Tidal Power: A Mystery

Earlier in the month on a thread about hydrogen, somebody raised the topic of tidal energy and I said we’d cover that in a specific post.  I voiced my perennial puzzlement that no material progress has been made – anywhere in the world – towards effectively generating electricity from tidal power.  A breakthrough on this would be important for the UK particularly, as we have some of the greatest tidal ranges anywhere on the planet.  Why would we expect it to be a good energy source?  And what’s gone wrong?  Here’s some background.

The theory:  Tidal energy has been harnessed, for hundreds of years (there’s an old tidal mill in Bow, East London).  Obviously, vast quantities of “free” energy are sloshing around when tides rise and fall tens of feet, regularly and reliably.  But can they be captured efficiently, and used to generate electricity – even if in a rather peaky profile?  You’d think so: there’s not much that isn’t known about tidal flows; and in the maritime nation that is the UK, we have longstanding expertise in marine engineering, civils, turbines and, since the 1960s, offshore installations.  What could be missing?

The practice:   Well, since tidal power schemes have been trialled in a stunning variety of different specific designs for 15 years or more, quite evidently a good design is what’s missing.   Quite a lot of money, both public and private, has been thrown at this – much of it in benighted Wales, where anyone offering schemes that might generate jobs is pretty much given carte blanche, however dubious their credentials – to no practical avail.  Unless, that is, you consider it worthwhile to be able to rule out certain apparently prospective designs that have been tested and failed.

The scheme that made the most waves (if you’ll excuse the idiom) is probably the Swansea Bay Tidal Lagoon.  The physics looked simple enough, and it was very energetically pushed by its promoter, one Mark Shorrock.  Choosing my words carefully, let’s say that Shorrock is a showman and somehow persuaded a lot of folks in South Wales, not only to sign up for his elaborate PR schemes but to pitch in with their own money – from small punters putting in a few hundreds, to big players putting in millions.  Shorrock spent the lot, tens of millions in total, much of it going to, errr, himself by way of “management fees”.  If it had gone ahead, his scheme was structured financially to yield him personally a vast sum upon completion – not completion of the project but of its financing package.  

Anyhow, after eight years or so of constantly rising costs he’d still failed to get several of the big regulatory approvals needed and the government called time on his application for public money.  (He now has a very large house in Gloucester … and peddles solar panels in Vietnam.)

He never satisfied the marine authorities on critical matters like silting-up, and disturbing the flows (& wildlife) of the Severn Estuary.  He also came unstuck on wild claims like: if you have enough tidal lagoons situated at key points around the UK coast (he was “planning” five of his own), the regional variations in tidal peaks and troughs all balance themselves out and you get baseload electricity.  This was demonstrated to be, errr, Not True.

Other higher-tech schemes, like this whacky one, have shaken themselves to pieces when trialled at even small scale, and have been abandoned (after many millions of public money have been spent, and Welsh dreams shattered once again).

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As a non-engineer I am bemused because, well, it all seems so logical.  The raw energy is there, alright.  Maybe we do simply await that really cunning design that squares all the circles.

Does anyone have a sound,  knock-down, science-and-engineering argument as to why tidal power is a chimera?   

ND