April 2020 | SMITHSONIAN 49SO
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Naval architect
Jason Hayman,
on the Bay of
Fundy, has led
development of
a tidal energy
system that
he says could
transform coast-
al communities
around the
world.athan White notes in his excellent Tides: The Science
and Spirit of the Ocean, astronomers know exactly
how celestial bodies aff ect tides, but what actually
happens to water down here on earth “is unimagin-
ably messy. Scientists are still working it out.”
All told, some 400 diff erent variables are involved
in creating the tides, but you don’t have to account
for each and every one to appreciate that harnessing
energy from this perpetual motion machine is an ex-
tremely good idea. The resource is clean, inexhaust-
ible and, to an extent that even solar and wind are
not, highly predictable.
Humans have derived power from the ocean for
more than a millennium, trapping high tides in mill
ponds behind dams, then releasing the fl ow at lowtide through sluiceways directed at the paddles of
waterwheels. The motion generated enough force
to turn grinding stones or other mechanical devic-
es. The fi rst tidal mill in North America was built
in 1607, in Annapolis Royal, Nova Scotia, some 60
miles from Grand Passage. Tidal mills were common
throughout the province and the eastern U.S. in the
18th and 19th centuries, but it was in the 20th centu-
ry that the Bay of Fundy became tidal engineering’s
crucible of experimentation.IN 1915, RALPH CLARKSON, an engineering profes-
sor at Nova Scotia’s Acadia University, prototyped
a tidal-power generator with four pumps, powered
by a horizontal waterwheel, that lifted water 335HYDROPOWER FOR THE 21ST CENTURY
Renewable. Nonpolluting. It works in the dark, unlike solar power. And in a calm, unlike wind power. SME’s
fl oating tidal power station is gearing up to go online in Nova Scotia • Graphic by Matthew TwomblyThe center hull supports
a control room complete
with video monitors and
computers. A com-
plex converter system
transforms the power
generated by the spinning
turbines into alternating
current of a frequency
required by the local
power grid.The hulls of the Plat-I span 88
feet and provide stability and low
resistance in the tidal stream.
The turbines can be submerged
to generate power or lifted out of
the water for maintenance.Each turbine bears a rotor
21 feet across and is posi-
tioned 15 feet deep when
deployed. In tests, says
the company, there was no
observed “contact between
marine animals and the
turbines.”Because of water’s density,
a tidal turbine can be much
smaller than a wind turbine of
equivalent capacity. In Grand
Passage, tidal currents up to
several knots move beneath
the Plat-I, turning each rotor
and thus a generator that
creates electricity.The fl oating Plat-I is
anchored to the seafl oor
with cables attached to a
rotating turret, allowing
the entire platform to pivot
and generate power on the
ebb as well as the fl ow.