EP2697509A1

EP2697509A1 - Non-rotating wind energy generator

Info

Publication number: EP2697509A1
Application number: EP12771594.4A
Authority: EP
Inventors: Dylan THORP; Liam BYERS; Mitchell NOAH; Thomas Olsen; Evan WEINER; Mohammad TASLIM
Original assignee: Northeastern University Boston
Current assignee: Northeastern University Boston
Priority date: 2011-04-15
Filing date: 2012-04-16
Publication date: 2014-02-19
Also published as: CN103732915A; JP2014510877A; WO2012142563A1; EP2697509A4

Abstract

In an embodiment of the invention, a non-rotating wind energy generator uses the fluid flow principle of vortex shedding and self-excited oscillations to generate oscillatory, linear motion of a beam, and linear magnetic inductors, optionally located near both ends of the beam, generate electrical power when the beam is in motion.

Description

NON-ROTATING WIND ENERGY GENERATOR

RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 61/476103, filed April 15, 201 1 entitled "Non-Rotating Wind Energy Generator," which is herein incorporated by reference in its entirety.

FIELD

[0002] This invention relates to generating electrical power from wind.

BACKGROUND

[0003] The ever-increasing demand for sustainable, environmentally-friendly power generation from wind is currently met with devices such as the wind turbine. Although wind turbines are the most commonly used method of generating electrical power from wind, they have several inherent drawbacks. These devices are costly, difficult to construct, install, and maintain, highly visible, noisy, large, susceptible to damage, and relatively difficult to transport and assemble. Their tall stature makes them susceptible to damage from flying debris, birds, and even low flying planes. The U.S. Military has also voiced concerns claiming the placement of wind turbines in a radar system's line of sight may adversely impact the unit's ability to detect threats. Rotating wind turbines are also not suitable for military applications that require quiet, inconspicuous power generation in remote locations. Additionally, when facing high wind speeds, a mechanical brake must be applied, creating losses and inefficiencies. Therefore, there is a need for portable, non-rotating devices that can generate useful amounts of electrical power in a quiet, inconspicuous manner.

[0004] A system created by Vortex Hydro Energy uses the principle of vortex shedding in water to harness wave energy. The company has developed a device called the Vortex Induced Vibration Aquatic Clean Energy (VIVACE). This product uses vortex shedding as a primary means of creating mechanical motion from fluid flow. The system is designed to operate underwater in ocean currents. This system uses an electrically variable spring constant system that dynamically changes the natural frequency to allow for optimization at different flow speeds. This system is unsatisfactory for wind power generation due to the large difference between the fluid flow properties of air. The frequency of vortex shedding in air is much faster that the shedding frequency in water. Therefore, matching the system's natural frequency with the shedding frequency would result in an extremely large spring constant. A spring this size requires a great deal of force to move. Unfortunately the lift characteristics of this application do not provide enough lift to overcome this spring constant, and no vibrations will occur.

[0005] Therefore, a need exists for portable, non-rotating devices that can generate useful amounts of electrical power in a quiet, inconspicuous manner.

SUMMARY

[0006] Aspects of this invention relate to a novel approach to harnessing wind power. In an embodiment of the invention, the device uses the fluid flow principle of vortex shedding and self-excited oscillations to generate oscillatory, linear motion of a beam. In an embodiment of the invention, linear magnetic inductors optionally located near both ends of the beam generate electrical power when the beam is in motion.

[0007] In an aspect of the invention, a non-rotating wind energy generating apparatus comprises a suspended bluff body operable to initiate and sustain oscillatory motion in response to wind energy using vortex shedding and an inductor system operable to generate energy via the motion of the suspended bluff body. In one or more embodiments, the suspended bluff body may comprise a frame movably supporting at least one beam, one or more first springs, one or more second springs, wherein the one or more first springs attach a first portion of the frame to a first portion of the beam and the one or more second springs attach a second portion of the frame to a second portion of the beam such that the beam is suspended between the first and second portions of the frame, and wherein the inductor system comprises at least one inductor attached to one of the beam or a third portion of the frame, at least one magnet attached to one of the third portion of the frame or the beam, wherein motion of the beam when exposed to wind causes the first inductor to pass the at least one magnet. In any of the proceeding embodiments, the beam may have a D-shape. In any of the proceeding embodiments, the beam may be hollow. Any of the proceeding embodiments may further comprise one or more guide rails. Any of the proceeding embodiments may further comprise one or more additional beams, one or more additional upper springs, one or more additional lower springs, wherein the one or more additional upper springs attach a first portion of the additional beam to a third portion of the beam and the one or more additional lower springs attach a second portion of the additional beam to a fourth portion of the beam such that the one or more additional beams are suspended between the first and second portions of the frame. In any of the proceeding embodiments, the first portion of the frame may be an upper portion, the first portion of the beam may be an upper portion, the second portion of the frame may be a lower portion, and the second portion of the beam may be a lower portion. In any of the proceeding embodiments, the third portion of the frame may be a side portion. In any of the proceeding embodiments, the beam may be suspended substantially horizontally. In any of the proceeding embodiments, the motion of the beam may be substantially vertical. In any of the proceeding embodiments, a surface of the beam may be uniformly smooth. In any of the proceeding embodiments, a surface of the beam may be partially smooth. In any of the proceeding embodiments, a surface of the beam may be uniformly rough. In any of the proceeding embodiments, a surface of the beam may be partially rough. In any of the proceeding embodiments, the at least one inductor or the at least one magnet may be attached to a first end of the beam. In any of the proceeding embodiments, the spring mass may be selected to promote self-oscillatory motion. In any of the proceeding embodiments, the beam may have a cross-sectional geometry selected from the group consisting of a square, a cylinder, a reversed D-Beam (where the wind is primarily incident on the round portion of the beam rather than the flat portion), and an equilateral wedge in either a "greater than" or "less than" orientation relative to the incident wind. In any of the proceeding embodiments, the springs may be stretched in a resting state. In any of the proceeding embodiments, the beam mass may be selected to promote self-oscillatory motion. In a further aspect of the present invention, exposing the non-rotating wind energy generating apparatus of any of the proceeding embodiments to wind generates oscillatory motion in response to wind energy using vortex shedding and generates energy via motion of the non-rotating wind energy generating apparatus using induction.

[0008] It is an object of the present invention to provide a non-rotating alternative to wind turbines, which produces comparable electrical power and which is portable, easy to transport, and less susceptible to damage. In some embodiments, the device is considerably smaller than a residential or large scale wind turbine. In some embodiments, the device can be easily disassembled, stowed, and transported to remote areas such as a campsite or forward operating military base. In some embodiments, the device operation allows for inconspicuous and virtually silent operation. BRIEF DESCRIPTION OF THE DRAWING

[0009] The foregoing and other objects, features and advantages of the invention will be apparent from the following description of the preferred embodiments of the invention, as illustrated in the accompanying drawings.

[0010] Figure 1 is a schematic illustration of Vortex Shedding, demonstrating the formation of vortices and subsequent motion.

[0011] Figure 2 is a graph of Reynolds Number vs. Strouhal Number showing the relationship between Strouhal number and Reynolds number for circular cylinders.

[0012] Figure 3 is a schematic illustration of a non-rotational wind generating energy generator according to one aspect of the invention as shown in side view (3 A) and front view (3B).

[0013] Figures 4A and 4B provide perspective views of a non-rotating wind energy generator according to an embodiment of the invention.

[0014] Figure 5 is a perspective illustration of a beam according to one or more embodiments.

[0015] Figure 6 is a plot of the coefficient of lift vs. time (sec) for a series of beams having four different cross-sectional shapes, each at the same characteristic length.

[0016] Figure 7 is a plot of the coefficient of lift vs. time (sec) for a series of D-beams having a characteristic length of 0.001m, 0.025m, 0.05m, 0.075m and 0.1 m.

[0017] Figure 8 is a plot of lift force (N) vs. time (sec) and demonstrates how the size of a beam (here a D-beam) affects the lift force produced by vortex shedding.

[0018] Figure 9 shows the inductor assembly according to an embodiment of the invention.

[0019] Figure 10 is an illustration of a mounting system for the non-rotating wind energy generator according to one or more embodiments.

[0020] Figure 11 illustrates a mounting system for mounting a beam onto a frame according to one or more embodiments. [0021] Figure 12 is a perspective drawing of a beam according to one or more embodiments of the invention.

[0022] Figure 13 is a voltage trace of a non-rotating wind energy generator according to one or more embodiments.

DETAILED DESCRIPTION

[0023] Aspects of this invention relate to a novel approach to harnessing wind power. In one aspect, a device is provided to generate electricity from non-rotational motion caused by wind flow. Wind is typically characterized as unsteady flow; therefore the device is capable of operation in unsteady flow characteristics. To maximize the system efficiency, losses due to friction and drag is minimized, and methods of electrical energy harvesting are optimized. The device is easy to transport and deploy. A nominal wind speed of approximately 6 m/s is used as the basis for the prototype design and testing. However, the full-scale system is able to operate over a wide range of wind speeds.

[0024] Non-rotating wind energy generation is provided by first establishing non-rotating motion from wind flow, and then using that motion to generate electricity. In one aspect, a device does not use rotational motion similar to wind turbines currently on the market, but instead, the device uses the fluid flow principle of vortex shedding and self-excited oscillations to generate oscillatory, linear motion of a beam.

[0025] The phenomenon of vortex shedding involves the formation of alternating vortices which form behind a bluff body when it is placed in fluid flow. An oscillating resultant lift force acts on the body as these vortices are shed. Vortex shedding is caused when a fluid flows past a blunt object. The fluid flow past the object creates alternating low-pressure vortices on the downstream side of the object and the object will tend to move toward the low-pressure zone. Eventually, if the frequency of vortex shedding matches the resonance frequency of the structure, the structure will begin to resonate and the structure's movement can become self-sustaining.

[0026] The intensity of these vortices and resulting lift force are directly related to the cross-sectional shape and size of the bluff body. The formation of vortices and subsequent motion is shown in Figure 1. It is possible to predict the frequency at which these vortices will occur by using a dimensionless constant called the Strouhal Number (St) (See Equation 1, below).

St -— ^f CD

v " ^~

In this equation, is the vortex shedding frequency, L is the characteristic length (See Equation 2, below), and v is the velocity of the fluid flow before it contacts the body.

, 4,4

L =— p i 2)

Equation 2 gives the definition of hydraulic diameter where A is the area of the submersed body, and P is the wetted perimeter of the body. Characteristic length L appears in both Strouhal and Reynolds numbers.

[0027] When a body is placed in a fluid flow within a certain range of Reynolds number, a series of vortices occur at a frequency which can be predicted by the Strouhal number. Equation 3 defines Reynolds number as a function of the velocity of the fluid before it contacts the body (approach velocity), V, the characteristic length, L, the density of the fluid p, and the viscosity of the fluid, μ.

Re—- *— 13>

[0028] An acceptable range of Reynolds numbers for predictable vortex shedding is displayed in Figure 2. The curves in Figure 2 are for a circular cylinder. The reported value for the Strouhal number for a D-Beam is 0.21 (See, e.g., Applied Fluid Dynamics Handbook by Robert D. Blevins, Van Nostrand Reinhold Company, 1984) and is independent of the Reynolds number. Figure 2 depicts a straight horizontal line that is representative of the Strouhal number for a D-beam. From equation (1) above, f = StV/L, thus with a constant St for a D-beam, the frequency of oscillation increases with the wind speed and decreases as L increases. For a given average wind velocity, one can size the beam for the desired frequency. For other shapes, the Strouhal value may differ, but a similar process can be used to size a bluff body for a desired frequency. A certain set of flow conditions must exist in order for the shedding frequency to occur. Each vortex created in this series of vortices, called a Von Karman Vortex Street, carries alternating high and low pressure regions. The bluff body is drawn to the low pressure regions creating an oscillating resultant force. In embodiments of the present invention, this force is used to initiate motion of the generator system.

[0029] In one or more embodiments, the beam design is selected to provide self-excited vibrations when exposed to wind. Self-excited vibration is a phenomenon in which the motion of a system causes it to oscillate at its natural frequency with continually growing amplitude. In one or more embodiments of the invention, vortex shedding will initiate self- excited vibration of a beam. In one or more embodiments, a beam will continue to oscillate at the system's natural frequency when exposed to a wind flow. In one or more

embodiments, the system controls the amplitude of oscillation using springs. In further more embodiments, the system utilizes stops to limit the amplitude of oscillation.

[0030] Figure 3 is a schematic illustration of a non-rotational wind energy generator 300 according to one aspect of the invention. In one aspect, a beam 303 is slidably mounted in a frame 305 to provide oscillatory motion of the beam due to vortex shedding that is substantially perpendicular to the wind direction 302, or which has a component that is substantially perpendicular. The beam is equipped with at least a pair of springs 304 positioned above and below the beam to provide restorative force to the beam subjected to vortex shedding. This provides oscillatory motion of the beam while in wind contact. The springs can be secured to the frame using conventional methods such as latches, hooks, welds, bonds and the like. Due to the high stress experienced by the spring or other joining device, the securing method desirably provides high material strength and low fatigue life. To maintain a constant spring rate, coil diameter and/or number of coils must increase as wire diameter increases. Linear magnetic inductors 301 are shown located near both ends of the beam; however, they can be located anywhere in any number. They generate electrical power when the beam is in motion. A damping system 307 can be provided to further control the amplitude of the oscillations.

[0031] The non-rotating wind energy generating device uses the interaction of the beam with wind to induce vortex shedding and linear motion, which is then converted to electrical power with electromagnetic inductors. In one or more embodiments, the inductors incorporate magnets that are concentric with the wire coil. Other embodiments may use multiple pairs of parallel, stationary magnets and square coils that are fixed to a beam that passes between the magnets during operation. The use of a parallel magnet/coil configuration has been experimentally proven to be superior to a concentric magnet/coil configuration in at least one embodiment. This configuration permits a larger clearance between the magnets and coils. This helps prevent damping caused by rubbing during beam motion. The use of parallel stationary magnets increases the strength of the magnetic field in the linear inductors.

Magnetic field strength is a contributing factor of electrical power generation in magnetic inductors.

[0032] Figures 4A and 4B depict a non-rotating wind energy generator according to an embodiment of the present invention. In this embodiment, there are magnets 401 , inductor assemblies 402, a beam 403, springs 404, a frame 405, guiderails 406, and adjustable L- brackets 408. In this embodiment, the beam 403 and the frame 405 each have four connection points consisting of J-hooks 407. The frame height is adjusted by moving the top member up or down to pre-drilled hole locations. The frame is constructed of wood, metal, plastic or any other material that provides sufficient support for the beam during oscillation. For example, the frame should not distort or bend under operational forces. In this embodiment, four springs 404 attach the beam 403 to the frame 405 via the J-hooks 407. In this embodiment, there is clearance space between the beam 403 and the adjustable L- brackets 408 and between the beam 403 and the wind guards 406. Wind guards reduce the lateral pressure of the wind against the beam in the guide rails and keep the beam oscillating in the correct direction while reducing the amount of friction.

[0033] In an embodiment of the invention, wind energy is used to induce self-excited oscillations and vortex shedding of the suspended beam 403. The fluid flow phenomenon of vortex shedding is harnessed to initiate and sustain oscillatory motion of one or more beams 403. This reciprocating motion is used to generate electricity via magnetic induction using the magnets 401 and the inductor assemblies 402. An embodiment of an inductor assembly is described in greater detail in Figure 9. In some embodiments of the invention, magnets are stationary and wire coils move relative to the magnets. In further embodiments of the invention, wire coils are stationary and magnets move relative to the wire coils. In still further embodiments of the invention, both magnets and coils may move.

[0034] When the vortex shedding frequency matches the natural frequency of the system, extremely large amplitude of motion will be achieved. In embodiments of the invention, the spring system controls and maintains oscillatory behavior. The springs may have the same spring tension in order to keep the beam suspended. In embodiments of the invention, the number, size, and stiffness of the springs may be varied. Oscillatory movement is not solely caused by vortex shedding. A phenomenon called self-excited-oscillations may also be responsible for continuous motion in embodiments of the invention. In embodiments of the invention, after vortex shedding induces a small displacement input, the motion of the system itself causes it to oscillate at its natural frequency while in a wind flow. In some

embodiments of the invention, springs 404 range in constants from 0.1 lbs/in up to 3 lbs/in.

[0035] In embodiments of the invention, a second beam (or more) may be mounted in parallel to the first beam for a two degree (or more) of freedom system.

[0036] Figure 5 shows the beam 501 according to an embodiment of the invention. In this embodiment, the beam is hollow on the inside and has a D-shape, and the inductor assemblies 502 are attached to each end of the beam 501. In an embodiment of the invention, the D-shaped beam has a length of 24 inches (exclusive of the inductor assemblies), a diameter of 2 inches, wall thickness of 1/8 inch, and a weight of 0.5 pounds. In an

embodiment of the invention, an equivalent spring stiffness of 0.5 lbs/in may be used with a 0.5 lb beam.

[0037] In other embodiments, other beam shapes may be used. For example, the beam may be a square, a cylinder, a reversed D-Beam (where the wind is primarily incident on the flat portion of the beam rather than the round portion), and an equilateral wedge in either a "greater than" or "less than" orientation relative to the incident wind. Additionally, in embodiments of the invention, the surface of the beam may be smooth, and in further embodiments of the invention, the surface may be rough, uniformly or at selected locations. In embodiments of the invention, the beam may be fitted with weights for optimal mass to adjust the frequency and amplitude.

[0038] One or more beams can be used in the non-rotating wind energy device. In some embodiments, the plurality of beams can include a rigid spacer between beams and the multi- beam system can be secured to the frame by springs attached to the upper and lower beams. In other embodiments, the plurality of beams can be joined by springs to one another and to the frame.

[0039] Each beam can be secured to the side of the frame using a variety of conventional means. For example, the beams can terminate at each side in a ring 1100 having a central conduit 1101 and a rod 1102 can be mounted through the central conduit for securing the beam to the frame 1103. The central conduit can be fitted with linear or ball bearings to reduce resistance. An exemplary mounting system is shown in Figure 11. In this

embodiment, four pre-stretched springs 1106 are attached to the top and bottom of the assembly. This pre-stretch can be adjusted by raising the top beam of the frame.

[0040] In other embodiments, a bumper style system is used in which the system should oscillate freely. If there is a large gust of wind, the wind guards will keep the beam oscillating in the correct direction while reducing the amount of friction. Figures 4A and 4B show wind guards oriented vertically and placed near the sides of the frame on the front and back of the apparatus; however, they may be located anywhere in any number.

[0041] A further embodiment of the beam is shown in Figure 12. The beam 1200 itself can be hollowed out to minimize mass. At either end, there are two cylindrical containers 1210. Weight can be added to the containers to adjust the mass of the beam for certain applications, or a coil 1230 can be fabricated to slip into the container to accommodate the induction system. Snap-in caps 1220 that cover the cylindrical containers also serve the function of acting as bumpers. A hole 1240 can be drilled in the top of each cap with a diameter larger than the guide rail on which it lies.

[0042] Figure 6 is a plot of coefficient of lift v. time for a beam having different shapes. In order to provide the ability to compare, the characteristic length of each beam was kept constant at 0.1 m. Beams having cross-sectional shapes of cylinder, D-beam, 'greater than' wedge and 'less than' wedge were compared. D-beams showed a lift that was steady and that maintained large amplitude as compared to other modeled beam systems.

[0043] The length of the beam can be varied to provide oscillatory amplitude and frequency for any desired application. Each characteristic length of a beam for a given beam shape and material typically provides the same magnitude of the coefficient of lift. However, as the characteristic length decreases (all things being equal), the frequency of vortices increases. This is demonstrated in Figure 7, where the properties of D-beams having different characteristic lengths were modeled. In Figure 7, the coefficient of lift is plotted vs. time (sec) for a series of D-beams having a characteristic length of 0.001m, 0.025m, 0.05m, 0.075m and 0.1 m. While amplitude was similar, frequency varied with the change in beam length. While such a relationship between frequency and beam length is observed, the spring force will also play a significant role in the oscillation frequency. In one or more

embodiments, amplitude is dependent upon working spring length, initial stretch, spring constant, and wind speed. A range of springs with varying spring constants and spring lengths can be used to provide the desired spring constant.

[0044] Figure 8 is a plot of lift force (N) vs. time (sec) and demonstrates how the size of a beam (here a D-beam) affects the lift force produced by vortex shedding. As size increases, frequency decreases and lift force increases. The selection of the beam having length, shape and diameter provides a non-rotating wind energy generator having a selected (high) frequency and amplitude. In a preferred embodiment of the invention, the beam has a D- shape. Beam frequency and lift force are provided in Table 1 for an exemplary D-beam.

Table 1.

Shape Characteristic Frequency (Hz) Maximum Lift Forcing Function

Length Force (N)

D-Beam 0.001 1041.667 0.073 F(t)=0.073cos(654

4.985t)

D-Beam 0.025 40.161 2.396 F(t)=2.396cos(252

.337t)

D-Beam 0.050 20.000 4.890 F(t)=4.89cos(125.

664t)

D-Beam 0.075 13.423 7.312 F(t)=7.312cos(84.

338t)

D-Beam 0.100 10.204 9.458 F(t)=9.458cos(64.

114t)

[0045] In one or more embodiments, the beam design is selected to provide self-excited vibrations when exposed to wind. Self-excited vibration is a phenomenon in which the motion of a system causes it to oscillate at its natural frequency with continually growing amplitude. In the case of this design, a D-beam will continue to oscillate at the systems natural frequency when exposed to a wind flow. In order to provide a self-exciting system that oscillates at its natural frequency, the force required to move the beam can be decreased by using lower mass and spring rates.

[0046] Linear magnetic induction is provided for generating usable amounts of electrical power. Faraday's Law states that voltage is equal to the rate of change of magnetic flux. Faraday's Law and magnetic flux are shown in Equations 6 and 7 respectively. A permanent magnet forms the magnetic field and the energy is captured via a loop of wire moving through that field. c — —:— (6)

ψ_Β = BAcos(Q) ε is the induced voltage, ψΒ is the magnetic flux, B is the magnetic field strength, A is the cross sectional area of the loop, and Θ is the angle that the magnetic field makes with a vector normal to the area of the loop.

[0047] Some current designs involve moving a magnet through a stationary coil, while others involve the movement of a coil over a stationary magnet. It is important to note that the change in magnetic flux defines the amount of voltage generated. All rotational electric generators use magnetic induction to generate voltage by spinning a coil of wire through a magnetic field. The ever-changing magnetic flux due to the continuously changing Θ creates a constant voltage.

[0048] Figure 9 shows the inductor assembly 901 according to an embodiment of the invention. In this embodiment, the inductor assembly 901 comprises a spool 902, wire 903, which wraps around the spool 902, and an end-cap 904 of the beam, into which the spool 902 and wire 903 fit. In one or more embodiments, the moving beam contains the spool of wire and the coil of wire passes over a stationary magnet. In other embodiments, the support frame holds the coil of wire and the moving beam bearing a permanent or electric magnet passes over the stationary wire coil.

[0049] In embodiments of the invention the number of turns, wire gauge, and other properties of the inductor assembly may be varied. In an embodiment of the invention, 32 gauge wire may be used.

[0050] In embodiments of the invention, a parallel magnet inductor is used to generate electricity from the reciprocating beam motion. Such an inductor can overcome motion- damping issues that can occur in embodiments with concentric magnet and coil

configurations.

[0051] Figure 10 shows a cross-sectional view of a non-rotating wind energy generator according to an embodiment of the invention. As can be seen in Figure 10, in this

embodiment, the magnets 1001 attach to the guide rails 1004 via an adjustable L-bracket 605. In this embodiment, there is clearance between the beam 1003 and the guide rails 1004, as well as between the beam 1003 and the adjustable L-brackets 1005. In embodiments of the invention, the location of the magnets 1001 and the inductor 1002 may be reversed. In an embodiment of the invention, 8020 aluminum framing material may be used to create the frame. Adjustable slides may be used on both sides of the assembly to hold the magnets and aluminum guide walls.

[0052] In an embodiment of the invention, the system is capable of generating

approximately 30 VAC and 2.7W of electrical power.

[0053] A prototype was constructed as shown in Figure 4B. The prototype was set up using a large industrial fan capable of producing an average wind speed of 4 m/s. The D- beam had a length of 24 inches (exclusive of the inductor assemblies), a diameter of 2 inches, a wall thickness of 1/8 inch, and a weight of .5 pounds. Three sets of springs were tested to obtain a general range of spring constant in which the system would self-excite. The springs ranged in constants from 0.1 lbs/in up to 3 lbs/in. Using this approximate range of spring stiffnesses, an equivalent spring stiffness was identified to accommodate the weight of the beam and cause self-induced vibrations to occur (e.g., 0.5 lb beam self-excited with an equivalent stiffness of 0.5 lbs/in). 8020 aluminum framing material was used to create the frame. A prototype with an equivalent spring constant of 3.24 lbs/in was tested with 32 gauge wire in the inductor, which resulted in a total voltage of 22 V. The voltage trace of the assembly is shown in Figure 13. 32 gauge wire is only rated for a maximum of 0.09 Amps of current before it will melt. Therefore, the maximum power was limited by the current limitation of the wire. At the maximum allowable current of 0.09 amps, the power output was calculated using the following: P = IV = .09 A * 22 V = 1.98 W.

[0054] In an embodiment of the invention, the device may be considerably more compact and transportable than current wind energy generators. Its compact design makes the embodiment inherently less susceptible to airborne threats (birds, flying debris, etc.) that can easily damage the spinning blades of wind turbine generator. In an embodiment of the invention, the unique design of the generator makes it more useful in a variety of

applications. Its portable and easily collapsible design makes it practical for mobile charging of electronic devices (for consumer and military purposes). Its compact, low profile form factor makes it ideal for larger scale applications (e.g. wind farms, urban/suburban settings) where visually obtrusive wind turbines are unsuitable. Additionally, in an embodiment of the invention, the moving parts of the embodiment are contained within the body of the system and pose less of a safety hazard than large, rotating blades that could be harmful to humans and animals. The potential applications for embodiments of the invention are essentially

Claims

What is claimed is:

1. A non-rotating wind energy generating apparatus, comprising: a suspended bluff body operable to initiate and sustain oscillatory motion in response to wind energy using vortex shedding; and an inductor system operable to generate energy via the motion of the suspended bluff body.

2. The non-rotating wind energy generating apparatus of claim 1, wherein the suspended bluff body comprises: a frame movably supporting at least one beam; one or more first springs; one or more second springs; wherein the one or more first springs attach a first portion of the frame to a first portion of the beam and the one or more second springs attach a second portion of the frame to a second portion of the beam such that the beam is suspended between the first and second portions of the frame; and wherein the inductor system comprises at least one inductor attached to one of the beam or a third portion of the frame; at least one magnet attached to one of the third portion of the frame or the beam; wherein motion of the beam when exposed to wind causes the first inductor to pass the at least one magnet.

3. The non-rotating wind energy generating apparatus of claim 2, wherein the beam has a D-shape.

4. The non-rotating wind energy generating apparatus of claim 2 or 3, wherein the beam is hollow.

5. The non-rotating wind energy generating apparatus of claim 2, 3 or 4, further comprising one or more guide rails.

6. The non-rotating wind energy generating apparatus of claim 2, further comprising: one or more additional beams; one or more additional upper springs; one or more additional lower springs; wherein the one or more additional upper springs attach a first portion of the additional beam to a third portion of the beam and the one or more additional lower springs attach a second portion of the additional beam to a fourth portion of the beam such that the one or more additional beams are suspended between the first and second portions of the frame.

7. The non-rotating wind energy generating apparatus of claims 2-5, wherein the first portion of the frame is an upper portion, the first portion of the beam is an upper portion, the second portion of the frame is a lower portion, and the second portion of the beam is a lower portion.

8. The non-rotating wind energy generating apparatus of claims 2-7 wherein the third portion of the frame is a side portion.

9. The non-rotating wind energy generating apparatus of claims 2-8, wherein the beam is suspended substantially horizontally.

10. The non-rotating wind energy generating apparatus of claim 9, wherein the motion of the beam is substantially vertical.

11. The non-rotating wind energy generating apparatus of claims 2-10, wherein a surface of the beam is uniformly smooth.

12. The non-rotating wind energy generating apparatus of claims 2-10, wherein a surface of the beam is partially smooth.

13. The non-rotating wind energy generating apparatus of claims 2-10, wherein a surface of the beam is uniformly rough.

14. The non-rotating wind energy generating apparatus of claims 2-10, wherein a surface of the beam is partially rough.

15. The non-rotating wind energy generating apparatus of claim 2-14 wherein the at least one inductor or the at least one magnet is attached to a first end of the beam.

16. The non-rotating wind energy generating apparatus of claim 2-15 wherein the spring mass is selected to promote self-oscillatory motion.

17. The non-rotating wind energy generating apparatus of claim 2-15 wherein the beam has a cross-sectional geometry selected from the group consisting of a square, a cylinder, a reversed D-Beam (where the wind is primarily incident on the round portion of the beam rather than the flat portion), and an equilateral wedge in either a "greater than" or "less than" orientation relative to the incident wind.

18. The non-rotating wind energy generating apparatus of claim 2-17, wherein the springs are stretched in a resting state.

19. The non-rotating wind energy generating apparatus of claim 2-15, wherein the beam mass is selected to promote self-oscillatory motion.

20. A method of generating wind energy comprising: exposing the non-rotating wind energy generating apparatus of any of claims 1-19 to wind to generate oscillatory motion in response to wind energy using vortex shedding; and generating energy via motion of the non-rotating wind energy generating apparatus using induction.