Plans to build a barrage across the Severn Estuary could be back on the agenda after the UK Government confirmed it was open to working with affordable and environmentally friendly projects.
Harnessing the tidal power could provide 5% of the UK's energy needs.
Environmentalists have urged caution , amid fears over the scheme's potential to damage the natural habitat for wildlife in the area.
"We accept that the power of the Severn could well be used, but we'd like to see it done in a way that will minimise the impact on wildlife " says Katie-Jo Luxton, from RSPB Cymru.
MPs say developers "failed to address commercial and environmental concerns" in the barrage plan and the scheme's viability isn't proven.
Bristol Port attack barrage project, but unions champion the economic boost to South Wales.
The Prime Minister instructs ministers to explore the development of a hydroelectric barrage across the River Severn.