The ocean has long provided humans with a bounty of food. However, a new type of untapped resource is now lapping at our feet: tidal energy.
Our seas contain an abundance of energy in the form of moving water. In fact, if we were able to find a way to harness all this energy efficiently, we would be able to meet the entire world population’s energy needs with some to spare.
Using tidal energy is not exactly a new idea. Humans have used the power of the tide for centuries. People have used it to help with laborious tasks like grinding grain.
But with the aid of modern technology, we can harness the unlimited power of tides. We can use it to produce electrical energy that’s clean and renewable.
The Basics of Tidal Energy
In short, tidal energy is within the gravitational and kinetic energy of our planet’s large bodies of water. The pull of the Moon, Sun and rotation of the Earth creates the ebb and flow of water.
Every day, these astronomical forces move a mind-boggling number of liters of water. And where water is moving, there is kinetic energy that people can harness.
A turbine that converts kinetic energy into electrical energy can harness the energy that all this moving water creates. This form of energy production is similar to hydroelectric energy, except it doesn’t require falling water.
Tidal energy is different from many other forms of renewable energy in that it is very predictable, unlike wind or solar power. Often times, the weather can severely affect the efficiency of many eco-friendly power solutions.
However, the tides are constant and operate on a well-established schedule around the world, which is an invaluable asset for any would-be energy producers.
1. Kinetic energy: The energy an object or mass (like a body of water) has due to its motion. For example, dropping a ball from the top of a building would create kinetic energy.
2. Gravitational energy: The potential energy created between one smaller object and one larger object due to gravity. For example, there is a lot of potential gravitational energy before you drop a ball from the top of a building because gravity will pull it to the ground.
How is Tidal Energy harnessed?
Before you can harness tidal energy, you must first convert kinetic energy into electrical energy.
The best way to accomplish this is with a turbine which spins from the physical push of the tides and converts the water’s movement into usable electricity. There are currently three different types of tidal turbine systems:
- Tidal Barrage: Tidal barrages are the most efficient way of harnessing tidal energy. They require the construction of a dam-like structure that forces water at high speeds through a bottle neck where a turbine is at. The higher speeds of water mean more kinetic energy, which in turn means more power. In many ways, this is like a hydroelectric dam system.
- Tidal Turbines: This system functions similarly to that of a wind turbine. People place a simple turbine in the water. There, the water passing over it can drive the rotors. This type is probably the simplest of all the systems and has a cheaper installation cost, although it does produce less energy than others.
- Tidal Fences: Tidal fences are similar in design to that of tidal turbines but with one major difference: a different rotor. These systems use a turnstile-like design which spins with the direction of the water. People have proposed several variations of this design but the most popular is a spinning cylinder shape that stands vertically.
The Newbie: Floating Tidal Turbines
This type of design is currently being tested and isn’t officially in commercial use quite yet. The system utilizes a floating barge that has turbines on its underside.
The turbines can spin in the current that flows near the surface of the water. This design eliminates the need for any type construction on the seabed which makes it easier, cheaper and less environmentally damaging than any system currently in use.
This promising technology could make tidal energy farms possible in locations all over the world.
The Pros and Cons of Tidal Energy
As with any type of innovative technology, tidal energy has its own host of upsides and downsides. Before committing to one path forward in the renewable energy sector, it’s important to consider all potential pitfalls.
However, tidal energy is overwhelmingly a positive addition to the roster of eco-friendly technologies.
- Clean and Renewable: Tidal energy is as clean and renewable as any sustainable resource available to us today. It creates no pollution and doesn’t take up that much physical space when compared to other renewable energy systems.
- Predictable and Reliable: Most areas experience two high tides and two low tides per day. This cycle is easily predicted and isn’t subject to unexpected changes unlike many other renewable resources. Some systems also harvest energy from tidal currents regardless of which direction they are flowing, allowing the production of energy to go completely uninterrupted.
- Long-lasting Equipment: Tidal energy systems are inherently age resistant and have long lifespans. The average estimate for most tidal systems is 75-100 years of working use. In comparison, a solar panel usually degrades after an average of 25-30 years. This converses time, energy and money and is overall more economical when implemented on a large scale.
- Effective at Low Speeds: Tidal energy systems can produce energy even when the water passing over or through them is moving relatively slowly. Water is 1,000 times denser than air, which means it can power a turbine even when moving a snail’s pace.
- Environmental Impact: While placing tidal generators under water may be quite convenient for humans, the same can’t be said for all the critters of the sea. Since the systems require turbulent water to power them, a large foundation needs to be built. This type of underwater construction can result in habitat destruction. The greatest offender is the tidal barrage which utilizes dams that can impede the movement of sea life and potentially wreak havoc on aquatic ecosystems.
- High Construction Costs: Building structures strong enough to withstand the turbulent, corrosive nature of sea water is by no means a cheap undertaking. Other renewable resource solutions have cheaper upfront costs. While tidal energy systems have long lifespans and eventually pay themselves off, governments are more concerned with their 5-year budget rather than a 60-year projection. The initial investment for these systems is often the biggest wart on the face of potential projects.
- Scarcity of Suitable Locations: Not every seascape near a shore is suitable for a tidal energy facility. They require a very specific set of factors in order to operate effectively and efficiently. For example, the height of the sea during low and high tide. The scarcity of available locations for installing tidal energy systems is one of the main reasons why they are not more popular.
Tidal Energy Farms
While tidal energy is still a long way from becoming as mainstream as solar power, there are still several tidal energy farms spread around the world that are pushing the boundaries of this innovative resource.
MeyGen Tidal Stream Project (Scotland)
For the best example of what a successful, full-scale tidal energy farm looks like, there is no better candidate than the MeyGen project in Scotland. This facility is one of the newest and most promising tidal energy farms out there, and it has done wonders to highlight how powerful the seas can be.
Construction of the MeyGen Tidal Stream Project began in 2015 but it didn’t start exporting energy to the grid until 2017. Over the past two years, this tidal energy farm has produced 17GWh of clean, renewable energy. The project currently powers an approximate 100,000 homes.
The tidal energy farm uses massive 49 feet tall tidal turbines with 52 feet long blades that spin as the tide pass through them. The farm has been very successful because of the powerful tides in the area.
In fact, Scotland alone accounts for 25% of potential offshore wind and tidal energy resources for the entire European Union. The project is a shining success for tidal energy and hopefully it will inspire more projects to follow suit.
Rance Tidal Power Station (France)
Located in Brittany, France and established in 1966, this is the oldest tidal energy farm on Earth. It uses a tidal barrage system to produce energy, harnessing 600 GWh annually at a capacity factor of 40%. This power station produces enough energy to satisfy 0.12% of the total energy demand in France.
As the oldest tidal energy farm, we can learn a lot from the Rance Tidal Power Station regarding tidal energy efficiency and its real costs. To date, this tidal energy farm has recovered its initial development costs and now produces energy at a cheaper rate per kWh than that of a typical nuclear power plant.
The establishment of this tidal power station has been criticized for its environmental impact as the initial construction caused considerable harm to the estuary the barrage system calls home.
Estuaries are notorious for their sensitive biomes, and any fluctuations in salinity and sedimentation caused by interruptions in water flow can be detrimental to the fauna and flora.
Although the initial impact was quite large, the estuary recovered in its first 10 years of operation. People now consider it as biologically diverse as it was pre-construction.
Shiwa Lake Tidal Power Station (South Korea)
Shiwa Lake Tidal Power Station is big. In fact, it’s the largest tidal energy farm on Earth and is so gigantic that people can even see it from space.
With a tidal barrage spanning over 12.7 kilometers, the builders did not even intent the massive structure to be a tidal energy farm at the time of its construction.
The project was originally intended for the reclamation of land and to provide desalinated water for agriculture. However, once construction was completed, the water within it soon became polluted, stagnant and unfit for use. This forced the government to rethink its plans and find a use for the tidal lake while also helping the ecosystem within it to recover.
The answer came in the form of a power plant that made use of the massive amounts of water passing through the tidal barrage’s sluice gates and converting this moving water into a considerable amount of energy. The tidal power station became operational in 2011 and currently produces 550 GWh annually, with a capacity of 254MW.
This massive project has helped progress the study of environmental impact management of tidal energy farms and has highlighted the potential for existing tidal management systems to be converted into power producing systems. Shiwa Lake has also attracted millions of tourists over the years with its water sports and lively ecosystem.
Why haven’t we seen more Tidal Energy Farms?
As previously discussed, there are many disadvantages that tidal energy production still needs to tackle.
- Construction Difficulties: A turbulent sea is a difficult place to perform any sort of construction and finding companies with the expertise to build and install these structures is no easy task. There is a lack of skills and investment in the sector and more research needs to be done to perfect our methodology when it comes to efficiently harnessing tidal energy.
- Environmental Factors: The specific environmental requirements for tidal energy farms make them inaccessible for most seaside towns. On the bright side, as technology advances and these energy farms become more efficient, it lowers the standard.
The Future of Tidal Energy
The industry is still in its infancy, but with more investment and expertise, it will become cheaper and more accessible to implement around the world. With each tidal energy farm that is put into operation, we learn more about the difficulties and how to overcome them.
As interest in tidal energy grows around the world, people are doing further research and development. You can see a simple indicator of the growth in this industry in its market value. Experts valued the tidal energy market at $487 million in 2014 but experts expect it to be worth $11.3 billion by 2024.
Development in the USA
Due to America’s large and diverse coastal regions, there are many potential sites that people could use to produce electricity through tidal energy. To date, there are no large-scale tidal farms in the United States.
However, there have been many proposed projects which have yet to be realized. Several areas have the best opportunities to harness the power of the tide:
- West Coast (WA, CA, OR)
- Gulf of Mexico
- East Coast (ME through NC)
Experts need to conduct more research on where the best potential sites for tidal energy farms are in the U.S. However, the raw data already presents enormous potential. This sector of renewable energy may be the clean, fuss-free answer we’re looking for in the modern age.