Energy Sources
Tidal
INTRODUCTION
Nova Scotia Power
Hydro power is usually generated through the release of water from human-built reservoirs. But the Moon’s gravitational pull controls the biggest movement of water on Earth—the tides. Twenty-four hours a day, 365 days a year, oceans churn against Canada’s coastlines powered by surface waves and tides.
Tidal and wave energy are produced by a combination of natural forces that cause ocean waters to move. For example, the gravitational forces of the moon and the sun produce tides - the gradual rise and fall of ocean levels – twice a day around the world. Winds contribute to wave energy by blowing across the ocean surface producing waves. Finally, atmospheric winds and the natural rotation of the Earth create ocean currents. Electricity is generated by capturing the power contained in these moving waters, and the global potential from tidal is substantial: an estimated 1,800 terawatt hours could be harnessed worldwide.
Ingenium
The total wave energy potential at depths of 1 km off Canada’s Atlantic and Pacific coasts is more than double Canada’s current electricity demand. The potential tidal power at 190 sites on the Atlantic, Pacific and Arctic coasts collectively exceeds an annual average of 42,000 MW, or roughly two-thirds of Canada’s current electricity demand. Canada is also among the few countries with expertise in ocean energy.
HARNESSING TIDAL
The most common way to commercially harness tidal power is with a “barrage.” A dam is built across an inlet and the change between low and high tide causes water to flow through tunnels in the dam. The flow of water turns a turbine, which powers a generator, transforming mechanical energy into electricity.
Successful tidal power sites depend on a large “tidal range”—the difference between the low and high tides. The shape of the shoreline must allow for the construction of a barrier. The features that make a site ideal for a power station often make it ideal for marine life. It is unknown how the environment will adapt to tidal developments.
New developments are on the horizon such as tidal lagoons, tidal in-stream systems, ocean thermal energy converters, and wave energy technology. Canada is one of the few countries to have begun to harness tidal energy; the country's only tidal station is located in Nova Scotia, in the Bay of Fundy. Our oceans are a vast source of energy that can be harnessed to produce different forms of usable energy including tidal and wave energy.
Opportunities:
- Canada is one of very few countries around the world with an operational tidal station and expertise in this area
- Movement of tides is predictable
- New fish-friendly design reduces the impact of turbines on sea life
- Studies show that marine life may increase at tidal power sites
- After an initial change in their ecosystems, estuaries usually reach a new ecological balance
- New technologies, such as tidal lagoons, lessen environmental impact of tidal energy
Challenges:
- Estimated per watt costs for tidal power installations range from $3/W to $6/W, significantly higher than for other power generation technologies
- Tides are periodic, and tidal energy requires a good storage system
- Commercial exploitation is relatively new
- Many environmental effects are unknown
- Barrage dams alter tidal range
- Studies indicate a reduction of up to 85% in the amount of suspended sediment within a barraged estuary
- Studies predict a 76% reduction in the expose time of the inter-tidal zone, a habitat used extensively by migrating waterfowl
- Considerable reduction in the extent of the mudflats and a significant reduction in the extent of upper salt marshes
- Noise of underwater turbines can mask vocalizations of certain marine animals
- Underwater cables may affect electrosensitive and magnetosensitive species, such as migrating fish