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Tidal turbines, like this one in Nova Scotia, can be used to produce large amounts of clean renewable energy. Image source: Hakai Magazine
With climate change becoming more and more of a threat, there has been an increased focus on renewable energy sources and the demand for clean energy. This has brought on rapid development of new ways to harness energy, like tidal power.
Tidal power is a form of hydropower that has incredible potential to power our future. There are three ways to harness tidal power: tidal turbines, tidal barrages, and tidal fences.
Generating tidal energy is renewable and predictable, and it can produce huge amounts of power. However, there are limited sites that are suitable for tidal power generation, and the equipment is very expensive to build.
Read on to take a closer look at some of the advantages and disadvantages of tidal power.
What is tidal energy?
Tidal power is a renewable energy source that turns energy created from changing tides and currents in the ocean into usable electricity. Tidal power can be captured by using different types of technologies, such as tidal barrages, tidal stream generators, and tidal fences.
All of these types of tidal energy plants make use of tidal turbines, so it's most important to understand how a turbine can capture the kinetic energy within the tides for energy production.
Tidal turbines harness tidal energy similarly to how wind turbines capture wind energy. As the currents and tides change, the moving water pushes the blades of the turbine. The turbine turns a generator that then produces electricity.
How does tidal power work?
There are three main ways to harness the energy created by tides and currents in a body of water: tidal turbines, tidal barrages, and tidal fences.
1. Tidal Turbine
Tidal turbines are very similar to wind turbines, except they are below the water’s surface instead of above or on land. The water’s current pushes the blades of the turbine, which is connected to a generator that creates electricity.
Tidal turbines are able to produce much more electricity than wind power plants, mainly because water is much denser than air. However, water’s high density also means that tidal turbines need to be much stronger than wind turbines, making them more expensive to manufacture.
Tidal turbines are large, but they create relatively little disruption to the ecosystem around them. They could cause collision damage, like wind turbines, however, with marine life, the blades tend to move slowly so it isn’t that much of a concern. They also emit low-level noise, which can impact marine mammals.
Tidal barrages are low-walled dams, usually installed at tidal inlets or estuaries.
Similar to traditional hydroelectric dams, sluice gates are used to create a reservoir on one side of the barrage. The barrage is secured to the sea floor, while the top of the barrage is just slightly above where the water level hits during the highest tide.
Tidal turbines are located towards the bottom of the barrage, inside a tunnel, which allow water to flow through.
Tidal barrages look like traditional hydropower dams. Turbines located along the bottom of the barrage are turned with the incoming and outgoing tides.
During an incoming high tide, water flows over the turbines as the water rises. Then, the water flows back through the turbines as it becomes low tide. The turbines are connected to a generator which produces the electricity.
Tidal barrages are the most efficient way to harness tidal energy, but they’re also the most costly.
They require an entire concrete structure to be built, which can cost a pretty penny. Barrages also have a larger environmental impact on the surrounding ecosystem than tidal fences or turbines.
Because they are essentially an underwater wall, fish and other sea creatures can’t pass through, causing a myriad of effects on the local ecosystem.
A tidal fence is like a hybrid between tidal barrages and tidal turbines.
The vertical tidal fence turnstiles are installed together in a ‘fence-like’ structure, hence the name ‘tidal fence’. Instead of spinning like a propeller, tidal fences spin like a turnstile.
To create electricity, the energy from tidal currents pushes the turnstile blades, which are connected to a generator.
Tidal fences have vertical blades that are pushed by moving water. These vertical turbines are installed together like a fence, but they don’t require the large, concrete structure that tidal barrages do.
Usually, they will be installed in between land masses in things like inlets and fast-moving streams. They are submerged entirely underwater, and have little impact on the surrounding ecosystem.
Tidal energy pros and cons
Like all energy sources, tidal power comes with its own set of benefits and drawbacks. Here are the main tidal energy pros and cons:
| Pros | Cons |
|---|---|
| Renewable | Limited site availability |
| Zero-carbon emissions | Expensive |
| Predictable energy generation | Environmental impact |
| High power output | Energy demand |
Advantages of tidal energy
1. Renewable
Tidal energy is a renewable source of energy, which means the energy doesn’t deplete as it is used.
So, as you are harnessing energy from the changing tides, you don’t decrease the amount of energy the tides can produce in the future. The gravitational pull from the sun and the moon, which controls the tides, won’t cease to exist anytime soon.
2. Zero carbon emissions
In addition to being a renewable energy source, tidal power stations do not emit greenhouse gasses during electricity generation.
Because greenhouse gas emissions are one of the leading causes of climate change, finding zero-emission energy sources is more important than ever.
3. Predictable
Tidal currents are highly predictable. Low and high tides follow well-known cycles, making it easier to know when power will be produced throughout the day.
It also makes it easy to know how much power will be produced by turbines, since the power of the tides and currents can be forecasted accurately.
4. High power output
Tidal power plants are able to produce high amounts of electricity. One of the main reasons for this is because water is so dense - almost 800 times more dense than air.
This means that a tidal turbine will produce substantially more energy than a wind turbine of the same size.
Plus, even when water is moving at low speeds, the density of water allows it to power a turbine. So, tidal turbines have the potential to produce large amounts of electricity even if the conditions of the water aren’t ideal.
Disadvantages of tidal energy
1. Limited installation sites
In order for a tidal power plant to be built, the potential installation site must meet very specific requirements. First, they need to be located on a coastline, which limits potential station sites to coastal states.
There are additional requirements a potential site must meet. For example, tidal power stations need to be built in places where the difference in height between high and low tide is significant enough to power turbines.
This limits where the power stations can be installed, making it difficult for tidal power to be implemented widely.
2. Expensive
One of the biggest drawbacks to tidal power is the high upfront costs. Tidal energy turbines need to be much sturdier than wind turbines, because of the high density of water. The cost of constructing a tidal power generation plant varies depending on what type of technology they use.
Most of the tidal power plants that are currently in operation are made of tidal barrages, which are essentially low-walled dams. The construction of a tidal barrage is extremely expensive, since a whole concrete structure - plus turbines - needs to be put in place.
The cost barrier is one of the main reasons why tidal power has been slow to be adopted.
3. Environmental effects
Just because tidal energy is renewable doesn’t mean it is completely environmentally friendly. The construction of tidal energy power stations can have a substantial impact on the surrounding ecosystem.
Tidal turbines have the same issue that wind turbines face with birds - marine life collisions. As turbines spin, fish and other sea life could swim into the blades leading to serious injury or death. Tidal turbines also create low level noise beneath the surface of the water that negatively impacts marine mammals, like seals.
Tidal barrages have an even larger impact on the local environment. Not only do they cause the same problems that turbines do on their own, they also have a similar impact that dams have. Tidal barrages prevent the migration of fish, and cause flooding of surrounding areas that forever changes the landscape.
4. Energy demand
While tidal power does have predictable power generation, it doesn’t have constant power production. We can know exactly when the tidal power plant will generate electricity, but that electrical generation might not match up with the demand for energy.
For example, if high tide is at noon, the tidal electricity will be produced around noon. Peak energy demand is usually in the morning and the evenings, with the lowest energy demand in the middle of the day.
So, the tidal power plant will produce all of this electricity, but it won’t be needed. So, tidal power would realistically need to be paired with battery storage to make the most out of the energy it produces.
The future of tidal power
Tidal power has huge potential, especially as new technologies, like dynamic tidal power, continue to be developed.
Currently, there are less than ten tidal power stations in operation globally. The two most popular tidal power plants, Rance Tidal Power Station and Sihwa Lake Tidal Power Station, produce enough tidal energy to power 94,507 homes in the United States for an entire year. Not only is that a substantial amount of power, the power produced is predictable, and carbone-free.
However, tidal power plants can have a substantial impact on the surrounding ecosystem, high upfront costs, and there are limited suitable sites for them. Hopefully, as technology continues to improve, we will be able to take advantage of the energy stored within the tides.
In the meantime, if you want to start moving away from fossil fuels now, you should consider making the switch to solar power. A solar panel system will not only decrease your carbon footprint, it can eliminate your electric bill entirely.
Use our solar panel calculator to find out how much solar panels will cost to install on your roof.
Key takeaways
- Tidal power utilizes the energy created by changing tides and ocean currents and turns it into usable electricity.
- Tidal power can be captured using different technologies including tidal barrages, tidal stream generators, and tidal fences - all of which use tidal turbines.
- The main advantages of tidal power are that it is renewable, it releases no carbon emissions, it is predictable, and it has a high power output.
- The main disadvantages of tidal power are that there are limited installation sites, it is expensive, the turbines can impact the surrounding ecosystem, and the power produced does not always match up with peak energy demand.
- As tidal power technologies and energy storage improve, tidal energy has the potential to become a major energy source.
Looking for lists of pros and cons for other types of energy sources?
Jen Merithew
Written Content Manager
Catherine is the Written Content Manager at SolarReviews, where she has been at the forefront of researching and reporting on the solar industry since 2019.