The Marietta journal. (Marietta, Ga.) 1918-1944, 1921-04-14
HUGE TIDAL-PowER PROJECT.


Since the mechanical potency of
had of water first was known, en-
a;neers have gazed with rovetous eyes
1non the almost infinite energy of the
+;des. and schemes of all degrees of
nracticibility have been proposed for
tbe salvage of a modicum of that
Wasted power for the work Of civili-
nation. Most Of these rather fanciful
suggestions have been unable to sur
vive the test of practical mechanics,
and the whole idea has remained in.
the comfortable but unprogressive
stage of development of the fut-
ure." From this category, however,
i now appears to have been suddenly
removed, by the announcement, from
no less authoritive body than the
British ministry of transport, of re-
markably comprehensive plans for an
enormous tidal-power plant on the
estuary of the Severn River, between
England and Wales.
The Severn project calls for a
usable output Of 100000 hip. continu-
ously for 20 hour day, requiring the
installation Of two complete plants,
with the stupendous total rating of
more than 10000 hp. It is the ar
rangement Of these two separate pow
er plants for operative action that
constitutes the ingenious feature Of
the plan.
The first work to be undertaken
would be the construction of rein
forced concrete dam extending lat
orally from each shore as far as the
central channel, and then turning up
stream along its sides and terminating
in lock, large enough to accommodate
any vessel. In the lateral parts Of
this wall it is the intention to hang
automatic sluice gates, opening in
ward when the tide presses against
them, and then closing to prevent the
escape of the impounded water.
Built into the parts Of the dam par
alleling the channel will be the power
plant itself, equipped with a huge
battery of vertical mixed-flow tur-
bines, 10 feet in diameter, the chan
mel serving as their tailrace. These
will have working period Of seven
hours, beginning with 5-foot head
soon after the tide begins to ebb,
reaching a minimum 30-foot head in
three and half hours, with a posi-
BILE drop of 10 feet in one hour, and
then diminishing until there is FIVE
hour period of no operation at all.
With this changing head, the tur
bine speed would vary between 40
and 80 r. p. m. Direct-current gen.
orators of separately excited type
will be driven through helical caring
at 800 to 500 r. p. M, and will de-
velop constant voltage of SIS, with
a varying current output controlled
either automatically or by an atten-
dant. The current will be used to
drive large rotary converters, deliv-
ring alternating current at $50 volts,
and this will be stepped up by trans
formers to 10000 volts for transmits
sion. Not less than 100000 hp, will
be the maximum output of this plant.
Ten miles from this huge installa-
ton is the proposed location Of the
secondary plant, of over 5OO,OO-hp.
maximum capacity. 1t is on the bank
of the river Wye, Severn tributary,
near Tintern Abbey, and its main
feature is concrete dam. across a
neighboring valley, forming gigan-
tic storage reservoir at considerable
elevation above the river mouth. Be-
tween this artificial lake and the Wye,
a tunnel Of 40 feet diameter is to be
driven through solid rock for more
than mile. The plant equipment,
as planned, consists of sbank OF
13,000-kw. acknowledgements mot
ors, of type operatable also as gen.
orators. Of these machines, 80 per
cent will be of the induction type and
the remaining 10 per cent synchro-
nous. They will operate at speed
of 375 r. p. M, at 1900 volts pres
sure.
This enormous group of electrical
machines will absorb all the current
the primary plant generates in excess
of the first 100000 hp., which will be
distributed for industrial purposes.
Thus at the peak Of the tidal head,
when the estuary plant is producing
100000 hp. or more, the powerful
motors of the secondary plant on the
Wye will be running to full capacity.
Paul H. Woodruff, in the Popular
Mechanics Magazine.