Tidal energy from UK coastal waters
Some 20 per cent of the UK’s present demand for electricity could be met by tidal energy. Scientists at the National Oceanography Centre and the University of Liverpool have developed a tidal model to examine the scope for reliable and predictable electricity generation from UK coastal waters.
Details of this model were published in the journal Philosophical Transactions of the Royal Society. The authors say the most attractive locations for harnessing tidal power are estuaries with a high tidal range for barrages, and other areas with large tidal currents such as straits and headlands for tidal current arrays.
The UK is well placed to take advantage of tidal power. Suitable sites are relatively few globally but it is estimated that of the 500-1000 TWh/year of energy potentially available worldwide, the UK holds approximately 50 TWh/year. This is nearly 50 per cent of the European resource. An added bonus for the UK is that these sites are close to electricity users and transmission grids, which makes connection much more efficient.
The North West of England has some of the best locations – the estuaries of the Dee, Mersey, Morecambe Bay and Solway Firth.
According to the paper’s lead author, Dr Nicholas Yates: “Tidal barrages, with their tried and tested technology, could provide around 15 per cent of the UK’s present electricity needs. Tidal streams, where there is considerable technological development taking place, could offer upwards of a further five per cent.”
Tidal barrages delay the natural motion of the estuary flows as sea level changes holding back the release of the high tide out of the inner estuary basin. There are three scenarios – ‘ebb-mode’ which generates electricity when the water level difference across the barrage is sufficient for turbine generation; ‘flood-mode’ when entry of water is deferred into the estuary as the tide level rises; and ‘two-way, or dual-mode’ which is a combination of both.
“Of all the potential UK sites, the Mersey, with a very narrow mouth – which would need a relatively short barrage length – might offer power production at the lowest unit cost of all UK sites.”
Tidal barrage technology is fully proven. In Brittany, France, the La Rance scheme has been operating for 40 years. In addition to generating energy, La Rance barrage offers coastal protection and road access across the estuary.
Crucial to the success of these projects is predicting the amount of electricity generated. With increased commitment to reducing carbon emissions, more UK power will need to be supplied in the form of electricity.
Appraising the Extractable Tidal Energy Resource of the UK’s Western Coastal Waters was published in a special issue of the journal Philosophical Transactions of the Royal Society A devoted to the topic of tidal energy.