Just like wind turbines which use the force of wind to generate electricity, hydrokinetic turbines use the force of water:
- marine currents
- river currents
- tidal currents
Hydrokinetic power uses water-driven turbines which transform the kinetic energy of water into electricity.
The technology is referred to as marine current technology in tidal applications and river current technology on inland water courses. The sizes and models used differ according to the environment.
Like the wind turbine which harnesses the kinetic energy of wind, hydro power turbines capture the kinetic energy of tidal or river currents. The kinetic energy is transformed by the turbine into mechanical energy, which is then converted into electrical energy by an alternator.
The tidal current or river current rotates the turbine blades. An alternator harnesses this mechanical energy and converts it into electricity. The current is transported over an electric cable.
Various techniques exist.
Hydrokinetic turbines generate renewable energy through the motive force of water, offering a smart solution for electricity access issues around the world: 1.5 billion people still have no access to a power grid and not even one third of potential hydroelectric power is generated.
The benefits are multiple compared to other renewable energy sources (solar or wind):
- Greater availability of water resources: predictable power generation (known currents & tides) and almost permanent supply.
- Limited energy storage requirements compared to solar or wind.
- Compact size of hydrokinetic turbines: at equal power output, more compact than wind turbines as water is 1,000 times denser than air.
- Negligible environmental impact: unlike fossil fuel energy and solar power – energy storage and end-of-life recycling – and even conventional hydroelectric power (impact of civil engineering, methanization).
- Possible decentralized production to serve local energy needs.
- For HydroQuest river turbines, a high load rate of 65 % to 95 % (solar = 21 %, wind = 40 %, diesel = 90 %).
- Hydrokinetic turbine lifetime: 25 years and more for HydroQuest River turbines.
The renewable energy is generated by the motive force of water, without major modifications to the surrounding environment, in particular for river current turbines:
- No civil engineering work, no major constructions.
- No impact on fauna and flora, tested with the BIOTOPE laboratory on the river current turbine installed in the Loire river in Orléans.
- Long lifetime for HydroQuest river current turbines, over 25 years.
- Easy to recycle as they are made of construction-grade steel, no composite materials that are costly to recycle.
On average, the cost per MWh produced by river current turbines is between €50 and €200. This costs depends mainly on the place of installation and the power generated.
For river current turbines, the power output itself depends on:
- speed of flow
- turbine confinement
- proximity of river banks
- the river bed containing the current stream within the machine and thereby improving its yield.
This is the primary reason for installing river current turbines: deliver a portion of the power required by isolated villages by connecting them to a local grid, most commonly powered by diesel generators. This produces stable, long-term green energy.
The idea was tested by HydroQuest in French Guiana, in the village of Camopi on the Oyapock river. The test was part of a program to electrify Guiana’s communities that had no access to the power grid, led by EDF SEI.
The hydrokinetic energy produced by the movement of water has been used for years: water mills have been used since the second century to harness the motive force of river currents to mill grain.
Today, hydroelectricity production using a dam system is the most common form of use of water to generate electricity, indeed it is the second most common mode in France after nuclear power generation.
However, hydrokinetic turbines which harness the power of river currents, sea currents or tidal estuary currents are becoming increasingly popular.
|Hydroelectric plants||Hydrokinetic turbines|
|Principle of operation||Electricity produced by water falling downward and spinning turbines when released from dam||Electricity produced using natural water currents|
|Power generated||Tens of kW to 1800 MW||Tens of kW to 5 MW for river current turbine farms
Several MW for marine current turbines
(worldwide potential for river current turbines by 2025: 3,000 MW
almost 100 GW* for marine current turbines)
|Conditions||Generate electricity using falling water released from reservoir
Build artificial dams
|For river current turbines:
No dam or reservoir needed but minimum water flow speed of 1.5 m/s
– Possibility of flooding of villages
– Obligation to build fish passes
|– Environmental continuity: no significant impact|