Severn study heads down the tubes

Independent British engineering and environmental consultant Gifford has been appointed by offshore energy specialist VerdErg to provide engineering and cost estimation support for its proposed Severn tidal fence scheme.

The project has now received funding for further development from the Severn Embryonic Technologies Scheme (SETS) supported by the Department for the Environment, Food and Rural Affairs, the Welsh Assembly Government, the South West of England Regional Development Agency, and the Department of Energy and Climate Change.

The proposal for a fence rather than a barrage makes use of the natural tidal currents flowing up and down the Severn estuary. An array of vertical and horizontal tubes exploits pressure differences to drive water at high speed through the horizontal connecting tubes to generate electricity, rather than use tidal power directly to drive turbines.

The structural design means there is minimal restriction to normal water flows and therefore much less impact on the natural estuary and river habitats either side of the structure, one of the biggest potential objections to barrage designs.

VerdErg estimates that the tidal fence will produce approximately 80% of the power of a barrage but for approximately two-thirds of the capital cost, together with vastly reduced environmental impacts.

Nick Clarke, technical director at Gifford said, ‘This design has the potential to be used at many tidal estuaries such as the Mersey, as well as the Severn. It is also likely to be ideal for micro-hydro power generation on inland rivers and for open water offshore installation. It can be constructed to any length required. It is a very exciting development.’

Peter Roberts, Managing Director of VerdErg added, ‘We applied our 30 years of experience in the marine environment to the development of the tidal fence which we call a spectral marine energy converter (SMEC), concentrating on simplicity, robustness and reliability. The only underwater moving part is a propeller turbine, a device that has been around for over 100 years. SMEC offers the unique capability of reliably converting abundantly available zero to low head hydro power into electricity on a large scale, at a competitive price.’