Note: Descriptions are shown in the official language in which they were submitted.
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GOKHMAN TIDAL POWER PLANT FOR LAGOON
BACKGROUND OF THE INVENTION
Tidal power plants are the most reliable sourss of clean energy. There are two
types
of tidal power plants. The first type is the tidal power plant to be
constructed on
the bays and estuaries like The Bay of Fundy, Severn Lake, etc. The second
type is
the tidal power plant to be constructed on the lagoons like Swansea Lagoon.
The
are two tidal plants of the first type constructed in 1966 in France, Rance
Tidal
Power Station ; and in 2011 constructed in South Korea, Sihwa Lake Tidal Power
Station. There are no already constructed of the second type. The first tidal
plant
for lagoon is being designed in U.K for Swansea Lagoon. The present invention
is the first effort to propose economically effective concept for the design
of power
plants for lagoons.
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DESCRIPTION OF PRIOR ART
This invention relates to tidal power plants for lagoons.
As far as it is known to me there are no tidal power plants built on lagoons,
and
there is the only one conceptual design of a tidal power plant for Swansea
Lagoon
in U.K. which was developed by Inazin.
As it is well known, lagoons are wide and shallow, therefore it is impossible
to design
for any lagoon an economically feasible tidal plant with a barrage comprising
a power
house between two different points on the lagoon shore. So the Inazin
conceptual
design is based on the idea of constructing an artificial basin separated from
the rest
of the lagoon by a barrage that is a vertical wall erected along a closed line
which
in plan approximates a circle with diameter, Du, = 3, 5km, that touches the
lagoon
shore at a point with elevation, Z 0. The power house in the Inazin design is
an
integral part of the barrage and is located at the lowest part of the barrage.
The
cylindrical wall forming the basin (basin wall) is built from concrete and has
the
height variating from 4 meters at the shore to 8 meters at the deepest part in
order
to operate with the tide having an amplitude, At = 4m. The Inazin tidal plant
equipped with 15 bidirectional turbines with runner diameter, Dt = 6m,
annually
generates 425.17GWh. So the lagoon tidal power plant developed by Inazin is
also
not economically very attractive, because of the high cost of the basin wall
and small
annual energy output.
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SUMMARY OF THE INVENTION
The invention is tidal power plant for lagoon. It has two versions.
The first version of the invention has a head reservoir located either on the
lagoon
shore, or on the lagoon bed along the shore edge, a power house separately
located
on the lagoon bed, a flow distributor delivering the water from the head
reservoir to
the power house turbines during power generation and at the end of flood
delivering
the water from lagoon to the head reservoir to fill it up.The power house is
located
at the dip place of the lagoon providing the requirement that the upper part
of the
hydro-turbine draft tube i.e. it is under water at the lowest level of the
ebb.
The second version of the invention is different from the first one by the
presence
of the tail reservoir. In this version the power house is located inside the
tail reser-
voir. The cylindrical wall surrounding the tail reservoir keeps the water
level in it
significantly lower than the water level in lagoon during the power
generation. This
cylindrical wall has vertical sluices emptying the tail reservoir at the end
of ebb.
Due to the fact that the construction cost of the first version of invention
is much
smaller than of artificial basin in well known Inazin design it can have for
much
smaller cost the larger area. As the result with the same power equipment it
annually
generates on 45% more energy than Inazin design.
The construction cost of the second version is higher than the first if they
have the
same power equipment, however due to the higher head during power generation
the second version annually generates on 30% more than the first version.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic plan view of Gokhman tidal power plant first version
which
has a head reservoir, a flow distributor connected with head reservoir by
means of
open channel, a power house, and common intake delivering the water from the
distributor to the power house during power generation.
FIG. 2 is a schematic elevation view, in cross-section, of a head reservoir.
FIG. 3 is a schematic plan view of a flow distributor.
FIG. 4 is a schematic side elevation view, partially in cross-section, of a
the power
house.
FIG. 5 is a schematic plan view of Gokhman tidal power plant second version
which
as the first version, presented in FIG 1, has a head reservoir, a flow
distributor
connected with head reservoir by means of open channel, a power house, and com-
mon intake delivering the water from the distributor to the power house during
power generation. The difference between the second and the first versions is
in the
presence of tail reservoir.
FIG. 6 is a schematic side elevation view, partially in cross-section, of a
power house
of Gokhman tidal power plant second version The difference between the second
version and the first version on the FIG 4 is only in the presence of tail
reservoir.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
The first version of Gokhman tidal power plant for lagoon
The first version discloses a Lagoon tidal power plant without either natural
or
artificial basin, but with an artificial head reservoir constructed on the
lagoon shore
at an available place. It also has a separate power house equipped with Bulb
turbines
and located inside the lagoon at some place providing the upper parts of the
turbine
draft tubes to be below the lowest water level at the ebb end. In addition to
that,
the first version of tidal power plant has a flow distributor located at the
lagoon
shore and connected with head reservoir by means of an open channel. It also
has a
common intake connecting the flow distributor with the power house bulb
turbines.
The flow distributor has gates which are opened at the very end of the flood
to
admit water from the lagoon to fill the upper reservoir. Said power plant is a
one-
way tidal power plant working during ebb and the flood and getting water from
the
head reservoir via the channel, the flow distributor, and the common intake.
The
lagoon itself presents the tail reservoir for this version of of the plant.
The first version of the invention will now be described by way of example and
with
reference to the accompanying drawings in which:
FIG. 1 is a schematic plan view of Gokhman tidal power plant first version
which
has a head reservoir, a flow distributor connected with head reservoir by
means of
open channel, a power house, and common intake delivering the water from the
distributor to the power house during power generation.
FIG. 2 is a schematic elevation view, in cross-section, of a head reservoir.
FIG. 3 is a schematic plan view of a flow distributor.
FIG. 4 is a schematic side elevation view, partially in cross-section, of a
the power
house.
Referring now to FIG. 1, a schematic plan view of Gokhman tidal power plant
for
lagoon first version which has a head reservoir, a flow distributor connected
with
head reservoir by means of open channel, a power house, and common intake
deliv-
ering the water from the distributor to the power house during power
generation.
The tidal plant comprises a head reservoir 1 located on the lagoon shore 2, an
open
channel 4, a flow distributor 5, common intake 6, and a power house 7 located
on
the bed of the lagoon 3. During the very end of the flood the flow distributor
5
fills the head reservoir 1 with the water from the lagoon 3 through its gates
via the
channel 4. The flow distributor 5 also supplies the power house 7 during the
ebb
and flood power generations with the water from the head reservoir 1 via the
open
channel 4 and the common intake 6.
Referring now to FIG. 2, a schematic elevation view in cross-section, of a
head reser-
voir of the first version of Gokhman tidal plant. The head reservoir is
constructed
on the lagoon shore dry land 1 with elevation, VZdi. As can be seen in FIG. 2
the
head reservoir is formed with a flat bottom 3 having elevation VZhrb and
cylindrical
side wall 4. The head reservoir is open at the top and the top elevation of
its side
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wall 4 is V47.1. The water 2 in the head reservoir is always below VZhrt.
FIG. 2 shows the head reservoir for the case:
Zhrb < Zdl < Zhrt (1)
The current head of Gokhman tidal plant first version is determined as:
H = Zh AtideSin[Ct(T TO)] (2)
where:
T is the time in seconds,
Zh = Zh(T) is the current water level in the head reservoir,
Atide is the tide level amplitude, and
Ct = 7r/21,600
It is clear from equation (2) that in order for the head reservoir to be
filled to the
lagoon highest water level Zhrt in (1) must be equal to Atide . The value of
Zhrh in
(1) has to be equal to minimum water level in the head reservoir, (Zh),t,
required
by the tidal plant operation.
So the equation (1) can be rewritten as:
(ZOntin < Zdl < Atide (3)
The equation describing the change of the water level in the head reservoir,
Z11 as
the function of time is the well known nonlinear ordinary differential
equation of the
first order:
dzh
dT Ah (4)
where:
T is the current time in seconds,
= 4(T) is the water level in the head reservoir,
Q = Q(T) is the flow through the power house, and
Ah is the head reservoir horizontal cross-section area.
As can be seen from equation (4) with bigger values of Ah the values of dZhIdT
are
smaller and, therefore the value of Zh is higher for the same function Q =
Q(T).
Now it is clear from equation (4) that the power plant head, H, is higher with
nigher
values of Ah for the same function Q = Q(T). Consequently the decrease of head
in
Gokhman tidal power plant for lagoon first version (Gokhman tidal plant)
during
operation strongly depends on the head reservoir area.
The computations conducted by the applicant for the comparison of the present
invention with Inazin tidal power plant showed the following results. The
power
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houses of both plants are equipped with frequency converters permitting to the
turbines of both plants to work at optimal operating regimes.
Inazin tidal plant.
Input data:
The diameter of the basin wall, Dbu, = 3.46km
The area inside the basin wall, Alm, = 9.37km2.
The number of bidirectional turbines, Nt = 15.
The turbine runner diameter, Dt = 6m.
The optimal discharge capacity in ebb direction, (Qii)op.,= 2.031m3/sec.
The optimal discharge capacity in flood direction, (Qii) op. f = 2.031M3 /sec.
The peak efficiency in ebb direction, rime = 0.95.
The peak efficiency in flood direction, np.f = 0.80.
Output data:
The minimum water level in the basin, (Zb),,in, = ¨1.69m
The maximum head Hma, = 5.38m
The annual energy output, Eõ= 425.17GWlir.
Gokhman tidal plant first version.
Input data:
The diameter of the head reservoir, DI, = 6.92km
The area of the head reservoir, Ah = 37.48km2.
The number of one-directional bulb turbines, Nt = 15.
The turbine runner diameter, Dt = 6m.
The optimal discharge capacity, (Qii)op = 2.031m3/sec
The peak efficiency, ?II, = 0.95
Output data:
The minimum water level in the head reservoir, (Zh )Tnin = 2.31m
The maximum head 1-1,-õ, = 7.087n
The annual energy output, Eõ = 646.66GWhr
This comparison between Gokhman and Inazin tidal plants for lagoon shows that
with Dh = 2131hzu Gokhman tidal plant generate annually 52% more energy than
Inazin tidal plant. It is also clear that if the Swansea lagoon shore dry land
elevation,
Zdi, satisfies equation (1) the head reservoir for Gokhman tidal plant will be
less
expensive than the Inazin concrete basin. Indeed, in the case of Zdi =
(Zh)rnin
Gokhman head reservoir can be made of earth round wall with height of 1.69
meters
and the diameter of 6,920 meters versus Inazin basin concrete wall with the
diameter
of 3,460 meters and the average height of 6 meters. It easy to see that the
surface
area of Inazin basin wall will be 50% bigger than Gokhman head reservoir wall.
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Generally speaking the head reservoir of Gokhman tidal plant can be built on
dry
land if the geography and topography of the lagoon shore allow this
construction.
And besides equation (3) there are two other substantially different cases:
Z dl < (Z11)111in (5)
The land available for the head reservoir is bellow the water in the head
reservoir
at required minimum elevation. In this case no land excavation is required and
the
head reservoir has to be constructed by surrounding its future bottom with the
wall
of the appropriate hight.
Atide < Zdl (6)
The land available for the head reservoir above than of the water in the head
reservoir
at the flood highest level. In this case the head reservoir has to be
constructed by
land excavation.
There are also other environmental considerations prohibiting the construction
of
the single head reservoir on the lagoon shore dry land. In some cases the head
reservoir can be formed from several reservoirs connected with water ways. In
some
cases the head reservoir parts can be constructed on the lagoon bed along the
lagoon
brim. It is clear that these head reservoir parts must be separated from the
lagoon
by concrete walls.
Referring now to FIG. 3, a schematic plan view of a flow distributor. The flow
distributor is constructed along the brim 9 of the lagoon 8. The flow
distributor is
formed with the vertical wall I and the flat rectangular bottom 2 and is open
at
the top. The frontal part 6 of the wall I facing the lagoon 8 is fitted with
vertical
sluices 6. The lower brims of the sluices 6 are located at the level below the
lagoon
water at the highest level, A. The rear part of the wall 1 facing the head
reservoir
located at the lagoon shore 7 has the opening for the channel 5 connecting the
flow
distributor with the head reservoir. At the flat bottom 2 there is an opening
3 for
the common intake 4 delivering the water to the power house.
Referring now to FIG. 4, a schematic side elevation view, partially in cross-
section,
of a power house. The power house 1 is a separate structure constructed on the
lagoon bed 2 at the location providing that the elevation of the draft tube
exit 5
top, Z dtet, is lower than the minimum level of the water 3 in the lagoon,
Zimin. The
maximum level of the water 3 in the lagoon is Zintax. The power house 1
turbines
receive the water from the common intake 4.
The second version of Gokhman tidal power plant for lagoon.
The second version is different from the first version only by comprising an
artificial
tail reservoir built around the power house.
The second version of the invention will now be described by way of example
and
with reference to the accompanying drawings in which:
FIG. 5 is a schematic plan view of Gokhman tidal power plant second version
which
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=
as the first version, presented in FIG. 1, has a head reservoir, a flow
distributor
connected with head reservoir by means of open channel, a power house, and com-
mon intake delivering the water from the distributor to the power house during
power generation. The difference between the second and the first versions is
in the
presence of tail reservoir.
FIG. 2 is a schematic elevation view, in cross-section, of a head reservoir.
The head
reservoir of the second version is identical to the head reservoir of the
first version.
FIG. 3 is a schematic plan view of a flow distributor. The flow distributor of
the
second version is identical to the flow distributor of the first version.
FIG. 6 is a schematic side elevation view, partially in cross-section, of a
power
house of Gokhman tidal power plant second version The difference between the
second version and the first version on the FIG. 4 is only in the presence of
tail
reservoir.
Referring now to FIG. 5, a schematic plan view of Gokhman tidal power plant
for
lagoon second version which has a head reservoir, a flow distributor connected
with
head reservoir by means of open channel, a power house, and common intake
deliv-
ering the water from the distributor to the power house during power
generation.
The tidal plant comprises a head reservoir 1 located on lagoon shore 2, an
open
channel 4, a flow distributor 5, common intake 6, and a power house 7 located
on
the the bed of the lagoon 3. During the very end of the flood the flow
distributor
fills the head reservoir 1 with the water from the lagoon 3 through its gates
via
the channel 4. The flow distributor 5 also supplies the power house 7 during
the
ebb and flood power generation with the water from the head reservoir 1 via
the
open channel 4 and the common intake 6. The power plant also comprises the
tail
reservoir 8 formed by the cylindrical wall 9. The power house 7 is located
inside the
tail reservoir 8 and is facing sluices 10 in the wall 9. The sluices 9 are
emptying the
tail reservoir 8 at the very end of the ebb and bring the water level in the
reservoir
8 to the lowest tide level.
Referring now to FIG. 6, a schematic side elevation view, partially in cross-
section,
of tail reservoir with power house of Gokhman tidal power plant for lagoon
second
version. The tail reservoir 3 is constructed on the lagoon bed 1 and is formed
by the
cylindrical wall 6. The elevation of the wall 6 top Ztrtot is higher than the
maximum
level of the water 7 in the lagoon VZimax. The power house 2 is a separate
structure
constructed on the lagoon bed 1 inside the tail reservoir 3 at the location
providing
that the elevation of the draft tube exit 5 top, Zdtet, is lower than the
minimum
level of the water in the lagoon 7, VZirnin. .The power house 2 turbines
receive the
water from the common intake 4. The wall 6 has vertical sluices 8 facing the
exit
draft tube exit 5. The sluices 8 are emptying the tail reservoir at the end of
ebb. As
the result the maximum level of the water 7 in the lagoon, VZ/niax, is
significantly
higher than the maximum level of the water in the tail reservoir 3, VZtrmax=
The current head of Gokhman tidal plant second version is determined as:
H = Zh ¨ Zt (7)
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where:
Zh is the water level in the head reservoir described by equation (4), and
Zt is the water level in the tail reservoir
The water level in the tail reservoir is described by the following equation:
dZ t Q
(8)
dT At
where:
Zt = Z(T) is the water level in the tail reservoir
Q = Q(T) is the flow through the power house, and
At is the tail reservoir horizontal cross-section area
So using equations (4), (7), and (8) one is getting the differential equation
for current
head, H, in the Gokhinan tidal plant second version:
dH
dT A (9)
where:
A, = AhAt/(Ah + At) is the effective power plant reservoirs area
Let
Qi ND(Q11)0p (10)
where:
Nu is the number of units in the power house,
Dt is the turbine diameter runner diameter, and
(Qii)op is the unit flow at optimum operating regime
=
Then the formula for Q:
Q = Q (11)
and from (9) and (10):
dH-QiH 5
¨dT (12)
A,
The integral of equation (11) gives the equation for H in the Gokhman tidal
plant
second version:
H = (BT + H8.5)2 (13)
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where:
B = ¨Q1/(2,4e) and
Ho = H(T0)
The equation (13) enables the analytical computation of the annual energy
output
for the Gokhinan tidal plant second version. For the same power equipment and
the
head reservoir as for Gokhman tidal plant first version the second version
annual
energy output, Ea, = 842.69GWhr, or 30% higher.
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