25 Years of Tidal Power

Producing electricity by harnessing the power of nature’s tides, especially the fearsome tides in the Bay of Fundy, has been very much in the news lately.

Unfortunately, the news hasn’t been all that good. Mostly it’s been about broken propellers and dashed expectations.

Meanwhile, back in Annapolis Royal, the tide-driven generator there is merrily cranking out 30 million kilowatt hours per year, enough to power 4,500 homes, and has been doing that every year for the past quarter century.

While building more units just like that might seem an obvious route, it’s not going to happen. Cost is one of the major roadblocks, along with the environmental concerns that come with building new dams to create reservoirs. Finally, on the commercial scale, the Annapolis Plant’s 30 million kilowatt hours barely registers on the production meter.

So what we have is a power generating anomaly – the only one of its kind in North America and one of only four in the entire world. Built initially as a feasibility test for a larger plant to be built further up the Minas Basin (which never happened), it was built in Annapolis Royal because the existing causeway and sluice gates (those two giant concrete blocks on the bridge) had created the necessary reservoir. The plant today remains an efficient, productive generating station/tourist attraction.

Like any hydro plant, it had to address the issues of its effect on the environment – water levels and the safety of fish – and downstream reporting centers and fish ladders seem to have done their jobs.

How It Works

At the causeway, there is the “headpond” on the inland side and the Annapolis Basin on the other. With an incoming tide, the sluice gates are lifted to allow the water to flow inland. When the tide changes and starts to flow back to the Bay of Fundy, these gates drop, separating the headpond from the outgoing tide. At the appropriate time, the wicket gates in the turbine open and for the next five plus hours the plant generates electricity.

About That Brown Foam

If you’re a frequent traveller across the causeway, you’ve almost certainly had the experience of being “foamed” by a brown froth engulfing your car, particularly behind a stiff westerly breeze. Between sluice gates, generators, fish ladders and the comings and goings of the world’s highest tides, there is ample explanation for the foam. The brown part comes from upstream, the runoff from the streams and rivers that empty into the Annapolis River. The effect of that mix is amplified as fresh water meets salt water in the proximity of the bridge.

NSPI has accepted that its location at the Route 1 gateway to Annapolis Royal and its position as an area tourist attraction come with certain “good neighbour” responsibilities.  Robert Duran, Superintendent of Fundy Hydro, noted that NSPI has made upgrades at the tidal plant’s Interpretive Center, including the addition of a cutaway model of the generator, to make the displays more interesting to visitors. Area residents may also have noticed the recent improvements to the building, signage and surrounding grounds, and, said Duran, there is more to come.

Tours

It’s fascinating, scary (unless you don’t mind being below water level) and you have to wear a hard hat, goggles and sensible shoes, but if you can meet those requirements, you are cordially invited to tour the Annapolis Tidal Generating Station. Tours are scheduled from 10:00 am to 4:00 pm, Monday through Friday. Times vary with the tides – no tours while the generator is at work. In the words of tour guide, Les Smith, “tide’s low, no go.” To arrange a tour (it’s free), call 532-0502.

Story by Freeman Butland

The Anna[polis County Spectator

August 3, 2010