On 18/10/2010 12:40, Peter Scott wrote:

I am sure I have heard knowledgable people talking about dams. The
message was that we don't have enough flow in most of our rivers to make
hydro dams viable. Tidal can be used where there is a sufficient tidal
rise and fall, but it seems we haven't many places for that either. The
Rance barrage in Brittany works fine but the tidal range there is
amazing to watch. Can't give a figure off-hand but I visited a few weeks
ago and didn't believe that the sea would rise high enough to cover the
tidal marks on the rock outcrops. The Severn and Morecombe Bay are OK
but the length of barrage in each case makes it horribly expensive.


Average tidal range is 8 metres. The Severn has slightly more. You may
have hit springs, which are over 12 metres.

Of course it doesn't run 24 hours. It's nicely predictable though, and
I guess a few dozen pumped storage schemes could buffer up the power for
slack tides. So long as we don't mind filling every valley in the
Brecons with water twice a day.

Andy