Tidal power in Wales
Tidal power, a form of renewable energy harnessing the natural rise and fall of ocean tides, offers a consistent and predictable source of electricity. As the world seeks sustainable energy solutions, tidal power projects have gained prominence, particularly in regions with significant tidal ranges.
The Severn Estuary: An Ideal Location for Tidal Power
The Severn Estuary, located between England and Wales, boasts one of the highest tidal ranges globally, reaching up to 14 meters. This unique characteristic positions it as a prime candidate for tidal energy projects. Experts suggest that harnessing the estuary’s tidal potential could contribute up to 7% of the UK’s electricity needs.
Over the years, several proposals have emerged to exploit the Severn’s tidal potential. Notably, the Severn Tidal Barrage concept envisioned constructing a dam-like structure across the estuary to generate electricity as water levels changed. While technically feasible, concerns about environmental impacts, high costs, and ecological disruptions have hindered its realisation.
Tidal Lagoons: A Sustainable Alternative
A tidal lagoon is a man-made enclosure that captures a body of seawater to harness tidal energy. Unlike a barrage that spans an entire estuary, a lagoon is typically built along the coast, minimising environmental disruption. Water flows into the lagoon during high tide and is released through turbines during low tide, generating electricity in both directions. This method offers a more controlled and potentially less ecologically damaging approach to tidal energy extraction.
Environmental Considerations
While tidal power presents a renewable energy opportunity, it’s essential to address potential environmental concerns:
to start with, habitat disruption: Construction and operation can affect marine and bird habitats, particularly in ecologically sensitive areas like the Severn Estuary. In addition tidal structures can alter natural sediment movements, impacting water quality and shoreline stability, it can affect marine life as turbines pose risks to fish and other marine organisms, necessitating designs that minimise harm.
Global Examples of Tidal Power Projects
Several locations worldwide have explored or implemented tidal energy projects:
La Rance, France: Operational since 1966, this tidal power station remains one of the largest, producing around 240 MW.
Sihwa Lake, South Korea: Commissioned in 2011, it generates approximately 254 MW, making it one of the most significant tidal power installations globally.
MeyGen, Scotland: An ongoing project in the Pentland Firth aims to be the world’s largest tidal stream array, with plans to generate up to 398 MW upon completion.
Recent Developments and Future Prospects
In light of global energy challenges, there’s renewed interest in the Severn Estuary’s tidal potential. The Severn Estuary Commission, established by the Western Gateway Partnership, is exploring sustainable energy opportunities in the region. Comprising experts from various fields, the commission aims to balance energy production with environmental preservation.
Furthermore, the Crown Estate has pledged £150,000 to support the commission’s work, underscoring the significance of this initiative. The commission’s objectives include determining the estuary’s sustainable energy potential, understanding environmental considerations, and identifying challenges and opportunities associated with tidal energy development.
Tidal power represents a promising avenue for renewable energy, with the Severn Estuary offering substantial potential. Balancing technological advancement with environmental stewardship will be crucial to realizing this potential. Continued research, stakeholder engagement, and thoughtful planning are essential to harness tidal energy effectively and sustainably.
How Tidal Power is Generated and Its Controllability
Tidal power generation relies on the kinetic and potential energy of moving water caused by tidal movements. There are three primary methods of harnessing tidal energy:
- Tidal Barrages: These work similarly to hydroelectric dams, using a barrier to trap water at high tide and release it through turbines at low tide.
- Tidal Lagoons: Artificially enclosed bodies of water where the incoming and outgoing tides drive turbines.
- Tidal Stream Generators: These function like underwater wind turbines, capturing the kinetic energy of fast-moving tidal currents.
The amount of power generated depends on the tidal range (difference between high and low tide), water flow speed, and turbine efficiency.
One of the major advantages of tidal power over other renewable energy sources is predictability. Unlike solar or wind power, which depend on weather conditions, tides follow precise astronomical patterns. This allows for accurate forecasting of energy generation.
However, while tidal power is predictable, it is not entirely controllable like fossil fuel or nuclear energy plants. Power output fluctuates throughout the day as the tides change. To improve grid integration, modern tidal systems can include pumped storage, where excess energy is stored and released when needed. Additionally, multi-lagoon systems can help provide a more consistent energy supply by staggering energy generation.
Why Previous Tidal Power Projects Were Rejected
Despite its advantages, many tidal power projects, including the Severn Barrage, have faced rejection due to a combination of environmental, economic, and technical challenges. One of the primary concerns has been the disruption of marine ecosystems. Tidal barrages can significantly alter water flow, affecting fish migration, sediment transport, and overall water quality. The 
Severn Estuary, for instance, is a crucial breeding ground for migratory birds, and any changes to its ecosystem could threaten bird populations. Additionally, the presence of turbines introduces risks to marine life, as fish and other sea creatures may be injured by the moving blades, despite efforts to design safer, more fish-friendly systems.
Beyond environmental concerns, the high construction costs have been a major deterrent. The estimated cost of the Severn Barrage project alone was around £30 billion, requiring massive upfront investment before any electricity could be generated. Compared to offshore wind and solar power, which have seen significant cost reductions over time, tidal energy has remained an expensive option. Moreover, the energy generation window for tidal power is limited—it operates on a predictable 12-hour tidal cycle, meaning electricity is only produced at specific times of the day. This intermittency necessitates backup power sources or storage solutions, adding further costs and complexity to its implementation.
Political and public opposition has also played a role in stalling past projects. The Severn Barrage, for example, faced strong resistance from environmental groups and local communities concerned about its impact on wildlife and the landscape. Governments have been hesitant to fund such large-scale tidal projects, often opting instead to invest in offshore wind farms, which have proven to be more cost-effective and easier to implement on a large scale.
Technological challenges have further complicated matters, as early tidal projects struggled with maintenance issues due to harsh ocean conditions causing corrosion and biofouling, where marine organisms accumulate on turbine blades and reduce efficiency. While advances in materials and turbine design are addressing these problems, the concerns they raised contributed to the rejection of earlier proposals.
Despite these setbacks, modern tidal lagoon proposals, such as the Severn Tidal Lagoon, offer a potentially more viable and environmentally friendly alternative. Unlike barrages, lagoons have a lower ecological impact and could provide a more cost-effective solution. Additionally, improvements in tidal stream technology and turbine efficiency could make tidal power a more competitive option in the future, especially as the need for reliable renewable energy continues to grow.
