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The Call of the Moon
 

Earth's New Season by Guy Dauncey

  Scripting Our Own Lives
Underwater turbine illustration from Marine Current Turbines Limited
Long before humans walked this Earth, before the dinosaur or the humble shrimp, a power as ancient as creation wove its spell into matter. We called it gravity. Non-scientifically, it is like a kind of love.

What causes it, nobody knows. It is as if all matter longs to re-unite with itself, in an eternal memory of its cosmic birth some 15 billion years ago. From that moment on, even while racing through space at the speed of light, all matter was filled with a desire to re-unite with itself. The apple, as it falls from the tree, sings to the Earth “I’m yours!” The Earth, as it circles the sun, repeats the song. All over the universe, the galaxies sing of their ancient memory.

And so it is at Skookumchuk, at the top end of Sechelt Inlet, where the tidal waters pour through the narrows in a wild dance. It’s that old devil moon pulling at the world’s oceans, which respond to the ancient call.

But enough of this romance. The challenge that we face, as we come to terms with the enormous folly of continuing to burn fossil fuels, is to find a way to tap the tidal power of gravity and make it turn our turbines, producing megawatts from matter’s magic.

In December 2002, near the far-northern Norwegian Arctic town of Hammerfest Strom, an ocean-bottom windmill-like device began producing 300 kW of energy, signalling the rebirth of tidal energy. I say rebirth, because this is not the first time we have tapped the world’s tides. At La Rance, on France’s northern coast, the tide is impounded behind a barrage as it rises up the river, yielding 240 MW as returns. In Nova Scotia’s Bay of Fundy, there’s a 23 MW tidal barrage. The problem is that the barrages destroy the delicate inter-tidal ecosystems, so nobody is proposing them any more. Today’s challenge is to tap the power within the tides.

There are various technologies being developed. Blue Energy (www.bluenergy.com), in Vancouver, has a Davis turbine that sits on the ocean floor, turning first one way and then the other as the tide changes. The turbines turn at a slow 25 rpm, allowing fishes to swim through, while whales, seals and dolphins are protected by cages. The turbines can be strung together into a fence, with a road, railway or buildings on top.

Marine Current (www.marineturbines.com), from England, has a 2-3 metre wide steel tower that sits on the ocean bottom, with two large blades that stick out on either side like aircraft propellers. The towers can be grouped in an ocean wind farm, return the power to shore by cable.

Clean Current (www.rvcogen.com), in north Vancouver, has a secret ducted turbine. An American company has an underwater ‘kite’ turbine that is suspended in the tidal flow; a British company called Hydro Venturi has a device which channels the tide into a high-pressure flow which is delivered to the shore in a pipe, where it turns a conventional turbine.

The challenge is to make these devices safe for shipping, and to protect them from floating logs and the wrath of winter storms. For the time being, this means using various anchors and bolts drilled into the ocean floor. One day, we may be able to copy the kelp, which clings to rock with incredible strength.

So now we come to the billion dollar question: how much tidal power is available in places where it might be tapped? BC Hydro (www.bchydro.com/environment) recently took an exciting step forward by commissioning a study of BC’s tidal energy potential. Triton Consultants looked at potential technologies, the complexities of BC’s tides, and 100 sites along the coast (excluding Haida Gwaii) where the current is over 3 knots (1.55 metres/sec). They found ten sites which could produce over 100 MW each, the best being in Johnstone Strait. There are 55 sites where the current reaches 2 metres/sec, which could produce 2225 MW; that’s a quarter of BC’s entire power production, more than is used by all Vancouver Island.

So what will it cost? The estimated price is 11-25 cents/kWh, falling to 5-7 cents as the technology matures. This is a very good proposition, when you consider that it is a clean, safe energy which is perpetually available; that coal, oil and gas are dirty fossil fuels which are endangering our planet’s climate; and that North America’s natural gas supply may soon run out.

Tidal energy. It’s as simple as gravity, as ancient as the oceans, and as natural as love. It’s time to turn the tide in our own minds. There’s something in my soul that is calling for it, just as the ocean calls to the moon, and the moon calls to this whole, incredible cosmos.

Guy Dauncey is the author of Stormy Weather: 101 Solutions to Global Climate Change. He lives in Victoria. www.earthfuture.com.





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