In looking for alternative energy sources to meet future needs, some common physical phenomena are obvious candidates. One of these is tidal power. Twice each day on every coastline in the world, bodies of water are pulled onto and off of the shore as a result of gravitational forces exerted by the moon and sun. Only on ocean coasts is this change large enough to notice, however, and therefore, to take advantage of as an energy source.

The potential of tidal power as an energy source is clearly demonstrated. Pieces of wood are carried onto a beach and then off again every time the tide comes in or goes out. In theory, the energy that moves this wood could also push against a turbine blade and turn a generator.

In fact, the number of places on the earth where tides are strong enough to spin a...