On Wed, 12 Sep 2007 21:11:09 -0400, Ned Simmons
wrote:

On Wed, 12 Sep 2007 11:31:29 -0500, "Pete C."
wrote:

Ed Huntress wrote:

"Pete C." wrote in message


The tidal generation I'm referring to involves no dams and no waves, it
is based on solidly anchored buoys. When the tidal level lowers the buoy
anchor cable retracts into the buoy to remain tight to the ocean floor.
When the tide comes in the buoyancy of the buoy produces tremendous
tension on the anchor cable which is used to spin the generator as the
buoy slowly rises (and the anchor cable extends) until the tide maxes
out. There were some recent innovations in this design that simplified
it and improved efficiency.

At any rate, a low profile buoy bobbing up and down with the tide has
extremely low environmental impact and there is a massive amount of
available energy at high densities waiting to be captured.

That certainly sounds interesting, and it sounds extremely simple. Why don't
we have them now?

'Cause we're stupid???


I think there's a bit more to it than that. Here on the Gulf of Maine
we're probably positioned better than the vast majority of the rest of
the world to take advantage of such a scheme - tides of approx 10 ft
amplitude, deep water close to shore and only rare tropical storms.
With two daily tides there's about 20 ft of rise available per day. In
our house we use a modest 10 kwh of electricity per day which equals
2.7 x 10^7 ft*lb. Divide by 20 ft and you need 680 tons of force to
generate that much power. That translates to buoy of 22000 ft^3. If
the water's deep enough, that's a buoy 100 ft tall x 17 ft in
diameter.

Another way to look at it is the displacement of one of the Aegis
destroyers, built in the next town, would be enough to power about 4
small homes.

If the tides are the more typical 2 or 3 feet, 100 foot deep water is
far from shore and hurricanes are a regular occurrence, the problems
are compounded

Some times in the 1960's there was a Maine state referendum to build a
tidal powered power station. Was all the local newspapers talked about
for nearly a month.

There were hordes of people ranging from lobster fishermen to collage
professors arguing pros and cons for weeks.

The motion was defeated and my impression, as an outsider, was that
whether tidal power is really practical, or not, is a far from simple
question.


Bruce in Bangkok
(brucepaigeATgmailDOTcom)