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Earth's New Season by Guy Dauncey
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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