Note: Descriptions are shown in the official language in which they were submitted.
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LOW HEAD HYDROPOWER GENERATI_G APPARAI'US
_BACKGROUND OF THE_INVENTION
This invention relates generally to hydro-
power generating stations, and more particularly, to
hydropower generating stations intended to operate on
relatively low hydraulic heads, on the order of three
meters or less~
Although there are significant numbers of
potential hydropower sites available with effective
heads of three meters or less, the development of
these sites has been severely limited. This has not
been due to the absence of equipment capable of
producing power at such sites~ Rather, it is due to
the absence of equipment that can produce hydropower
at such a site in a cost-effective and reliable manner
as compared to larger conventional power plant de-
sign.
For example~ United States Patent No.
2,783,39~ to Corbiere discloses a device intended for
such use, as does United States Patent No. 4,289,971
to Ueda~ The patent to Corbiere discloses a side
intake turbo-generator disposed in a siphon-type
arrangementr and the patent to Ueda discloses a con-
ventional bulb-type turbine generator.
Both of these devices require the generator
to be immersed in the flow of water used to provide
power, and both include a turbine which turns on the
same shaft as the generator. This arrangement gives
rise to substantial problems in providing perfect
seals to keep water out of the generator and further
requiring that each unit be custom designed for a
given site to provide a turbine which will rotate at
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the optimum rotational speed for the generator.
Accordingly, there has existed a need for a
low head hydropower generating device which is inex-
pensive to install, is trouble free and reliable in
use, and which attains these advantageous results
without requiring that a custom designed unit be
developed for each location to which it is to be
applied. As will become apparent from the following,
the present invention satisfies that need~
SUMMARY OF THE INVENT:[ON
The present invention resides in a new and
improved hydropower generating device which is par
ticularly suited to low head app~lications, and which
includes a conventional marine thruster adapted to be
driven as a hydro turbine by water or other liquid,
such as treated efluents, industrial discharges~ and
the like, flowing through a conduit. The conduit is
adapted and fabricated to control the Elow volume
and velocity required to operate the thruster as a
turbine. More significantly, the power generating
device of the present invention is relatively inex-
pensive to manufacture and install, is trouble ree
and reliable in use, and can be adapted for use
in a variety of different low head si.te applications.
More specifically, the hydropower gener-
ating device of the present inve~tion includes a
conduit through which the liquid flows from a region
of a first hydraulic head to a region of a second,
lower hydraulic head, and the marine thruster, which
i~ of the type normally used to propel marine vessels,
is arranged in the conduit to be driven by the liquid
flowing through the conduit. The mechanical output of
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the thruster is connected directly to a machine or
drives a generator for converting the mechanical power
to electrical power outputO Wherever necessary,
the mechanical output of the thruster is connected to
the generator~ or other machine, through a trans-
mission, thereby permitting the thruster to operate at
a speed determined by the flow rate through the
conduit and permitting the generator or machine to be
driven at its optimum operating speed, which may
be different from the speed of the thruster.
As required by the site conditions, the
hydropower generating device of the present invention
can be adapted for use in a number of different types
of low head site arrangements. That is, the conduit
which directs liquid across the thruster can receive
the liquid through an opening in a retaining structure
substantially below the level of liquid retained by
the structure, and can conduct the liquid in a gener-
ally horizontal direction to the region of the second,
lower hydraulic head. Alternatively, the conduit can
receive the liquid through a structure at a level only
slightly below the level of the liquid retained
by the structure and direct the liquid through a 90
degree turn vertically downwardly across the thruster
to the region of lower hydraulic head. In still
another embodiment, the conduit can draw liquid over
the top of a structure by siphon action and direct
the liquid across the thruster before discharging the
liquid to the region of lower hydraulic head. In the
second above-mentioned arrangement, guide vanes may be
used in the conduit to facilitate directing the liquid
downwardly across the thruster.
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Other features and advantages of the present
invention will become apparent from the following
detailed description, taken in conjunction with the
accompanying drawings, which illustrate, by way of
example, the principles of the invention
BRIEF DESCRIPTION OF TllE DRAWINGS
FIGo 1 is a perspective view, partly in
section, of a low head hydraulic power generating
device embodying the present invention, and illu-
strated as installed at a typical low head power
generating site;
FIG. 2 is an enlarged perspective view of a
marine thruster turbine employed in the power gener-
ating device of FIG. l;
FIG. 3 is an enlarged fragmentary view,
partly in section, illustrating the marine thruster as
mounted in the conduit of the present invention;
FIG. 4 is a diagrammatic elevational view of
an alternative embodiment of the present invention;
and
FIG. 5 is a diagrammatic elevational view
of another alternative embodiment of the present
invention.
DETAILED DESCRIPTION
As shown in the exemplary drawingst the
present invention is embodied in a hydropower gener-
ating device primarily intended for use at a site
designed to generate power from a relatively low
hydraulic head, on the order of three meters or less.
An example of such a site is illustrated in FIG. 1 in
which the hydropower generating device is identified
generally by reference numeral 10.
Generally, the site includes a body of
liquid 12 retained by a structure 14, which structure
includes an opening (not shown in FIG. 1), below the
level of the liquid retained by the structure~ through
which liquid flows to a downstream region 16 having a
lower hydraulic head than the liquid retained by the
structure. A conduit 18 is secured over the opening
of the structure and conducts the liquid from the
structure to the region 16 of lower hydraulic head7
To withdraw energy from the liquid flowing through the
conduit 18, a turbine assembly, indicated generally at
20, is mounted in the conduit 18 to be driven by
liquid flowing through the conduit, and the turbine
assembly provides mechanical power at the output shaft
for direct application, or to drive a generator 22
which converts the mechanical power to the desired
electrical p~wer output from the generating device
10 .
In accordance with the present invention,
the turbine assembly 20 is comprised of a standard
marine thruster 24 (FIG. 3) of the type normally
designed to be powered by an engine or electric
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motor and move liquid for the purpose of propelling a
marine vessel. In this application, however, the
marine thruster 24 is mounted in the conduit 18 and
is driven by the liquid flowing through the conduit.
Further, the thruster may be connected to the electric
generator 22 or mechanical device by a transmission
26. With this arrangement~ the generator 22 is not
immersed in the flow of liquid which drives the
turbine, and both the thruster 24 and the generator 22
can be arranged to operate at their optimum operating
speeds, even though those speeds may differ. More-
over, the power generating device of the present
invention is relatively inexpensive to manufacture and
install, is trouble free and reliable in use, and can
be adapted for use in several different low head site
arrangements~
The thruster 24 generally includes its own
cylindrical housing 28, a propeller or turbine blade
30, a right-angle gearbox 32~ and an output shaft 34.
Marine thrusters, which are variously referred to as
tunnel thrusters, bow thrusters, and maneuvering
thrusters, are commercially available in a wide
assortment of sizes. Maximum power ratings and
standard operating speeds Eor these various sizes are
easily obtainable from the thruster manufacturers.
From the foregoing information, a standard thruster 24
which most closely matches the calculated power
available at a particular low head side can be se
lected and purchased for installation in the power
generating device 10.
Having selected the proper thruster 24, a gener-
ator 22 can be selected to generate electrical power
commensurate with the hydro-power available~ Since
the optimum operating speed of the generator 22 may
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not be the same as the rotational speed of the output
shaft 34 of the thruster, the transmission 26 can
be employed to connect the output shaft 34 of the
thruster to the generator 22. Although a gearbox type
transmission can be used, it has been found that a
belt drive type transmission performs satisfactorily.
Referring to FIG. 4, an alternative embodi-
ment of the present invent-on is illustrated in which
the conduit 18a takes the form of a siphon tube
receiving liquid from a point near the surface of the
liquid retained by the structure 14a, and conducting
the liquid over the top of the structure, through the
tube 18a~ across the turbine assembly 20a, and dis-
charging the liquid at a region 16a of lower hydraulic
head~
Another alternative embodiment of the
present invention is illustrated diagrammatically in
FIG. 5. In this embodiment, an opening 36 is formed
through the structure 14b at a level slightly below
the surface of the liquid retained by the structure,
and the conduit 18b includes a right-angle turn 38
directing the liguid vertically downwardly across the
turbine assembly 20b before the liquid is discharged
to the region lbb of lower hydraulic head. If desired,
a series of guide vanes 40 can be provided in the
right-angle turn 38 of the conduit 18b to facilitate
directing the liquid across the turbine assembly
20b.
From the foregoing, it will be appreciated
that the hydropower generating device 10 of the
present invention provides a cost-effective and
reliable means for tapping an important and here-
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tofore undeveloped energy resource, the low headhydropvwer site. This is accomplished by applying
a relatively inexpensive standard marine thruster to
an environment which previously required expensive
custom made turbines, and in effect, running the
thruster backwards to drive a generator located
oukside of the flow of liquid~ By employing this
invention, it has been found that an efficient and
reliable hydropower device based on marine thrusters
can be produced and installed at a cost from one-third
to one-tenth the price of more conventional hydropower
equipment. Moreover, since the thruster 24 is designed
to operate in the saline and debris-cluttered environ-
ment of a ship harbor, its application to a fresh
water stream results in highly reliable operation.
While several particular forms of the
invention have been illustrated and described~ it will
also be apparent that various modifications can be
made without departing from the spirit and scope of
the invention.
