Advantages and Disadvantages of Tidal Energy

Tidal energy is a form of hydropower that has the potential to lead to a more sustainable future. There are three ways to harness tidal power:

• Tidal turbines

• Tidal barrages

• Tidal fences

Tidal power is a renewable form of energy, meaning that utilizing it will not deplete the source. Much like other renewable sources, tidal energy comes with a few drawbacks, as well as many benefits. 

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Pros and cons of tidal energy

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Advantages of tidal energy

There are several reasons why the use of tidal energy is beneficial, including that it’s a renewable energy source, releases no carbon emissions, it’s predictable, and it can generate a lot of power. 

Tidal energy is a renewable source

Tidal energy is a renewable energy source, meaning the energy source doesn’t deplete as it is used. For example, harnessing wind energy through turbines doesn’t make it any less windy.

Tidal energy is harnessed by the changing tides. Doing so does not decrease the amount of energy the tides can produce in the future. Also, the gravitational pull from the sun and the moon, which controls the tides, isn't going anywhere anytime soon.

Zero carbon emissions

Greenhouse gas emissions are one of the leading causes of climate change, which makes having clean sources more important than ever. Thankfully, tidal power plants are a clean energy source and don’t emit any harmful gasses. 

As reported by the Environmental Protection Agency (EPA), carbon dioxide emissions have decreased by 3% in the United States since 1990. By using more renewable sources, like tidal power, we can further decrease the amount of carbon dioxide that is released into the atmosphere. 

Predictable energy generation

Producing energy using tidal power is predictable because it relies on tidal currents. Although tides change regularly depending on the time of day, they follow a consistent pattern and can be accurately forecasted.

For example, solar power is considered less predictable due to weather patterns and sunlight exposure being more difficult to gauge. Weather patterns can be forecasted, but can change at the drop of the hat. 

High generation capacity

Although many tidal power technologies are not yet available on an industrial scale, existing tidal energy plants have the potential for high electricity generation. The Sihwa Lake tidal power station located in South Korea is currently the largest in the world and has 254 megawatts (MW) of electricity generation capacity. 

Even when water is moving at slow speeds, the density of water allows it to power a turbine. So, tidal energy generation has high potential even if the conditions of the water aren’t ideal.

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Disadvantages of tidal energy

Although tidal power has huge potential, there are a few reasons why it isn’t utilized as much as other renewable sources, like limited installation sites, it’s expensive, there is some environmental impact, and it is an intermittent energy source. 

Limited installation sites

Tidal power plant sites have to meet specific requirements to function properly. Tidal power stations must be located on a coastline, which limits potential stations to sites located in coastal areas. 

Aside from this, tidal power stations need to be built in places where the high tides and low tides have a significant difference in height – powerful enough to move turbine blades. Due to these heavy limitations, it is difficult for tidal energy technologies to be implemented in most areas. 

Expensive source of energy

Constructing a tidal power plant has a high upfront cost. The Department of Energy (DOE), reported that the levelized cost of energy (LCOE) for commercial-scale tidal power is between $130 and $280 per megawatt-hour (MWh). 

To put this into perspective, the LCOE of utility-scale solar energy projects is about $24 to $96 per MWh. So, it's evident that tidal power is a more expensive source of energy. Tidal energy also cannot be harnessed effectively on a small scale – meaning the construction costs of these power systems are usually wildly expensive and take years to complete.

Environmental impact

Although tidal power is considered a green energy source and doesn't emit any harmful gasses, the construction of tidal energy systems can have a substantial impact on surrounding ecosystems, like ocean habitats. 

Tidal turbines face the same issue as wind power turbines have faced with birds – wildlife collisions. As the tidal power turbines spin, fish and other marine life could swim into the blades leading to serious injury or death. Also, the turbines create low-level noise beneath the surface of the water, which negatively impacts marine mammals, such as seals. 

Intermittent energy source

Although tidal power has the potential for high levels of power generation, its functionality makes it an intermittent source. Tidal energy produces power by the natural rise and fall of tides. Since it is dependent on the tides, tidal energy stations might not always be able to meet high energy demand. 

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. Thus, tidal power plants will produce most of its electricity at times when it’s not needed as much. 

Battery storage would be a solution to help make the most out of produced energy because you can store any energy generation to be used at any time. But, adding battery storage would bring up costs.

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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

Similar to wind turbines, tidal turbines utilize spinning blades to generate energy. Located below the water’s surface, the water’s current pushes the turbine blades, which are connected to a generator that creates electricity.

Tidal barrage

Tidal barrages are low-walled dams, usually installed at tidal inlets or estuaries. These systems are similar to traditional hydroelectric dams. The barrage itself is secured to the sea floor and has turbines towards the bottom that are turned with the incoming and outgoing tides.

During an incoming high tide, the tidal stream flows over the turbines as the water rises. Then, water flows back through the turbines as it becomes low tide. These turbines are connected to a generator which produces electricity.

Tidal fence

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.

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How is tidal energy used in the U.S.?

Due to the limited space available to build tidal energy plants, there are not currently any large-scale power plants in the U.S. However, there are a few smaller-scale projects that exist. Most major tidal energy plants are located overseas.  

However, a large project in Alaska may be on the horizon. The National Renewable Energy Laboratory (NREL). found that there is huge potential for tidal power in the Cook Inlet of Alaska, and several locations in Maine. 

Some of these projects are already in various stages of development and could be completed in the years to come, furthering the United States' reliance on fossil fuels.

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