Power from the Waters

Dams, Tidal, Wave, Current and Ocean Thermal Energy

The waters that cover three-quarters of our Earth's surface are sources of huge quantities of clean, green energy...but in many different ways.

Dams have been with us for centuries as sources of reliable clean energy.  Wheels moved by river currents have moved water to irrigate crops since time immemorial.  Newer versions throughout Old and New England powered the looms and factories that began the industrial revolution. 

But as hydro-electric generators, dams have exploded in size, and are often sources of bitter controversy.  The great eco-pioneer David Brower long lamented his assent to the Glen Canyon Dam, which flooded one of the world's great eco-systems.  China's Three Gorges project has become a human and environmental catastrophe of global proportion. 

Some older, smaller dams may have been in place long enough to have become well integrated into the riverine ecology.  But many dams continue to damage the general ecology by creating silt deposits and stagnant, carbon-emitting backwaters from which migrating fish cannot escape.  The impact on salmon by some of the dams in the American northeast and northwest has been devastating.

Yet new technology is being developed that can allow rivers to flow freely while still harnessing much available energy.    Ironically, then, green power advocates in the coming years will advocate freeing many of our rivers from the stoppages of large dams while simultaneously working to install "run of the rivers" generators that can harvest energy in ways that would allow those same waters to run free.

Similar issues are likely to arise over reaping energy from the tides.  A 330-meter tidal generator has been in place at La Rance, France, since the 1960s.  Another has been installed at Newfoundland's Bay of Fundy.  Each generates significant quantities of electricity without apparent damage to the regional eco-systems.  But as demand rises, the possibility that tidal generators could do ecological harm will have to be watched.

Likewise, new wave generators.  Looking for all the world like gigantic sea-borne sausages, these huge tubular bobbers are absurdly simple.  As the waves rock them up and down, they squish water through tubes to generate electricity.  The devices seem to have great promise with little apparent eco-impact.

Then there's the potential energy from the ocean's currents.  An "underwater windmill" has been anchored to the ocean floor off Norway, harvesting moving waters which are far more dense and steady than the wind itself.  Whether such machines can withstand salt corrosion and other stresses from these "rivers within the sea" remains to be seen.

Ocean thermal energy also waits in the wings.  OTEC exploits the temperature differential between the solar-heated water at the sea's surface and the cold depths.  Suited primarily for tropical waters, ocean thermal generators seem a theoretical good bet.  However OTEC pans out in the real world, overall the waters that cover our planet represent a huge source of potentially clean, reliable energy for centuries to come.


La Rance Tidal Power Plant

Ocean Thermal

Wave Generation

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