BBC: Turbines put in place in the UK’s tidal estuaries and streams could cover 20% of the nation’s current demand for electricity, according to a study published in the Philosophical Transactions of the Royal Society A. Because tides are regular, tidal generators could provide a more reliable source of energy than wind turbines. However, the technology for tidal generators is also very expensive. One design is a barrage, built across tidal estuaries, where the turbines are turned by the ebb and flow of the water. An alternative design is an underwater turbine powered by tidal streams. A proposal for a massive barrage generator across the Severn River was rejected by the government because of its environmental impact. Nicholas Yates of the National Oceanography Centre, coauthor of the study, says that the Severn project is too big and that tidal energy efforts should begin with smaller generators. One such project is a 40-MW tidal stream turbine to be constructed in the Pentland Firth by MayGen later this year. It will be the first array of tidal stream turbines in the UK and will join the SeaGen project in Northern Ireland as a major tidal electricity provider in the UK.