Trends and currents

Before there was a causeway across the Annapolis River, a bridge (one lane) linked Annapolis Royal with Granville Ferry.

A child could count almost to 100 while a car shimmied its way across that bridge, on our way “up the Valley.” We were as excited as any child to see the big earthmovers push rocks, gravel and dirt into the river as construction of the new causeway went forward.

Perhaps it wasn’t necessary to build the causeway. Maybe a causeway was considered, at the time, a more functional alternative to building a new bridge. The reason didn’t register on my child’s mind.

Did anyone predict the effect of the change in current on the old bridge? One day, as the causeway neared completion, the old bridge trembled a little deeper and a little longer and crumpled into the Annapolis Basin! I wonder what it was like for the people in the car who made it in time to the other side, but were actually on the bridge when it collapsed?

The Annapolis Royal Tidal Power Generator* - innovative, functional and still contributing 18MW to 20 MW of power to the grid for going on 25 years - is a tidal power success story. What is rarely talked about, however, is how the Annapolis Basin and the very river itself have been affected by the causeway, in which the housing for the generator sits. Although the water power that turns the turbine is a pre-existing, natural force, you could certainly persuade me the cost of installing a causeway to support the turbine is high enough to bar the project from owning a “green” badge.

A quarter of a century later, we hope we all have our eyes open wider - and some in the back of our heads! The pressure is on to reduce nasty and toxic emissions from coal- and oil-fired electrical generators. Tidal generators are one of the great hopes for the near future; there are some 40 to 50 tidal generators being developed around the world. A few have even been installed and are producing power**. But, let’s not recommit the errors of the past.

Many eyes are turned toward the Minas Channel, where researchers, partners and planners are pooling their resources to install three tidal turbines in the near future. In the channel, boulders have grooved the bedrock with rolling in and out with the tide; currents dimple the water surface with whirlpools that shove a 45-foot boat sideways. And the current races by at a rate of seven or eight knots - faster than anywhere else in the world. If a turbine can be built to withstand the turbulent forces of the channel - and a cable be connected from it to a distribution point on the mainland - it is possible to make tidal power workable anywhere in the world where the tide waves “Howdy!” *http://www.electricalline.com/images/mag_archive/18.pdf **http://www.openhydro.com/images.html

http://uekus.com/UEK_at_Work.html

http://www.racerocks.com/racerock/energy/tidalenergy/videncana.htm

http://www.cleancurrent.com/media/backgrounderfundy.htm

http://www.emec.org.uk/