Case Study

ESRU Energy Systems Research Unit

University of Strathclyde


Environment: Evaluation

    Suggested Action    Potential Obligations    Recommendations    Environmental Impacts     SIF    
Environmental Organisations Criteria

Suggested Action for Organisations

Organisations should consider deploying a clearly defined marine renewables section on each of their websites, enabling a developer to quickly assimilate the locational constraints on deployment, e.g., immediate no-go areas, which may speed up the site selection and subsequent consent process markedly.

It may also be beneficial to realise that there exist particular consultants or businesses that can help with laborious areas such as the Environmental Impact Assessment.

There are a number of feasibility studies into the potential of marine renewables which can be linked to from the references section. Some of the commissioning bodies such as the Carbon Trust, DTI and the Scottish Executive, may also have provision for economic assistance or guidance, so it will be well worth locating the relevant material. On the same note, it will be interesting to see the results of the forthcoming study by Fauber Mansel on marine renewables, as each subsequent report seems to build on the work of the earlier efforts (Black & Veatch, Garrard Hassan, Atlas of Marine Renewables etc.), and all make very informative reading for the potential developer, as a significant attempt has been made to quantify and locate the best resources around the UK. To date, the most recommended reading would be Black & Veatch’s phase 1 & 2 reports for the Carbon Trust, as they take into account areas such as the Significant Impact Factor (SIF) highlighted by Robert Gordon’s University, compared to the traditional ‘farm’ methodology. A full discussion and modelling exercise highlighting the SIF can be found here.

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Potential obligations

To give an idea of some of the potential obligations an offshore renewable developer might face, a list has been compiled as follows:

  • Refuge in piled structures may have to be provided for surface breaching installations, thus in storms mariners in difficulty may be able to safely await rescue. To this end, a tidal farm should also have individual coding with respect to global positioning to aid the authorities. Such a locational marking will most likely be constantly up-lit at a preset height above the sea’s surface.
  • Before submitting an application site traffic surveys will have to be undertaken for a period of up to 4 months, including provision for seasonal adjustment. It is likely, from second hand experience, that this survey will be a 24 hour, 7 days a week affair, with a note taken of the type of traffic observed, destination and previous location. This information will likely be gleaned from radio contact with the passing sea-craft, or may be available based on the craft’s registered details.
  • If international shipping is encountered at the desired farm site, it must not be hampered by installation, otherwise the site will have to be moved, based on information from MCA.
  • Parametric models for seabed disturbance and impact will be called for by some of the relevant bodies to enable a better understanding of marine renewable impacts for future developments, as well as likely disturbances to the immediate site. Bear in mind these may not be mandatory, but preferred, and likely be beneficial in any case.
  • 24 hour permanently manned control units for emergency shutdown and potentially CCTV monitoring of farms/units.
  • Guidance for mariners on the potential effects of radar interference: such that small vessels that may encounter shadowing effects from structure and hence may be difficult to pinpoint within arrays will be aware of the potential dangers. Less specifically but equally likely is the requirement for guidance and notification for/to mariners/pleasure craft operators due to the common law rights of free passage in and around UK waters.
  • Moored infrastructure will very likely have to be fitted with real time radar or satellite tracking systems in the case of breaking moorings. This will allow the relevant authorities to plot courses and warn effected mariners of the dangers, allow recovery operations and, of course, peace of mind for the developer.
  • To satisfy MCA, an International Hydrographic Organization (IHO) Order 1 standard multibeam bathymetry survey is required, and a scale dependent EIS, possibly in addition to, or in substitution of part of, the surveying work that would have to undertaken normally to ascertain the tidal climate and seabed topography, form and type.
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As discussed previously in tidal sections, the flow rate given on many admiralty charts is a mean spring tide surface velocity, which tends toward zero m/s at the seabed, as the models generated predict. However, it might be very sensible to perform Acoustic Doppler Profiling in conjunction with the other survey work to build up the most accurate picture of how a turbine will perform. In this way the theoretical velocity profiles can be substituted for the actual velocity profiles to ascertain whether any peculiarities are present at the desired location. While the models will likely be sufficient to calculate operational parameters, this approach will remove a portion of risk associated with uncertainty. For a more in-depth discussion of this concept, please consult the DTI publication, 'Development, installation and testing of a large-scale tidal current turbine' (2005)(3).

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Environmental Impacts and Concerns

There are a number of potential environmental impacts that can arise due to marine renewables, but it is still something of a grey area due to the lack of physical testing. As such, many organizations are advocating an ongoing investigative modelling approach to try and discern the magnitude of any marine environment disruption. To date, however, environmental effects that can be attributed to tidal current turbines are generally described as ‘minor’ and as such, present no significant prohibitive barrier to their implementation.

Potential issues include the following, (please refer to an environmental study (4) published by the DTI for more detail):

  • Seabed habitat disturbance during construction to marine and intertidal habitats – effects on sand eels (a major seabird food source) may be significant in the same way as the off shore wind installation experience has established
  • High solidity of turbines therefore must withstand relatively large tangential forces
  • Collision risk of marine species, though gratings on diffuser augmented/shrouded turbines would alleviate this. It is however doubtful that even large marine mammals would be unable to detect the turbine.
  • Risk to diving seabirds
  • Antifouling – need for regular maintenance or antifouling paints and potential toxicity
  • Effect on tidal flow patterns, downstream currents, sedimentation patterns/sediment transport, scouring and seabed morphology
  • Acoustic emissions of the devices and the effect on marine mammals, inclusive of installation operations
  • Visual impacts from shore areas
  • Vibration effects

Navigational risks to surface craft have been investigated, and in addition some of the following issues have been noted, though for more information please go to a publication by the Maritime and Coastguard Agency.

  • Shipborne and shore-based radar interference
  • The possibility of electromagnetic interference
  • Collision risk due to shadow effects around substantial structures
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Significant Impact Factor (SIF)

One of the most important factors to consider for a developer will be what has been defined as the Significant Impact Factor (SIF) due to the following:

Structures themselves could cause changes in the set and rate of the tidal stream... MCA (2005)

...if tidal farms began to significantly reduce the flow in their area, this would have a detrimental effect on the energy output of the farm, something developers will wish to avoid. DTI (2005)

Due to the fact that the power that can be extracted by a marine current turbine is related to the cube of the current velocity, even a small reduction in flow rate can translate as significant decrease in generated power. Robert Gordon University are perhaps the main exponent of this ‘flux’ methodology, which has hitherto been unaccounted for in most resource quantifications. As a constraining factor therefore, the SIF is very important as it has been suggested that the maximum permissible reduction of flow rate could fall between 6 and 10%, up to a maximum for more robust sites and estuarine waters of 15%.

The consensus of many investigative reports is that there is huge marine resource potential around the UK, and a large portion of this is found in Scottish waters. Marine current generation is still a nascent technology and consequently there is still scope for streamlining in the application procedure, and a good deal of knowledge to be gleaned in environmental terms. However, “man has been putting things in the sea for a long time” (MCA 2006), inferring in turn that the challenges of coordinating the consent process are in no way insurmountable, if not a little logistically challenging.

1 HOWARD, M. and BROWN, C., Maritime and Coastguard Agency & QinetiQ: Results of the Electromagnetic Investigations and Assessments of Marine Radar, Communications and Positioning Systems Undertaken at the North Hoyle Wind Farm [QINETIQ/03/00297/1.1; MCA MNA 53/10/366]. [PDF] 2004 [cited 03 May 2006]; Available from
2 Maritime and Coastguard Agency: Proposed Uk Offshore Renewable Energy Installations (Orei) - Guidance on Navigational Safety Issues [MGN 275 (M)]. [PDF] 2004 [cited 03 May 2006]; Available from
3 DTI, Development, Installation and Testing of a Large Scale Tidal Current Turbine [T/06/00210/00/REP; URN 05/1698 ]. [PDF] 2005 [cited 02 May 2006]; Available from
4 DTI, The Robert Gordon University: A Scoping Study for an Environmental Impact Field Program in Tidal Current Energy [ETSU T/04/00213/REP; DTI Pub/URN 02/882]. [PDF] 2002 [cited 03 May 2006]; Available from


Recommended resources:

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Environmental Organisations Criteria

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