Energy

Japanese turbines catch the waves to harvest energy and protect the coastline

Japanese turbines catch the wa...
Japanese researchers have outlined a system of turbines that would harvest wave energy, while also protecting shorelines from erosion
Japanese researchers have outlined a system of turbines that would harvest wave energy, while also protecting shorelines from erosion
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Japanese researchers have outlined a system of turbines that would harvest wave energy, while also protecting shorelines from erosion
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Japanese researchers have outlined a system of turbines that would harvest wave energy, while also protecting shorelines from erosion
The turbines would be placed in front of tetrapods or coral reefs to harness the fast-moving jets of water created by breaking waves
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The turbines would be placed in front of tetrapods or coral reefs to harness the fast-moving jets of water created by breaking waves
Electrical energy is created through a permanent magnet electric generator, and fed back to land through a cable in the support column
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Electrical energy is created through a permanent magnet electric generator, and fed back to land through a cable in the support column
The team members on the project, led by Professor Tsumoru Shintake (far right)
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The team members on the project, led by Professor Tsumoru Shintake (far right)
The turbines have been designed to withstand rough seas and extreme weather like typhoons, while also ensuring the safety of sea life around them
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The turbines have been designed to withstand rough seas and extreme weather like typhoons, while also ensuring the safety of sea life around them

Star-shaped concrete structures called tetrapods are often used to protect coastlines from eroding away under the constant barrage of waves. Now a project from the Okinawa Institute of Science and Technology (OIST) has outlined plans for turbines that would sit alongside tetrapods, helping to not only dissipate wave energy, but harvest it.

The constant crashing of the waves represents an essentially limitless amount of energy. Current techniques to tap into it include; Azura in Hawaii, which uses a 360-degree rotating float mechanism; a system of buoys attached to a jetty in Gibraltar that rise and fall with the waves; a proposed system from UC Berkeley that would absorb that energy by carpeting the seafloor; and an "artificial blowhole" in development in Australia that captures energy from air displaced by waves.

The OIST system is designed to not only harvest wave energy but dissipate it, working with tetrapods to reduce the impact on Japanese coastlines. Turbines would be placed in the direct line of fire, such as in front of tetrapods or around natural structures like coral reefs, to take advantage of fast-moving jet flows of water created where waves break.

These Wave Energy Converter (WEC) turbines would be anchored to the sea floor with mooring cables, and peek up just above sea level where the waves can wash over them. Each turbine would feature five blades with a diameter of 70 cm (27.6 in) attached to a permanent magnet electric generator encased in ceramic to keep the damaging seawater out. The electrical energy created would be channeled through a cable in the support stem and back to shore to feed into the grid.

Electrical energy is created through a permanent magnet electric generator, and fed back to land through a cable in the support column
Electrical energy is created through a permanent magnet electric generator, and fed back to land through a cable in the support column

While spinning blades might not sound safe, the team says there are a few precautions built in to protect sea life and the turbines themselves from harm. The speed of the blades' rotation has been carefully calculated so that any animals that get swept up into them can escape. To protect the turbines during rough swells or extreme events like typhoons, the team took a cue from dolphin fins and made the blades flexible so they release stress. The supporting structure is also designed to bend under pressure, like the stems of flowers.

According to the team, the turbines have a working life of 10 years, and maintenance can be undertaken by the same crews who inspect tetrapods. While the researchers haven't given any figures for how much energy each turbine could produce, they have given a rough estimate for the amount produced by a fleet of them over a wide area.

"Surprisingly, 30% of the seashore in mainland Japan is covered with tetrapods and wave breakers," says Professor Tsumoru Shintake, lead researcher on the project. "Using just 1% of the seashore of mainland Japan can [generate] about 10 gigawats [of energy], which is equivalent to 10 nuclear power plants. That's huge."

The next step for the project is to install two half-scale model turbines, with blade diameters of 35 cm (13.8 in), which would power LEDs to demonstrate the technology.

"I'm imagining the planet two hundred years later," says Shintake. "I hope these [turbines] will be working hard quietly, and nicely, on each beach on which they have been installed."

Source: OIST

7 comments
Daishi
I think it would also protect the water from swimmers and the beach from wildlife.
Bob
Waves are like the wind in that only a tiny fraction of the total energy can be realistically harvested. Between the tides, storms, erosion and the abrasion of moving water, rocks and sand; I seriously doubt the projected lifespan of these tiny turbines and the cables that transfer their energy. Nothing can stand up to the power of moving water.
WolfeSA
@ Bob, I live by the sea, the waves never ever stop, they might be smaller and larger each day, but they are never ending. The erosion issued you raise are already part of life for ships and port equipment and they survive. If you weight the maintenance cost against the cost of nuclear plants it's immensely cheaper.
Bob
Well Wolfe, I have lived on a boat in the ocean. I guarantee the maintenance never ends. If you think cleaning and maintaining thousands of tiny turbines and their blades will be economical, you might want to reconsider. Even with toxic bottom paint on a boat the job is continuous. As far as the power of water, my favorite dive site which consisted of a sunken steel coast guard ship and military trailers was ripped to pieces and scattered over a two mile area even though it was five miles from shore by a fairly mild hurricane and my marina was completely destroyed. While water could provide a tremendous amount of power, harvesting it is a much more daunting task than most people realize. Theoretical yield and reality are very, very different.
ljaques
I think this idea is great. The only concern is the noise these might impart to the area. Without skewed magnets on the rotors, those would be very noisy. Early wind turbines were banned from neighborhoods due to the loud whine they made because of the camming of the magnets over the windings, inducing vibration. Skewed-magnet rotors were developed which severely diminished that noise. Doesn't sea life deserve the same courtesy?
StWils
All of these comments have merit, especially about the impact of crashing waves. However the maintenance costs do not begin to compare to the costs of nuclear or fossil plants and it seems every month that goes by another small-to-large innovation occurs in energy storage. The two key elements are the total cost of ownership and that the system be modular, rugged, and resistant. The damage in Texas and throughout the Caribbean shows how fragile our infrastructure systems are. In Florida however, many home & small businesses have individual solar systems. The systems that were built to capable of standing alone enabled those owners to have power the day after the storm went by. Everyone who was tied into a sole, central system went without power & lights for days and in Puerto Rico especially, it could be weeks before power is back. Fixing these system flaws is achievable and, over time, affordable. This Japanese design gives Japan's large coastal communities a tremendous degree of system resilience even if in a given area and after given violent weather event an area is knocked down hard. Overall, everyone benefits and recovery should be quick as expertise and equipment spreads. While Bob is right about the power of the sea this does not seem to have discouraged anyone from going out again. We always seem ready to build more boats.
JonStron
i agree, japan is already succesfully harvesting waves, so no need to debate wether it would work, it will !