Select Committee on Environmental Audit Written Evidence

Memorandum submitted by Tidal Electric Limited

  As Chairman of Tidal Electric Limited, I welcome the opportunity to submit evidence to the Committee inquiry. The inquiry comes at an important time for the country: oil and gas prices are significantly increasing, there is no clear policy on new nuclear and the Government's target of 10% market share for renewables by 2010 appears unlikely to be reached.


  1.  Tidal Electric is a British-based development company that was established in 2000 with the sole intention of building a tidal lagoon electricity generation scheme in UK waters.


  1.  Offshore tidal lagoon power generation utilizes the vast potential of the ocean's tides. Using an offshore impoundment structure built of rubble mound construction materials (loose rock, sand, and gravel) sited in a shallow tidal flat with a large tidal range, predictable and sustainable electricity can be generated by the rise and fall of the tides. It is not directly comparable to a tidal barrage scheme (such as the Severn Barrage) as the power is generated offshore via the impoundment structure. The tidal lagoon scheme enables tidal energy to become a mainstream technology choice.

  2.  Offshore tidal power generators use familiar and reliable low-head hydroelectric generating equipment, conventional marine construction techniques, and standard power transmission methods.

  3.  The optimal site for offshore tidal power generation is the shallow water of near-shore areas, away from major shipping lanes that require deeper water. The offshore siting is the distinctive characteristic of the design and one of the fundamental claims of its patents. Turbines are situated in a powerhouse that is contained in the impoundment structure and is always underwater. Power is transmitted to shore via underground/underwater cables and connected to the grid. The structure need not be more than a few yards beyond the low tide level and the optimal site is one that is as shallow as possible, thereby minimising the cost of building the impoundment wall.

  4.  The impoundment wall structure is a conventional rubble mound breakwater, with ordinary performance specifications and is built from the most economical materials. In the event of a failure of the structure, the consequences do not include safety issues or major property damage. The most likely cause of a failure would be a strong nearby earthquake (unlikely in UK waters) and the most likely type of damage would be a breach of the impoundment structure. Thus, the principle consequence of failure would be economic (temporary interruption of service) and, therefore, economics are the primary driver in choosing the materials and the construction method.

  5.  Two sites in UK waters have been identified as suitable for the construction of the world's first tidal lagoon generation scheme: Swansea Bay and the North Wales coastline, off Rhyl. Both areas have high tidal ranges and relatively shallow waters. Feasibility work started in 2000 and preliminary consultation with local planning authorities has been undertaken. There has generally been a favourable response to our proposed schemes as they provide a sizeable renewable and predictable generation resource. Swansea Bay has a capacity of 60MW and North Wales has a capacity of 420MW.

  6.  We have also identified a number of other potential sites around the UK coast which meet the requirements of high tidal range and shallow tidal flats. We believe that it would be possible to generate from numerous sites, approximately 21 TWh, representing 8% of current UK electricity consumption.


  1.  Tidal Electric's financial advisers, NM Rothschild, have undertaken a detailed analysis of the construction and generation costs of tidal lagoons. They conclude that our generation, excluding subsidisation and economies of scale, is competitive with offshore wind, and arguably with more conventional methods of generation. The graph below highlights Tidal Electric's costs compared to all other forms of generation, except nuclear.

  2.  The cost per unit output of the offshore tidal power generator is less than that of the tidal barrage for the following reasons:


  Hydrostatic and hydrodynamic forces increase markedly with depth. The impoundment structure is built on near-shore tidal flats proximal to the low tide level and avoids deeper areas. In contrast, the barrage must span an estuary and must cope with whatever depths exist on the site. In the case of the Severn Barrage, the depths are up to 40 meters below low water.

Load Factor

  Barrages must generate primarily in one direction (on the ebb tide) in order to minimise progressive disruption of the intertidal zone that would eventually lead to the silting up of the head pond. The offshore tidal power generator is free to utilise both the ebb and the flood tides for generation, thereby roughly doubling the load factor of the barrage. Double the load factor is equivalent to halving the capital cost per unit output.


  Both the impoundment structure and the barrage are intended to hold back water. The power of the tides lies only in the tidal range, the difference in water levels between high tide and low tide. The impoundment structure is built so as to perform only that function, whereas the barrage also holds back all the water below low water level and all the water in the intertidal zone. None of this water produces any power, yet it is very costly to contain.

Generation Equipment

  The offshore tidal generator uses conventional low-head hydroelectric generation equipment and control systems. The equipment consists of a mixed-flow reversible bulb turbine, a generator, and the control system. Low-head hydroelectric generation equipment has been in existence for more than 120 years and state-of-the-art equipment is mature, mechanically efficient (96%+), familiar (over 100,000 units in use world-wide), reliable, and durable (the equipment comes with performance guarantees and a design life of over 50 years.) Manufacturers/suppliers include Alstom, GE, Kvaerner, Siemens, Voith, Sulzer, and others.

  5.  The estimated capital expenditure cost of constructing the Swansea Bay 60MW lagoon is £79 million, and the capex cost for the North Wales scheme is £375 million.


  1.  To date, the proposed schemes have been welcomed by Swansea Council, xxx Council, Friends of the Earth and the RSPB as well as a number of Members of Parliament and Peers, and members of the Welsh Assembly. In order to develop each scheme, we will require the consent of the DTI and other government departments and agencies. Discussions with the DTI, the Crown Estate, the Environment Agency and the Welsh Assembly are on-going.

  2.  To assist us in taking our projects forward Tidal Electric has assembled an experienced, advisory team consisting of: NM Rothschild (finance), WS Atkins (civil engineering consultants), APBmer (marine engineering consultants) and RW Beck (hydrology consultants).

  3.  Subject to receiving the necessary planning consents and environmental permissions, the timescale from first construction to operation is two years.

  4.  During the construction phase, construction jobs will be created. Once each scheme starts operating, we expect that there will be permanent jobs for maintenance and operation. Secondary business activities and tourism will also add to the local economies.


  1.  The project economics will allow the effective use of project finance for the development of Swansea Bay and/or the North Wales coast scheme, subject to receiving the necessary consents from government. Importantly, this means that we will not be reliant on financial support from the taxpayer.

  2.  We have strong indicative interest from a number of UK and overseas financial institutions, for both debt and equity financing. In addition, we are also in discussions with several major energy companies with respect to potential equity financing of one or more facilities.


  1.  While understanding the need to prioritise the development of additional and alternative sources of energy, we believe that the overall needs in the UK (and in the world as a whole) will eclipse the capacity of any one technology and necessitate the ongoing development of a range of technologies, including nuclear. As tidal lagoon generation does not compete for resources (eg land, tidal flow etc), we believe that the technology is complementary and additive to other technologies.


  1.  We consider that tidal lagoon generation could be applied in many sites around the UK coastline and so could reasonably generate 8% of the UK's generation needs by 2020.

  2.  Tidal lagoon generation offers the UK clean, renewable and predictable generation at a comparable cost to offshore wind and arguably others forms of generation. It also has potential social, economic and environmental benefits, including the protection of the North Wales coastline from further erosion and flooding.

  3.  Importantly, this new form of generation will help to meet the UK government's renewable and climate change targets. It would also be a significant step in the commercial development of the marine renewables sector. We are determined that this project will succeed and so enable Wales (and ultimately the rest of the UK) to showcase the technology to the rest of the world.

20 September 2005

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