What is hydrokinetic power?
Hydrokinetic power is the electricity generated by harnessing the kinetic energy of tides and ocean or river currents.
Hydrokinetic turbines transform the water’s energy into mechanical energy, just like wind turbines transform the wind’s energy. That energy is then converted into electricity.
There are three main types of hydrokinetic turbines:
- vertical-axis hydrokinetic turbines
- horizontal-axis hydrokinetic turbines
- oscillating-foil hydrokinetic turbines
Current state of knowledge
Ocean current turbines are currently seeing large-scale development because of their considerable potential, given the current speeds and depth of water in the ocean. Their rated output can reach 1 MW or more. River current turbines, which operate at lesser depths, are necessarily smaller, and their rated output rarely exceeds 400 kW, even in very strong currents of 4.5 m/s.
In Québec, hydrokinetic power is in the experimental and pre-commercialization stage. In September 2010, a first industrial prototype was connected to the Hydro-Québec grid. The RER Hydro turbine was submerged in the Fleuve Saint-Laurent (St. Lawrence River) near the Old Port of Montréal. With a planned capacity of 100 kW, it fed electricity into Hydro-Québec’s grid from 2010 to 2013.
In theory, the global hydrokinetic potential of ocean and tidal currents near shorelines is 7,800 TWh/year. That’s roughly 40% of the world’s total electricity output in 2013. The hydrokinetic potential of tidal currents alone accounts for 10% to 15% of the total. Current strength varies around the globe, depending primarily on local submarine morphology (bathymetry) near shorelines.
River current potential
Canada’s potential is estimated to be 15,000MW. In Québec, which has approximately 35% of the country’s annual surface flow, the potential can be estimated at 5,250 MW on a proportional basis. Given the level of technical feasibility (10%–15%), the province’s deliverable potential would be between 525 and 788 MW.
Ocean current potential
- According to the National Research Council of Canada’s Canadian Hydraulics Centre, Canada has 190 sites with a theoretical capacity exceeding 1 MW. The country’s total potential is 42,000 MW.
- Québec’s theoretical potential is estimated to be 4,288 MW (38 TWh/year), only a portion (10%–15%) of which would be technically feasible. Over 97% of the resource is near the Ungava Bay coast, a region far removed from Hydro-Québec’s transmission system and major load centres.
Output and costs
- River turbines: It is rare to find locations with all the right operating conditions (depth > 6 m and current speed > 2 m/s). Moreover, although their energy conversion efficiency is 30% to 40%, the maximum capture rate for a body of water’s total kinetic energy is 15% because a significant quantity of water is diverted around the turbine. Once this energy source has reached maturity, the estimated cost of electricity generated by a river turbine is over 15¢/kWh.
- Ocean turbines: Energy conversion rates are identical to those of river turbines, but these turbines are usually much larger and generate power measured in megawatts. Since this source of energy is in its infancy, investment costs are currently high and vary depending on the developer. Once the energy source has reached maturity, the gross production cost will be over 11¢/kWh and start-up costs will vary from $3,000 to $5,000/kW, according to most developers. Estimated costs for ocean turbines are comparable to those of offshore wind turbines. Eventually, the cost of hydrokinetic power may come down slightly thanks to technological advances in underwater connections for wind turbines.
Advantages and disadvantages
- In terms of output, more predictable than wind power
- No retaining structure, and few or no civil engineering works required
- Discreet or even invisible due to the turbine components’ near-total immersion
- Winter operations possibly problematic. To optimize power output throughout the year, local variations in water levels have to be considered—a complex challenge.
Since there are very few hydrokinetic turbines in operation at this time, information on sustainable development issues is still incomplete. Here are the main potential impacts:
- Modifications to currents, wake effect and noise masking
- Modifications to sedimentary dynamics that may affect the estuary regime
- Modifications to substrates and the transportation and deposit of sediments: variable, depending on the type of anchor and underwater cables
- Habitat modification, including benthic organism habitat
- Modification of vegetation and possible impact on aquatic fauna
- Interference with the circulation and migration of certain aquatic species, particularly as a result of magnetic fields generated by electrical cables
- Risk of animal injury or death in the event of contact with moving machinery
- Noise pollution during construction and operation
- Possible conflicts with shipping, fishing, recreational boating, etc.
- Zero greenhouse gas and atmospheric contaminant emissions during operation
- Small environmental impact over the facility’s life cycle
To learn more about hydrokinetic power, see the data sheet.
- Types of hydrokinetic turbines
- Canada’s hydrokinetic potential
- Scenarios under consideration
- Climate change and air quality
- Life cycle assessment
- Ecosystems and biodiversity
- Health and quality of life
- Land use, regional economy and social acceptability