Aberthaw Tidal Power Station

2021 Outline Design by Edward Grist

(5) The Present

Rt Hon Greg Clark MP
Department for Business, Energy & Industrial Strategy
1 Victoria Street
London SW1H 0ET
29 August 2018
Dear Mr Clark,
Aberthaw-Minehead Tidal Power Station House of Commons Select Committee – A Request
I ask you to set up a Select Committee with the remit ‘To determine the value and need for a tidal barrage across the Bristol Channel from Aberthaw to Minehead’. In my view a barrage is required that is capable of :-
  1. delivering a substantial amount of electricity to National Grid
  2. meeting the needs of both wildlife & shipping
  3. providing flood protection for the upper Severn Estuary. This includes Cardiff, Newport, Gloucester, Bristol and Hinkley Point C.
I respectfully suggest the functional requirements on Attachment A to help determine the scope of the Select Committee investigations to ensure the views of appropriate expert witnesses are sought.
In 2013 I expressed concern at the increased risk of electrical power ‘rota cuts’ due to an insufficient generation capability by power stations (see Attachment B). Please review the margin you consider acceptable in your forward planning to ensure that, in addition to the normal seasonal increase in load and potential for unusual weather patterns, the effect of power plant reliability is considered. The fact that it never happened does not mean it never will. The hardship imposed on families and employers in the 1970’s by ‘rota cuts’ is no longer acceptable. Statements afterwards like ‘Lessons will be learned’ will not be acceptable.
Yours sincerely Edward Grist
Continued on following pages
Attachment A (one page)
Attachment B (two pages)

Attachment A
29th August 2018

Functional requirements are suggested below to assist in determining the engineering boundaries to be investigated and appropriate expert witnesses be identified.
  1. Barrage Design – Provision of electricity to National Grid by tidal water-turbine/generators and tidal energy stored in batteries.
    1. A ‘base-load’ function that provides power up to 4,000 megawatt 24/7 for a lifespan of 60 years minimum.
    2. A ‘standby’ function that can replace up to 1,320 megawatt on the Grid within three minutes. This replacement, available 24/7, is produced using two sources.
      1. Tidal water-turbine/generator output.
      2. Tidal energy storage in batteries.
    3. Utilisation of tidal power generation using water-turbines each day for a period of over 16 hours. (Each 12.4 hour lunar tidal cycle is nominally 4.2 hours during ebb and 4.2 hours during flow).
  2. Barrage Design – Flexibility to reduce off-shore maintenance in challenging sea conditions.
    1. A water-turbine/generator unit (‘TG box’) that can be replaced within 24 hours.
    2. A TG box design that provides rapid transfer of components as a unit to an on-shore centre to minimise off-shore maintenance/replacement activity.
    3. A design that has the ability to meet changing flow patterns brought about everyday by the changing mass and position of sediments in suspension and in sedimentary deposits.
  3. Security by Design – Minimise the effect of a major accident. Maximise the design features that increase the perceived risk of failure to a potential terrorist
    1. Eliminate the possibility of terrorist attack or major incident (such as a ship collision) causing loss of power to National Grid that takes a long time to replace. Replace quickly.
    2. Damage from a ship collision or a comparable credible event must be limited to a maximum of 20% of barrage electrical output to National Grid by a design that makes components readily replaceable.
    3. Provision two independent powerlines has the ability to take all electrical output from the barrage to National Grid by one of these powerlines. One line connects to the National Grid terminus at the Aberthaw shoreline ; one line connects to the National Grid terminus at the Minehead shoreline. (This significantly dissuades any terrorist from attempting to disconnect the Power Station output to the Grid.)
  4. Flood Protection – All tidal shorelines upstream of the barrage, including those at Cardiff, Newport, Gloucester, Bristol and Hinkley Point C require protection.
    1. The design should include a means of controlling the upstream maximum height to less than that of a previous high-tide by closing flows through the barrage.
    2. The design should recognise that the tidal flow into the Bristol Channel is spectacularly large. By comparison the total flow from rivers is very, very small.
  5. Marine Life – All Bristol Channel and Severn Estuary marine life should, as far as is practicable, continue to live or migrate as in recent years.
    1. The design should include Marine Life Transit Channels that enable all the multitude of fish varieties, the ‘bottom-crawlers’ and the air-breathing surface swimmers to continue to pass through the barrage for eight hours a day, two hours at each high-tide and two hours at each low tide.
    2. The Channel design width should prevent ships to breach the barrage. (A maximum width of four metre is suggested.)
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