Turning tidal current into electrical current

Published Tuesday, October 15, 2013 in the New Brunswick Telegraph Journal.

In 1921, Thomas Edison said, “Someday we will harness the rise and fall of the tides and imprison the rays of the sun.”

Fortunately, Edison’s words are beginning to resonate.  In particular, the promise of tidal power is beginning to attract attention – potentially good news for a province that borders a bay where 100 cubic kilometers of water slosh back and forth twice a day.  Here’s a snapshot.

Potential

Tidal energy in Canada was first studied in 2006.  Among the places identified as having the fastest tidal flows – and therefore the greatest potential for power generation – were the Hudson Strait in Nunavut, Ungava Bay in northern Quebec, straits around Vancouver Island and, of course, the Bay of Fundy.  In the Fundy, the best site by far is the Minas Basin, between Parrsboro and the Annapolis Valley, but NB sites include Old Sow and Head Harbour Passage, both near Deer Island.

Since that study, most research and development has centered about the Minas Basin.  In 2006, it was estimated that its power generating potential was about 360 megawatts (MW), or about half the output of the Mactaquac Dam.  But that early forecast was made on the basis of fairly scant data about water volumes and speeds.  The Minas Basin has since been studied and modelled extensively, and researchers at Acadia University now believe that it alone may have 7000 MW of energy potential, of which 2500 MW are extractable.  That’s more than Mactaquac, Coleson Cove and Belledune generating stations combined.  In 2008, a facility dedicated to developing, testing and commercializing tidal power was established in Parrsboro, NS.

Presently, tidal power research appears to be at a standstill in NB.  However, there is little doubt that sites on our side of the bay – though perhaps not as energy-rich as the Minas Basin – hold considerable potential for the future.

State of technology

One of world’s first tidal power stations is in Annapolis Royal, NS.  It consists of a small dam with turbines that spin when water rushes in on the rising tide and out on the ebbing tide.

In recent years, the focus has switched to in-stream turbines – machines not unlike wind turbines installed on the ocean floor in areas where tidal water flows fastest.  In-stream turbines are very much an emerging, evolving technology; worldwide, it’s estimated that at least 50 different prototypes are in various stages of development, and no sure-fire design has yet emerged.  Given that reality, it’s expected that large scale tidal electricity will not happen before 2020.  However, the Parrsboro research facility hopes to install its first commercial power generating turbine in 2015.

Advantages and challenges

The beauty of tidal energy is that it is entirely renewable and, unlike solar or wind, 100% predictable.

But there are plenty of challenges too.  It’s intermittent, so at slack tide times it will need to be paired with something that can fill in the gaps, such as hydro or some type of power storage system (perhaps electric car batteries).  

Creating machines that can withstand tough marine conditions remains a daunting engineering challenge.  Ice, debris and salt water make for extremely harsh working environments.  As well, the force of tidal currents can be crushing: the first prototype tested off Parrsboro in 2009 was heavily damaged within three weeks by currents that were far stronger than expected. 

Getting power from the bottom of an ocean onto a power grid is technically difficult too.  (Thankfully, the Bay of Fundy is near a commercial power grid, unlike sites in the Hudson Strait or Ungava Bay).  

Tidal power is presently expensive – about three to five times commercial rates, though this can be expected to decrease over time.  No doubt we will be able to benefit and learn from the experiences of others as technology improves.

And since no form of power is without consequences, the potential environmental impacts of tidal power on marine life and sensitive intertidal zones need to be monitored closely. 

Current from the current

Clearly, much remains to be done before we can count on tidal energy to keep our lights on and our electric cars driving.  But we’d do well to monitor the technology as it improves, and then jump in at the appropriate time so that we can start reaping power and economic benefit from the massive resource at our doorstep.  Call me an optimist: I look forward to the day when Albertans will be coming East to work in our clean, renewable energy sector.