Behind the Grid: Tidal Power

Tidal Power

Tidal Power Generator
This newly constructed tidal turbine is made ready for deployment on the ocean floor in the Bay of Fundy.

(Published, 2/01/2021, Ruralite)

The most common way to generate electricity begins with motion. If nature can provide the motion, all the better. Standing at the ocean shore, it is easy to sense the raw power in the motion of the tide. There are many novel ways that the tide’s motion can be captured and converted to electricity. Tidal energy is special because, unlike many other renewables, tides are stable and predictable. As with all forms of electric generation, there are benefits and drawbacks. Here are some of the methods used to capture tidal energy:
Tidal Stream
This is the most common method to turn tidal energy into electricity. A series of turbines are placed in a fast-flowing stream that is filled and drained by tides. The rushing water moves past the blades, spinning them like little windmills under the water’s surface. These tidal stream generators are currently deployed in Ireland, Scotland, Norway, Holland and England.
Tidal Barrage / Lagoon
A barrage structure is similar to a dam installed across an inlet of an ocean bay. As the water in the bay rises and falls, water flows through special gates causing turbines to spin. Power is generated by both the incoming and outgoing tides. One way to lessen any environmental impact is to build an artificial lagoon at the ocean’s shore.
Experimental Methods
A ‘serpentine’ generator floats on the water’s surface and spins with incoming and outgoing wave activity. A ‘buoy’ generator rises and falls with the tide. A ‘magic carpet’ uses a long rubber mat that ripples up and down with the current, powering a series of double-action pistons. A ‘shore-mounted floater’ converts the rise and fall of waves to move paddles. That motion compresses biodegradable hydraulic fluid and powers a turbine.
There are countless other ways to capture the awesome power of millions of tons of moving water. All of these methods benefit from the reliable and predictable nature of tides. Reliability is critical for power generation. Satellites and other monitoring devices can accurately predict upcoming tides so energy output can be calculated. However, any tidal energy infrastructure impacts the environment and installation and maintenance costs are considerably higher, as it is much more difficult to build structures over water than it is to build them on land.
The United States does not have any commercially operating tidal energy power plants, although several demonstration projects are in various stages of development.
How much electricity comes from tidal energy?
  • South Korea 511 MW
  • France 246 MW
  • United Kingdom 139 MW
  • Canada 40 MW
  • Belgium 20 MW
  • China 12 MW
  • Sweden 11 MW
By comparison, Dworshak Dam can generate 400 MW and Lower Granite Dam on the Lower Snake River can generate 810 MW