lagoons is dependent on the size of the scheme and the tidal range, and that the economies of scale are significant- noting that the DTI briefing appears to draw on the generation cost of a tiny scheme proposed by Tidal Electric to supply a small fishing community in a remote area of Alaska. They say that electricity from such a tiny scheme in a low 3 metre tidal area is going to cost far more than very large lagoons in the globally high 13 metre tidal range of the Severn Estuary. They add that, according to Tidal Electric Ltd, although the generation cost of the Swansea Bay scheme is 3.4 p/kWh, a scheme 5 to 10 times bigger and further east up the Severn Estuary where the tides are higher would have costs of below 3p and as low as 2 p/kWhour.  For comparison, the cost of gas generated electricity is around 2.4 p/kWh.  Given that there are also potential sites for tidal lagoons elsewhere in the UK, including the N.Wales/Liverpool bay area, FoE Cymru say that tidal lagoons could supply up to 8% of the UK electricity demand. Neil Crumpton, from FoE Cymru, said: “Several lagoon schemes in the optimum areas of the Severn Estuary alone, if assessed as environmentally benign, could generate enough electricity to supply three and a half million people or about 6% of UK electricity demand”.

* Tidal Lagoons, built of loose rock, sand, and gravel, holds water at high tide and create power by releasing that water back to the open sea at low tide through conventional hydroelectric turbines and then repeating the cycle at high tide by refilling the lagoon. The technology is a new approach to tidal power conversion, which does not have the environmental or economic problems of the tidal barrage. Tidal lagoons should have benign or minimal impacts on marine environment and will foster biodiversity by creating new habitats for fish, birds and marine wildlife. Situated a mile or more out to sea, the structures have a low profile and look like a rocky shoreline or island.

 There are now plans for a tidal lagoon in China- see later.