Note: Descriptions are shown in the official language in which they were submitted.
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Thi6 is a divisional of Canadian Application Serial
No. 284,887 filed August 17, 1977.
BACKGROUND TO THE INVENIION
This invention relates to devices for extracting power
from wave energ~ and more particularly, but not exclusively,
wave energy from sea waves.
In one kno~n device for utilising wave energy invented
by Yoshio Masuda and described in Briti6h Patent Specification
No. 1~014,196, a working gas in a cha~ber is caused to flow
through a turbine positioned above the chamber by the
oscillation of a column of water in the chamber, the chamber
being defined by a buoy device. Such devices have so far
been used for applications requiring relatively low power
output~ and the present invention is more particularly
concerned with applications for deriving relativel~ larger
amounts of power from wave energy.
SUMMARY OF THE INVENTION
Accordi~g to the present invention there is provided
a device for extr-cting energg from uaves on a liquid upon
which the device is adapted to float, comprising
(a) a plurality of chambers, each chamber baving,
(i) port means for flow of the liquid therethrough
into and out of the chamber so as to cause a
column of liquid to oscillate in the chamber fro~
the action of the waves;
~li) inlet port means for the flow of a working gas into
the chamber; and
(iii) outlet port means for the discharge fro~ the
cha~ber of ~orking gas pressurised b~ the 06ciL-
lations of said column of liquid, the chambers
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being connected ln series relationship so that
pressurised working gas tlscharged through the
outlet port means of one chamber enters an
ad~aceot chamber along the serles through the
lnlet port ~eans thereof, and the lnlet port `~--means of the first chamber providing an lnlet -
for the worklng gas into the series of chambers, ~ -
and
~b) mechanlcal means for extractlng energy from the
pressurised working gas and to which the pressurl~ed ` ~
working gas is dlscharget through the outlet port ~ans ~ ~-
of the last chamber in the ~eries.
Some of the chambers ma~ be arran8ed in series relation-
Jhip and so~e in parallel relationship, the Jeries and ;`
parallel arran8ements being adapted for connection together.
The device may be sdapted to operate as a generator
uging alr as the working gas, and Jeawater as the liquid
fro~ which wave energ~ is to be extracted, and the mechanical
o ans may cooprise a turbine means adapted to drive an electric
gen-rator _ n8. Alternativoly~ the device may be adapted
to functlon a~ a breakwater, the mechanical means comprising
an oriflce.
BRIEF EXPLANATION OF THE DRAWIJGS
The in~ention will now be particularl~ described by ;;
wa~ of ex y le only and with reference to the accompan~ing
drawingJ, ln ~hichs-
Flgure 1 shows in sectional elevation a diagra~atic
repr-seDc-elon ol a d-~lce In ehe frr ol
,
- 3 -
w~:, . ... .
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generstor structure having a parallel
arran8ement of chambers allgnet perpendicular
to the dlrection of the incoming waves;
Figure la shows a dlagrammatlc sectlonal representation
on the line I-I in Pigure l; ~; ` i-
Flgure 2 shows a generator structure similar to that of
Figure l;
Figure 3 shows in sectlonal elevation a dlagra _ tlc
representation of a generator structure having
a serles arrangement of chambers perpendlcular
to the inconing waves;
Figure 3a shows a dlagrammatlc sectional representatlon
about the line III-III ln Figure 3; and
Figure 4 shows a part-sectional vlew in the dlrectlon of
arrow 'D' in Figure 3.
In the abo~e-mentloned Flgures, llke p-rts have l~ke ;~-
numerals.
DETAILED DESCRlPTION OF THE INVENTION ;~
Referring now to Flgures 1 and la, the floating generator
structure sho~n i8 lntended for derlvlng power from sea waves, ~ -
nd comprlses a plurallty of chambers 1 for a working g-s (e.g.
lr) defined fore and aft with respect to the direction of the
inco~lng waves a8 sho~n by the arrow ~A~ ln Flgure 1 by a
generally trlangular-shaped buoyanc~ tank 2 and a generally
rectangular-shaped buoyancy tank 3, both of whlch have a rounded
lower edge and extend for the entire length of the generator
structure to support the structure on the surface of the sea.
The top of the chamber 1 is deflned b~ a roof 5, and an
_ 4 -
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outer casing 7 spaced from the roof S and the aft ;~-
buoyancy tank 3 defines therebetween a common plenum
duct ô whlch extends for the entire length of the
generator structure. The lower ent 9 of the duct 8 extends
below the sea level and is left open so as to provide an
inlet for seawater which closes the lower end 9. -
An outlet non-return valve 12 in the roof 5 allows ~-~
air to be discharged therethrough from the chamber 1 into
the plenum duct 8. An inlet duct 13 of tubular form extends
from the aft portion of the casing 7 to the roof 5 to
provlde an lnle~ for alr from outside the caslng 7 into the
chamber 1~ a non-return valve 14 in the inlet duct 13 ~-
inhibiting the reverse flow of air from the chamber 1, and
a hood 15 protecting the end of the inlet duct 13 at the caslng
7 fron sea spray.
The side~ of the chambers 1 are deflned by slde walls 16
and end walls 19 as shown ln Figure la. A mechanical means
in the form of an air turbine 17 is coupled to an electric
generator (not ~hown) and is posltioned in a duct 18 extending
upwardly from an orifice 10 in the casing 7 80 as to be fed
bg air contained in the plenum duct 8 to drive the electric
8enerator.
In operation, the level of seawater in each chamber 1
oscillates with the motion of the generator structure and
that of the seawaves and is shown in Figure 1 st its mean
,
lowest level~ the mean upper level being shown by the broken
line x-x. The oscillaeing seawater therefore acts in the
manner of a piston member in the chamber 1~ causing an
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~06S738
indraught of air through the inlet duct 13 into the
chamber 1 as the level of seawater falls, and discharge
of air through the outlet valve 12 into the common plenum
duct 8, as the level rises, where the air is collectively
conducted to the turbine 17. The pressurized air in the
plenum duct 8 acts on the surface of the seawater at the -
lower end 9 depressing the level of seaw~ter and thereby
provides a restoring force from the seawater in the lower
end 9 which pressurizes the air in the plenum duct 8 to
~mooth out and reduce pressure fluctuations in the air
therein.
It will be appreciated that there is a greater volume
. , -- . . .
of air available to operate the turbine 17 continuously
than the possibly more intermittent use of the turbine in
the device described in British Patent Specification -
No. 1,014,196. Although the generator structure of Figures
1 ant la has been described in relation to the use of a ~`
single turbine 17~ everal turbines 17 may be installed and
fod from a single plenum duct 8.
As n alternJtive to a generator structure having the
air in the plenum duct 8 pressurized by seawater at the `~
lower end 9 of the plenum duct 8~ an alternati~e arran8enent
may be used, for example, as shown in Figure 2 to which reference
i8 now mate.
The gener-tor structure shown in section in Figure 2
is similar to that shown in Figure 1 and la except that the
plenun duct 8 nc~ only extends above the roof and not behind
the aft buoyanc~ tank 3. The air in the plenum duct 8 i5
- 6 -
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;, - .
pressurlzed by a close-flttlng weighted cap 20 slidably ~ -
disposed in a relatively large diameter duct 21 extenting -~
upwardly from the casing 7, an 'O~ ring seal 22 in an
annular groove 23 extending around the cap 20 preventing
the egress of air from the plenum duct 8. In operation ~-
the cap 20 pro~ides a constant pressurizing force on the
air in the plenum duct 8, so that the turbine 17 can be
operated at a substantially constant head by the pressurised
air in the plenum duct 8. If desired the pressure exerted
by the cap 20 may be supplemented by resillent means (not
shown)-
As an alternative to the parallel arrangements ~hown in
Figures 1, la and 2, the chambers 1 may be arranged in a
linear series relationship as shown in Flgure 3 to which
reference i- now made.
In Figure 3, a floating generator structure ha~ing a
plurality of chambers 1 - ln 1- shown~ chamber la at one
end of the structure ha~ing non-return inlet val~e 14 for the
lndraught of air fro~ the at sphere~ and chamber ln at the
other end having an upwardly extending duct 18 within which
n air turblne 17 is disposed so as to drive an electric
generator (noe shown). me chambers la - ln are separated
from each other b~ slde walls 16 and plenum chJmbers 40a -
40n whlch h ve non-return lnlet ~alves 42a-42n and non~
return outlet ~alves 43b - 43n to allow air to flow there-
through the structure in serles rel~tionship from chamber la
through to chamber ln. Each plenum chamber 40a - 40n connects
rearwardly with a plenum duct 50 which itself extend~ rear-
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wardly to dip below the sea le~el so as to maintain a
pressure on the air therein and also extend~ along the
length of the structure to connect with the turbine duct
18 as shown ln Pigures 3a and 4 to which reference may be
made. Shut-off valves 51 are disposet along the plenum
duct 50 at the medlan position with respect to each chamber
lb - ln. In other respects the structure shown in Figure 3
is similar to that shown in Figure 1 in that it is provided
with fore and aft buoyancy tank~ 2 and 3.
In operation with shut-off -lves 51 closed and the
lncomlng waves ln the dlrectlon of arrow "B" in Figure 3a,
the level of seawater ln the chambers la - ln oscillates -
with the motion of the generator structure ant that of the
seawa-es, and is shown ln Pigure 3 at its mean le~el ln ~ -
each chamber la - ln. As the seawater level falls, there
ls an lndraught of air into chamber la through inlet
valve 14. As the seawater level rlses, air is discharget
unter pressure fro~ chamber la through inlet valve 42a into
the plenum chamber 40a and that portion of plenum duct 50 between ;
closed shut-off valves 51 to whlch sald plenum chamber 40a is
connected. ~hen the seawater level falls again, causing
a fresh lndraught of air into chamber la, the pressurized ~ ;
alr in plenum duct 40a flows into chamber lb through outlet
valve 43b, its pressurized state tepressing the mean seawater
level in chamber lb below that in chamber la. The sequence ~ -
of the collectively conducted flow of air from one chamber
to another vi- a plenum tuct 40a - 40n continues along the
series connectet chambers la _ ln with lncrease ln alr pressure
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-: . .. ~....... ; ~ .
:
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.: . . .: .
lQ65738
along the series, untll at chamber ln the pressurlzet alr
ls discharged lnto pleDum chamber 40n ant then lnto plenum
tuct 50 and through the turblne 17 at a hlgher air pressure
than can be achle~et by chambers connected in parallel.
The series arrangement shown ln Flgure 3 ls of partlcular -
beneflt when the lnconing wa~e power falls to a level whlch
. i .
would requlre the alr turbine 17 used in the parallel ~-
arrangement shown in Figures 1 and and la to work outslte
its efficient working range. The series arrangement may be
co m ertet to a parallel arrangement similar to that described
in relation to Figures 1 ant la by opening val~e~ 51 and
closing val~es 43b - 43n using a switchlng means (not shoun).
With such a series/parallel arrangement, the parallel
arrangement of chambers la - ln may be uset at hi8h inco~ing
wavepower le els but switchet bg theswitching ~eans to a series
arraDgement of chs~bers la - ln at low incoming wavepower ~ -
levels. Combinations of part-series and part-parallel flo~
arrangements through the structure y also be arranged bg
sult-ble selectlon of thoJe ~al~es 51 snd 43b to 43n to be
op-Ded or closed by the switchlng means.
Although the in~ention has been described in relation ~-
to the use of single air turbine, several turbines may be
used depending on the quantity and pressure of the air
discharged by the ~tructure. Alternati~e working gases may
be u-ed~ for example~ ~here the g-s is to be cont-ined in
closed circuit system, exhaust gas fro~ the turbine bein8
contucted to the inlet ducts to the chambers.
Alternative shapes for the buoyancy tanks 2 nd 3 may be
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.
used to suit particular applications.
The structures shown ln Figures 1 to 4 may be made~
for example, from metal or of a reinforced concrete construc-
tlon, e.g. ferro-concrete or glass flbre relnforced concrete.
The forward buoyancy tank 2 shown ln Figures 1, 2, 3a ~-
and 4, has been deslgned so that its forward face, upon - -
which the incoming waves are incident, slopes downwardly
and outwardly away from the freeboard of the floating
generator structure in a direction towards the incoming waves,
since it has been found that such an inclination of the
forward face reduces the heave forces acting on the structure.
It will be appreciated that devices incorporating the -`
invention will usually be located with moorlng means (not
shown). ~
Although the invention has been described as deriving ' --
electrical ehergy from wave power~ the alr turblne 17 may be
arranged to operate a mechanical device, for example a pump
to derlve hydraulic or pneumatic power from wave power, or ~ ~;
nay be replaced by ~ome other alternatlve mechanical means such
as a reciprocating air engine for deriving power from --
the pressurized working gas. -~
Alternatively the device may be adapted to operate
as a breakwater, by dispensing with the turbine 17 and
., .
eurbine duct 18 of Figures 1 to 4 and selecting the
dimensions of the orifices 10 so as to maximise the energy
lost b~ the gas ln flowing therethrough~ thereby dlsslpating
some of the energy of the sea waves. For example, in a
breakwater having parallel connected chambers 1~ a ratio of
-- 10 --
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.. '.- ~ ~' '` ' ' . .. :, ... -.
~ : : : , - : : - - :. ... : .. .. , , ~ . . . - .:
'.'. . ' - ~ : - '"':', ." -, . . :' ' ~; ' , ,
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area of orifice `1
sum of croSs-sectional of between 107 to 200 is tesirable.
areas of the chambers
; :
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.. , . .,, . , . , ~ ... - .. , .-.~ . :.
