Oceans cover more than 70% of our planet’s surface, but the unrelenting power of the seas has yet to be harvested. The emerging tidal energy industry wants tidal power to revolutionize how we create energy for work and home.
There are an estimated 3,000 gigawatts of energy produced by tides globally. Some experts think there could be enough to meet a substantial portion of global electricity consumption, but much is speculation, and conclusions vary wildly.
Let’s see if tidal power is a clean energy panacea to meeting rising energy demands while reducing greenhouse gas emissions.
What Is the Meaning of Tidal Power?
Tidal power is part of a group of energies that come under the umbrella of marine energy. Marine energy covers several energy systems within the oceans.
- Wave Energy: The movement of the waves is converted into electrical power
- Ocean Currents: Deep-sea turbines spin thanks to the power of passing currents
- Tidal Power: Electricity is created using the tides
- Offshore Wind Power: Turbines rotate in the wind to generate electric power
- Ocean Thermal Energy: Using the difference in the deep cold sea and warm surface sea temperatures to create electricity
Tidal power relates to a power system that harnesses tidal currents to produce energy.
What Is Tidal Power?
Our oceans experience tides thanks to the Earth’s rotation interacting with the moon and sun’s gravitational pull. There are two daily high tides and low tides.
Unlike a 24-hour day — the time the Earth takes to rotate once fully relative to the sun — the moon takes 24 hours and 50 minutes to orbit Earth. The moon travels in the same direction as the Earth’s rotation, so it takes longer to “catch up” and complete a full orbit from the earth’s reference point.
This lunar or tidal day creates tides 12 hours and 25 minutes apart each day. That means it takes 6 hours and 12.5 minutes for shoreline water to go from high tide to low tide or vice versa, known as tidal ranges.
The most significant tidal ranges globally are at the Bay of Fundy — located between Canada’s Nova Scotia and New Brunswick provinces, which touches the U.S. state of Maine. The water levels there have a mean average difference of almost 40 feet (12.2 meters). Anchorage, Alaska, has the highest tides in the United States, up to 40 feet (9.15 meters).
Tidal ranges change too. With the sun, moon, and Earth in line, spring tides create the highest tides, while neap tides are the weakest and occur when the three planets are at right angles.
The movement of the water caused by this gravitational pull is called the tidal stream. These tidal streams are what tidal power companies seek to create tidal energy. Tidal streams are stronger where the ocean currents funnel through natural features like the seafloor, inlets, straits, channels, or islands, all of which can amplify the tidal stream.
A tidal range of at least 23 feet (7 meters) is suitable for energy production at large-scale tidal power plants.
Is Tidal Power a Renewable Energy?
Tidal power is considered a renewable energy source because the power of the oceans and tides will not run out, thanks to the gravitational pull of the Earth, sun, and moon. Tidal power doesn’t create carbon emissions other than those associated with the construction, maintenance, and recycling of the infrastructure. However, tidal energy technology is not as developed as other renewable sources like wind energy or solar power.
How Do We Capture Tidal Power?
Ocean energy is found in its waves and currents, which are moving. The energy of movement is called kinetic energy.
The primary method of capturing this kinetic energy is to use tidal turbines. These are similar to wind turbines, but instead of the blades being turned by wind energy, a tidal turbine’s blades are rotated by the tidal currents.
Water is almost 800 times denser than air, meaning tidal turbines are usually smaller and more robust than wind turbines. Tidal turbines can deliver significant power generation results.
The turbines create electricity by the blades turning a rotor, which spins a generator to produce electric power. There are other generation methods, which we’ll discuss more below.
How Reliable Is Tidal Power?
The Earth, sun, and moon movements are predictable and accurate. Tides, sea levels, and tidal power are, therefore, quite reliable. We know precisely when and how much a tide will rise and fall in every part of the world, and we can measure how much energy we can produce from each tide.
What Types of Tidal Turbines Exist?
There are several types of tidal devices suitable for use on the seafloor. Projects may include an array of these turbines or small-scale installations of just one or two.
- Horizontal Axis: A horizontal axis turbine attaches to the seabed. It looks and works very similar to a wind turbine with the tidal stream rotating its blades.
- Vertical Axis: This type of turbine works the same way, but its blades are attached to a vertical axis and rotate more like the blades of a mixer in a bowl.
- Venturi Effect: This setup passes the moving seawater through a funnel to turn internal rotary blades.
- Hydrofoils: This device looks like an elephant’s trunk moving up and down, using the tidal stream to move up and down and powering a hydraulic system to create electricity.
- Archimedes Screw: This a helical corkscrew-shaped device that uses the tide to turn its spiral blades — imagine how a rotating barber pole sign looks in motion.
- Kites: These are attached to the seafloor (with a turbine attached) and swoop in a figure of eight to increase the power of the tidal stream.
How Do Tidal Barrages Work?
It’s worth noting that not all tidal energy generation options attach to the seabed. Tidal barrages look and work similarly to hydropower. Developers build a barrier across a sea opening where the barrage is to sit to prevent water flow.
A traditional hydroelectric dam releases water to drive turbines to create electricity. However, a tidal barrage has turbines that rotate when the tide comes in and goes out, called two-way generation. Barrage operators can also close the turbines at high tide and keep the water behind the dam. They release it later to maximize the water flow, called ebb generation.
Tidal lagoons use the same principle as tidal barrage. Instead of building a solid barrier across a watercourse, a tidal lagoon is a natural or artificial lagoon that captures ocean water. Its turbines work as the lagoon empties and fills.
How Do We Capture Wave Energy?
Wave energy, or wave power, is very much in its infancy as an energy technology. Winds that move water and create waves instill kinetic energy into the moving waves.
There are many ideas for capturing wave movements and converting them into electricity. Some designs float on the sea surface, and waves push moving parts to create power; others oscillate underneath the water in the form of “sea snakes”. The European Marine Energy Centre has a list of wave energy devices under trial, and new ideas often come to light.
Practical Uses of Tidal Power
Numerous countries have pledged to reduce greenhouse gas emissions to net zero by 2050 to halt global warming. To reach this goal, governments will need to move away from using fossil fuels and utilize cleaner energy resources.
Global renewable energy generation capacity is increasing, with solar and wind leading the increases. Hydropower is the primary renewable energy provider worldwide. Tidal power isn’t usually mentioned because it’s a minor player in the global market, but that doesn’t mean it hasn’t already shown promise.
Who Discovered Tidal Power?
In 1920, Dexter Cooper, an engineer working in the hydroelectric power sector, came up with a way to transfer that technology to the tides. Cooper discovered how to make electricity from tidal power, not the tidal power concept itself.
He almost succeeded in building a tidal barrage for the Passamaquoddy Tidal Power Project. Funding — and support — came and went. The project was eventually dropped, which almost perfectly mirrors tidal power’s journey thus far.
When Did We First Use Tidal Power?
Humans have been using tidal power for more than 1,000 years. In Europe, people stored incoming tidewater in ponds that they would let out at low tide, driving water wheels to mill grain.
The first fully operational tidal barrage saw tidal power become a reality in La Rance, France, in 1966. Its 240 megawatts (MW) electricity generation capacity is still working.
North America’s first tidal power site opened in 1984 in the Bay of Fundy, the Annapolis Royal Generating Station, with a 20 MW installed capacity.
In 2011, South Korea’s Sihwa Lake tidal power station came online to become the world’s largest tidal power plant with its 254 MW capacity.
Is Tidal Power a Growth Energy Sector?
Governments of countries close to seas with fast tidal currents and high tidal ranges are exploring the potential benefits of tidal power.
The United Kingdom, which lies in an area with some powerful tides and wide tidal ranges, has several horses in the race. Studies show the country could supply up to 11% of its current total electricity usage from tidal energy sources.
Northern Ireland’s Strangford Lough Tidal Turbine came online in 2008, producing 1.2 MW of electricity, the first of several planned installations.
The MeyGen tidal energy project in Scotland came online in 2018. It will eventually become the world’s largest tidal power station, with almost 400 MW capacity. The MeyGen array of up to 61 turbines — on the seabed between the far northeastern Scottish mainland and the nearby and uninhabited island of Stroma (pictured above) — could eventually power up to 175,000 local homes.
In Wales, government money is pouring into the Morlais project. A 13.5 square mile marine zone (35 sq km) will be developed offshore from the island Anglesey. Here, tidal power companies will be able to test tidal stream devices, checking for efficiency and environmental impacts.
Also in Wales, Swansea Bay Tidal Lagoon claims it will be the world’s first tidal lagoon power plant. A sizable U-shaped wall will keep tidewater locked in for three hours, by which point there will be a 13 feet (4 meters) height difference with the sea. Once emptied, the sea wall will keep the incoming tide out. It flows back in once there is a 13 feet height difference. That way, Swansea Bay Tidal Lagoon can generate electricity four times a day, with a maximum capacity of up to 320 MW.
According to the International Renewable Energy Agency, tidal barrage projects have been slated in India, South Korea, Russia, and the Philippines. The United States could consider tidal power stations in places like Maine or the Cook Inlet of Alaska, where tidal ranges are high. Globally, however, many potential sites never leave the planning stage.
Is Tidal Power Sustainable?
As we’ve seen, tidal power is reliable, consistent, and renewable. Once built, it creates minimal greenhouse gases. Tides will continue to rise and fall, so tidal energy is sustainable. But aside from high development costs, tidal power’s primary challenge is its environmental impact.
What Is Bad About Tidal Power?
Marine renewable energy does come with environmental costs. Tidal turbines require precious metals and materials in their construction, leaving a carbon footprint plus associated emissions for transporting and installing them. Tidal barrages require tons of cement and other materials and alter landscapes with their access roads and finished appearance.
This emerging technology is expensive to install and connect to the power grid. Often, prime tidal power sites are far from the point of use, adding to potential transmission costs. However, the visual impact of turbines and barrages is minor compared to potential issues underwater.
Turbines are heavy and require extensive and strong foundations built into the seabed, disturbing local wildlife and marine life. Although they move more slowly than wind turbines, their rotating blades are dangerous to passing fish, seals, and other sea life.
Noise pollution and electromagnetic radiation may also affect delicate ecosystems, blurring maritime animal navigation and communication. Turbines may disrupt breeding sites, kicking up sediment from the seafloor and pushing sensitive species from their natural habitat.
Large-scale tidal power stations can also reduce tidal ranges, sailing routes, navigation, and recreational sports by altering water quality and flows.
Tidal barrages and tidal lagoons, which store tidal waters, can change water salinity and make it unbearable for some creatures. Like dams, a barrier can block fish migration paths, limiting bird food sources. Other species may flourish and attract new life, but the area will alter.
The Ups and Downs of Tidal Power in the Energy Mix
The immense power of the seas has inspired poetry, music, and adventure through the centuries. While much of the deep blue remains a mystery, the unrelenting rhythm of the tides makes tidal energy generation an enticing prize in the race for clean, renewable, and sustainable energy.
Installation costs, environmental concerns, and the remoteness of suitable locations may prove to be barriers to using tidal power on a larger scale.
However, tidal power could be a valuable addition to renewable energy sources in the future. Like solar and wind power before it, tidal power is waiting for a technological leap so it can ride a wave of mass adoption. The question is more about when it happens rather than if it happens because time and tide indeed wait for no one.
Brought to you by amigoenergy
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