An idea from the past may make a Severn barrage practical

COMPARED with solar and wind energy, which are booming, tidal power is an also-ran in the clean-energy stakes. But if you did want to build a tidal power station, there are few better sites than the estuary of the River Severn, in Britain. Its tidal range, the difference in depth between high and low tides, of around 15 metres is among the largest in the world. Engineers and governments have been toying with the idea since at least 1925. But none of the proposed projects has materialised. Price ...