UK TIDAL ENERGY POTENTIAL



UK TIDAL ENERGY POTENTIAL

Politics and Funding

Tidal Stream

Current Government Poilcy

The UK government has set up a number of funding sources for the development of tidal stream applications. These sources provide funding to further develop, evaluate and test tidal stream device concepts and components. The funding is provided by:

• Marine Renewables Deployment Fund (MRDF)

• Renewables Obligation (RO)

• Technology Programe

• EU Structural Fund (Wales)

• Research and Demonstration Programme (Northern Ireland)

• Wave and Tidal Energy Support Scheme (Scotland)

The most prominent of these schemes is the MRDF, a £50m fund set up by BERR (Department for Business, Enterprise and Regulatory Reform) which allows for the provision of capital grants and revenue support to technologies that are entering early commercial deployment. Other important source, the RO is a revenue support mechanism designed to facilitate the large-scale deployment of renewable electricity generation, thus leading to long-term cost reductions.

The Renewables Obligation places an obligation on electricity suppliers to source an annually increasing percentage of their sales from renewable sources, reaching 15% by 2015. This creates a premium for renewable electricity generators of around 4p/kWh (SDC; 2007), and hence motivating investment in the operation of lower cost renewables such as onshore wind and landfill gas. However BERR and the UK Government now aim to introduce technology banding for the RO, meaning higher cost renewables will obtain an elevated payment. As the RO would provide an additional source of revenue for pre-commercial tidal stream devices, the technology would qualify for double the standard level of support under the RO, leading to a premium of around 8p/kWh (DTI; 2007). This would allow the focus of the MRDF to be changed from revenue to grant support, encouraging pre-commercial demonstration.

Planning and Regulatory Framework

Planning and consenting regimes are in position across the UK for pre-commercial marine developments; however frameworks for commercial scale development are not yet in place. Unfortunately these planning systems are complex, with projects falling under a number of different regimes. In England and Wales, BERR have published a set of guidelines of the planning arrangements for demonstration phase projects. Consent is required under:

• Electricity Act 1989 – Any installation with an excess capacity of 1MW

• Coast Protection Act 1949

• Food and Environmental Protection Act 1985

• Town and Country Planning Act 1990

(Source: BERR; 2005)

The UK Government also insists that a Strategic Environmental Assessment (SEA) will be conducted on the tidal stream resource once the industry reaches an appropriate stage of commercial development. Similarly complex planning applications are necessary in Scotland and Northern Ireland following devolved responsibility for consenting requirements for marine energy development.

Furthermore developers must obtain a site lease from the Crown Estate and are legally bound to decommission their tidal device at the end of its operating life.

Tidal Barrage

Current Government Policy

Even though there is no clear Government support programme for tidal barrages or lagoons, a developer looking to build a tidal barrage or lagoon would qualify for assistance under the Renewables Obligation. It would provide revenue support once the project is commissioned and generating electricity, and consequently tends to approve of low risk technologies with comparatively low capital costs.

Controversially, it is doubtful whether the RO would offer enough encouragement to stimulate private sector investment in tidal barrages or lagoons on its own. Although the funding available under the RO is due to be banded according to technology type, it is currently unclear whether barrages and lagoons will qualify for additional support once the bandings are announced.

For very large schemes, such as a Mersey or Severn barrage, there is a robust argument for providing backing outside the RO. The level of output represented by such schemes could have a damaging effect on the rest of the renewables sector due to reservations of a collapse in the price of Renewables Obligation Certificates (ROCs). Smaller schemes could probably acquire money under the current funding system, despite the constraints imposed by such capital-intensive technologies. However, the economics of barrage and lagoon schemes are likely to improve with scale, making larger (and less easy to finance) schemes potentially more viable than smaller ones.

A lot depends on the perceived risk of a technology, which relates to concerns over obtaining development consent (and in particular, uncertainties over the cost of compliance with any environmental designations), but also uncertainties over design and construction methods, and concern over possible delays. This is likely to affect tidal lagoon proposals more than tidal barrage projects, as there is no existing evidence to draw on and the concept remains unproven.

Policy Options

It has been recommended by the Sustainable Development Commission that the inclusion of transport links and flood defences would help to validate any tidal barrage development. (SDC; 2007) To further complicate matters, all barrage developments would have to ensure that there was minimal conflict with similar tidal schemes, particularly in the circumstance of habitat compensation. The Government must not be seen to favour one estuary habitat above another unless detailed environmental impact studies are undertaken.

In the case of tidal lagoons, the lack of a single international demonstration project justifies the need for the UK to advance the technology. This would be an invaluable opportunity for Great Britain to make headway in this field. Governments around the globe, as well as the private sector, would then be in the position to decide whether this is an economically and environmentally sound option.

Currently there is a large funding gap for tidal lagoon developments, which is partly due to the low banding status of lagoon schemes in the Renewables Obligation. A higher banding and additional grant funding would substantially reduce this financial barrier. Another possible opportunity to promote the benefits of tidal lagoons would be to organize a national competition, within the private sector. This type of scheme has been successful with the development of carbon capture and storage technology (BERR; 2007).

Impacts of the Tidal Stream Method

Tidal stream devices offer clear and potentially substantial benefits for obtaining a renewable energy source and producing low carbon electricity. However, the decision to employ tidal stream devices must take a sustainable development perspective, considering the benefits within a framework of environmental, social and economic impacts. These impacts are a mix of positive and negative influences and their importance in practice will vary according to the location and the scale of development. The construction of a tidal energy scheme requires an environmental baseline assessment (and subsequent monitoring) as part of an Environmental Impact Assessment (EIA), which will also indicate mitigation measures to reduce environmental effects.

Environmental Impacts

The scale of each installation and the total number of installations around the coastline will be the key determinants of overall environmental impact. Accordingly, given the relative immaturity of the industry, and the small number of devices being installed, the risk of any significant impacts is at present very low.

To date very limited environmental monitoring has been required for prototype devices, which mean that opportunities to develop the baseline data on effects of devices could be missed. Nevertheless, the SeaGen test project at Strangford Lough will be subject to considerable environmental monitoring over the period of its five year consent.

In addition, the environmental impacts of such prototype devices cannot necessarily be taken to represent the potential impacts of generating power from an array of devices on a commercial scale. There are additional issues when the impacts of one prototype device are multiplied up to assess the cumulative effects of a tidal stream array.

Despite the lack of direct observational data relating to tidal energy, a considerable amount of information exists regarding the environmental effects of other marine developments. For example, the offshore wind, and oil and gas industries provide information on the environmental impacts of drilling, piling and sub-sea cabling in the marine environment. This illustrates some of the synergies between both different categories of offshore renewables, and between offshore renewables (which are experiencing steep growth) and the UK’s large offshore oil and gas industry (which is in long-term decline).

There are 5 key areas which need to be considered when evaluating the environmental impacts of a tidal stream development:

• Ecology (habitats and species)

• Landscape and seascape

• Noise (airborne and underwater)

• Seabed, sediments and currents

• Water quality

These impacts should be reassessed during the 3 stages of development; construction, operation and maintenance and finally decommissioning.

During the construction stage, the significant environmental impacts will concern a growth in noise and pollution risk associated with the activities of drilling and piling. The construction stage will see the greatest direct effect on the seabed itself. For most tidal stream devices, the construction of the device itself would usually take place onshore, followed by the installation and associated cabling at sea.

At the operation and maintenance stage, the device will have an effect on water movements and sediment, as energy is extracted from the tidal flows. Underwater noise and the turbine operation also have the potential to affect the indigenous ecology. Commercial tidal devices are expected to have a lifetime of around 20 years. (SDC; 2007)

At the decommissioning stage, similar effects to those identified for construction can be expected. However, marine organisms will that have become established on the device will need to be relocated. The environmental effects of associated onshore infrastructure, in particular power cabling, will also need to be taken into account, and can often be a significant practical issue during consenting (as separate planning consent must be sought).

Ecology

Tidal stream devices have the potential to affect numerous habitats around the UK’s coastal waters. Dwelling in these habitats include species of birds, fish, marine mammals, plankton and benthic organisms. These terrestrial species may also become affected by infrastructure works to accommodate the transmission of electricity to the mainland.

Changes to the physical environment pose the most significant predicament for these species. The alteration to any of the following factors can cause concern:

• Water flow

• Tidal mixing

• Wave action

• Tidal inundation

• Sedimentation and erosion patterns

• Seabed disturbance by construction and cabling

Such changes can change the activities of marine communities or displace species from feeding or breeding areas. Fish and marine mammals may be particularly distressed by the generation of underwater noise, and the electromagnetic fields produced by sub-sea transmission cables. Collision risk is another factor which has been discussed in detail for the Seagen project, but will need to be revaluated for each device.

There is also the potential for a positive effect on nature conservation. A tidal installation may function as a refuge area for fish populations as a result of ‘no-catch’ zones, and shipping will also be redirected away from the tidal scheme sites. The potential benefits of this will depend on the specific impacts of a device, the scale of its deployment, and consideration of decommissioning implications. Nevertheless this may offer an opportunity to integrate renewable energy generation and a commercial activity with nature conservation objectives.

Visual

Surface-piercing structures close to the shore will make a visual impact on the landscape and seascape of the many coastal areas. Such areas have an important amenity and natural heritage value for local communities, visitors and recreational users. With this in mind Scottish Natural Heritage has suggested that development should be avoided in isolated or undeveloped coastal areas (SNH; 2004).

Whilst tidal stream development is likely to have a lower impact than wind development, lessons can be drawn from that industry about the importance of early engagement on these issues with local communities. In the case of a new technology, this may mean providing good information to demonstrate the very low visibility of a device or development. The visual effects of supporting infrastructure – substations, pylons – will also be a key issue.

Noise

Due to noise and vibrations traveling significantly further underwater, increases to background noise during construction and operation may have serious effects on marine mammals and fish, depending on the level, frequency and duration of noise. Again, this is an area where there is insufficient information on the potential effects of noise levels from tidal stream devices. Depending on the distance from shore, climatic conditions and wind direction, noise from construction, maintenance and decommissioning activities may also affect local communities.

Seabed, Sedimentation and Currents

The placement of tidal energy structures and their associated cabling on the seabed will result in a change to the physical characteristics of the area, and may involve a loss of habitat. Fixed tidal stream devices will have a relatively small footprint for each individual device, varying in accordance with whether the device is fixed or floating. For an array of tidal devices, cabling arrangements are complex, effectively increasing the footprint of an installation. Cabling may have a significant but short-term adverse impact on the seabed. At the decommissioning stage, cabling may be left in place to avoid further disturbance, or re-used with a new installation of devices. The placement of a solid structure on the seabed in an area of strong tidal flows will affect patterns of sediment erosion, transportation and deposition. By extracting energy from the flow, a tidal stream device can reduce the downstream velocity of the turbine considerably, with the effects discernible some distance away. This is one of the key areas where the potential cumulative effects of deploying tidal stream devices in large arrays are unknown and further research will be required.

Water Quality

The main issues for water quality from tidal stream development are the potential leakage of lubricants and hydraulic fluids, and the chance that increased volume of vessel traffic associated with the scheme may result in increased levels of fuel and oil leakage into the water.

Social and Economic Effects

There are both positive and negative consequences of a tidal stream development in relation to social and economic factors. Although there is very limited information to draw on, it is likely that social, economic and environmental factors will be closely linked. A large scale tidal stream development may influence the following other users of the marine environment, if not all;

|Commercial fishing |Oil and gas industry |

|Commercial shipping and navigation |Other offshore renewable energy |

|Dredging and mineral extraction |Ports |

|Ministry of Defence activities |Recreational fishing |

|Navigational aids and lighthouses |Recreational shipping |

|Tourism |Undersea cabling and pipelines |

It has become apparent that the compatibility of tidal stream developments with other commercial and recreational sectors is the key to success. The new industry must engage with these sectors and listen to their concerns. The Marine Bill White Paper (DEFRA; 2007) aims to clarify the current uncertainty, adding that “the sustainable management of our seas is one of the biggest environmental challenges we face”.

Case Study: The Seagen Project (Source: Fraenkel; 2006)

An example of such an EIA relates to the Seagen project at Strangford Lough, undertaken by Haskoning UK Ltd for Marine Current Turbines. The Seagen is a HOAT with a rated output of 1.2MW.

Due to the location of the proposed site being in a Marine Nature reserve, a highly sensitive ecological area; the project must satisfy the European Habitats Directive. Although there is no risk to birds above the water, there is the remote possibility that diving birds could collide with the turbine blades. Haskoning evaluated this risk, arising from the presence of these birds within the working area of the turbine itself, along with bird behaviour and hunting characteristics, and current speed and depth of turbine blades below the water surface. Taking account of these factors, it was considered that the overall risk of collision is extremely low or potentially non-existent under the large majority of situations, but nevertheless, it was advised that Marine Current Turbines check that these assumptions are correct when the system is operational.

A greater concern was the possibility of impact by Harbour seals and Basking sharks, although further study proved this risk to be superfluous. The flow conditions through a tidal turbine are somewhat gentle, with the maximum rotational speed with Seagen being 15 rpm (one revolution every 4 seconds) and the maximum rotor blade tip velocity being 10–12 m/s. As water passes through the rotor, it follows a helical path and passes by at a very shallow angle to the rotor blades ( ................
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