Energy and Climate Change CommitteeWritten evidence submitted by VerdErg Renewable Energy Ltd (SEV 10)
Executive Summary
1. VerdErg is developing “SMEC” technology for cost-effective and environmentally safe conversion into electricity of the energy in both river and tidal flows. SMEC was one of the three embryonic technologies selected by DECC for investigation under the Severn Embryonic Technology Scheme (“SETS”) programme in 2009–2010. This submission gives a précis of these SETS findings and provides an update on the further development of SMEC in the three years since the SETS programme reports were prepared.
2. All candidate SETS technologies were compared using the same unit cost data base provided by DECC to ensure consistency between concepts. Several of VerdErg’s SETS reports are on the DECC website, including the Final summary report: http://www.decc.gov.uk/assets/decc/what%20we%20do/uk%20energy%20supply/energy%20mix/renewable%20energy/severn-tp/651-severn-embryonic-technology-scheme--final-report-.pdf.
3. The SETS report established the following SMEC features:
A SMEC barrage on the Cardiff-Weston alignment was costed at £9.85bn including habitat loss compensation and 15% contingency. This is somewhere between one third and one half of the capital cost of a tidal barrage fitted with conventional turbines.
Power output was conservatively calculated to be 75% of that potentially available from a barrage. Now that greater design experience has been gained with SMEC over the last three years, a figure closer to 80% is thought to be appropriate.
Permanent inundation of wetlands upstream of the alignment currently forming the feeding grounds for migratory birdlife was shown to be 1,775ha with SMEC turbines fitted compared to 20,000ha for a conventional Ebb-Flow Barrage with bulb turbines. (just 8.9% of the environmental impact of a conventional barrage.)
SMEC would produce electrical power during the full range of the ebb and flow tides at an attractive cost of £68/MWh, calculated in accordance with the DECC-specified costing metric.
A shipping lock in a conventional barrage on the Severn has to cope with an 11m water head difference across it. A lock in a SMEC barrage on the same alignment is much simpler and easier to operate as the maximum water height difference across is can never exceed 2.5m.
4. In March 2010 when the SETS programme reported, SMEC was correctly seen to still be an embryonic technology, requiring further proof of its compelling economic and environmental advantages. Its development has continued since then, however, and a prototype has now been built (November 2012) on the river Caldew in Cumbria, with funding support from the Technology Strategy Board.
Commercial river SMEC projects are planned from Spring 2013 onwards.
Several tidal estuary projects are under consideration. A crossing of the river Camel is thought suitable for early development.
SMEC has been selected for the Solway Energy Gateway across the Upper Solway Firth.
Early studies by PEEL Energy of a possible Mersey Estuary crossing found SMEC to be attractive but not sufficiently developed, at that time, for early adoption.
The projection made in the SETS Road Map Study for SMEC to be ready for adoption in the Severn Estuary Barrage by 2020 remains valid.
Unlike a conventional barrage, SMEC can alternatively be installed on the Minehead-Aberthaw alignment to produce considerably more power with an even lighter environmental footprint. This is because the Minehead to Aberthaw alignment lies downstream of the very large body of suspended sediment that migrates up and down the Bristol Channel with every tide. Additionally, this downstream location favours shipping access to the Port of Bristol by offering a much larger expanse of water upstream of the barrage for vessel manoeuvring.
Further explanatory material can be found on YouTube at “VERDERGRE” and on VerdErg’s website at www.VerdErg.com.
5. SMEC is not a competitor to other barrage proposals; it is a powerful potential enhancement to all of them. This is because it can simply replace the conventional turbines in any candidate barrage proposal. This will enable a better than 50% capital cost reduction to be made in any barrage scheme and deliver an order of magnitude reduction in environmental damage.
6. It is thought that one or more recent Severn Estuary barrage proposals may have been “de-rated” to extract less energy from the tidal flow in order to reduce the environmental footprint of the proposed barrage. Sketches of one such proposal recently published in the Sunday Times also appeared to show adoption of a new design of sophisticated, large-diameter, multi-blade turbine under development by a French manufacturer and said to be able to produce power at unusually low water height differences. This could be a design compromise intended to mitigate the power output having to be sacrificed to achieve less environmental damage. A radically better outcome to any such experimental “high-tech” machinery would result from simply fitting small, proven and conventional, high-speed turbines in SMEC ducting. Expected benefits would include more power at lower cost, even less permanent inundation of migratory bird habitats plus no damage to fish, as they are totally excluded from the 20% of the flow passing through the SMEC’s small, high-speed turbines.
Other points
7. The current status of SMEC is:
The essence of the patented SMEC technology is a no-moving-parts passive, low-cost duct. 80% of the flow goes straight through this duct and boosts the pressure drop in the rest of the flow by four times or more. A comparatively small, lower-cost, high speed ordinary turbine in this residual flow produces a similar amount of power to the huge, expensive, slower-moving “bulb turbines” of a comparative barrage where all the flow goes though the turbine at much lower pressure. In addition to first cost turbine savings, turbine maintenance or replacement costs through-life will be much lower for the simpler, smaller turbines in a SMEC.
SMEC produces about one quarter of its energy output during each quarter-cycle of the tide compared to nearly all the energy from an ebb-flow barrage coming in the single quarter-cycle as the high tide falls to still water level. This even distribution of power from a SMEC barrage during each day improves Grid compatibility.
SMEC is fish-friendly because they pass straight through unharmed, in the 80% primary flow. It is relatively easy to screen off the 20% flow through the small, high-speed turbines.
Unlike a conventional barrage, SMEC preserves the shape of the tidal signal because it is porous and doesn’t stop the flow, as does a conventional ebb-flow barrage. Upstream on the landward side of a SMEC barrage, the tide still rises and falls much as it did before installation. The entire tidal cycle in the closed upstream lagoon, however, lags behind the tide out in the open sea by a few minutes. This once-only “phase shift” of the tidal signal is irrelevant environmentally.
Behind an ebb flow barrage, the upstream water level barely ever gets below mean water level and can permanently inundate much of the upstream wetlands, a vital habitat for migratory birds. A barrage fitted with SMEC turbines causes less than a tenth of this damage. Preserving the tidal signal also minimises disruption of the sediment transport patterns.
With a SMEC turbine fitted, a barrage across the Severn Estuary (or any other estuary) works differently. The maximum head difference between the upstream and downstream water levels is around 2.5m. An ebb flow barrage, by contrast, has to withstand the overturning force of the full tidal range of around 11m, over five times more load. Any barrage designed to use SMEC turbines instead of conventional “bulb” turbines can therefore be significantly less massive. This is why compared to an ebb-flow barrage of the same annual energy output, a SMEC will be somewhere between one third and one half of the capital cost. The power it produces will be cheaper by an even greater factor because of the substantially lower maintenance costs and improved Grid compatibility.
It would be highly advantageous economically and environmentally for any Severn Estuary Barrage consortium to install SMEC-encased turbines instead of the huge traditional “Bulb Turbines” or any complex new-technology low-head turbines. The SMEC’s novelty is in the precise shape of a passive duct; the actual turbine inside the SMEC duct is absolutely conventional, as well as being very much smaller than the massive bulb turbines in a conventional barrage.
8. Contribution to the security of the UK’s energy supply
The Cardiff—Weston scheme is expected to supply just under 5% of the UK’s electrical energy demand. This is immensely valuable, and would be vital in the event of interruptions to availability of conventional fuel sources. The tidal energy “fuel” source is highly predictable; inexhaustible; not dependent on foreign oil and gas supplies, shipping routes and pipelines across potentially unfriendly states.
9. Climate change
Negligible quantities of carbon dioxide will be produced in the operation of the plant. Some CO2 will be produced during construction, as with all infrastructure projects. Note however that the total material mass of a SMEC barrage is substantially less than that of a conventional barrage. CO2 produced in decommissioning any such scheme is normally counted in the environmental assessment, but it is arguable that this is not relevant here since the lifetime is expected to be around 120 years, by which time the climate situation will undoubtedly be completely different. Tidal energy (and hydro power in general) is not subject to some of the disadvantages of well known alternatives:
Wood as a fuel is, in the long term, carbon dioxide neutral, but only over a timescale that is much too long to affect the current problems. It takes 30 or 40 years to replace the fuel and achieve “carbon neutrality”. (An exception to that argument could be the burning of wood waste.)
Large scale bio-ethanol from plant material is now widely thought to have been a wrong turning. It occupies so much food-growing land that serious problems are already occurring with sharp price rises in poorer countries. It is likely that those concerns will halt any further expansion.
Wind undoubtedly has a place in the energy mix, although the negative effects on people and the landscape in the crowded UK look likely to become politically troublesome in the future, at least for on-shore sites.
10. Opportunity for UK industry
Recent barrage proposals in the Press have indicated the very considerable positive effect on jobs and the local economy of designing, constructing and operating a Severn Estuary barrage.
The hydro-mechanical machinery and electrical plant, however, could well be sourced abroad in at least one of these proposals.
“SMEC” is a unique, patented, turbine configuration that has some UK-specific benefits:
It is being developed by a UK company: Verderg Renewable Energy Ltd.
The conventional higher-head and higher-speed turbines used in a SMEC can be manufactured in the UK.
If SMEC is adopted for the Severn Estuary, the creation of a large UK manufacturing industry with great export potential would be facilitated.
Furthermore, for any barrage design, the UK Balance of Payments would be improved by a Severn Barrage because in the long-term, less fossil fuel would be purchased from overseas.
The Severn Estuary could be developed using SMEC turbines after successful development of smaller estuaries such as the Camel, Duddon, Wyre and Upper Solway. The Mersey is another potential site. Subsequently, other West Coast estuaries including the Lower Solway Firth could be developed with substantial socio-economic benefits.
11. Concluding remarks
The UK is fortunate to have arguably the world’s best tidal energy site in the Severn Estuary. Access to such significant tidal power will reduce the UK’s need for supply of fossil fuel from abroad and the attendant political risk and future price uncertainty. In addition, there is considerable current concern over greenhouse gasses and global warming; substantial low-carbon energy generation mitigates any such risk. The Severn Estuary is therefore a strategically vital resource to this country. By adoption of SMEC-encased turbines in any consortium’s barrage design, it is possible to exploit that resource cost-competitively with future fossil fuel and without undue environmental impact.
November 2012