• Four turbines off the north coast of Scotland generated enough energy to power nearly 4,000 homes in 2019.
  • Sitting in a natural channel, they harness the energy of the changing currents and are helping build the case for tidal as the energy source of the future.
  • To date, very little research has been done into the impact tidal projects have on the surrounding marine environment.

Sitting off the north coast of Scotland, on the depths of the ocean floor, a gigantic feat of engineering has just achieved a significant milestone.

MeyGen, the world’s largest tidal array, has completed the longest ever run of uninterrupted generation by a multi-megawatt tidal turbine, powering almost 4,000 homes in 2019.

The four giant turbines have now exported 24.7 gigawatt hours (GWh) of predictable renewable power to the national grid. And this is just the first phase of a project that could eventually power 175,000 homes with more than 250 submerged turbines.

The array is off the mainland of Scotland, near the uninhabited island of Stroma, in a natural channel that speeds up the tidal flow of water between the North Sea and Atlantic Ocean.

Like giant underwater windmills, the turbine rotors are driven by the fast-moving currents, which in turn drive generators that then produce electricity. They are fixed to the sea bed and connected to the grid via an armoured cable.

Low-voltage supply from the turbines is converted onshore for export to the grid.
Image: SIMEC Atlantis Energy

Awash with potential

Although tidal energy as a concept has been around for some time – the first project launched in 1966 – there has been renewed focus on its potential as an energy source. A 2016 estimate from the European Commission said wave and tidal power could account for 10% of the EU’s energy needs by 2050. And back in 2013, the UK estimated 20% of its power needs could be met by tidal.

What's the World Economic Forum doing about the transition to clean energy?

Moving to clean energy is key to combating climate change, yet in the past five years, the energy transition has stagnated.

Energy consumption and production contribute to two-thirds of global emissions, and 81% of the global energy system is still based on fossil fuels, the same percentage as 30 years ago. Plus, improvements in the energy intensity of the global economy (the amount of energy used per unit of economic activity) are slowing. In 2018 energy intensity improved by 1.2%, the slowest rate since 2010.

Effective policies, private-sector action and public-private cooperation are needed to create a more inclusive, sustainable, affordable and secure global energy system.

Benchmarking progress is essential to a successful transition. The World Economic Forum’s Energy Transition Index, which ranks 115 economies on how well they balance energy security and access with environmental sustainability and affordability, shows that the biggest challenge facing energy transition is the lack of readiness among the world’s largest emitters, including US, China, India and Russia. The 10 countries that score the highest in terms of readiness account for only 2.6% of global annual emissions.

To future-proof the global energy system, the Forum’s Shaping the Future of Energy and Materials Platform is working on initiatives including, Systemic Efficiency, Innovation and Clean Energy and the Global Battery Alliance to encourage and enable innovative energy investments, technologies and solutions.

Additionally, the Mission Possible Platform (MPP) is working to assemble public and private partners to further the industry transition to set heavy industry and mobility sectors on the pathway towards net-zero emissions. MPP is an initiative created by the World Economic Forum and the Energy Transitions Commission.

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As a green energy source, it offers a number of advantages over other renewables. It is not reliant on the sun shining or the wind blowing. And as water is far more dense than air, smaller turbines can be used to generate equivalent amounts of electricity, and they can be placed much more closely together than on land.

energy tidal turbine
Each turbine sits on a foundation weighing between 250 and 350 tonnes, coupled with 6 ballast blocks weighing 1,200 tonnes.
Image: SIMEC Atlantis Energy

A power source still in its infancy

There are a number of large-scale projects in various stages across the world, including the Sihwa Lake power station in South Korea and the Jiangxia Pilot Tidal Power Plant in China. But compared to many other renewable energy sources, tidal is still in its comparative infancy.

There are also a number of questions that remain over the impact of tidal arrays and barrages on the marine environment. Initial research has looked at the impact the noise of the turbines might have on marine animals and how the flow of water might be affected, but more in-depth and up-to-date studies are needed.

energy mix
OCED renewable primary energy supply by product, 1990-2018
Image: International Energy Agency

Tidal energy is still quite an expensive way to generate electricity, but given the consistency it offers there is great optimism about its potential. As projects such as MeyGen increasingly come online, there has been a rise in the proportion of energy generation it accounts for. But it is still a much smaller piece of the pie than other renewable sources. The growth in the solar PV and wind power sectors outstrips tidal by some margin.