Severn tidal power shortlist finalised

The government yesterday published a shortlist of five proposals for harnessing the tidal power of the Severn estuary, which it hopes could eventually supply up to five per cent of the UK's electricity needs.

There are two tidal lagoon options and three barrage options on the shortlist, and the government confirmed that it could choose a combination of different projects – or none at all.

The government response to the first consultation, published yesterday, says the scheme has huge potential, but also warns that planning approval for the controversial projects is far from a foregone conclusion.

"Drawbacks include the cost of detailed feasibility work and the risk that a scheme might not be consented, impacts on the natural environment and on industries such as ports and fisheries that currently use the estuary, and the multibillion-pound construction cost with a long payback period," the report warns.

The schemes under consideration are a 0.625GW barrage at Beachley, costing £2.3bn; a 1.05GW Shoots barrage, costing £3.2bn; a larger 8.64GW Cardiff-Weston barrage, costing £20.9bn; or two 1.36GW lagoon proposals at Bridgewater Bay and Welsh grounds, costing £3.8bn and £4bn respectively.

The lagoons and Shoots Barrage proposals were backed by a Friends of the Earth consultation, which said they would have less of an impact on the local environment than a barrage.

Among the schemes omitted from the shortlist were a number of smaller innovative tidal technologies, which were considered to be too far from commercial viability. However, the government said it will continue to provide funding to support their development.

Also rejected were larger outer-barrage schemes considered too expensive.

Variants of the shortlisted options are constantly under consideration, the government said, a process called design optimisation.

In addition to the shortlist, the government set out a number of options for funding, including a market-priced revenue support mechanism, similar to the Renewables Obligation (RO) or a separate "Severn Obligation", as well as fixed-price support mechanisms, such as a feed-in tariff.

The government's initial analysis suggests that a large Cardiff-Weston barrage could not be supported under the existing RO in view of the volatility this would create for ROC prices and the resulting impact on other renewable investments. Smaller barrages or tidal lagoons do, however, have the potential to be accommodated within the current RO.

Next year, a second public consultation will take place on whether or not the government should support a Severn tidal project. Construction on any chosen scheme is envisaged to begin after 2015, with operation commencing after 2018.

Neil Crumpton, energy spokesperson for Friends of the Earth, said the government had rejected less-intrusive and financially risky ways of harnessing power from the Severn Estuary such as offshore lagoons and tidal reefs.

"Though we welcome the establishment of a feedback loop where these ongoing technologies could be introduced as they develop," he said.

Friends of the Earth says offshore lagoons could be constructed for about a third of the price outlined in the original consultation.

Offshore lagoons would still be relatively more expensive than the land-connected lagoons and barrage options shortlisted, but they would have less effect on the local environment, according to Crumpton.