Tidal energy – generating electricity from the tides
What Is Tidal Energy?
Tidal energy is a renewable source of electricity generated by harnessing the natural movement of the sea, caused by the gravitational interaction between the Earth, Moon and Sun. Unlike solar or wind power, tidal energy is highly predictable due to the consistency of tidal cycles, which follow known astronomical patterns.
The process involves capturing the kinetic and potential energy from the rising and falling tides using technologies such as barrages, underwater turbines, or floating systems. These devices convert tidal motion into electrical power that can be fed into the national grid.
In the United Kingdom, where coastal areas stretch over 12,000 kilometres, tidal energy presents a strategic opportunity. As the country aims to achieve net-zero carbon emissions, expanding its use of clean and dependable tidal power may play a key role in building a resilient, low-carbon energy system.
History and Evolution of Tidal Energy
The concept of tidal energy is centuries old. During the Middle Ages, tidal mills were used in coastal parts of the UK and Europe to grind grain by channelling the incoming and outgoing tides through water wheels. These early mechanical systems laid the foundation for the modern tidal power technologies we see today.
The breakthrough in tidal energy came with the construction of the La Rance Tidal Power Station in France in 1966. It was the first commercial facility of its kind, using a barrage to trap seawater and drive turbines as the tide ebbed and flowed. This project proved that tidal forces could generate significant amounts of electricity reliably and with low emissions.
In the decades since, numerous countries have developed tidal power further, but the UK has emerged as a global leader in this field. Scotland, in particular, has invested heavily in marine energy innovation, driven by the powerful tidal streams found in areas such as the Pentland Firth and the Orkney Islands.
British firms and research institutions have been at the forefront of developing tidal stream generators and underwater turbines. These technologies have made it possible to generate electricity without the need for large-scale dams or barrages, offering greater environmental compatibility and scalability.
How a Tidal Power Plant Works
A tidal power plant captures energy from the sea’s natural movement and converts it into electricity using a range of technologies. The method employed often depends on local geography and the strength of tidal flows in the area.
The most traditional approach is the tidal barrage system. This involves constructing a dam-like structure across a tidal estuary. As the tide comes in, water is trapped behind the barrage. When the tide recedes, the stored water is released through turbines, generating electricity. While effective, barrages can significantly alter ecosystems and require specific tidal conditions to operate efficiently.
A more modern and environmentally friendly alternative is the tidal stream turbine. These turbines are installed on the seabed in areas with strong tidal currents. As water flows through them, the turbines spin, much like underwater wind turbines, and produce power. This method is currently being tested and deployed in various parts of the UK.
There are also floating tidal platforms, which sit on the surface and use submerged turbines to harness energy. These are particularly useful in deeper waters and locations where seabed infrastructure is more difficult to install.
All systems are connected to the electricity grid via underwater cables. Due to the harsh marine environment, tidal power infrastructure must be built to resist corrosion, strong currents, and marine growth. While the upfront costs are considerable, the durability and reliability of these systems make them a sound long-term investment.
Advantages of Tidal Energy Over Other Renewables
One of the key strengths of tidal energy is its predictability. Unlike wind and solar power, which depend on weather conditions, tidal patterns can be forecast years in advance. This makes tidal energy highly reliable and suitable for providing baseload power, an essential part of maintaining grid stability.
Another advantage is its consistency. While it does not generate electricity around the clock, tidal energy produces power multiple times a day, based on tidal cycles. This regularity allows for better planning and integration into existing energy systems.
Tidal energy also has a low environmental footprint in terms of emissions. It produces no greenhouse gases during operation and, depending on the technology, can have minimal impact on marine life compared to other large-scale energy developments.
In addition, tidal turbines are long-lasting. With proper maintenance, they can operate for 30 to 40 years. Their reliability and longevity make them cost-effective over time, particularly in comparison with shorter-lived renewable technologies.
For the UK, tidal energy offers a unique chance to make use of its extensive maritime resources. It could also help to decarbonise isolated coastal and island communities, such as those in the Scottish Highlands and the Isles of Scilly, where renewable generation and storage remain challenging.
Environmental Impact and Technical Challenges
Despite its benefits, tidal energy also poses environmental and technical challenges that must be addressed to ensure sustainable development.
Barrages, for instance, can cause significant changes in estuarine ecosystems by altering sedimentation, salinity, and the migration routes of fish and other marine species. Even tidal stream turbines, while less intrusive, may still impact local wildlife through noise, vibration, or collision risks, although studies suggest these impacts are generally low with proper design.
From a technical standpoint, operating equipment in the ocean is demanding. Saltwater corrosion, extreme pressure, and marine fouling (the accumulation of organisms like barnacles) can wear down components and reduce efficiency. Maintenance is also more complicated and expensive due to limited access and harsh weather.
Another challenge is the high initial capital cost of building tidal installations. Though operational costs are relatively low, the significant upfront investment has often slowed the pace of commercial deployment.
In the UK, regulatory processes can also be complex, involving environmental permits, planning permissions, and multiple governmental bodies. While necessary for protection, these layers can delay or deter projects. Simplifying these processes, without compromising environmental standards, is key to accelerating deployment.
Tidal Energy: Notable Projects Around the World
Several projects across the globe showcase the viability and potential of tidal energy. The aforementioned La Rance plant in France remains an iconic example, still operational after nearly 60 years and producing over 500 GWh of electricity annually.
In South Korea, the Sihwa Lake Tidal Power Station currently holds the title of the world’s largest tidal energy facility. Built into a seawall initially intended for flood control, it demonstrates how tidal generation can be integrated with existing infrastructure.
Here in the United Kingdom, multiple pilot and pre-commercial projects have been launched, especially in Scotland. MeyGen, located in the Pentland Firth, is the largest tidal stream project in the world and is currently expanding its capacity. Its success has positioned the UK as a leader in tidal energy development.
In Canada, the Bay of Fundy is known for having one of the world’s highest tidal ranges. Several experimental turbines have been installed there, although harsh conditions have posed ongoing technical challenges.
These international efforts show that tidal energy, while still emerging, is a proven and scalable technology that can play a major role in reducing global carbon emissions.
The Future of Ocean Energy
The future of ocean energy, including tidal power, is closely tied to technological innovation, investment, and supportive policy frameworks.
A key trend is the development of modular, scalable systems that can be deployed incrementally, reducing costs and risk. This model is particularly attractive for coastal communities or island territories with limited grid capacity.
Advances in materials and remote diagnostics are also improving the durability and efficiency of tidal turbines. Anti-corrosive coatings, real-time monitoring systems, and autonomous maintenance drones are helping to lower lifetime costs and reduce downtime.
The UK government has recognised tidal energy as part of its net-zero strategy. In recent years, the Contracts for Difference (CfD) scheme has included ringfenced funding for tidal stream technologies, encouraging further investment and industry growth.
If technological progress continues and regulatory pathways become more streamlined, the UK has the potential to lead globally in the commercial deployment of tidal energy, creating jobs and stimulating economic activity in its coastal regions.
Tidal Energy Potential in the United Kingdom
The United Kingdom is exceptionally well positioned to benefit from tidal energy. With strong tidal currents in places like the Pentland Firth, the Channel Islands, and the Bristol Channel, the country possesses some of the best tidal resources in Europe.
According to the UK Marine Energy Council, the nation has the technical potential to generate up to 11.5 GW of electricity from tidal stream technologies alone. This could supply millions of homes and significantly contribute to national decarbonisation targets.
Scotland has already taken the lead, with sites like MeyGen and Nova Innovation’s Shetland tidal array showing real-world viability. Wales and Northern Ireland are also exploring opportunities, particularly in the Severn Estuary and Strangford Lough.
Moreover, the UK’s existing offshore engineering expertise—developed through the oil, gas, and wind sectors—provides a solid foundation for tidal energy expansion. British universities and research institutions continue to contribute cutting-edge developments to the sector.
With sustained investment, public backing, and supportive policy, tidal energy could become a cornerstone of the UK’s renewable energy future—helping meet climate goals while fostering innovation and regional development.
Frequently Asked Questions (FAQ)
1. Is tidal energy currently used in the UK?
Yes. Projects like MeyGen and Nova Innovation are operational in Scotland, generating tidal electricity and feeding it into the national grid.
2. Is tidal energy more reliable than wind or solar?
Tidal energy is highly predictable, making it more reliable in terms of generation timing, although not constant like wind in some areas.
3. Are tidal turbines safe for marine life?
Modern turbines are designed with marine safety in mind. Ongoing monitoring and adaptive design help minimise any ecological impacts.
4. What are the downsides of tidal energy?
High capital costs, maintenance challenges, and potential ecological disruption are key concerns, though they are being addressed with new technologies.
5. Can tidal energy meet all of the UK’s electricity needs?
Not entirely, but it can significantly contribute to a balanced renewable mix, especially in coastal and island regions.