SEA POWER

So we are running out of energy, are we? The sea alone can wash away such gibberish. It contains enough uranium and thorium to sustain the world's energy needs at estimated 21^st century levels for several million years. If controlled fusion materializes, the supply of deuterium and lithium will last for the life of the solar system. To which add all the other forms of energy available from the sea: thermal gradients, salinity, tides, currents, and waves.

If the access to that energy is kept open, it will enable man to bemoan the lack of energy for tens of billions of years.

The trouble is diluteness. There are only two known cases where nature concentrates the energy so man can tap it abundantly: thermal gradients and salinity. (And tidal power, but only in the few places with the right type of inlet [AtE Aug 79].)

Wave power, for example, amounts to little more than 10 kW per meter, and sea currents to even less. If that is a story reminiscent of solar power, there is a good reason for it: Sea power is solar power. We again neglect tides (mostly due to the moon). It is the sun that heats the surface layers of the sea, creating thermal gradients downward. Since the heating is not uniform, equalizing currents arise both in the sea and in the air (wind), the latter causing waves on the surface. The sun is even responsible for the sea's salinity: It evaporates the water which comes back via rain and rivers washing minerals and salts into the sea.