Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM FOR DISCHARGING WATER TO A TURBINE
TO GENERATE POWER
Cross-Reference to Related Application
The present disclosure claims priority from U.S. provisional patent
application
no. 61/178,250, filed May 14, 2009, the entirety of which is hereby
incorporated by
reference.
Technical Field
The present disclosure is generally related to the field of power generation.
In
particular, the present disclosure relates to hydropower generation.
Background
Hydropower generation presents with several challenges:
1) The apparently diminishing amount of water available from lakes and rivers
for hydropower generation.
2) The location for clean hydropower generation is limited. Generation
facilities
are generally located where significant amounts of water are available.
3) Dams are often expensive to construct and maintain, and tend to be highly
regulated, foe example, for environmental issues.
4) Water irrigation to cities and to farms may use tremendous amounts of
electricity and may be costly.
A solution to address at least some of these and other challenges is
desirable.
Summary
In some aspects, the present disclosure describes a system for discharging
water to a turbine to generate power. In the disclosed system, molecular
reaction is a
generally uni-directional compression force, such as the weight of a liquid
confined in
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an open top rigid container and is volumetric with the wall of the rigid
container
acting as a compression force. Thus, the total compression force exercised
upon the
liquid, is not only the weight of the liquid but also the restrictive force of
the wall of
the container against the liquid which increases the stored compression force.
Generally, the disclosed system may provide greater efficiency in flowing
water (e.g.,
by decreasing water loss) through a turbine generator, compared to
conventional
hydropower generators.
The total stored compression force of a liquid in a container may be converted
into kinetic energy as a jet, if the opening allowing the liquid to expand
occurs with
sufficient speed that the decompression wave of the liquid can pass through
the
opening before the decompression wave is able to reverse the direction of
expansion.
Use of the compression of water may allow the construction of power
generating systems that reduces the amount of falling water required to
generate the
same power as hydraulic turbines using continuous flow of water.
The disclosed system may not require a large amount of water to flow through
it in order to provide large amounts of power. The reactor pulses the water,
for
example around six to nine times a second (this rate may be higher or lower),
through
a high speed valve and thus propels a turbine to generate power. Power may be
thus
generated using less water than a conventional water turbine, or more power
may be
generated for the same water consumption as a conventional water turbine.
The system may be equipped with one or more water pumps that pump water
from the bottom of the system to the top. Once water flows through the pipe
and
through the valve, it may be collected at a lower reservoir and may be then
pumped
up to the top to be run through the system again. This may allow the system to
be
installed anywhere regardless of the location of a mass water supply. Pumping
of
water back to the top of the system may be powered by off-peak power or excess
power from other power sources. Thus, the system may, for example, serve to
store
energy (in the form of a compressed water column) at off-peak hours and
relatively
efficiently convert the stored energy into useable power during peak hours.
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The system may be installed on the bank of a river or lake without
installation
of a dam, though the system may also be used with a dam in some aspects. The
system may only need a minimal flow rate of water and only the required flow
may be
diverted towards the intake pipe and used in the system. Once the water has
flowed
through the valve, the water may be released back into the main stream of the
river or
back into the lake.
The system may be used to pump water inland from water supplies located far
from highly populated areas. The system may provide at least some of its own
power
to run all the pumps required, and may use the same water that is being
transported to
flow through the system and generate at least some of the power. This may
reduce or
eliminate the cost of electricity needed to power the pumps. The water pumps
may
also be powered by relatively inexpensive power, for example off-peak or
excess
power from other power sources. The system may thus, for example, serve to
store
energy (in the form of a compressed water column) during off-peak hours and
relatively efficiently convert this to useful power during peak hours.
In some aspects, there is disclosed a system for discharging water to a
turbine
to generate power, the system comprising: a rigid container for containing
contain a
water column having a height sufficient to cause elastic compression of water
in the
water column and to accommodate propagation of compression waves in the water
column; a valve attached to the rigid container for intermittently discharging
water at
a lower end of the rigid container, the valve having an open/close cycle with
a time
duration in the range of about 10 to about 200 milliseconds, to facilitate
generation of
compression waves in the water column, wherein opening and closing of the
valve is
dynamically controlled by a feedback controller; and a turbine positioned
adjacent to
the valve, the valve being directed to periodically discharge water to drive
the turbine.
In some aspects, the system further comprises a water pump for pumping
discharged water into the rigid container.
In some aspects, the system has two or more rigid containers, each having a
respective valve, the valves being directed at one or more turbines for
driving the one
or more turbines.
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In some aspects, there is disclosed a valve for a container of liquid
comprising:
a piston adapted to fit in an opening in the container, the opening being
sealed when
the piston is in a closed position and opened when the piston is in an opened
position;
and an arm for driving opening and closing of the piston; wherein the valve
has a high
rate of opening and closing.
In some aspects, the valve comprises an elastic member to assist in driving
opening and closing of the piston.
In some aspects, the valve is adapted to fit in a container having a wide bowl
around the opening.
In some aspects, there is disclosed a method of discharging water to a turbine
to generate power, the method comprising: compressing a water column; and
intermittently discharging water from the water column to drive a turbine for
generating power, the water being discharged in a cycle having a time duration
of
about 10 to about 200 milliseconds, to facilitate generation of compression
waves in
the water column; wherein the water column has a height sufficient to cause
elastic
compression of water and to accommodate propagation of compression waves in
the
water column.
In some aspects, the method further comprises returning discharged water to
the water column.
Brief Description of Figures
Figure 1 is a schematic diagram of an example of the disclosed system, in
accordance with some aspects of the present disclosure;
Figure 2 is a schematic diagram of an example of the disclosed system having
two water columns, in accordance with some aspects of the present disclosure;
Figure 3 is a schematic diagram of another configuration for the system of
Figure 2;
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Figure 4 is a close-up schematic diagram of the valve and turbine of the
system of Figure 3;
Figure 5 is a schematic diagram of an example of the disclosed system having
three water columns, in accordance with some aspects of the present
disclosure;
5 Figure 6 is a schematic diagram of a valve suitable for an example of the
disclosed system, in accordance with some aspects of the present disclosure;
Figure 7 is a schematic diagram of a turbine suitable for an example of the
disclosed system, in accordance with some aspects of the present disclosure;
and
Figure 8 is a table showing example results achieved with an example
prototype of the disclosed system.
Detailed Description
A system for discharging water to a turbine to generate power is disclosed.
Although the present disclosure makes reference to examples, these are not
intended
to be limiting. Theories of operation are also presented in this disclosure,
which are
not intended to be binding or limiting, and the function and operation of the
system
are not dependent on these theories. Such theories are presented merely to
assist one
skilled in the art in understanding the embodiments disclosed.
In the mid 1700's, Leonhard Euler and Daniel Bernoulli, who were
mathematicians and not hydraulic engineers, indicated that to make their
equation of
flowing water energy and conservation feasible, they considered water to be
incompressible. Bernoulli ignored the stored elastic compression as a source
of energy
because he studied water in continuous flow and he did not have the
instruments
available today. To develop a new water power technology, the bulk modulus of
elasticity for water is included. The motion of water caused from the stored
elastic
compression is included in the calculations for the amount of energy produced.
The
jets of water develop an elastic reaction to the compression of the water with
a
moment of a stationary condition between the jets to allow the elastic
compression to
occur.
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To better understand the disclosed system, time and elasticity may be
considered when applying the fundamentals of motion with water. Relationships
that
assist in implementing or understanding this new technology may include
equations
relating to force, weight, and kinetic energy.
Force may be defined as the unbalanced agent which changes the motion of a
body. Simplified, force, F, is generally equal to the mass, m, of the body
multiplied by
the acceleration, a, that the mass develops.
This equation is applicable to mass that is motionless. For example, the
weight, W, of an object is a force relative to the mass of the object
multiplied by the
acceleration due to gravity, g. This means the object can move downwards if it
was
free tofall: F=W=m=g
A body in motion has kinetic energy. The kinetic energy, Ek, is defined by the
distance, or displacement, s, over which the force moves: Ek = F = s = ma = s,
or
traditionally: Ek ='/2mv2 for any moving body.
With waterpower, acceleration is automatically considered to be that of
falling
water due to gravity: a = g. The equation for velocity, v, then becomes: v = g
= t,
where t is the time of the vertical fall of distance h. When using h in the
calculation of
t: t = h / (v/2). When t is substituted into the velocity equation, the
equation becomes:
v = g = h / (v/2) and thus v2= 2gh. Therefore, for an object moving in free
fall, the
energy produced is Ek = %2mv2 ='/2m = 2gh = mgh
To avoid the `force of habit' in hydraulics, it may be clarified that the
acceleration in the force equation, F = ma, can be different and higher than
the
acceleration provided by gravity, g = 9.81 m/s2, even in water power.
A liquid confined in a rigid container when subjected to a compression force,
converts and stores the compression force into elastic deformation within its
own
mass and makes restitution of the compression force by expansion
(decompression),
either by expelling from the container the volume equal to that of the elastic
deformation or pushing out any selected area of the container wall when and
where
the resistance to compression force is less than that of the stored
compression forces.
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System
In addition to the weight of the water used in traditional hydropower
generation, the technology of the presently disclosed system introduces into
standard
power calculations the reaction of water to compression. This reaction of
water to
compression includes the introduction of the elasticity of water, a property
often
ignored by traditional technology, which when applied may be useful for
hydropower
generation.
Figure 1 shows an example general configuration for a system for discharging
water to a turbine to generate power. The system includes a rigid container,
such as a
penstock, for a column of water, a valve for periodically discharging the
water from
the lower end of the rigid container, and a turbine positioned to be driven by
water
discharged from the valve for generating power.
In this example configuration, water (which may be provided by a continuous
or periodic input) in the rigid container experiences compressive forces due
to gravity,
including stationary compression (Cw) and operational compression (which may
be
referred to as a "water hammer") (CH). The operational compression typically
propagates in a wave-like manner (i.e., in the form of a compression wave),
which
may be oscillatory, cyclic or intermittent. The stationary compression reduces
the
volume of water elastic compression qw and the operational compression reduces
the
volume of water by elastic compression qH. The elastic compression results in
energy
stored in the water column (qw + qH). The water is released in intermittent
jets by the
opening/closing of a valve B (e.g., a super fast jet valve), which is
controlled by a
valve operation activator Ce (which may be an electrical or mechanical
control, for
example). The water jets provide kinetic energy K to drive a turbine C,
powering a
generator Me. The generator produces electrical power EW. In the example
shown,
portions of Ew are directed to power the valve operation activator and a water
return
pump Pe, with the remaining being net useful power NMe.
In some examples the valve operation activator and/or the water return pump
may be powered using another source of power, including, for example, power
from
solar power, wind turbines, gas, diesel, natural gas or any other suitable
means, and
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which may be off-peak or less expensive power. This may allow a larger portion
of
the power generated by the water jets to be delivered as useful energy.
The container may be any suitable shape, such as cylindrical, for example
having a cross-sectional area A and a height H. The container may have a
varying
wall width, for example it may have thicker walls near the bottom. For the
high water
column, the suitable dimensions of the column of water may vary or be
dependent on
the amount of power needed. The column may have a sufficient capacity and
height
for the water to develop, in static condition between jets, a useful amount of
stored
elastic compression energy to transfer to the jet of water, coming from the
valve, the
acceleration for developing a large value of energy per volume of water in a
very
short period of time.
The valve may be a relatively fast open/close water valve. For example, the
valve may open at a fast enough rate that an open/close cycle may be completed
in
around 2/10 of a second or less. Such a valve may be used to release the
stored elastic
compression energy in a penstock or column of water by accelerating a water
jet and
develop, intentionally, a controlled high level water hammer effect. In some
aspects,
the valve may be a super fast jet valve (SFJV). For the SFJV, there is a
liquid
OPEN/CLOSE control valve that may operate at a rapid speed. The valve may open
fast enough to have the power benefit of the water's elastic expansion,
compressed
under its own weight and a water hammer effect, before the energy would be
wasted
by the water bouncing up and down in the column. Operation of the SFJV may be
controlled by a valve operation activator. The SFJV may be any valve capable
of an
open/close cycle on the order of milliseconds, for example in the range of
about 10 to
about 200 milliseconds. The SFJV may be any valve capable of sustaining such
rapid
open/close cycles repeatedly (e.g., about 31 trillion or more repeated cycles)
over a
suitable lifetime (e.g., about 20 years).
The turbine may be any suitable turbine. The turbine may be designed to
optimize power output when the turbine is driven by water jets from the valve.
The
power output from the turbine may be transmitted for useful consumption. In
some
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examples, a portion of the power output may be diverted to operate at least
some
aspects of the disclosed system.
The system may additionally include a water return pump for returning ejected
water back to the rigid container, to recover the height of the water column.
In some
examples, power for the return pump may be at least partially provided by
another
power source, for example off-peak, inexpensive or excess power from another
power
source (e.g., power from solar power, wind turbines, gas, diesel, natural gas
or any
other suitable means). In this way, the system may, for example, take
advantage of
inexpensive or excess off-peak power to store energy in the form of the water
column,
and relatively efficiently convert this to useful energy (by driving the water
turbine)
during peak hours. In some aspects, in place of or in addition to the return
pump,
water may be introduced into the column from some other source, such as a
stream,
lake, reservoir, dam, water tank and the like, to recover the height of the
water
column.
A brief description of the function of the water column in the system is
provided below.
Consider that: Water pressure at bottom = pgh
Water pressure at top = 0.00
When the valve, such as the SFJV at the bottom of the column of water is
opened:
1) The pressure locally at the valve opening becomes zero.
2) The energy stored in the water in the form of elastic compression is
instantaneously released.
3) The drop in pressure is transmitted upwards through the tank as a negative
pressure wave, as water exudes through the valve nozzle.
4) As the negative pressure wave moves through the tank, which may be at the
speed of sound, the release of elastic energy takes place over a short period
of
time.
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5) Due to the small size of the valve orifice, the released energy is
concentrated
in a relatively small mass of water discharged at a high speed.
6) After a short time, when the rate of release of the kinetic energy of the
water
jet has been reduced, the valve closes. The entire cycle from valve opening to
5 valve closing may take about 1/10 of a second. This time may be longer or
shorter as suitable.
7) Meanwhile, the negative compression wave is reflected as a positive
compression wave from the top of the column back towards the valve. In
combination with the restored gravitational pressure at this location due to
the
10 valve being now closed, this reflection creates a water hammer overpressure
on the valve.
8) The valve is re-opened and the cycle is repeated.
In operation, it is believed that gravity acts on the water column in the
rigid
container and develops two compression forces - a stationary compression Cw
and an
operational compression (a water hammer) CH. Cw reduces the volume of water by
qW
elastic compression. CH reduces the volume of water by qH elastic compression.
This
is believed to store energy in the form of elastic deformation.
Stationary water is compressed under its own weight and stores elastic
deformation energy that can be released in the form of a jet of discharged
water. The
power of the water hammer may increase the velocity of the water jet
discharged from
the valve and useful power may be output, such as in the form of a pulse or
stream of
water. The stored elastic energy may be renewed after it is discharged, by
closing the
valve and recovering the pressure at the bottom of the water column, between
the
release of two consecutive water jets discharged from the valve, which may
allow a
fast cycle sequence of power output through bursts of fluid.
1) The column of water of suitable height in a rigid container in a stationary
condition can store the elastic compression energy of the water compressed
under its own weight. In the example of a column of water held in a rigid
cylindrical container, the width of the column may, for example, range from
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about 700mm to about 8m, in particular from about 746mm to about 7.62m.
The height of the column may, for example, be from about 60m to about 90m.
Other dimensions may be suitable, for example the diameter of the container
may be about 50mm and up, and the height or head of the column may be
about 10m and up. These dimensions may be varied, for example depending
on the amount of power to be generated and/or depending on where the system
is installed.
2) The stored elastic compression energy creates a volume reduction that can
be
suddenly let to expand to the normal volume, by allowing the water to push
through the valve located at the bottom of the column. This creates a water
mass in the form of a jet discharged from the valve. When the water is allowed
to expand suddenly in this manner, it creates waves of `pressure drop';
starting
at the valve and moving upwards, layer by layer, to the top of the column.
When the pressure drop wave reaches the top, the pressure of the water has
been released through the valve. To limit the water loss when at a low
pressure, the valve has to close fast, for example at the moment when the
lowest or near lowest pressure in the column is reached (closing of the valve
may not be exactly at the lowest pressure, for example due to response time of
the control system). The amount of water discharged in each water jet may be
dependent on the dimensions of the water column and the open/close speed of
the valve. For example, a jet of water may discharge from about 1.2L to about
3.6L of water over a duration of about 1/20 to about 1/10 of a second.
3) When the valve closes, the pressure in the column begins to rise due to the
gravity and water hammer effect creating a downward over pressure, due to
the closing of the valve. The over pressure is higher than the static pressure
when the valve is open.
4) When the overpressure reaches the peak or near peak, the valve is opened
again (opening of the valve may not be exactly at the peak of the
overpressure,
for example due to response time of the control system), creating a stronger
jet
of water than the one developed by the static pressure in the column. The
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rhythmic open/close of the valve releases an ongoing series of intermittent
jets.
5) The overpressure of the gravity and water hammer may help to increase the
stored elastic compression energy.
6) The mass of the intermittent water jet expelled through the opening valve,
by
the force of weight, and the expansion, caused by the discharge of stored
elastic compression energy, gains a generally higher velocity than the water
that would have been expelled by the force of weight alone through the same
opening. The higher velocity of the water jets also tends to be created in a
shorter time.
Like some phenomena related to elasticity, the element of time may cause
reaction changes. There may be challenges in analyzing water's elastic
reaction due to
changes from one time frame to another. By addressing the time element when
studying water power, it was discovered that time is a factor for the
conversion of
elastic compression energy into kinetic energy, and from kinetic energy into
power.
When considering the force experienced by the water in the column, it was
found that the acceleration due to gravity, g, and the weight of the body, mg,
does not
disappear; it acts as a compression force, C. The would-be kinetic energy is
transformed into stored elastic energy, K, of deformation, or compression in
this case,
in the order of. K = mC2 / 2e, where e is the bulk modulus of elasticity for
water. This
energy storage may be a result of a reduction of volume which is a temporary
state in
the disclosed system. When the water is free to move by the fast opening of
the valve,
the stored elastic energy becomes kinetic energy and is joined by the energy
of the
down moving force of the weight from the water exiting the container. The
total
kinetic energy of the jet of water is: Ejet = Ek + K = mgh + mC2 / 2e
The overpressure of the water hammer increases the stored elastic energy of
compression and converts it to kinetic energy so that it increases the
velocity of the jet
of water well above that of falling weight.
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Because the system may be used in numerous situations and in different
layouts, certain criteria may be taken into consideration for better
efficiency and/or
power output.
A) The location of the SFJV - The SFJV may be placed at the bottom of
the water column, at the center or on one side, vertically or
horizontally.
B) Shape of the bottom of column - The column of the column may have
different shapes to control and/or improve water flow (e.g.,
hemispherical, conical, etc.).
C) Valve open time and moment of maximum pressure - The moment the
pressure waves of the water hammer reaches the maximum pressure at
the bottom of the column of water, the pressure at the top of the
column is converted into kinetic energy moving the water upward.
This movement may continue for a fixed time, such as approximately
0.046 seconds in some examples, until the pressure waves moving
downwards reach the bottom of the column and change the kinetic
energy of the upward movement into pressure. This time may be
determined in order to know the time to open the valve to release the
pressure before a negative water hammer effect. This time may be
dependent on the dimensions of the water column, such as the height
and/or cross-sectional area. This timing may be taken into account in a
feedback controller for the valve.
In conclusion, to reduce the amount of water used in the system and still
maintain the power output of the generating system, the kinetic energy of the
moving
water may be improved in at least one of the following three ways:
1) The velocity, v, of the moving water may be increased;
2) The time in which the higher velocity is attained may be reduced;
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3) The increased velocity and the reduced time which is attained may be
sustainable.
A column of water in a stationary condition stores elastic compression energy
under its own weight. With the aid of mathematical equations, it may be shown
that
the use of the stored elastic compression energy may achieve conditions for
improvement over the standard continuous flow method of power generation. It
was
shown experimentally that:
a) The stored elastic energy may be converted into the kinetic energy
of a water jet by letting the water expand rapidly at the base of the
column;
b) The velocity of the jet of water through the valve may be higher
than v = ugh and may be reached in a shorter time than v = gt;
and
c) The stored elastic energy may be renewed with elastic waves at a
speed close to that of the propagation of pressure moving up and
down through the water. This happens so that the valve may open
and close in short cycles for sustained power output.
Examples
In an experimental setup, the water column was 30.7 meters high, contained in
a steel penstock 742mm (or 30") in diameter. Within the steel penstock, the
water is
compressed by two forces - its own weight and water hammer. The testing
included a
single penstock. The SFJV was set to develop 9.5 water jets per second, with
the
energy of expansion developing in 0.045 seconds. The duration of time is
equivalent
to the duration of the over-pressure provided for by the pressure waves,
commencing
upon the closing of the SFJV up until the corresponding reverse pressure waves
would commence lowering the increased pressure. The power due to expansion was
successful in developing 3860 watts of hydropower while operating at 16.66
revolutions per seconds or 1000 RPM.
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Figure 2 shows an example of the disclosed system having two water columns.
Figure 3 shows another example of the disclosed system having two rigid
containers, each having a SFJV. In this system, the water jets from one of the
SFJV
valves drive a triplex power water pump to help raise the water to the
original high
5 level (e.g., with the aid of external power to drive the water return pump).
The volume
of water raised is expected to be in excess of the water loss to drive the
pump. The
excess of water is directed to a twin pipe system to drive an electric
generator. A
small fraction of the power output of the electric generator is used to drive
an air
compressor for SFJV operation and have an excess of power to be used outside
the
10 system.
The system may use power from another power source including, for example,
power from solar power, wind turbines, gas, diesel, natural gas or any other
suitable
means, and which may be off-peak or less expensive power, to help pump the
water
back to the original high level.
15 Figure 4 shows an example arrangement of the SFJVs on an example of the
disclosed system with two water columns. As shown, the SFJVs may be arranged
to
increase the efficiency in driving the turbine.
Figure 5 shows an example of the disclosed system having three rigid
containers for the water columns. In this configuration, each column is
provided with
an upper water reservoir, and the upper water reservoirs are in communication
with
each other. The SFJV from each column may be directed at the blades of a
single
turbine and arranged for increase efficiency. Each column may have an
isolation
valve for shutting off water from that column. In this way, the system may
also be
used as a two-column or one-column system. There may also be a water pump for
returning discharged water as described above, and a spill duct for collecting
discharged water. In this example, each rigid container may have a diameter of
about
609mm, and be made of steel.
In some examples, the system may include a housing for a valve and turbine.
An example suitable housing may include a pressured water input for receiving
water
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from the rigid container, an orifice opening for the water, and a turbine
placement and
turbine shaft for connecting to a turbine. The housing may also include a cam
shaft,
cam motor and cam wheel.
Figure 6 shows an example of a valve suitable for use in the disclosed system,
in some aspects. A description of a suitable valve is provided in Canadian
Patent
Application No. 2,363,221, the entirety of which is hereby incorporated by
reference.
The valve may include a piston that fits in an opening in the rigid container,
which
seals the opening when the piston is closed. In the example shown, the valve
includes
a valve body A in which a plunger B is driven by a piston C. The distal end of
the
plunger fits in an opening in the jet nozzle D. The valve may further include
a plunger
bushing E and a piston housing cover F. In the example shown, the valve
communicates with the rigid container via a water supply port al, and may be
driven
by pneumatic power (e.g., provided through pneumatic ports a5). An optional
nozzle
reducer d4 is also shown. The valve may also include seals (e.g., as indicated
at el, cl
and f2). Other arrangements may be suitable.
Although certain configurations are indicated in this example, these are for
the
purpose of illustration only and are not intended to be limiting. In designing
a suitable
valve for use in the disclosed system, factors for consideration may include:
wear and
tear due to rapid repeated open/close cycles; mass of the valve piston;
precise timing;
leakage; and durability. To address wear and tear, and to help increase the
durability
of the valve, an elastic member, such as a spring, may be included with the
piston to
provide the valve with a soft close such that the piston does not collide with
the
opening with excessive force when closing. Decreasing the mass of the piston
and/or
plunger may be useful in increasing the speed of the valve, and to address
this, light-
weight materials and/or a hollow core design may be used for the piston and/or
plunger. Precise timing of the valve may be provided by using a cam-driven
system.
Leakage may be decreased by using high quality seals, which may be
replaceable, at
the opening. In some examples, the valve may be designed to provide at least
31
trillion open/close cycles over a life span of about 20 years. For example,
the valve
and the valve housing may be configured based on any conventional design,
provided
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the valve is capable of high-speed opening and closing (e.g., on the order of
milliseconds) and has a relatively long life for repeated rapid open/close
cycles.
Figure 7 shows an example of a turbine suitable for use in an example of the
disclosed system, in some aspects. The dimensions, number of blades, spacing
of
blades, orientation of blades, and other similar variables may be modified to
increase
efficiency of the turbine. Although the present disclosure describes the use
of water,
other fluids may be suitable for power generation using the disclosed system
and
method.
In some examples, the timing of the opening and closing of the valve may be
controlled using a feedback loop, for example a proportional-integral-
derivative (PID)
controller, for example based on the power load feedback from the turbine
generator
and/or based on the pressure in the water column (e.g., as described above).
Opening
and closing of the valve may be controlled by electrical or mechanical means.
For
example, opening and closing of the valve may be controlled on the order of
milliseconds. In some examples, a PID controller may receive feedback from the
generator (e.g., using conventional feedback devices) and dynamically change
the
timing for opening and closing of the valve in response. This may help ensure
that the
generator is at a relatively stable or constant revolutions per minute (RPM)
value,
which in turn helps to ensure that the frequency of the generated power is
relatively
constant. This may be similar to conventional feedback control, such as Pelton
turbine
systems in which PID controlled governors maintain a constant RPM for the
generator.
Another feedback for controlling the valve may be based on the pressure
sensed in the water column (e.g., by a conventional pressure sensor or
pressure
transducer located, for example, at the bottom or near bottom of the rigid
water
container, near the valve or inside the valve body). At lowest or near lowest
water
pressure, the valve may be controlled to close, and at peak or near peak
pressure, the
valve may be controlled to open. The generator load feedback and/or the
pressure
feedback may be synchronized at the PID controller (e.g., by a processor that
controls
the PID controller) in order to control the valve.
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In example systems having a water return pump, power load feedback from
the generator may also be used to control when to pump water to replenish the
water
column. For example, during low power demand, the water return pump may be
powered by the generator to pump water back into the system, which would also
help
to maintain a relatively constant load on the generator.
Figure 8 is a table showing test results of an example prototype system using
the example valve of Figure 6, compared to a conventional continuous flow
system
(sample 13). In this example, the valve had a nozzle of about 15mm the system
had a
head (i.e., water column height) of about 20.1m, with a water volume of about
5-6 m3.
As shown, the example valve was controlled to open/close for periods ranging
from
about 30 to about 80 ms, with each valve opening releasing a water jet having
a
volume in the range of about 0.000110 to about 0.000140 m3 at an average
velocity in
the range of about 15 to about 20 m/s. This resulted in jet energy in the
range of about
to about 25 Nm and jet power in the range of about 350 to about 650 W. The
15 results of these tests indicated that the example prototype system was able
to provide
jet velocity about 20% higher than water velocity in the conventional
continuous flow
system and therefore more power generated using the same water consumption.
Although a range of about 30 to about 80 ms is shown for opening/closing of
the
valve, other timing may be used, for example anywhere in the range of about 10
to
about 200 ms for each opening and closing. As described above, the higher
velocity of
water jets in the example system may be due to micro water hammer effects and
water
compression when the valve opens and closes in short bursts. Although fixed
timing is
shown for opening and closing of the valve, the opening and closing timing of
the
valve may be variable, for example as tuned by a feedback control loop (e.g.,
PID
controller) and may depend on the system size.
In some examples, the disclosed system may be retrofitted to existing water
turbine systems (i.e., those using continuous flow to drive turbines) to help
improve
the efficiency of energy conversion. This may allow more power than
conventional
systems to be delivered with the same water consumption as conventional
systems.
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Although the present disclosure makes reference to examples and theories of
operation, these are for the purpose of illustration only and are not intended
to be
limiting. A person skilled in the art would understand that variations and
modifications, based on technologies both current and yet to be developed, may
be
possible within the scope of this disclosure. All references mentioned are
hereby
incorporated by reference in their entirety.
