Tapping tidal power

Engineers at Liverpool University claim that building estuary barrages in the north west could provide more than five per cent of the UK's electricity.

Researchers, working in collaboration with Proudman Oceanographic Laboratory, examined ways to generate electricity from tidal sources of renewable energy in the Eastern Irish Sea. The study showed that four estuary barrages, across the Solway Firth, Morecambe Bay and the Mersey and Dee estuaries, could be capable of meeting approximately half of the north-west region’s electricity needs.

Funded by the Northwest Regional Development Agency, the team investigated different types of tidal power, including barrages – which run from one bank of an estuary to another and guide water flow through sluices and turbines – using advanced two-dimensional computational modelling.

The team found that the most effective mode of generating electricity was ‘ebb generation’, which involves collecting water as the tide comes in and releasing the water back through turbines once the tide has gone out.

The barrages would provide substantial sea defence, as well as flood alleviation, by draining the estuary following heavy rainstorms. Electricity generation could also help to achieve the UK’s CO₂ emission-reduction targets.

Prof Richard Burrows, from the Maritime Environmental and Water Systems Research Group, in the university’s Department of Engineering, said: 'The best places to harness tidal power at meaningful scales are areas with a high tidal range, such as estuaries. Tidal barrages would alter the natural motion of an estuary’s flow as the sea level changes, usually by holding back the water at high tide and then releasing it when the tide has subsided. This water-level difference across the barrage is sufficient to power turbines for up to 11 hours a day, and, in terms of the four north-west barrages, the energy extracted could equate to five per cent of the UK’s electricity generation needs.'

Dr Judith Wolf, from the Proudman Oceanographic Laboratory, added: 'The problem with renewable energy generation is that it is intermittent; electricity can only be generated in line with the tidal flow. However, the tide arrives in the north west around four hours after the Severn, where plans to build a barrage of similar scale are currently underway, so together they could increase the number of daily generation hours.'

According to the Department for Business, Enterprise and Regulatory Reform, only five per cent of electricity in the UK came from renewable sources in 2007.

The research, 'Tapping the Tidal Power Potential of the Eastern Irish Sea', can be found at www.liv.ac.uk/engdept/tidalpower