Tidal model

Tidal stream farms, in which electricity is generated by turbines from regions of strong tidal flow, may influence the natural balance of marine sands, according to researchers at Bangor University.

In contrast to a tidal barrage, tidal stream turbines harvest the energy of the tides in a similar way to wind turbines. But what is significantly different from wind turbines is the environment in which tidal stream turbines operate and their potential to interact with their environment.

Dr Simon Neill and Prof Alan Davies from the School of Ocean Sciences at Bangor University, along with colleagues from Edinburgh University and Plymouth Marine Laboratory, developed a computer model to investigate the environmental impact of extracting energy from the Bristol Channel, one of several proposed sites in the UK for harvesting tidal streams.

They found that a large tidal stream turbine farm would have a significant and widespread influence on the natural transport of sands in the Bristol Channel.

Neill said: ‘Tidal stream farms remove energy from the environment. But if you take energy out, then there will be less energy available for moving sand around. So, sand transport would be weakened as a result of energy extraction.’

The research shows that this influence on sand transport will change the equilibrium of the coast over the 30-year lifecycle of a tidal stream farm.

He explained: ‘This can have positive or negative consequences for coastal protection. Changes to the deposition of sand in an exposed estuary such as the Bristol Channel can affect wave breaking. If a change in the deposition of sand causes storm waves to break further offshore, this may lead to enhanced coastal protection. In contrast, a change in the deposition of sand that causes waves to break closer to the shore may lead to increased coastal erosion and flooding.

‘Although generating considerably less electricity than a tidal barrage scheme, the environmental impact of a large tidal stream farm in the Bristol Channel would be much lower. In contrast to the major construction undertaking of a large barrage project, a tidal stream turbine farm can be incrementally extended and environmental responses constantly monitored,’ Neill added.

Around half of the European tidal stream resource is located in UK territorial waters. For this reason, the UK is home to many of the most advanced tidal stream turbine technologies.