How tidal power technologies should be used.
Key issues
England and Wales have a large part of Europe's tidal power resource, and we are well placed to exploit this energy source due to the high tidal range in our estuaries and the tidal currents around our shores. The ebb and flow of tides can be exploited through structures and barrages which trap the high water for release though turbines. Devices underwater can tap the tidal stream resource near our coasts.
Tidal power technologies could play an important role in reaching renewable energy targets and limiting climate change. Yet we have to be aware of other environmental impacts. Our estuaries, in particular, are of international importance for migratory birds and fish. Many are protected under the EU Habitats Directive and other conservation legislation. Estuaries are now recognised as some of our most productive, fragile and dynamic aquatic ecosystems.
The key issue for the Environment Agency is to ensure that all environmental implications are fully taken into account in the exploitation of tidal energy resources, so that the most sustainable option is selected.
Our role
... in managing estuaries & coastal waters
We have a range of responsibilities relating to estuaries and coastal waters including managing flood risk, improving water quality, regulating fisheries, and improving the environment for wildlife. We have responsibilities for coastal water quality up to three nautical miles from the shore and for managing certain kinds of migratory fish up to six miles from the shore.
... in responding to new developments in the marine environment and strategies including regional and local land use plans
We have to be consulted for planning applications and associated environmental impact assessments. Issues include protection of groundwater and water quality, impacts on flood risk, effects on our infrastructure, and safeguarding wildlife habitats and fisheries. We have to consider the environmental implications of new developments, including changes in tidal range and tidal surges, sedimentation and erosion, and their implications for wildlife and ecology. We also have a duty to promote recreation. Recreation can be adversely affected by such developments, though they can often create new opportunities.
... in limiting climate change through sustainable energy
We are committed to helping limit and adapt to climate change. We want to avoid unnecessary regulatory barriers to help increase renewable energy supplies towards a target of 20 per cent of electricity generation by 2020 and cuts of 80 per cent of carbon dioxide, the main greenhouse gas, by 2050. We support effective renewable energy sources which have an acceptable impact on the environment. We agree with the Royal Commission on Environmental Pollution (RCEP), and the Government’s Energy White Paper (DTI) that there needs to be further study of the opportunities for barrage and stream generation, and would like to be involved in this work. Given the likely environmental impacts of such facilities, we recommend a precautionary approach.
Environmental impacts and tidal power developments
Estuarine barrages & impoundments
We have concerns about the impacts of barrages and impoundments in estuaries, including the way they are built, operated, and shut down. These include: project planning; the impacts of construction; impacts on fisheries and conservation; navigation rights; and landscape and habitat changes. Water quality may be affected, and changes to the flow will affect tidal events including surges and currents - altering salinity and the movement of silt, as well as effects on pollution. The estuary will be altered when sedimentation and erosion change - for instance less flow in some places and higher water levels in others. Barrages will always affect the way we manage flood risk, but could be designed to reduce that risk. They can alter the way water moves underground, the impacts of waves downstream, and surface water drainage. They could also affect the Environment Agency's facilities, including embankments and structures fish pass through.
We must also plan for the long-term effects of climate change on our operations and on new developments. For example we must take into account how rising sea levels and changing weather patterns will affect both average and extreme events including drought, drainage patterns, rainwater flooding, tidal flooding and storm surges.
Tidal stream generators
These devices have to capture energy from the currents flowing past our coasts. Some are already being tested and equipment already looks promising. This will help attract more funding, make more schemes possible, and may pave the way for large-scale schemes generating electricity supplies around the coast.
The impacts of tidal stream generators have been studied in less depth. Taking energy from currents will cause changes to the sea, and local effects will include seabed disturbance due to the impacts on silt. Although the impacts of tidal stream generation are expected to be relatively mild, environmental impact studies must be carried out as part of the technology trials. If this is done, we are supportive of further research and development of these technologies.
Impacts of tidal stream turbines or similar machines on marine wildlife - specifically by collision - is a concern, but studies have argued that both device design and animal behaviour can adapt to such risks.
The shutting down of generators should be addressed in feasibility studies and environmental impact assessments.
Solutions - we call for:
We support the Government's view that tidal power technologies should be given the opportunity to play the fullest part they can in contributing to renewable energy supplies.
- Government should take a strategic overview of the development of tidal energy resources, to ensure our climate change commitments are balanced with other national, European and international environmental obligations. A case-by-case approach by individual developers is unlikely to achieve the most sustainable solution overall.
- Techniques such as risk assessment, Environmental Impact Assessment (EIA), Strategic Environment Assessment (SEA), and public participation should be used to help decision making for possible developments.
- We call for all proposals to be discussed with us at the earliest stage and for our guidance on 'Scoping the environmental impacts of barrages' to be used.
- If a proposal goes ahead, developers should address all environmental impacts on site or elsewhere.
- We need an environmental impact assessment of tidal stream generation as soon as possible.
Background
The effects of the moon and sun's gravity on the earth create tides. Their daily ebb and flow means high water can be trapped, to release energy as it flows back out to sea at low tide. The rotation of the earth also creates tidal (or ocean) currents around our coast and the regular flow of these can also release energy.
The technologies can be applied in three different ways:
- tidal power barrages - complete estuary barrages or dams;
- tidal impoundments or lagoons - structures in estuaries which trap tidal water for release later through turbines;
- tidal stream turbines - undersea devices capturing energy from the natural circulation of water in oceanss.
Technologies for barrage power are tried and tested, but they depend on tides. The predictability of tides can enable the power to be used for base load grid supply; the flow can be held back to extend the generation period to match demand better. But only about 23% of the equipment potential is reached as it stands idle much of the time. Building a full estuary barrage is a major construction project with many environmental impacts.
