Severn tidal power shortlist contains two lagoon proposals

Up to 5% of UK electricity could be generated

Both controversial barrages and innovative tidal lagoons favoured by conservationists have made it onto the shortlist of schemes to generate electricity in the Severn estuary. If the largest were to go ahead, it could produce enough electricity to supply all of Wales' needs.

New funding of £500,000 has also been announced to further develop new technologies like tidal reefs and fences. Their progress will be taken into account before a final decision is made. The tides in the Severn estuary are the second highest in the world.

A year-long feasibility study has been investigating ten options that are now whittled down to five. A consultation is now underway until 23 April on which projects to take forwards (which includes the five schemes that didn't make the shortlist). The five schemes are:

• Cardiff Weston Barrage: crossing the estuary from Brean Down, near Weston-super-Mare to Lavernock Point, near Cardiff. Estimated capacity: over 8.6 gigawatts - nearly 5% of UK electricity
• Shoots Barrage: further upstream of the Cardiff Weston scheme. Capacity: 1.05GW (similar to a large fossil fuel plant)
• Beachley Barrage: just above the Wye River. Capacity: 625MW
• Bridgwater Bay Lagoon: on the English shore between east of Hinkley Point and Weston-super-Mare. Capacity: 1.36GW
• Fleming Lagoon: on the Welsh shore between Newport and the Severn road crossings. Capacity: 1.36GW.

The projected costs range from £2.1bn to £21bn. PricewaterhouseCoopers is reporting on financing options.

Rare habitat

The estuary is designated as a Special Protection Area (SPA), under the European Union Birds Directive, in recognition of its internationally important overwintering bird populations.

Energy and Climate Change Secretary Ed Miliband said: "We have tough choices to make. Failing to act on climate change could see catastrophic effects on the environment and its wildlife, but the estuary itself is a protected environment, home to vulnerable species including birds and fish.

"We need to think about how to balance the value of this unique natural environment against the long-term threat of global climate change," Miliband concluded.

Under the Habitats laws a development can proceed if it is within the overriding public interest to do so, even if it may damage protected sites, but only if it can ensure that the appropriate compensatory measures to secure the coherence of the Natura 2000 network of sites and replace lost habitats before the project proceeds.

The study has considered this up to a point but come to no firm conclusion yet on whether it would be possible to deliver compensation on the scale required, calling it "a significant challenge".

The shortlisted schemes are based on relatively well understood hydroelectric technologies, with a mix of existing and new engineering structures.

The scope of the Strategic Environmental Assessment has also been published to ensure a detailed understanding.

> Severn Tidal Power Consultation