Thursday, July 26, 2012

Tidal Power

On the opposite side of the Nova Scotia peninsula from Halifax is the shore of the Bay of Fundy. This is across the Bay from New Brunswick, as reported here earlier. Since first experiencing the extreme tides in the Bay of Fundy I’ve wondered why the tides couldn’t be used to generate electricity. If course, if I was really, really curious, I would have researched it on line and found that a tidal generating station does exist near Digby in Nova Scotia.


The station has actually produced 20 megawatts of electricity since it went on line in 1984. It was built as an experiment to see if Fundy’s tides could be harnessed to generate electricity, and it definitely worked.


The Annapolis River feeds into the Bay of Fundy through a large basin. The Bay is actually about 15 miles away, but since the existing bridge over the river at this point needed to be replaced, it was decided that this was an ideal place to build the small dam and generating station.


When the tide comes in, the water level of the lake behind the dam increases. When the tide goes out, the water in the lake is released through a turbine built into and below the dam.


The turbine actually has the generator built into it so there’s no energy lost in transferring energy to a separate generator. By the way, I didn’t draw this cross-section, I borrowed it from the Nova Scotia Power web site. 


The station generates electricity only when water exits the lake, but the technology is used in other places in two directions – making power when the tide comes in, and making power when the tide goes out. Here in Nova Scotia the existing lake was considered too important to destroy to build a bi-directional generator. There are several demonstration projects around the world using this technology to make electricity, but this is the only one in the western hemisphere. There have been some environmental issues raised regarding this technology, but it does seem a whole lot cleaner than fossil fuels and nukes.


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