The Severn Estuary has seen countless proposals for tidal barrage technology dating back as far as 1849. Barrages act as a sort of dam across a bay entrance, collecting tidal energy from low-head turbines. The most recent plans for a 8,640 MW barrage were shot down in 2010 after a two year feasiblity study deemed that there was "no strategic case" for building the project.
This has set the stage for the Swansea Bay Tidal Lagoon, what could be the first bi-directional tidal lagoon generator. The UK firm, Tidal Lagoon Power (TLP), is just beginning assessments of the bay's physical characteristics and expects to be grid connected by 2017. This 250 MW project is composed of a sand core seawall and low-head turbines mounted in concrete turbine housing, in a design yet to be determined.