Tides turn for tidal power

Capricious air currents and passing clouds may thwart wind and solar power, but the tides, governed by the gravitational pull of the moon and the sun, might prove a more dependable energy source. In certain spots, the tides have already proved a good source of electricity. La Rance Tidal Power Station-a barrage on the Rance River´s estuary in Brittany, France-has converted the tides´ movements into as much as 240 megawatts of electricity since 1966. But support for new projects is less predictable: Backing has ebbed for some designs, while for others it´s just starting to flow.