We predict annual electrical output of a "Cardiff-Weston" barrage to be 20 terrawatt-hours. The oil-equivalent of this output therefore corresponds to our very own, almost onshore oilfield producing 12.66M barrels per annum, or in more industry-conventional parlance an average of some 34,680 barrels/day.
Since the cost of a barrel of oil may now be likened to the length of a piece of string, converting the annual value of this oilfield into monetary terms is likely to prove as contentious as the cost of the barrage.
But if $120 is used, together with a 2:1 $/£ ratio, the answer is £1.52bn in perpetuity plus inflation – as long as the turbines continue to turn and the moon goes round.
Perhaps worth noting that "today's" annual income from that many electrical units corresponds to a unit value of 7.6p, whereas renewable energy is currently fetching up to 50% more than this thanks to fuel prices – an escalator which relates to the cost of shipping, refining and distributing the oil, none of which would apply to the oilfield lying off the coasts of Somerset and South Glamorgan.
Is the predicted cost of the barrage really a financial burden at £1,500 to £2,000 per kilowatt (in current terms) for a return which shows no sign of following house prices?
TOM SHAW, Shawate, Bath BA3 4DN, email@example.com