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Not just for clean energy — scientists say tidal electricity generation can protect from coastal flooding

Every time the ocean’s tides rise and fall, pulled by the gravitational forces of the sun and the moon, they release energy. How much energy? Well, when there’s a large enough difference in the tidal range — the difference between the high and low tide — the world’s ocean surges can be enough to produce between 150 and 800 terawatt hours of renewable energy annually according to the European Commission’s 2020 report. 

As 2021 stats show, on the higher end, that’s about enough to renewably supply all the power needs of the United Kingdom and Canada. We’re using these countries as examples because when it comes to tidal power, everything is about location, location, and location. Northern regions in the Earth’s higher latitudes have the most potential for tidal energy because, as the National Ocean and Atmospheric Administration (NOAA) explains, that’s where North America, Europe, and Asia are pressed so closely together, that the constriction causes a higher range. 

The most range in the world can be found in the Bay of Fundy in Atlantic Canada, where the rise and fall is 12 meters or about 40 feet, which, in tidal terms is a lot, compared to the average microtidal coasts have a range of about 3 meters. In short, you don’t want to be caught out at the Bay of Fundy during high tide, or else you’re in for quite the wild ride. 

Despite the ocean of potential in tidal energy, it's still in its infancy, with only a pond of commercial power plants in the world with the first in France, the largest in South Korea, and none in the United States, because there are very few sites — except perhaps in the northern-most states of Alaska and Maine — where it can be produced at a price that makes sense.

Nevertheless, research shows there are rising tides of potential on further northern coasts of Canada, Russia, China, France, Germany, and England, just to name a few. 

That’s why, as proposed by scientists at Lancaster University, via a study published in the peer-reviewed journal Energy this month, the UK should not only tap its tidal potential to meet clean energy needs but also, protect its coastal habitats from erosion and sea-level rising. 

“Our studies show that with modern technology and operating procedures, estuarine barrages are the only practical way to protect these vital habitats,” Professor George Aggidis, Head of Energy Engineering at Lancaster said in a statement. 

“Coastal lagoons have also been proposed for several locations around Britain’s coast.,” he added. “Schemes will provide jobs in construction and manufacturing for generations to come as well as opportunities for transport, communication, conservation, and recreation. In the long-term, they will provide reliable power with reduced costs.” 

A tidal or estuarine barrage is a dam-like structure, that can capture energy from the water movements. However, unlike a traditional dam — or the behemoths constructed by beavers — these barrages allow water to continuously flow through, kind of like the osmotic energy devices we reported on early this week. The biggest difference is that the energy harvested comes from the ebb and flow of the water and water is taken in during high tide and released during low tide. 

Tidal energy isn’t exactly a new idea. The process of using falling water and spinning turbines to create electricity was first introduced in the 19th century, Canada and the U.S. conducted feasibility studies between 1924 and 1977, concluding that economically it did not make sense in the region between Canada and Maine, and finally the large tidal barrage, that was the first of its kind, was built in La Rance, France in the ‘60s and still operates today at a 240-megawatt capacity. 

However, tidal energy goes back at least 1,000 years in Europe where it was used to operate grain mills. Now, these British scientists are hoping to bring it back to meet clean energy needs in the face of the climate crisis and protect Britain’s eroding coasts

“Great Britain has the second largest tidal range in the world and major barrages have been considered since Victorian times,” Aggidis. “Globally, there are two large-scale schemes currently in operation, La Rance in France which was completed in 1967, and Lake Sihwa in South Korea from 2011; both schemes generate significant quantities of cheap sustainable electricity.”

Nevertheless, one of the biggest hindrances to tidal barrages taking off has been the potential impact on the marine environment. As the U.S. Department of Energy reports, while the barrage meets 0.012% of France’s energy needs, it has caused environmental issues like the temporary disappearance of marine flora and fauna due to salinity fluctuation during construction, resulting in a now “fragile” ecological equilibrium. Some species like the sand eel have permanently left, while mammals like seals have been displaced, with fish like sea bass and cuttlefish returning to the river.

Still, despite the fluctuation, the estuary is currently considered biologically balanced, richly diversified, and flourishing. 

Considering the impact on marine environments, the Lancaster researchers propose that if designed and operated appropriately, these barrages can, much like seawalls, protect low-lying areas from flooding, which they say would be vital to protecting habitats, housing, and businesses from a rising sea level estimated to be over one meter, or three feet, within 80 years.

However, instead of merely existing as a static wall, they can also provide power. With this dual purpose, the paper concludes the barrages “can help satisfy the government's legal commitment to protect valuable designated ecosystems.”

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