Note: Descriptions are shown in the official language in which they were submitted.
CA 02241686 1998-06-25
SPECIFICATION
MULTIPLE TIDAL PUMPED STORAGE POWER GENERATION ARRANGEMENT
AND METHOD OF CONSTRUCTING THE SAME AT TIDAL POWER SITE
This invention relates to a multiple tidal PumI)ed storaee Power
generation arrangement, free of sluices, harnessing both a pumped
storage power and a tidal power, and to a method of constructing the
same at a tidal bay site capable of tidal power generation.
Hitherto, a tidal power generation plant has been run using a
single basin at one bay, for e~r~mp1e, as in the Severn Barrage
Project,U.K. (General Report, Energy Paper Number 57, Dept. of
CA 02241686 1998-06-2~
-
multiplied by second power of the mean tide range, and even if the
size of a basin is made larger, the mean tide range at the barrage
site is sma11er, as a result of which the output energy is not so
much increased for that size enlargement.
It is a further problem that the mz~srirnum output of turbines is
determined by a m~rimum tide range occuring at spring tide, but the
output of the turbines at neap tide is reduced to about l/4 the
mz~imum output.
Still further problem consists in the troublesome manipulation
of sluices. For instance, at ebb tide generation mode, the
manipulation is repeated twice a day, wherein the sluices are opened
to fill flood tide to the basin every one power generation is
fini.~hed and the sluices are closed directly before ebb tide begins.
The sluices are not only laborious to manipulate, but also make the
mean tide range small and act to attenuate the output energy because
the sluices are closed in haste while the water level of the basin is
not fully elevated when the ebb tide begins. Moreover, the
construction cost of sluices is more expensive than that of barrages,
and consequently, it is desirable that sluices be dispensed with.
In order to avoid the foregoing problems, the invention is
designed to provide a multiple tidal pumped storage power generation
arrangement free of sluices by dividing a bay r~nging from its mouth
to its bottom into two or three watelw~y~, one of which is used for a
tideway and the other of which is used for sluice-free basins for
power generation. The basins are built each by enclosing a basin with
a barrage that extends along the tideway and a barrage that extends
CA 02241686 1998-06-2~
squarely to the tideway, and installing a caisson mounted with a
pump-turbine to the former barrage so as to face the tideway. One
half of the basins is for ebb tide power generation mode and the
other half of the basins is for flood tide power generation mode.
Accordingly, this inv~ ion is designed to provide a multiple tidal
pumped storage power generation arrangement keeping a natural tidal
range by constructing a power generation arrangement for a single
basin and ebb tide generation mode and then, a power generation
arrangement for a single basin and flood tide generation mode while
operating the previous power generation arrangement, or vice versa,
thus constructing power generation arrangements one after another in
sequence to ultimately complete the multiple tidal pumped storage
power arrangement composed of a plurality of power generation
arrangements and ~ttslinin~ a mzl~imum tidal energy.
According to one aspect, the present I nv~lltion resides in a
method of constructing a multiple tidal pumPed storage power
generation arrangement, which comprises dividing a bay site capable
of tidal power generation into at least two watel way~ one of which
is a tideway extending from a mouth to a bottom of the bay and the
other of which is a space for at least one series of basins for power
generation keeping a natural tidal range; surrolm-1ing each of the
basins with both barrages at the tideway side and at mutually
adjacent sides and inst~lling a caisson internally mounted with a
pump-turbine at the tideway side, the basins being grouped into at
least one basins operating at a single basin and ebb tide generation
mode and at least one basins operating at a single basin and flood
CA 02241686 1998-06-25
.. , ~
tide generation mode.
According to another aspect of this inv~ ioni a tidal pumped
storage power generation arrangement is providedj which cL~ JLises at
least one basins for a single basin and ebb tide generation mode and
at least one basins for a single basin and flood tide generation
mode, installed adjacent to one another so as to face a tideway of a
tidal bay site, wherein the basins are operated at nighttime in such
a manner that the water level of the former basins is elevated up to
a specified level which is higher than a m~rimum level at-spring tide
by nighttime electric power of grid, thus m~rimi~ing a water head of
the turbines and the water level of the latter basins is lowered to a
specified level which is lower than the datum level by ni~httime
electric power of grid, thus m~rimi7in~ a water head of the turbines,
whereas at daytime, both the basins perform tidal pumped storage power
generation by use of the water heads at an efflciency of 100% or
more, whereby a contilluous power generation is enabled at a m~imum
output of each turbine for 11 to 12 hours.
In a plerel~ed embodiment, the bay site is divided into two or .
three w~telw~y:~. The one waterway (an example of two watelway~) or
central w~telway (an example of three watelw2lys) is used for the
tideway to keep a natural tidal range. The rest of wat~l w~y~ is used
for a plurality of power generation arramgements each having a
relatively smail-scale output (e.g.,on the order of one million kW).
In dividing the bay site into watelways, first, for example, the
bottom of a bay is applied to one basin, which iS, in turn,
surrounded by barrages and a caisson mounted with a pump-turbine to
construct one tidal power generation arrangement. Then, a next basin
'
CA 02241686 1998-06-2~
is constructed likewise into a next tidal power generation
arrangement, while rl-nning the first tidal power generation
arrangement. Ultim~tely~ the division into the watelways: is completed
and a multiple tidal pumped storage power arrangement is thus
completed.
That is to say, a pump-turbine is mounted within the caisson and
installed to face the tideway, with its electric power line having
input and output connected to the land electric grid. When the water
level of the tideway becomes higher than the mean sea level, the
water level of the basin is elevated to a specified m~rimum level
(e.g., a mzl,rimum level at spring tide), irrespective of spring tide
and neap tide by pumping operation by the use of nighttime electric
power without using sluices. At daytime conventional operation for
ebb tide power generation is possible at a m~lrimum output even at
neap tide.
This is called a single basin and ebb tide pumped storage power
generation arrangement.
Next, a single basin and flood tide pumped storage power
generation arrangement will be constructed. A pump-turbine is
installed at a deeper place than the ebb tide power generation ~
arrangement since the the water level of the basin is used at a lower
level than the mean sea level. The ebb tide power generation
arrangement and the flood tide power generation arrangement are not
necessarily installed adjacent to each other, but the position
relation of the both may be chosen optionally.
The flood tide pumped storage power generation arrangement is
operated so that when the level of the tideway becomes lower than the
CA 02241686 1998-06-25
mean sea level, the basin level is lowered to a specified limit
which is lower than'the datum level by r1mnine the~pump by nighttime
electric power of the grid. The lowering degree depends on the depth
at which the pump-turbine is disposed, and consequently, the pump-
turbine is disposed at a deepest possible place (30 meter or less
beneath the mean sea level).
By combining the basin of the ebb tide pumped storage power
generation arrangement called "higher pond" and the basin of the
flood tide pumped storage power generation arr~ngement caliad "lower
pond", it is possible to generate, at daytime, electric power keeping
each m~ mum output continually for ll to 12 hours. Here, the water
levels of the higher pond and the lower pond are made sufficiently
higher and lower, respectively, than the natural tidal level by
nighttime pumping operation, so that the heads due to the turbines
a~e larger than natural heads, which results in an increase of
artificial mean tidal range and accordingly, a~l~inil~g a generating
efficiency of l007~ or more. The combin~tion of daytime tidal energy
portion (kWh) in addition to the pumped storage ener8y portion
enables to obtain an annual output (kWh) of'about two times the
purchased niEhttime energy (kWh). One reason why the generating
efflciency is impluved is that the pumps are operated at a .~m~11er
head (for example, when lowering the water~level of the lower pond at
nighttime, the water is evacuated from the pond to the sea with the
pump at a lower level than the mean sea level by talcing advantage of
the peLÇu~ ance that the ~m~11er is the head of the pump, the larger
the flow rate under the same shaft power condition).
In the ebb tide power ~generation arrangementi when the water
. ~ . '
CA 02241686 1998-06-2~
level of the tideway becomes higher than that of the higher pond at
nighttime when the pumps are not used, the rotary shafts of the
turbines are released to free rotation, instead of using sluices, to
assist sea water in refilling into the higher pond thereby to enable
to reduce the perchased nighttime power.
The preferred embodiments of this invention will be hereinafter
described in more detail with reference to the accompanying dl~willgs,
in which:
Fig. 1 is a dia~ tic plan view of a multiple tidal pumped
storage power plant constructed at a tidal bay site;
Fig. 2 is a transverse sectional view of the plant of Fig. 1
taken along 1~ line of Fig. 1 showing the relation between the
depth of the bay and the inst~ tion depth of the pump-turbines, and
the upper and lower limits of the water levels of respective basins
at ebb tide pumped storage power generation mode and at flood tide
pumped storage power generation mode, respectively;
Fig. 3 is a transverse sectional view taken along m-m line of
Fig. 1 showing the slope of the mean tidal range from the mouth to
the bottom of the bay.
Referring to Fig. 1, a bay A as a tidal power site faces the
ocean B and extends from a mouth Al-AZ of the bay to a bottom A3 of
the bay. The mean tidal range (the dirrerence between ebb tide and
flood tide through spring to neap) is gradually increased from the
mouth toward the bottom of the bay A in a slope of 34 to 35 as shown
in Fig. 3 relative to a datum horizontal line 33. The bay A is
divided into a tideway 1 extending at the bay shore side of Al to A3
CA 02241686 1998-06-2~
and a waterway 2 extending at the bay shore side of A2 to A3, where a
series of basins 4 to 9 for power generation are adapted to be built
in sequence thereby to l11tim~tely form a multiple tidal pumped
storage power generation arrangement 3.
Here, the basins 4, 8, 9 are used for ebb tide power generation
mode and the basins 5, 6, 7 are used for ~ood tide power generation
mode.
Each basin is enclosed by barrages 11 and the bay shore of A2-
A3, and the barrage 11 facing the tideway 1 has a caisson 12 mounted
with a pump-turbine 13.
In one ~x~mple of a bay A as shown in Fig. 2, its sea bottom
(dotted line) is shallow near the mouth of the bay and is deeper at
the middle place of the bay as shown at A4. A deep bay place that
has a depth of 30 meter or more from the mean sea level is not suited
for tidal power generation and is advantageously used for a tideway.
This is because the construction cost of barrages is proportional to
the second power of the depth. Taking the fact that a deep place of
the bay is not always its center place into accounti it is better to
make a n~luwest possible tideway 1 by linking deeper places of the
bay, which enables to allocate a greater area to the basins.
At flood tide power generation mode, it is desirable that the
pump-turbines 13 of the basins 5,6,7 be installed at a deeper
position 25 of within 30 meter below the mean sea level as shown in
Fig. 2, and thus it is possible to construct flood tide power
generation arrangements in series, insofar as a balance in the power
output (kW) between ebb tide and flood tide power generation modes is
eventually kept.
CA 02241686 1998-06-2~
The operation of the tidal pumped storage power generation
arrangement of the invention will be e~l~ined by way of example of
one higher pond (e.g.,4) and one lower pond (e.g.,5):
In the ebb tide power generation arrangement, the water level of
the basin 4 is, at nighttime, elevated to a m~imum specffled level
22 (for example, Z meter above the mean sea level 21) by pumping
operation irrespective of spring tide and neap tide, whereas at
daytime power is generated to produce a turbine power (kW) such that
the water level of the basin 4 may be changed from 22 to 21.
In the flood tide power generation arrangement, the water level
of the basin 5 is lowered to a minimum specified water level 23
(e.g.,2 X Z meter below the mean sea level 21) by pumping operation
at nighttime irrespective of spring tide and neap tide, whereas at
daytime, power is generated to produce such a turbine power (kW) that
the water level of the basin 5 may be changed from 23 to 21. Here,
the reference numeral 24 design~tes a datum depth, which is a depth
(Z meter) from the mean sea level 21 at a minimum water level at
spring tide.
As described above, the invention has advantages what follow:
1. Even when a plurality of tidal pumped storage power generation
arrangements are constructed in series, the provision of the tideway
extending from a mouth to bottom of a bay enables to keep a natural
tidal range. Consequently, it is possible to construct many
relatively small-sized tidal pumped storage power plants, with the
result that a m~rimum energy of the tidal power site can be
extracted.
CA 02241686 1998-06-2~
1 0
2. The basins 4 to 9 form each an independent tidal pumped storage
power plant constituting a pond (called here a higher pond or lower
pond) for pumped storage power generation coupled with the ocean
(tideway 1). VVhile rl-nning one tidal power plant after its
construction, it ispossible to undertake the construction of the next
power plant, thus constructing power plants one after another, and
consequently, it becomes possible to make a long-term construction
plan. This enables to secure ample annual budgets.
3. By taking advantage of cheap nighttime electric power of the grid,
the water level of the higher ponds is elevated up to a specified
m~imum limit for the ebb tide generation mode and the water level of
the lower ponds is lowered to a specified minimum limit for the flood
tide generatian mode irrespective of spring tide and neap tide. As a
consequence, it is possible to generate power every day at daytime
for 11 to 12 hours at each m~imum power output by availing
themselves of a time difference of 6.2 hours between the ebb tide
generation phase and the flood tide generation phase (one tide cycle
is 12.4 hours) .
4. Since the natural tidal range is amplified by operating the
pumps at nighttime, the efficiency of the pumped storage power
generation output portion is more than 100% even if the mech~niczll
efficiency is estimated to be 70%, seeing that the output energy
(kWh) is proportional to the second power the mean tidal range. In
1ition to this, a daytime output energy portion by tidal power
generation is obtained. An overall output energy obtained from one
basin is thus about 2 times that of the existing single basin type
tidal power plant, which contributes to the reduction in the
CA 02241686 1998-06-25
construction cost per kWh.
5. No sluices are used except for locks for ships, which reduces the
construction cost. Even where any sluice is necessitated, the pump-
turbines will do merely by releasing their rotary shafts to a free
rotation state, since their conduit tubes serve as a Venturi tube
type sluice.
