Tidal energy is an abundant source of emission-free power.
Canada has an estimated tidal energy potential of 35,700 megawatts (MW). That’s enough clean power to displace over 113 million tonnes of CO2 – equal to removing over 24 million cars off the road.
The Minas Passage area of the Bay of Fundy is home to an estimated 7,000 megawatts of energy potential, roughly equal to the power needs of 2 million homes – or all of Atlantic Canada.
Tides are created by the gravitational pull of the sun, moon and the rotation of the earth. Their orbits are predictable; so is the availability of tidal energy.
Tidal resources are often found in narrow passages. As coastlines approach each other, or as the seafloor shallows, the water is ‘pinched.’ This pinch increases the speed of the water: like pressing a thumb on to a garden hose. Power goes up exponentially with speed; every time water speeds double, power goes up eight times.
Tides deliver daily energy, on schedule.
As a renewable source of power, predictability is tidal energy’s game-changing strength. Intermittent renewables like wind and solar fluctuate: they require extra electrical infrastructure to ensure consumer demand for electricity is always met. Tidal is punctual: its availability can be predicted every day, every year, every century into the future. In the long run, tidal can offer system-wide cost-savings: its predictability cuts down on the need for extra power plants, extra transmission lines, and extra battery and smart grid storage.
Water vs Air
A tidal turbine must be more robust than a wind turbine, and for good reason: water is about 800 times denser than air.
The advantage of water density is that significant power can be produced with:
- slower rotation speeds (e.g. 6 RPM tidal versus 20 RPM wind), and
- smaller rotor diameters (e.g. 15-meter tidal versus 45-meter wind)
Tidal Stream Technology (also in-stream tidal, tidal current)
A tidal stream turbine uses the kinetic energy of moving water to produce electricity. Tidal stream technology is:
- Similar to a wind turbine under the water
- Placed in the natural flow of tidal currents
- Able to generate electricity on the outgoing (ebb) and incoming (flood) tides
Strengths of the technology include:
- Passive (allows water to flow freely through and around it, therefore smaller effects on water flow and sedimentation)
- Removable (if necessary)
- Scalable (they can be installed one device at a time, rather than built all-at-once)
- Low-impact (international research to date has shown no significant environmental effects)
Tidal Range Technology (also tidal barrage, tidal dam)
Tidal barrages work much like a conventional hydroelectric dam.
A tidal barrage contains water in a holding pool as the tide ebbs out. The height differential between the held water and the ebb tide creates potential energy; the held water can be converted to electrical energy when released through a turbine.
Canada is home to the only tidal barrage in North America in Annapolis Royal, Nova Scotia. This generates up to 20MW when in operation.
The proposed River Severn sites in England have an estimated capacity of nearly 16,000 MW; the Penzhinskaya Bay site in Kamchatka, Russia, has a potential capacity of 87,000 MW.
Two variations on tidal technology include:
Tidal Lagoon: A rock-walled impoundment built along a shallow ocean shoreline to create a ‘lagoon.’
Tidal Fence: An array of tidal stream devices connected to marine infrastructure running between two shorelines (e.g. a bridge). Energy is captured kinetically from the tidal flow, providing some freedom for marine life to pass between the turbines, and less restriction on tidal flow and area.
Canada is emerging as a global leader in tidal energy, with:
- strong resource areas close to existing grid infrastructure
- international demonstration centres
- marine renewable energy legislation
- market incentives, including a feed-in tariff of 53 cents/KWh
Some of the key organizations involved include:
- Acadia Tidal Energy Institute (ATEI): A non-profit organization conducting tidal energy research, training, education and outreach to promote responsible approaches to tidal energy development.
- Fundy Ocean Research Center for Energy (FORCE): Canada’s leading facility for tidal stream technology demonstration, including 64MW of subsea cable installed, a 30MW substation, tidal turbine test sites, and ongoing applied research and monitoring programs.
- Offshore Energy Research Association of Nova Scotia (OERA): An independent, not-for-profit organization that funds and facilitates collaborative offshore energy and environmental research and development including examination of renewable energy resources and their interaction with the marine environment.
WATCH: Overview of tidal energy development in Nova Scotia
- 15 metres: Tidal range of Nova Scotia’s Bay of Fundy, the largest in the world
- 152,000 MW: Total potential capacity of the 27 best locations in the world for tidal stream farms
- 7 cents/kWh: Cost of power generated by the La Rance in France tidal barrage, cheaper than most competitors
- 15,900 MW: generating capacity of the proposed Severn tidal lagoons in the UK, costing $65 billion
- $0.54 to $0.66 per MW: Cost of electricity from the first tidal stream farms, comparable to the cost of wind power in 1980
- 19: Countries currently investing in tidal power research