In 1980, construction began on a small
island in the mouth of the Annapolis River on an experimental tidal generating station.
After four years of construction this station was completed. It employs the largest
straight-flow turbine in the world to generate more than 30 million kilowatt-hours of
electricity per year, enough for 4500 homes.
Annapolis was chosen as the site because an existing causeway with sluice gates was
already in place. This was very important because it provided a head pond where water
levels could be controlled, an important component in the stations operation.
The station generates power by allowing the incoming tide to fill the head pond
through the sluice gates. When the head pond reaches its maximum level the sluice gates
are closed, trapping the water in the head pond. When the tide recedes outside of the head
pond and drops below by 1.6 m or more than 18 wicket gates to the distributor assembly
open. The gates control the flow of the water through the turbine. When the gates are open
water flows through at the rate of 400 cubic metres per second and turns a massive
four-blade runner. The power generating phase lasts for approximately five hours, at which
time the gates close and a new cycle begins. This is repeated twice daily.
One of the unique features is a huge four-blade propeller turbine or
"runner". Its 7.6 m in diameter making it the largest of its kind in the world by
4m. The 148 tonne turbine can generate 20 megawatts at peak output.
Larger projects with tidal power have been considered in the Bay of Fundy, but more
information about possible impact to the area and environment is needed. The main concerns
being effects on fish populations and the filling in of the head pond with sediment.