Come September, the fishy
inhabitants of New York's East River will acquire some sleek
new neighbours.
Verdant Power, an energy
company based in Arlington, Virginia, plans to plunge six
electricity turbines into the East River. If the
$4.5-million project is successful, the generators will form
the first farm of tide-powered turbines in the world.
The plan is to attach the
machines, which look like small wind turbines, to concrete
piles hammered into the bedrock nine metres below the
river's surface. As the tide surges in and out, the heads
pivot to face the current and the blades spin.
The project is a modest one
in electricity terms: the suite of turbines will generate
just 200 kilowatts of power at their peak, enough to power
perhaps 200 houses. Initially, the energy will be used to
run some lights and machinery in a local supermarket and
parking garage, avoiding the expense of transmission cables.
But if everything goes
according to plan, company president Trey Taylor says he
hopes to grow the field to 200-300 turbines stretched along
the river. The UN headquarters in Manhattan is among those
who have expressed interest in tapping into the
environmentally friendly energy that would be produced by
the project, he says.
Taylor's company chose New
York as a test bed because the city chews up power so
voraciously, and because state initiatives are encouraging a
switch to renewable energy. But he hopes that the turbines
might one day find a use across the United States and in
developing countries. "The potential is very big,"
Taylor says.
Winds and tides
Efforts to harness tidal
power have been relatively few and far between, particularly
when compared with wind, solar or geothermal power. But
moves to cut greenhouse gas emissions from conventional
power stations are driving renewed interest in the
technology around the world.
The biggest tidal project
that has been installed is a huge barrage across the river
in La Rance, France, which has a capacity of 240 megawatts.
Such barrages work like hydroelectric dams, holding back a
head of water to power generators. But they are expensive
and can damage river wildlife.
The New York project signals
a trend towards cheaper, free-standing turbines that can be
dropped into oceans or estuaries. The first experimental
tidal mills were installed last year: a 300-kilowatt turbine
was sited off the north Devon coast in Britain and another
of the same capacity was placed near Hammerfest, Norway. The
two European companies behind them are planning to expand
these individual mills into turbine fields.
Taylor believes he has an
advantage over his competitors, because the design of his
turbine blades means that they keep spinning even at slower
water speeds. His team tested a smaller prototype of the
turbine, suspended from a platform, in January 2003.
But Peter Fraenkel,
technical director at Marine Current Turbines, the company
that built the Devon turbine, is not convinced that Verdant
will be the first to get a set of turbines up and running.
"I'll be interested to see what they can do," he
says, "but I'm slightly sceptical of how quickly they
can do it."
Fraenkel believes that the
team will hit snags when installing the machines. He also
questions whether the small machines can generate power at a
competitive cost. His company, in contrast, is developing
huge one-megawatt turbines to bring down overheads. He hopes
to have a field of them in the water by 2007.
Other power companies will
be watching the New York project to see whether tidal power
is an area to invest in, according to Mike Bahleda, who
coordinates research on renewable energy at the Electric
Power Research Institute in Palo Alto, California.
"Tidal power never going to replace fossil or nuclear
power, it'll supplement them," he says.
