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As the world continues to grapple with the impacts of climate change, the need for clean and renewable energy sources has become more urgent than ever. Tidal energy, which harnesses the power of the ocean’s tides to generate electricity, has long been touted as a promising source of green energy. However, despite its potential, tidal energy remains a relatively untapped resource.
In this article, we will explore the reasons why tidal energy is not more widely used, despite its many advantages, and examine some of the challenges that must be overcome to realize its full potential as a key contributor to the world’s clean energy mix.
Tidal power captures the kinetic energy from the rise and fall of oceanic tides and converts it to electricity. There are primarily two methods employed to harness tidal power:
1. Using tidal barrages, structures that resemble hydroelectric dams.
2. Using underwater turbines. The flow of water rotates the blades of the turbines. The rotation movement powers a generator.
You can install tidal turbines in various coastal water sources. The environments range from areas with strong ocean currents to estuaries and tidal streams. You can install just one, or, for a larger energy project, you could connect rows of turbines. This interconnected row of turbines is called an array. The operation of a tidal barrage system is very similar to that of hydroelectric dams. The system uses dam-like structures and submerged underwater gates to achieve control over water levels and to direct water through the turbines.
The one main advantage of tidal power over other renewable energy sources like solar and wind is predictability. It is difficult to predict how much electricity a wind farm will generate because there is considerable variation in wind patterns, weather, and turbulence. However, scientists know and understand tidal patterns pretty well. The predictability of tidal currents reduces the need for obtaining backup energy sources. This predictability is an incentive for tidal power use.
Tidal power also provides a higher energy output. Water is around 830 times denser than air. Therefore, tides and ocean currents generate more energy per unit area as compared to winds.
The oldest form of tidal power provides electricity by harnessing the energy from height differences between a reservoir and the sea as the tides change. The Rance River Project in France, built in the 1960s, was the first power plant to use this technology. The power plant included a barrage (a dam-like structure). The barrage separated an estuary from the sea. The barrages housed turbines. Water flows through the turbines as the tides change. Today, only a handful of plants, like the Rance River, are running. The Rance River plant has a power generation capacity of 240 megawatts.
Even with these excellent advantages and the increasing demand for renewable energy, tidal power hasn’t generated the same interest and popularity as wind, and solar energy has. You could probably count the number of commercially operating tidal power plants around the world on your fingers. The largest tidal power plant in the world is the Shiwa Lake Tidal Power Station in South Korea. Its power generation capacity is 254 megawatts. The United States also has a few small-scale tidal projects.
If you’ve stood in front of waves during a day at the beach, you must’ve felt the sheer force of ocean waves. Judging by that force, tidal waves should be an abundant renewable energy source. Tidal waves are capable of producing hundreds of gigawatts of energy worldwide. However, the world still generates only a minuscule amount of power from tidal waves. Why is that?
It all comes down to economics. Because it is still in its early phase of technology development, obtaining tidal power is expensive. According to a 2019 study, one megawatt-hour of tidal energy can cost anywhere between 130 to 280 dollars. Comparatively, wind energy is much cheaper, costing just 20 dollars per megawatt-hour. There are high costs associated with building tidal power plants, maintaining machinery that can survive the corrosive action of seawater, and supporting the engineering that goes into building them. Additionally, tidal power’s supply chain isn’t capable right now of providing the components and technologies necessary to make tidal energy adoption widespread. The market price difference between tidal energy and other more common, mature renewable energies is increasing because the price of wind and solar energy is still dropping.
According to a World Energy Council report, tidal energy costs two to nine times higher than wind energy in Europe.
Even beyond these economic difficulties, there are many technical challenges that the tidal power industry needs to overcome. These include the lack of a well-established market for tidal energy and legislation governing its production and consumption. Also, many prime spots for tidal energy are not near electricity grids. This means that we would have to build new undersea cables.
We also need to consider the environmental impact of producing this energy, which scientists don’t fully understand yet. Large tidal power systems can kill marine fauna and flora. They can even change salinity and sediment levels and destroy coastal ecologies. Many researchers are currently trying to find a way of harnessing tidal currents with minimal environmental impact.
Around 70 companies around the world have developed the technology to obtain electricity from tides. There are more companies exploring techniques of electricity generation from ocean salinity and temperature. Some countries have a thriving tidal power industry. Scotland has a 600-ton tidal turbine located off the coast of the Orkney Islands. It is fully developed and already generating power. The name of the turbine is O2. For the next 15 years, it will meet the energy demands of 2,000 homes. The UK also recently announced incentives that specifically promote and support tidal power. Last year, in 2021, the United States Department of Energy announced that it was going to invest 27 million dollars to support tidal and wave energy research and development.
An ocean research centre in the Bay of Fundy recently laid 11 kilometres of undersea cables. The Bay of Fundy hosts some of the biggest tides in the world. These undersea cables will create the world’s largest transmission line for underwater tidal turbines. At peak capacity, the cables will carry enough energy to power 20,000 homes.
Tidal power can be an important source of renewable energy. We can use it in tandem with other forms of energy. Many times, the conversations around decarbonization pit renewables against one another. If decarbonizing the way we produce electricity is our true goal as a society, we can’t pick just one renewable source. We need to support all of them simultaneously.