The Severn Embryonic Technologies Scheme (SETS) is a fund to support new Severn tidal power technologies, which are not developed technically enough for more detailed analysis at this point, but which may offer the potential for less impact on the natural environment than conventional barrages and lagoons.
This funding programme was launched in April 2009 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.
Seventeen bids for funding were received and assessed and three schemes are now being supported. These include a low-head barrage and two tidal fences. These schemes will be considered alongside the shortlisted barrages and lagoons before decisions on Severn tidal power are taken by the new Government.
Update – The Severn Embryonic Technologies Scheme work-programme concluded on the 29th January 2010 with proposers submitting final reports and Development Route-Maps. Formal presentations were made to the SETS Programme Board on 8th February, who are now reviewing all the available information. The outputs from the SETS Programme will be published alongside the second Severn Tidal Power consultation expected ater this year.
The Schemes
Low Head Barrage – Rolls Royce-Atkins
This proposal is for a low head barrage, similar in structure to a conventional barrage but with a new type of turbine (not yet developed at scale). The turbine is likely to draw upon technologies from both tidal stream and tidal range schemes. The turbine design would generate electricity on both the incoming and outgoing tides. The turbine would operate at a lower depth and water level difference than conventional barrage turbines. By operating in this way tides would be held back behind the barrage for less time which should reduce the potential impact on large areas of the important Severn Estuary inter-tidal habitat and reduce the impact on fish.
The work through the SETS programme will allow Rolls Royce and Atkins to develop the turbine design and work to understand the costs and likely environmental impacts of schemes with such novel turbines installed
Severn Tidal Fence – Severn Tidal Fence Consortium
The tidal fence works by installing an estimated 500 - 800 tidal stream turbines in a line across the Estuary. The fence could be located between Brean Down and Lavernock Point (the same place as the Cardiff-Weston barrage) or between Minehead and Aberthaw. The study will look at a range of tidal stream turbines currently under development as single devices at around MW-scale and assess their feasibility to be scaled up and incorporated as several hundred devices in a fence.
Initial estimates are that a fence scheme could generate up to 3.5TWh per year at an estimated capital cost of £3-4billion. It does not need to hold back water to generate electricity (as the turbines use the movement of the water rather than height difference of water) and therefore the scheme will have little impact on the important inter-tidal habitat. It may also be better for fish .
The main areas outlined for developmental work under SETS are configuration of the fence structure, technological study for selection of a suitable turbine, energy yield and further work on potential environmental and navigation impacts.
Illustration – Tidal Fence, Severn Tidal Fence Consortium
The scheme is proposed by the Severn Tidal Fence Consortium, which includes IT Power and Clean TechCom, and is backed by commercial investors and other industry expertise. The consortium intends to work closely with turbine developers to assess the technologies available which will enable the group to make the best selection from a range of tidal stream turbines.
Tidal Fence - VerdErg
Severn Tidal Fence – VerdErg
This tidal fence is a radical new fence design and works in a completely different way to other fence schemes. It still makes use of the tidal stream (i.e.it uses the movement of the water from the naturally occurring tidal currents, rather than using the height difference between high and low tides), but instead of allowing the tidal currents to directly drive an underwater turbine, a large proportion of the tidal flow passes through a fence structure formed of a series of vertical and horizontal tubes. When water passes between the vertical tubes a pressure difference is created and this causes water to flow at high speed in the horizontal connecting tubes, which then drives turbines to generate electricity. This action occurs on both incoming and outgoing tides and hence facilitates 2-way generation. With minimum moving parts and a perforated structure it will not impound large volumes of water and hence has the potential to have less impact on inter-tidal habitats and be more fish friendly.
This Tidal Fence scheme is proposed by VerdErg. Originally proposed between Brean Down and Lavernock Point (the same place as the Cardiff-Weston barrage), VerdErg’s preliminary estimates suggest it could generate around 13.74TWh/year and cost around £9.9 billion. VerdErg will also examine whether a more downstream alignment between Minehead and Aberthaw could be more suitable.
SETS funding will initially be provided to check the concept is likely to work and the likely power output. If this is successful, the programme will then go on to further develop the design and assess costs to inform a development route map.