Tidal power systems have been under investigation for many years. The
earliest method to generate power was with ‘barrage’ systems, which
required the construction of dams across inlets and bays. Gates in the
dams allowed the basin to fill during high tide, then the gates would be
closed, and the basin would be allowed to drain out through turbines to
generate power. However, the environmental impacts of these systems,
along with the cost and the relative inefficiency, have kept them from
much further development. There are some ‘barrage’ installations still in
operation in Canada and in France, but no new projects are planned.
Instead, tidal power is being pursued as basically the same way wind power has been developed, turbines. In-line tidal power is
intriguing because it is much more regular and predictable than wind,
which can be intermittent and is much more dependent on local weather.
Water also has a much higher energy density than air does, which makes
tidal systems appealing because a water turbine can be smaller than an air
turbine.
A tidal power
system comprised of six 35-kilowatt turbines has been installed in the East
River near Roosevelt Island, New York. This study system is meant to
determine the best configuration for the equipment, and help develop
easily mass-producible versions of the turbines. A final configuration of
100 turbines is anticipated at this location.
Preliminary site approvals for in-stream turbine farms have already been
given for 25 sites along the Atlantic and Pacific coasts of the US, and a
further 31 sites are under consideration. Other companies are developing
other forms of tidal turbines, some with as much as 1 megawatt capacity.