For maximum power generation and efficency you need a good volume, a steady head of pressure over the longest possible time and not just high velocity flow - plenty of electrical analogies here. For this you need to use the barrier method. [Linked Image]

Used very successfully at St Malo in northwest France. I remember the place well from my days as a geology student. Our lecturer, the late and much lamented Stuart McKerrow was a superb fellow, ex-Royal Navy with tales of daring do off Alderney in WW2 and a favoured last resting place for good whisky. Our Brittany field trip started with some coastal rock exposures that could only be reached at low tide and our intrepid ex-matelot was detailed to schedule this part of the visit being familiar with tide tables etc. As it turned out it happened to be the first stop of a memorable week.

Imagine our surprise, as they say, when our small convoy of Ford Transit vans is brought to a halt line astern in a narrow French lane by an expanse of seawater. The outcrops are flooded – how could Her Majesty’s finest ex-serving officer of the Fleet have got it wrong? It soon became clear that the outcrops were on the inside of the St Malo tidal barrage and that, in producing power on both the ebb and flow tides, the “tides” inside the barrier were 90° out of phase of the real tides on the sea side of the barrier. Much healthy ribbing ensued and the first stop was abandoned.

For good tidal power you need a site of enhanced tidal range and funnel shaped estuaries where many tidal flows come together are favoured. In the UK, the Bristol Channel has the highest tidal range – it is host upstream to the famous Severn Bore. Studies have been conducted into the feasibility of a tidal power station here. The Bay of Fundy, between Nova Scotia and New Brunswick in Canada has the highest tides in the world and can reach a range of 16m (52½’ for Paul [Linked Image] ) . It would make an excellent tidal power site but like all these things, including wind turbines, there are environmental issues.

[This message has been edited by Hutch (edited 04-19-2005).]