The Spectral Marine Energy Converter (SMEC) was one of several technologies being studied under the auspices of the Severn tidal power project in the UK. Despite government rejection of the project at the present time, SMEC’s developer Verderg is confident that the technology has great potential for future development. Managing director Peter Roberts tells us more
The Spectral Marine Energy Converter (SMEC) converts the energy of moving water into electricity with complete indifference as to its periodicity. SMEC is a design technology that accelerates moving water between streamlined hollow vanes where its pressure drops, sucking water out through perforations in the vanes, creating a secondary flow across an axial flow turbine at a raised head drop under which the turbine works efficiently. SMEC is a 21st century application of the well-known 18th century Bernoulli’s theorem creating the fluid analogue of an electrical step-up transformer. SMEC concentrates the useless energy in a large volume of moving water at low pressure, into a sixth of the volume of water passing through a conventional axial-flow turbine at a six-fold amplified head drop.
By creating a slight rise in the upstream water level as a result of its operation, the marine energy converter is in effect a porous weir acting as a venturi pump. This induced head rise (typically around 1m) is amplified around six-fold across the conventional axial flow turbine inside the SMEC. All electrical apparatus can remain above water. It is inherently bi-directional and as no apparent head drop existed before deployment of the SMEC, it is marketed under the descriptive oxymoron of zero head power.
Following a successful Carbon Trust funded audit of SMEC technology by WS Atkins, VerdErg was identified by Department of Energy and Climate Change (DECC) as a renewable energy technology offering the potential for less impact on the natural environment than conventional barrages and lagoons when deployed across the Severn Estuary. As a result, SMEC was chosen to be one of three embryonic technologies which were studied between mid 2009 and early 2010 under the Severn Embryonic Technology Scheme (SETS).
SETS is a fund to support new Severn tidal power technologies, which are not developed technically enough for more detailed analysis but which may offer the potential for less impact on the natural environment than conventional barrages and lagoons. This funding programme was launched with the aim of:
• Developing new proposals to outline design stage
• Increasing confidence in their output, costs, impacts and technical feasibility
• Establishing a ‘route map’ to take to deployment stage proposals with the potential to generate significant amounts of energy affordably and with acceptable impacts on the natural environment and regional economy.
SETS was co-sponsored by DECC, the Department of Environment, Food and Rural Affairs, The South West Regional Development Agency and the Welsh Assembly Government. This project enabled VerdErg to present SMEC’s environmental credentials.
SMEC is porous and because water flows through it continuously, the tidal signal is preserved, which in turn ensures minimal impact on hydrodynamic and sedimentary regimes, and the aquatic life which they support. This is in complete contrast to the environmental footprint of a barrage. A barrage would permanently inundate around 75% of the upstream habitat for migratory wading birds, whereas SMEC would permanently inundate less than 10%.
The favourable economics of SMEC are a consequence of it only having to withstand the overturning moment of an upstream head rise of a couple of metres, compared with an approximate 10m tidal range of water held back behind a barrage, such as on the Severn estuary. A very much lighter and cheaper structure is needed for SMEC compared with a barrage. SMEC produces 80% of the power for less than half of the capital cost, with much less environmental impact, when compared with a barrage across the Severn estuary.
The cost effectiveness of the power output of SMEC is also helped by the fact that (compared with a conventional ebb-flow barrage of equivalent annual output) SMEC works over all four tidal quarter-cycles instead of less than two quarter-cycles in an ebb-flow barrage (no power is output from a barrage as the upstream lagoon is re-filling). Furthermore, only one sixth of the total tidal flow through a SMEC passes through the turbines, which are therefore much smaller, lighter and rotate at a higher speed than the monolithic horizontal bulb turbines typically specified for a barrage. This reduces gearbox size and cost.
The SMEC generation equipment is all above water and the turbines specified for the SMEC developed for the Severn estuary were designed to be capable of repair by wet replacement during ongoing generation, without having to isolate the turbine and be withdrawn vertically out of the water.
During 2011, some precursor activities are planned:
• A full-scale test apparatus was built by the BHR Group as part of the SETS project to create an auditable high-integrity database to defend the power output claims made for SMEC. This same rig will be used in further tests during 2011 to refine this work and beyond 2011, the rig will be used to further optimise SMEC’s design features over several years to come.
• Fish passage studies will be undertaken to identify any effects on fish of changes in water pressure and shear forces during passage through SMEC, and to facilitate selection of appropriate mitigation techniques.
• Installations are planned in several sites to provide a ‘staircase’ of increasing experience on progressively larger SMECs. Candidate sites include SMEC projects in the northwest of England, particularly in Cumbria. A number of overseas sites are also under investigation. Around 25 sites in total are currently under evaluation.
VerdErg welcomes the government’s decision not to select a barrage for the Severn estuary. It facilitates SMEC’s progress along its development road map through small river projects to smaller tidal estuaries. It will then become a fully credible candidate for the Severn estuary capable of attracting finance for the £9.8B (US$15.7B) estimated capital cost from the private sector. VerdErg believes that SMEC will be a fully mature technology when the appropriate Severn estuary solution is eventually selected.
One important milestone has been the recent selection of SMEC for the proposed Solway Energy Gateway. The flagship project is a tide driven scheme between Annan in Scotland and Bowness in England with a capacity of 200MW online by 2020. A collaboration agreement has been signed with the developers of the Solway Energy Gateway, and several smaller lead-in projects will be undertaken jointly with them over the coming years.
The question arises as to whether the government’s decision not to support a barrage across the Severn Estuary will have an adverse effect on the development of wave and tidal technologies across the UK? VerdErg welcomes the decision as mentioned above and must assume that other aspiring providers of new renewable energy technology will also welcome the decision as a major target kept available for their future aspirations.
We believe that small companies are the innovators of most truly new technology. Large companies prosper by staying within their comfort zone, following a risk management strategy that keeps their activity within their own market segment where their expertise is class-leading. Such large companies might innovate within their own technologies but can find it difficult to make paradigm leaps into a completely new technology; there are many reasons why this should be so including in some cases not just conservatism but shareholder pressure to stay focused. A small company cannot, however, compete head-on with a well-run big company in its own specialisation and small companies are left with new technology as the only available market niche in which they can succeed.
The problem wave and tidal power technology faces in meeting the challenges of the future is thought not to be the postponement of the Severn estuary barrage, but the inbuilt bias of public sector funding towards large companies which may not be the best new technology innovators. This bias occurs because development of wave and tidal power requires considerable capital expenditure to place a prototype or prototypes in the water. Since matched funding is usually required, only larger companies can participate. It could be that more flexible funding mechanisms are required. Examples could be credit guarantees or targeted feed-in tariffs.
VerdErg believes that the government’s ambitious renewable power targets can all be met with truly proactive government support extended additionally to small, nimble innovative companies. Such support of small companies cannot be risk-free but neither is grant funding given to a large stable company that fails to deliver true innovation. With appropriate investment support, SMEC technology can play a leading part in helping meet the published targets for carbon reduction in the UK.
VerdErg’s ultimate goal for SMEC is to develop and commission a renewable energy technology directly competitive with fossil fuels. This looks to be possible with river-based SMECs where a good load factor is available, and power costs down to 3p/KWh should be achievable.
Peter Roberts, Managing Director, VerdErg Renewable Energy Ltd, Lansbury Estate, Unit 5 & 6, 102 Lower Guildford Road, Knaphill, Surrey GU21 2EP, UK
|Severn Tidal Power
Following a two-year study to assess whether and on what terms the UK government could support a tidal energy scheme in the Severn estuary, it was concluded in October 2010 not to bring forward such a scheme at the present time. However, the government said it still wished to keep the option open for future consideration.