"The six lagoons - four in Wales and one each in Somerset and Cumbria
- will capture incoming and outgoing tides behind giant sea walls, and use the weight of the water to power turbines. The cost of generating power from the Swansea project will be very expensive, but the firm behind the plan says subsequent lagoons will be able to produce electricity much more cheaply. It says the series of six lagoons could generate 8% of the UK's electricity for an investment of £12bn."
"Tidal Lagoon Power is in negotiations with the government over how much it can charge for its power. It wants £168 per MWh hour for electricity in Swansea, reducing to £90-£95 per MWh for power from a second, more efficient lagoon in Cardiff. The £90 figure compares favourably with the £92.50 price for power from the planned Hinkley nuclear station, especially as the lagoon is designed to last 120 years - at a much lower risk than nuclear."
The bit that caught my notice was the comment on the radio that they would cost about as much as a nuke.(Not sure if that means each, or all together, or just for the electricity rather than the capital).
So why not build a nuke. At least they produce power continuously, not intermittently, and don't require an equivalent amount of generating power just sitting there for when the tides are slack!