Argument: Tidal power generates little return on investment so is unviable
Lewis Page. "Tidal power project fails to start on schedule". The Register. 23rd Aug. 2007 - There's also a question of costs. MCT reckons the Strangford Lough SeaGen project will cost £8.5m and is rated for 1 megawatt - one would hope this is average rather than maximum output. Consumers pay about 10p per kilowatt-hour for their juice in the UK, but some of that reflects transmission losses and costs, not to mention profit margins.
Being generous and saying that a generation facility might get 5p of revenue per kilowatt hour at the point of grid connection, SeaGen might make an average of £50 per hour - if indeed the 1MW rating is average. If that figure is a maximum it might rake in £20/hour tops over time.
At the optimistic rate, assuming it costs absolutely nothing to run - obviously not true - it will have only just paid for itself when it wears out after its predicted life of 20 years.
Or, to put it another way, it makes no commercial sense at all, barring a massive electricity price hike or equivalent government subsidy (paid by taxpayers - so a targeted price hike on those whose tax bills are a large part of their income - you and me, that is).
Of course, SeaGen is a pilot project, and the figures can be expected to improve in future - but it's already had the benefit of an earlier pilot, the £3.4m, 300kW SeaFlow off North Devon.