Energy and Climate Change CommitteeWritten evidence submitted by Evans Engineering & Power Company Ltd

1. Executive Summary

This Paper makes it plain that not only are there other proposals for Tidal Power Projects in the Severn Estuary under consideration, but that the project known as the “Reef” is quite simply “head and shoulders” above the rest. It would produce more power (30.4 TW per year), while protecting the environment; by not killing the fish and by maintaining an inter-tidal habitat for bird life. The Reef would also allow shipping to pass through it, to and from the Ports of Bristol, with less disruption than any of the other major energy generating proposals for the Severn. This includes the Coram Hafren proposal for the Severn Estuary, known as the Severn Barrage, a project which in it latest incarnation attempts to copy some of the Reef’s properties, such as bi-directional flow, but puts it in the wrong place (Cardiff to Weston), where less energy will be captured and where the high silt load will in all likelihood foul its operation. The Reef on the other hand is the only “future proof” design, allowing upgrading or modification after initial installation. It is the only project seeking to engage with environmental and shipping issues from the outset. It is the only project actively seeking the participation and investment of the British people in a “Green Legacy Project”.

2. Introduction

The simple answer to the question “Are there any other proposals for Tidal Power Projects in the Severn Estuary currently under consideration” is “yes”, this paper however seeks to shed further light on just one of these proposals know as the “Evans Tidal Power Reef”, named hereon as the “Reef”, a concept of the Cornish engineer and inventor Rupert Armstrong Evans. In 2009 Atkins, at the behest of the RSPB, undertook at study1 of a concept developed by Rupert Armstrong Evans (RAE) known as the “Tidal Reef” or “Tidal Power Reef”. The findings of this independent study were interesting in that they affirmed the claim that the Reef would do far less damage to the environment than the Severn Barrage and estimated that it could produce more power. So what is the Reef, how would it work? and what would the benefits be over a conventional barrage or a similar scheme built on the Cardiff to Weston-Super-Mare line? This paper seeks to address these three questions

3. History

The Severn Estuary has the second highest tidal range in the world. There is huge potential to harness this power and many proposals have been put forward throughout the last 100 years. Most of these proposed schemes (tidal range technology) would work by blocking off the estuary or lagoon with a dam/barrage, and by delaying the tides, these barrages produce a significant difference in water level between the inside and the outside of the dam in order to operate the hydroelectric turbines. These proposals are likely to be both expensive and environmentally damaging. The damage mainly would be caused by changes to water flow patterns and levels within the estuary. This in turn would impact on the mudflats and salt marshes and their bird populations, while the pressure differentials in the barrages themselves would be likely to kill a large proportion of any fish attempting to swim through the turbines. More recent developments in tidal stream technology (extracting kinetic energy) are also expensive and give a significantly lower power output.

4. What is the Reef and how would it work?

The REEF system, is a totally new concept, it is based on a relatively light impounding structure spanning the 12-mile estuary that maintains a small but constant head difference between the outer sea level and the inner estuary when the tide is coming in and the reverse when the tide is going out. Introducing only a short delay to the natural tidal cycle avoids almost all the adverse environmental consequences of a large fixed barrage of the type proposed between Cardiff and Weston Super Mare. The Reef proposal has already had positive feedback and support from a wide range of environmental groups including: the RSPB, Avon Wildlife Trust, The Wildfowl & Wetlands Trust, The Anglers Conservation Association, the Wye and Usk Foundation, The Burnham and Somerset Levels Sea Flood Study Group, the Green World Trust, Friends of the Earth, The Bore Forum, and TENONS the environmental network of North Somerset.

4.1 Location of the Reef

The favoured location for the Reef is between Minehead in Somerset and Aberthaw in South Wales. A recent study conducted by consultants W.S.Atkins suggests that a Reef type structure in this location could yield an annual energy output as much as 50% greater than a “conventional barrage” located between Weston Super Mare and Cardiff. Such a structure, it also concluded, would also be significantly cheaper and faster to build and would have significantly less environmental impact when compared to a conventional “barrage” between Cardiff and Weston.

Map showing the proposed location of the Reef in green and the Barrage in blue, this also graphically illustrates the difference of the impounded areas of the two schemes, with the Reef exploiting almost twice the volume of water.

The water turbines used in a barrage scheme, are usually unidirectional, so a significant portion of the civil engineering cost is associated with sluices and by-pass channels to let the tide into the inner basin, but this is “dead investment” in that it does nothing to increase the energy output and actually dissipates energy in friction. The Reef system uses bidirectional turbines and a “differential head” of less than three metres to minimise environmental damage and maximise the utilisation of the plant. The power output is lower but the operating period is longer, making it easier to integrate with the National Grid and to supply the national base load power requirement. Around 600 water turbines with diameters between 15 and 20 metres diameter will be required to generate up to 6000MW.

4.2 Navigation

Navigation has always and will continue to be vital to the community and commerce along the Severn estuary. To consider installing conventional ship locks that would cause significant delays to the passage of ships is unrealistic. Bristol Ports now account for over 12 million tons of freight annually and has embarked on a £600m development of a new “Deep Sea Container Terminal”, so only an innovative solution to the passage of very large containers ships with minimal delays will be acceptable, and this is what the Reef offers. For small craft wishing to navigate the Reef, a lock would be provided on both the Welsh and English sides of the Estuary.

Above: Proposed mini lock gates for small craft passing through the Reef

Above left: a schematic view of one of the proposed 600 reef turbines “man to same scale”.

Above right: how the Reef might look from above, showing how ships could pass through openings in the structure.

4.3 Structure of the Reef

The Reef is not so much a “power station built in the sea” as a chain of ships or floatable structures sitting on the seabed. The key to reducing both short-term risk and “future proofing” the whole project is flexibility. By separating physically and if necessary financially, the provision of the infrastructure (a seabed foundation) and the movable “power generation modules”, many partners can easily be combined and thus reduce individual risks. As an example of a similar marine technology, the Mulberry Harbours, a project involving similar scale, were built in secret during WW2 in only 6-months and installed in Normandy over a period of a few weeks; it is therefore not unreasonable to assume that with our present knowledge of offshore structures and project planning, that we are able to build a not dissimilar scale of project in a time scale of a few years rather than the ten to fifteen years for a “conventional barrage” or a nuclear power plant.

4.4 National Vision

Galvanising the many interested groups and getting the “nation” behind this project is important. A significant part of the capital investment and “direction” could come from the people of Britain. Both the Welsh and the English have major parts to play and would benefit from very significant numbers of jobs, both during construction and for ongoing maintenance. Our objective is to bring together the constituent parts of a major “green energy project” that we could be proud to leave for future generations, instead of a stockpile of spent nuclear waste.

4.5 Connection of the Reef to the National Grid

Grid connection may be achieved in a number of ways. Aberthaw power station on the Welsh side is already connected to the grid with a 400,000-volt line. This power station is scheduled for closure in about 15 years time. An underground connection would be possible on the Minehead side, running for part of its route along the West Somerset Railway before being connected into an upgraded but existing (132,000 volt) overhead line near Wiverliscombe. Anther possibility could include an undersea cable (possibly superconducting) connection laid directly to the Hinkley Point Power station take off, without the need for pylons.

4.6 Energy storage and other uses for energy produced by the Reef

Extra energy could also be stored by converting water into hydrogen using electrolysis and then by pumping the gas to the existing British Oxygen plant at Port Tolbert, or it could be used for desalination in drought years.

4.7 Technical feasibility of the Reef

The technical feasibility of a Reef like structure was outlined in a report by W.S.Atkins and Rolls Royce entitled “Concept Design of a very low head dual generation tidal scheme for the Severn Estuary, published in February 20102. Some of findings of this report are listed below and indicate that such a structure:

May produce a peak power output in a Minehead-Aberthaw alignment of 10,000MW with a total annual energy yield of 30.4 TWh (5)

May substantially reduce the loss of intertidal habitat relative to the STPG ebb-only barrage (8).

May theoretically reduce fish mortality significantly through the turbines (19).

Should be less disruptive to shipping than an ebb-only barrage due to the retention of existing navigation channels, shorter lock transitions, and higher structure permeability during construction, although a ship lock structure will still be required (12).

Would require reduced grid reinforcement for a given energy yield due to the lower peak capacity and longer generating window.

Be more likely to retain the natural flow patterns of the estuary, however higher fidelity modelling will be required to confirm this conclusion (13).

Have a majority of the components for a very-low head bi-directional turbine within the current supply chain scope and production of the required number of turbines is reasonably feasible (18).

And very-low head bi-directional turbines with high reversible efficiency are technically feasible and no new technology or engineering methodology is required (16).

5. What would the benefits be over a conventional barrage or a similar scheme built on the Cardiff to Weston-Super-Mare line?

The benefits of the Reef over a conventional barrage sited between Cardiff and Weston -Super-Mare are outlined above and can be summarised as follows: The Reef would produce more energy, while protecting the environment by not killing so many fish and by maintaining an inter-tidal habitat for bird life. The Reef would also allow shipping to pass through it to the Ports of Bristol with less disruption than any of the other proposals.

5.1 Coram Hafren

A consortium known as Coram Hafren is now proposing a barrage between Cardiff and Weston-super-Mare that has been modified to incorporate the Reef system of operation, namely bidirectional flow and a low differential head. They have however overlooked the other critical factors that make the Reef concept particularly attractive.

The Cardiff-Weston alignment is not as attractive as the Minehead-Aberthaw alignment because it captures less energy, is in the path of mobile silt, and makes navigation more dangerous and time consuming. Further more, storm surges are likely to be heightened in parts of northern Somerset and there will be considerable impacts from construction traffic.

The Reef additionally provides the opportunity for efficient energy storage without the risk of flooding. The innovative approach to turbine and caisson construction will provide far more local and UK jobs because it is based on “shipyard technology” as opposed to the conventional high precision water turbines that have very few potential suppliers.

6. The legacy and way forward

The Reef is our generation’s opportunity to build an “iconic green energy project”, it would be the “Greatest Machine on Earth” and visible from outer space with the naked eye. It would be our generation’s “Hoover Dam” or “Great Wall of China” and it would “say” that we care enough about future generations to invest in them, rather than leave a legacy of a resource depleted planet and a stockpile of spent nuclear waste”.

6.1 Public investment and funding

Public investment in the form of a “green bond” could mean that thousands or even millions of ordinary British people could own a stake in what is a part of our natural heritage.

The Reef proposal has had no public funding. A formal expression of interest by Government would be sufficient to bring forward the funds to proceed with an outline design and “due diligence”. The Reef cannot be dismissed on technical grounds, and there are significant “green energy” benefits, without many of the environmental or commercial impacts associated with the Cardiff-Weston Barrage. The economics depend to a large extent on the value placed by Government on renewable energy, energy security and “load levelling” within the “grid system”. If the value place on “head-range tidal with storage” were comparable with “offshore wind”, then the project would almost certainly be able to attract the necessary investment.

6.2 Future proof design

The Reef is the only “future proof” design, allowing upgrading or modification after initial installation. It is the only project seeking to engage with environmental and shipping issues from the outset. It is the only project actively seeking the participation and investment of the British people in a “Green Legacy Project”.

November 2012