Note: Descriptions are shown in the official language in which they were submitted.
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GENERATOR UTILIZING FLUID-INDUCED OSCILLATIONS
FILED OF DISCLOSURE
[0001] This application generally relates to harvesting energy from flowing
fluids, and more specifically, to a unique design of an energy converter and
generator that induce oscillations by flowing fluids and utilize the
oscillations to
produce electricity.
BACKGROUND AND SUMMARY
[0002] The kinetic energy present in flowing fluids, such as wind or water,
has been successfully applied towards productive human ends, such as grinding
grain or pumping water. Wind-powered generators were developed to harness
these fluid flows for the production of electricity. Today, wind-powered
generators take on the largely ubiquitous form of a turbine, or rotating
airfoil.
While these turbine-based wind generators are generally useful in certain open
spaces with consistently high-speed winds, drawbacks still exist, such as
heavy
initial capital costs, low efficiency at all but a narrow range of wind
speeds, the
lack of cost effectiveness at lower power outputs levels (<1 kW), etc.
[0003] To circumvent the drawbacks of the turbine-based devices, various
alternative generators were designed to utilize other natural flow phenomena.
However, these proposals were not satisfactory due to design complexities,
added cost, the need for a complex mounting structure, low efficiency in
energy
production, insufficient power generation, inefficient production of
vibrations,
restriction to high flow speeds, etc.
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[0004] This disclosure describes various embodiments of unique
generators that effectively promote oscillations induced by flowing fluids,
and
utilize the oscillations in generating electricity or other types of energy.
In one
aspect, an exemplary generator harnesses the energy of fluid flows by way of a
combination of flutter and vortices shedding induced along a tensioned
membrane, or "belt", fixed at two or more points. The membrane may have an
elongated shape or other kinds of shape that are known to promote vibrations
with the flowing fluids.
[0005] An exemplary electrical generator includes at least one magnetic
field generator, at least one electrical conductor, and at least one flexible
membrane having at least two fixed ends. The membrane vibrates when
subject to a fluid flow. One of the electrical conductor and the magnetic
field
generator is attached to the membrane and configured to move with the
membrane. The vibration of the membrane caused by the fluid flow causes a
relative movement between the electrical conductor and the applied magnetic
field. The relative movement causes a change in the strength of the magnetic
field applied to the electrical conductor, and the change in the strength of
the
magnetic field applied to the electrical conductor induces a current flowing
in the
conductor. One or all parts of the generator may be implemented as a MEMS
(Micro Electro-Mechanical Systems) device. In one aspect, the direction of the
magnetic field may be substantially perpendicular to an area enclosed by the
electrical conductor, when the membrane does not vibrate.
[0006] The exemplary generator may further include at least one mass
attached to the membrane, to promote movements or vibrations of the
membrane when it is subject to fluid flows. In one embodiment, a power
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conditioning circuit may be provided to condition the induced current. The
power
conditioning circuit may include a rectifying circuit configured to rectify
the
current. In another embodiment, the magnetic field generator includes at least
one permanent magnet. In still another embodiment, an exemplary generator
includes multiple sets of electrical conductors, such as coils. The currents
generated by the multiple sets of conductors may be combined in a serial
manner. A rechargeable electrical power storage device, such as a battery or
capacitor may be provided to be charged by the current or currents.
[0007] In one embodiment, the exemplary generator further includes a
supporting structure. The fixed ends of the membrane are affixed to the
supporting structure. The electrical conductor is attached to the membrane.
The
magnetic field generator is disposed on the supporting structure. In another
embodiment, the magnetic field generator is attached to the membrane, and the
electrical conductor is disposed on the supporting structure. In another
embodiment, the magnetic field generator is oriented so as to project the
magnetic field (i.e., pole to pole axis) perpendicular to the plane of the
membrane. In still another embodiment, the magnetic field generator is
oriented
so as to project the magnetic field parallel to the plane of the membrane. Of
course, the electrical conductors are rearranged in each corresponding
embodiment to account for changes in the magnetic field direction.
[0008] According to another embodiment, the exemplary generator
includes an adjustable tension provider, such as a motor, configured to apply
an
adjustable tension force between the fixed ends of the membrane according to
the speed of the fluid flow. A sensor may be provided to generate a signal
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indicating an effect of the fluid flow. In one aspect, the tension force is
adjusted
based on the current.
[0009] According to another embodiment, the exemplary generator may
include multiple flexible membranes. In one aspect, the membranes may affix to
the same supporting structure.
[0010] Additional aspects and advantages of the present disclosure will
become readily apparent to those skilled in this art from the following
detailed
description, wherein only exemplary embodiments of the present disclosure are
shown and described, simply by way of illustration of the best mode
contemplated for carrying out the present disclosure. As will be realized, the
present disclosure is capable of other and different embodiments, and its
several
details are capable of modifications in various obvious respects, all without
departing from the disclosure. Accordingly, the drawings and description are
to
be regarded as illustrative in nature, and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
(0011] FIG. I is a perspective view of an exemplary generator according
to this disclosure.
[0012) FIG. 2 is a side view of an exemplary mode of vibration of an
illustrative embodiment.
10013] FIG. 3 is an illustration of an exemplary orientation of permanent
magnets and the generated field thereof.
[0014] FIG. 4 is a schematic diagram of an electrical circuit for processing
the currents generated by an exemplary generator.
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[0015] FIG. 5 is a perspective view of another embodiment of an
exemplary generator.
[0016] FIG. 6 is a perspective view of still another embodiment of an
exemplary generator utilizing oscillations caused by flowing fluids.
10017] FIG. 7 is a perspective view of another mode of vibration.
[0018] FIG. 8 is a sectional perspective view of an orientation variation of
an exemplary generator.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0019] In the following description, for the purposes of explanation,
numerous specific details are set forth in order to provide a thorough
understanding of the present disclosure. It will be apparent, however, to one
skilled in the art that the present disclosure may be practiced without these
specific details. In other instances, well-known structures and devices are
shown in block diagram form in order to avoid unnecessarily obscuring the
present disclosure.
[0020] An exemplary electrical generator includes a magnetic field
generator and a flexible membrane for converting energy present in fluid
flows,
such as air flows, water flows, tides, etc., into vibrations or oscillations.
The
flexible membrane includes at least one electrical conductor attached thereto
and has at least two fixed ends. The membrane vibrates when subject to a fluid
flow. As used herein, the term "flexible" refers to a membrane that has the
ability
to morph into a large variety of determinate and indeterminate shapes without
damage, in response to the action of an applied force.
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(00211 The at least one electrical conductor may be implemented as
aluminum or copper coils attached to the membrane and configured to move
with the membrane. For instance, one or more coils are integrated into or onto
the oscillating membrane. Those coils are suspended over corresponding
magnetic field generators. In one embodiment, the coils are printed directly
onto
the membrane via techniques that have recently been developed for RFID tags
and patch antennae.
[0022] The vibration of the membrane caused by the fluid flow causes a
relative movement between the electrical conductor and the applied magnetic
field. The relative movement causes a change in the strength of the magnetic
field applied to the electrical conductor, and the change in the strength of
the
magnetic field applied to the electrical conductor induces a current flowing
in the
conductor.
[0023] When using wind or air flow to drive the exemplary generator, wind
flows perpendicularly to the long axis of the membrane, such as a membrane
having an elongated shape. The flowing fluid induces a spontaneous instability
in
the tensioned membrane known as flutter. The flutter of the membrane results
in a
regular, reduced torsion high energy oscillation mode in appropriately
designed
variations. This mode is often referred to as the first normal mode of
oscillation.
Additionally, vortices shedding may occur along the edges and surface of the
membrane, in some cases enhancing the oscillation.
[0024] The vibration of the membrane thereby causes the coils to move
relative to the magnets. A changing magnetic field cuts through the closed
area
defined by the coils, thus resulting in an EMF within said coils. Thereby an
electricity flow results, without requiring the physical coupling of the
vibrating
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membrane to a piston or cam system for power generation. This electric
generator
operates at a variety of wind speeds, including lower speeds than required for
most
turbine-based wind generators. Moreover, the cost of an exemplary generator of
this disclosure is substantially lower than most other wind-based generators,
and
the absence of physically grinding parts offers the possibility of long,
quiet,
maintenance-free operation. No leading bluff bodies are required, although
they
can be employed if desired.
[0025] Additionally, the exemplary generator achieves better efficiencies,
particularly at small scales, than that of turbine or turbine-less generators,
such as
those using conventional piezoelectric approach. Without the Betz limit
restriction
of airfoil-based rotary turbines, more relaxed efficiency limits can be
established for
this improved wind generator class.
[0026] The concepts disclosed herein address energy challenges in a wide
array of fields, from energy harvesting for small scale RF sensor arrays to
decentralized rural electrification to grid-connected large scale power
supplies.
[0027] In some embodiments, the oscillation is in a mode with two
relatively fixed nodes, while in other embodiments multiple nodes across the
membrane may be established. Also, in some embodiments, the coils are
positioned on the membrane and move relative to a stationary set of magnets,
whereas in other embodiments the coils are stationary on the mount, and the
magnets are affixed to the moving membrane. Additionally, the magnetic field
may be produced by permanent magnets or electromagnetic induction, with
some of the electricity created by the generator being routed into the wiring
of
electromagnets to maintain their field. The coils may assume various shapes,
configurations or forms.
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[0028] FIG. 1 depicts an exemplary generator 100 according to this
disclosure. The generator 100 includes an elongated membrane 2, two coils 4a,
4b and a support structure 6. The supporting structure 6 includes a base 8 and
two sections thereof for receiving permanent magnets 12a, 12b. Adhesives 14a,
14b are provided to join the membrane 2 to the base 8. A power conditioning
circuit is provided on or off the base/membrane to process the currents
produced
by the coils 4a, 4b. The coils 4a, 4b are adhered to the surface of or within
the
membrane 2, and suspended over the magnets 12a, 12b, respectively. Two
leads 16a, 16b are coupled to coils 4a, 4b, respectively. The tension applied
to
the membrane 2 is a function of the elasticity of the membrane 2 and the
physical characteristics (i.e., young's modulus, etc.) of the base 8, along
with the
particular distance between the ends of the base 8.
[0029] The exemplary generator 100 shown in. FIG. 1 operates as follows.
A flow of fluid, which may include liquid flows of water for instance, or a
flow of
air such as that found in artificial ventilation systems or in natural wind,
travels
across the elongated and tensioned membrane 2. This fluid flow travels in a
direction approximately perpendicular to the major axis of the membrane, after
which a self-exciting oscillation of the membrane will begin. This oscillation
often
will initiate with a slight torsion of the membrane 2. However, this initial
condition
will quickly (approximately <1 sec) stabilize to an oscillation of the lowest
normal
mode with reduced torsion, such as that depicted in FIG. 2. As the membrane 2
vibrates, the coils 4a, 4b will likewise oscillate with the membrane 2, above
the
fixed permanent magnets 12a, 12b. A side view of this vibration is illustrated
in
FIG. 2.
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[0030] FIG. 3 illustrates an exemplary orientation of the magnets 12a, 12b
beneath the coils 4a, 4b. The magnetic field is oriented such that the dosed
area of the coils 4a, 4b is crossed by perpendicular field lines, as
originally
described by Michael Faraday. It should be noted that several orientations of
the
magnets will produce appropriately oriented magnetic fields. The strength of
that
field through the coils 4a, 4b changes as the coils 4a, 4b move relative to
the
stationary magnets 12a, 12b. This change in the magnetic field produces an
electromotive force (EMF). The EMF creates a current, i.e., a flow of
electrons,
dependent on the load conditions, internal resistance, impedance, and a range
of other factors.
[0031] In the first normal mode of oscillation, the coils 4a, 4b oscillate
approximately in phase with each other. The electricity flowing through
respective leads 16a, 16b may be combined without significant destructive
interference. The leads 16a, 16b may be joined in parallel or series,
depending
on the desired voltages and currents fed into a power conditioning circuit
associated with the generator 100.
[0032] The configuration shown in FIG. 1 effectively concentrates the
energy of oscillation of the entire membrane at one or more discrete zones.
This
works in a similar fashion to the way in which a lever "concentrates" a large
translated motion into a smaller motion with a greater potential force. This
greater force nearer the ends of the membrane is what allows for the
incorporation of heavier and thicker coils without dampening out the
oscillation.
Hence, a smaller magnetic field is needed to fill the smaller volume of space
traveled by the coils, which translates to lesser magnet costs. Additionally,
by
placing the coils largely out of the path of the flowing fluid, the majority
of the
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center area of the membrane can respond to those flows without impediment of
wiring.
[0033) FIG. 4 shows a block diagram of an exemplary power conditioning
circuit 40 using a series connection to achieve higher voltages for low wind
speeds. The circuit 40 includes a rectifier 41, a smoothing capacitor 42, a
step-
up supply 43, and a power storage device 44, such as a rechargeable battery or
a super capacitor. The rectifier 41 and the smoothing capacitor 42 convert the
output of the coils 4a, 4b, which is in the form of an alternating current,
into
smooth direct current. The DC current is then fed into the step-up supply 43,
or
a boost converter, if a particular range of voltages is desired for the end
application. The power storage device 44 is provided to buffer between the
current drawn by the application and the supply from the coils 4a, 4b of the
generator 100.
[0034] As shown in FIG. 1, the base 8 assumes the shape of a bow. The
bow-shaped base provides an approximately constant tension on the membrane
2 over short deviations. So, as the membrane 2 stretches over time, the spring-
action of the base 2 ensures that the membrane 2 remains at a particular
tension. It is understood that other shapes of bases may be used to implement
the generator 100. A flat unbowed base can also be used, and the natural
elasticity of the membrane 2 itself can serve this same purpose. In another
embodiment, constant force springs (such as Belleville washers) or compliant
mechanisms may be attached to the ends of the membrane or incorporated into
the structure of the base itself, so that a more reliable constant tension on
the
membrane 2 can be maintained over longer periods of time. For embodiments
that the membrane(s) are vertically oriented, a constant restoring force can
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generated with gravitational attraction, by attaching weights to the membrane
2
or base 8.
[0035] In another embodiment, a feedback system is built into the
generator 100 to provide or apply greater tensioning of the membrane 2 in
higher
wind speeds. Thisfeedback system may be implemented in a variety of ways,
such as installing a solenoid within the base 2 of the mounting structure. The
pushing force of the solenoid can then be varied in step with the electrical
output
of the coils 4a, 4b. In another embodiment, memory alloys or dielectric
materials
that change shape with varying input voltages are used to alter tension of the
membrane 2 in response to the wind speeds detected by a sensor.
[0036] FIG. 5 depicts another embodiment of an exemplary generator 500
using the concepts of this disclosure, in which a coil 52 covers a larger area
of
the membrane surface 54. In order to maintain a similar electrical power
output,
more permanent magnets 56 would be needed to provide a similarly enlarged
magnetic field. The design depicted in FIG. 5 is particularly useful for very
small
generators, such as MEMS devices or "generators on a chip", wherein a coil
that
covers a greater percentage of the membrane is acceptable, as the magnetic
field needed to saturate the volume of the coil's translation is of a very
limited
order.
[0037) FIG. 6 illustrates a variation of the embodiment shown in FIG. 1.
At least one mass 62 is provided on the membrane 2. The mass 62 may include
one or more low-profile objects of either symmetric or asymmetric shape. For
membranes with larger sizes (such as >0.5 meters in length), the attached mass
62 provides a more vigorous oscillation of the membrane 2. In some cases, the
mass 62 acts to provide a source of instability at the onset of oscillation,
thereby
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causing a slight initial torsion of the membrane 2. However, the location and
geometry of the mass 62 and the tension, width, and length of the membrane 2
can be made such that this instability is quickly transformed into an
oscillation of
the first normal mode with reduced torsion.
[0038] FIG. 7 depicts another embodiment of this disclosure. In this
embodiment, the arrangement of the coils and the membrane are similar to the
generator shown in FIG. 1. However, the membrane in FIG. 7 is made to
oscillate in other normal modes of vibration, such as the second mode
illustrated
in FIG. 7. Some simple alterations may be necessary in the power conditioning
circuitry to accommodate the out of phase oscillation of a plurality of coils,
but for
larger generators these alternate modes may offer significant gains in
efficiency.
[0039] While the examples shown in FIGS. 1 and 5-7 involve one or more
coils moving with reference to a stationary set of permanent magnets, it is
understood that other embodiments may be implemented in which the magnets
are placed on the membrane and are thus made to move relative to stationary
coils. The advantage of such an arrangement is that the wire leads coming from
the coils do not suffer any bending stress, as may occur with the moving coil
embodiments.
[0040] Additionally, while the coil may be placed substantially parallel to
the surface of the elongated membrane 2 as shown in FIG. 1, another option is
to arrange the. coil more substantially perpendicular to the membrane, either
attached below or above the membrane 2. Of course, the orientation of the
magnetic field to the permanent magnets will need to be altered to accommodate
such a variation. Similarly, such reorientation options of the coil relative
to the
membrane also apply to embodiments in which the magnetic field generator is
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attached to the membrane 2 and the coil is affixed to the base B. FIG. 8
illustrates a sectional view of an example of orienting a magnetic field
generator,
such as a magnet 72, so as to project the magnetic field (i.e., pole to pole
axis)
parallel to the plane of the membrane 2, with the corresponding coil flanking
the
side of said magnetic field generator. As shown in FIG. 8, the permanent
magnet 72 is attached to a substantially rigid member 74, which itself is
attached
in a roughly perpendicular arrangement to the flexible membrane 2. The field
produced by the permanent magnet 72 is directed through coil 4a, which is held
in close proximity to the magnet 72 with a support 76. As the membrane 2
oscillates, the permanent magnet 72 will also oscillate. This oscillation will
cause
the strength of the magnetic field directed through coil 4a to change, thereby
producing an EMF. This particular embodiment has the advantage of avoiding
magnet-coil contact over a wide range of oscillation rates, as the magnet 72
moves along the face of the coil 4a rather than towards and away from said
coil.
Additional coils may be placed on the opposite side of the magnet 72 to
benefit
from the additional pole. According to a variation, the coil 4a and the magnet
72
may be backed with ferrous materials so as to form a complete magnetic
circuit,
as described in other sections of this application.
[00411 According to another embodiment, rather than adherring the coils
to the membrane, a linear generator can be coupled to the oscillating membrane
2. While the most straight-forward approach to accomplishing this coupling
would be to connect a shaft or thread between the magnet of the linear
generator and the membrane, a smaller magnet incorporated onto the
membrane can be used to stimulate oscillation in the linear generator's magnet
without contact, by either repulsion or attraction. The natural frequency of
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oscillation of the linear generator's magnet is preferably matching that of
the
driving oscillation of the membrane. This embodiment allows large generator
installments to gain in efficiency.
[0042] Additional variations may be provided to enhance the performance
of the exemplary generators for particular applications. For instance, it may
be
desirable to fill the coils of the generator with ferrite powder or laminated
ferrous
metals to enhance flux through the coils. Also, as is well known in the art,
the
magnetic field produced by the permanent magnets can be made into a
"complete circuit" by appropriately placing laminated or powdered
ferromagnetic
or ferromagnetic materials around the magnet core. This technique ensures that
the maximum magnetic field can be directed to the area of the coils.
[0043] A multitude of ferromagnetic materials can be used as the source
of the magnetic field in the generator. NdFeB rare earth magnets, ceramic
magnets, Alnico magnets, and Samarium-cobalt magnets are a few of the more
popular options.
[0044] Additionally, electromagnets, also known as field coils in generator
applications, may be used in place of permanent magnets as a source of a
magnetic field. One or more coils of wire with either air cores or with
ferromagnetic cores may function as the field coils. These field coils are
charged
with a small residual magnetic field in the core, to induce an initial small
EMF in
the moving membrane coils. A portion of this electrical flow is diverted back
into
the field coils, resulting in a still greater field. This increased field
leads to an
increasing EMF produced in the oscillating membrane coils, and this positive
feedback loop continues until an equilibrium is reached, at which point the
field
coils are producing a strong field similar to that produced by a permanent
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magnet. These self-excited generators, as they are sometimes called, are
usually classified into the subsets of "series" generators, "shunt"
generators, or
"compound" generators, the principles of which are well known in the art.
Another possibility is to use field coils that are separately excited, with
the
electrical flows necessary for a field provided by an external source. Both of
these non-permanent magnet options are particularly useful for larger
installations, where the cost of large permanent magnets would be prohibitive.
[0045] Some other variations involve the membrane. The form of the
membrane does not need to be limited to a rectangular shape. Rather, tapered
membranes and membranes of various geometries may offer significant
advantages at certain scales. Also, the membrane need not be limited to flat
webs of film or fabric, but can also be made into profiles more closely
approximating airfoils, to enhance the oscillation characteristics of the
elongated
flexible membrane. Moreover, the web need not be continuous throughout, but
rather may incorporate holes or depressions. In some cases, holes centered on
the membrane-mounted coils may allow the base-mounted magnets to pass
partially through said coils, thereby preventing membrane-magnet collision in
certain embodiments during vigorous oscillations.
[0046] Most embodiments described thus far can also be oriented in any
direction, such as vertically mounted on a pole, or horizontally mounted
between
two towers, or any combinations or variations thereof. A exemplary generator
of
this disclosure may be made with any number of membrane materials, such as
ripstock nylon, superthin polyester film, mylar-coated taffeta, Keviar tapes,
or
polyethylene film, to name a very few of a large set of possibilities.
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[0047] Multiple generators can also be used in power installations to
supply electricity at various levels for a given area or application. A cost
effective embodiment involves the use of two membranes with embedded coils,
each placed on opposite sides of the permanent magnets. This arrangement
allows for the utilization of both poles of the magnetic field. The AC output
of
each membrane of this dual membrane variation may not be in phase, and so
can be rectified and conditioned separately, and then recombined into an
additive bC output. Clearly, a multitude of these generators can be stacked
onto
a tower or arranged in a framework to capture the energy of a large cross-
sectional area of wind, rather than only capturing the small area seen by a
single
generator alone.
[0048] Another variation of an exemplary generator includes a membrane
stretched between two distant points, for example, between two buildings or
between two towers. In this case, a base that extends the entire length of the
membrane is not necessary. Rather, clamps at the ends of the membrane can
provide support for the membrane and the source of the field (whether that
source is a set of permanent magnets or field coils). A spring or a
specifically
engineered compliant mechanism may be incorporated into the clamps so that
constant tension is applied to the membrane, even across large distances.
[0049] An advantage of an exemplary generator according to this
disclosure relates to the response to very high wind speeds. Typically, in
conventional horizontal-axis turbine or vertical-axis generators, a furling
mechanism must be incorporated into the design of the generator. This furling
mechanism enables the blades of the generator to bend out of the wind flow, to
avoid catastrophic damage in high wind conditions. This addition is a costly
and
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complex feature in conventional wind-based generators. In some cases, the
substantial kinetic energy of the turbine blades remains a hazard despite the
precautions of furling. In contrast, an exemplary generator according to this
disclosure operates under carefully selected tension conditions. Therefore, in
high winds that may pose a danger to the generator, the tension of the
membrane can be simply reduced, or the membrane twisted slightly to greatly
reduce coupling of the generator to the wind flows. When that occurs, the
membrane will cease oscillation until it is safe to resume. Moreover, if the
membrane does fail catastrophically and detaches from-the mounting structure,
the danger to the surrounding area is small comparing to conventional turbine-
based generators.
[0050] Generators implemented according to this disclosure have many
applications across a wide range of power scales. For instance, hundreds of
small generators according to this disclosure can be disposed throughout the
HVAC ducting of abuilding. These generators can tap the flows of air
throughout the ducting network to provide a continuous supply of power to
wireless sensors in the vicinity. These arrays of sensors are critical in the
construction of "smart buildings." However, the sensors needed in the
construction often employ batteries with three to five year life spans, which
greatly increases the maintenance costs of the sensors over their ten or
twenty
year life cycles. The generators implemented according to this disclosure and
disposed throughout the HAVC ducting reduce the reliance on batteries, and
expand the reach of this field of distributed, long-life sensor arrays.
According to
another embodiment, the exemplary generators themselves may act as both a
wind sensor and the power source needed for transmitting that sensor
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information, if the voltages produced at different wind speeds are known for a
given design.
[0051] Another important application of the generators according to this
disclosure is rural lighting, largely in emerging economies. Most households
in
the developing world spend up to twenty percent of their annual income on
kerosene for lighting, a type of smoky, fuel-based lighting that is both a
fire
danger and an indoor air quality health hazard. A new lighting system may be
implemented by coupling generators according to this disclosure at scales of
tens of watts with highly efficient white LEDs. The new system can
continuously
provide clean, cheap lighting over a decade or more and could be paid for with
several months' worth of kerosene expenses (US$10-$50). A related application
of an exemplary generator of this disclosure is in powering nodes in a
wireless
data transmission network, such as WiFi, or meshed network.
[0052] According-to one embodiment utilizing the configuration illustrated
in FIG. 1, the membrane has an elongated shape having two fixed ends. The
membrane is made of Mylar coated taffeta, and the measurements are 440 mm
long, 25 mm wide and 0.1 - 0.15 mm thick. Two coils are adhered to the
membrane at 74 mm from each fixed end. The coils are made of 38 awg enamel
coated wire, each with approximately 150 turns and having a resistance of
approximately 25 ohms. The coils are approximately 3/4" in inner diameter, and
7/8" in outer diameter. These coils are wired in series to achieve a total
resistance of approximately 50 ohms. The base is made of acrylic. Two
cylindrical NdFeB magnets are positioned under the coils. The magnets are 1/2"
thick, 3/4" in diameter, and generate a 5840 Gauss surface field. The vertical
oscillation of the membrane, peak to peak, is approximately 20 mm. This
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embodiment generates approximately 15 - 20 mW across a matched load, in a
9-10 mph wind (4-4.5 m/s), sufficient for powering a wireless transceiver for
continuous RF transmission of information, such as temperature and voltage,
and charging capacitors in the wireless transceiver. The smaller size of this
embodiment makes it suitable for working in HVAC ducting for harvesting energy
of air flows to power sensor arrays.
[0053] In another embodiment, an exemplary generator constructed
according to the configuration shown in FIG. 1 utilizes a larger membrane that
is
made of mylar coated taffeta or ripstock nylon, and is 1.75 meters long, 50mm
wide, on both steel and HDPE bases. In one embodiment, a thin rectangular
piece of steel having a size of approximately 1.5" x 1.5" is adhered to the
middle
of the membrane to act as the mass illustrated in FIG. 6. Two rectangular
coils
of 28 awg wire are adhered near the ends of the belt and suspended over
corresponding rectangular NdFeB magnets. This power generated by this
exemplary generator across a matched load in 10 mph winds is approximately
0.5 -1 W, suitable for charging cell phones or providing power to lighting in
rural
areas.
[0054] While the above embodiments have been discussed using
examples of capturing the energy of air flows, it is understood that the same
designs may also be applied to capturing the energy of water flows. For
instance, a generator with a modified membrane, with less viscous drag
characteristics, could be placed at the seafloor to capture the energy of
ocean
currents. Additionally, in a similar fashion to the energy harvesting in HVAC
systems discussed, a generator based on the principles of the present
disclosure
can be incorporated into water piping. A combination of ocean current and wind
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generators could be used to form a remote sensor array on open bodies of
water, although either the ocean current or wind generator alone could also
serve this purpose.
[0055] It is understood that one or more parts or modules of the
exemplary generators described herein may be sold separately for assembly into
a generator as described in this disclosure. For instance, an energy converter
may be provided for use in an electrical generator having a magnetic field.
The
converter comprises at least one flexible membrane. Each membrane has at
least two fixed ends, and is exposed to the magnetic field when used in the
generator. In addition, the membrane vibrates or oscillates when subject to a
fluid flow. Each membrane has at least one attached electrical conductor. The
vibration of each membrane caused by the fluid flow creates a movement of the
conductor relative to the magnetic field. The relative movement of the
conductor
creates a change in the strength of the magnetic field applied to the
electrical
conductor. The change in the strength of the magnetic field applied to the
electrical conductor induces a current flowing in the conductor. it is also
understood that a generator may utilize multiple sets of energy converters to
produce power at a larger scale.
[0056] According to another embodiment, an exemplary energy converter
is provided for use in an electrical generator including one of at least one
magnetic field generator and at least one electrical conductor. The converter
comprises at least one flexible membrane and the other one of the at least one
magnetic field generator and the at least one electrical conductor attached to
the
membrane. Each membrane has at least two fixed ends. In addition, each
membrane vibrates when subject to a fluid flow. The vibration of each
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membrane caused by the fluid flow creates a relative movement between the at
least one conductor and a magnetic field generated by the at least one
magnetic
field generator. The relative movement creates a change in the strength of the
magnetic field applied to the at least one electrical conductor. The change in
the
strength of the magnetic field applied to the at least one electrical
conductor
induces a current flowing in the at least one electrical conductor.
[0057] The disclosure has been described with reference to specific
embodiments thereof. It will, however, be evident that various modifications
and
changes may be made thereto without departing from the broader spirit and
scope of the disclosure. The concepts described in the disclosure can apply to
various operations of the networked presentation system without departing from
the concepts. The specification and drawings are, accordingly, to be regarded
in
an illustrative rather than a restrictive sense.
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