Due to its huge tidal range, the Severn Estuary is very suitable for power generation. 
The most eco-friendly way to use tides is to place free-standing turbines (pictured) around the coast (to pre-distribute the generated electricity and to minimise the downtime). But there’s no quick financial return from such a widely dispersed investment.
Big business prefers a monstrous barrage across the Severn Estuary – ignoring the damage to the marine environment and its need for more fuel-fired power stations to cover its 30-40% downtime. That’s a definite ‘no-no’.
More enlightened business interests are promoting eco-friendly tidal lagoons with the first in Swansea Bay. A second tidal lagoon is proposed between Cardiff and Newport as a follow up and, if the Swansea lagoon is up to expectations, I anticipate that I will support it.
Dr John Cox blogs 