Page 321 - Alternative Energy Systems in Building Design

CURRENT TIDAL GENERATION TECHNOLOGIES 295

OTHER TIDAL TECHNOLOGIES

Stingray tidal energy An alternate way of harnessing tidal energy is applied in
Stingray. This technology consists of a parallel linkage that holds large hydroplanes to
the flow of the tides. The angle of these hydroplanes to the flow of the tide is varied,
causing them to move up and down. This motion is used to extend a cylinder that
produces high-pressure oil that drives a hydraulic motor, which, in turn, drives an elec-
tric generator.
This concept has received recognition for its potential from the U.K. Department of
Trade and Industry. Initially, the project was funded by the Department of Industrial
Technology and the Water and Power Technologies Panel.

Annapolis Royal and Bay of Fundy, Canada The following is a BBC news
report covering the Bay of Fundy Tidal Power Plant in Canada, which is recognized
as the world’s most significant geographic location for heist tides:

The one thing that every schoolchild learns about the Bay of Fundy is that it has the highest
tides in the world.
The North Atlantic waters are funneled up this deep inlet between the Canadian provinces of
New Brunswick and Nova Scotia, swirling through the narrowest parts of the bay with impres-
sive speed and power.
So when in the 1980s the Canadian government wanted to explore the feasibility of tidal power,
this was a natural site for an experimental station.
The site chosen at Annapolis Royal had already been closed off by a causeway, built to control
tidal flow further up the Annapolis River.
The idea was that water flowing through the sluices could also pass through a turbine and gen-
erate power on its way down the Bay of Fundy and out into the sea. Now there is a neat box-
like structure in the middle of the causeway, one of only a handful of operational tidal power
plants in the world.

PLANT ENGINEERING
Twice every day, as the tide rises, the sluice gates are opened to let water flow up into the lower
part of the Annapolis River, which now serves as the headpond for the power station.

Just before high tide, the gates are closed, leaving only a narrow passage for fish to pass. Now
all the operators have to do is wait for the tide to turn and the water level on the seaward side
to drop.
When there is enough difference between the water levels on the two sides, they begin to
let water flow through the giant turbine, slowly at first to get it turning, and then at full
strength.
Once the huge 25-m-diameter wheel is up to its operating speed of 50 revolutions per minute,
the station starts to generate. At peak power it supplies a very respectable 20 MW to the
Canadian grid.
Once the tide has gone out and the water level is equalized, the turbine slows to a stop, before
the whole cycle begins again.