US008067878B1

(12) Ulllted States Patent (10) Patent N0.: US 8,067,878 B1

Lu et al. (45) Date of Patent: Nov. 29, 2011

(54) BLADELESS WIND POWER GENERATOR 4,387,318 A * 6/1983 Kolm et a1. ................. .. 310/330
4,467,236 A * 8/1984 K 1 t l. 310/321
(76) IIWBIIIOFSI WeiXiIIg L11, L05 Angeles, CA (Us); 5,223,763 A * 6/1993 Charrlllgejlw. 310/339
Allan Roberts, Buena Park, CA (US) 2009/0230916 A1 * 9/2009 Fein et a1. ................... .. 320/101
* cited b examiner
(*) Notice: Subject to any disclaimer, the term of this y
patent is extended or adjusted under 35 _ _
U_S_C_ 154(1)) by 0 days_ Primary Examiner * Mark Budd

(21) Appl. N0.: 13/219,731 (57) ABSTRACT

(22) Filed: Aug‘ 29’ 2011 In a ?rst embodiment, a Wind to energy conversion system is
Related US. Application Data constructed out of a number of modular poWer units (110),
. . . . each modular poWer unit (110) comprised of 36 air jet tunnels
(60) 53031811061211 apphcanon NO' 61/378’068’ ?led on Aug' (106). Each air jet tunnel (106) is constructed using a canti
’ ' lever array mounted in a cascaded frame 104 With each
cantilever 102 attached on one ed e to a WindoW ed e of the
(51) Int. Cl. g g
H01L 41/08 (2006 01) frame (104). The cantilever (102) is constructed of a brass
(52) U 5 Cl ' 310/339 (130) layer sandwiched between tWo layers, each layer com
I. . . ...... .... ...... ... .............................. .. / posed of an electrode (126) attached to a Poly vmyhdene
(58) Field of Classi?cation Search ................ .. 33153332399, Fluoride (PVDF) (128) layer‘ Each modular power unit (110)
S 1, _ ?l f 1 h h, is mounted in a case (108), and a set of cases are mounted in
ee app lcanon e or Comp ete Seam lstory' a panel (114) attached to a pedestal (116). The cantilever
. arrays (117) are Wired together into electrical regulating cir
(56) References Clted cuits that generate poWer With a high Wind to poWer conver
U S PATENT DOCUMENTS sion ef?ciency. Other embodiments are presented.
2,509,913 A * 5/1950 Espenschied ............... .. 290/4 D
3,239,678 A * 3/1966 Kolm et a1. ................... .. 307/43 20 Claims, 9 Drawing Sheets
US. Patent Nov. 29, 2011 Sheet 1 019 US 8,067,878 B1

FIG. 1A

FIG. 1B
i /Ml! ”
VW1
WMi i/m1]
US. Patent Nov. 29, 2011 Sheet 2 of9 US 8,067,878 B1

[*114

110

/116

FIG. 1C
US. Patent Nov. 29, 2011 Sheet 3 of9 US 8,067,878 B1

122

117

119/\
106

DE
FIG. 1E
US. Patent Nov. 29, 2011 Sheet 4 of9 US 8,067,878 B1

Electric Output

Electric Output

. 126

f 128
" 130

128
126

FIG. 2B
US. Patent Nov. 29, 2011 Sheet 5 of9 US 8,067,878 B1

120

12

129

127

mx/d/l/ FIG. 3C
US. Patent Nov. 29, 2011 Sheet 6 of9 US 8,067,878 B1

102

FIG. 4A FIG. 45
US. Patent Nov. 29, 2011 Sheet 7 of9 US 8,067,878 B1

FIG. 5A

FIG. 5B
US. Patent Nov. 29, 2011 Sheet 8 of9 US 8,067,878 B1

108

FIG. 6
US. Patent Nov. 29, 2011 Sheet 9 of9 US 8,067,878 B1

136

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Power Reguiatian Circuii

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Power Storage System

FIG. 7B
 US 8,067,878 B1
1 2
BLADELESS WIND POWER GENERATOR of a uniquely designed air jet tunnel to form a bladeless Wind
Energy to PoWer (WEP) system. More speci?cally, the sys
This application claims the bene?t of the US. Provisional tem uses (1) a thin brass layer, sandWiched betWeen tWo Poly
Patent Application No. 61/378,068 ?led Aug. 30, 2010 by the Vinylidene Fluoride (PVDF) layers to form a cantilever With
present inventors. This provisional patent application is high pieZoelectric conversion; e?iciency (2) a unique air jet
incorporated herein in its entirety by reference. tunnel and phononic cascade con?guration With high coef?
cient of performance; and (3) a compact, modular poWer unit
TECHNICAL FIELD design.
The ?rst embodiment of the present invention has the fol
The present invention relates generally to generating elec loWing advantages over the prior art:
trical poWer from Wind motion energy. Bladeless: No rotating blades or mechanical moving parts
are involved in the WEP system.
BACKGROUND OF THE DISCLOSURE Quiet Operation: The WEP system is very quiet because no
mechanical moving parts are involved that are the main
Current Wind poWer generators generally employ Wind sources of sound vibration and the cantilever arrays are
turbines and electric motors to generate electricity. These made of a pieZoelectric polymer that does not generate a
systems are inef?cient and expensive to construct and main sound frequency perceptible by humans. The unique
tain. They are also noisy, intolerant to damage, and relatively phononic structure design and sound shielding case Will
dif?cult to transport and assemblel’2. They can also impose effectively prohibit sound propagation.
safety and environmental concerns. Unfortunately, a com 20 Modular: The WEP system is assembled With a basic
pact, modular, bladeless Wind energy system does not exist repeatable and modular small units that serves as build
although some approaches have been proposed. The potential ing blocks to be integrated into any siZe or shape to
advantages to its development include reduced noise, siZe, provide a Wind poWer generator.
and cost combined With improved portability, e?iciency, and High E?iciency: The unique WEP design including its
cost-effectiveness. 25 cascading phononic array and air jet tunnel con?gura
The most common approaches to the design of a bladeless tion, the PVDF-brass-PVDF sandWich cantilevers, the
Wind generator are based on electro-kinetic phenomena that high surface area ratio of cantilevers to inside Walls, the
involve the interaction betWeen an electrostatic and a charged speci?c ratio of air intake WindoW to air outlet WindoW,
medium in a liquid phase. Electro-kinetic systems require and the aspect ratio (the average cross section to the
designs that convert air movement to liquid movement and 30 length of air jet tunnel) to ensure that the WEP system
that separate and collect charge for electrical output. Air Will have a very high energy conversion e?iciency.
liquid and liquid-solid interfaces have to be included in such LoW Cost: Unlike the current Wind turbine generators or
system, resulting in very loW conversion ef?ciency and high electro-kinetics based approaches, WEP technology
cost of manufacture. For example, Marks, “Charged aerosol Will not require expensive equipments and micro struc
generator With uni-electrode source” US. Pat. No. 2,406,396, 35 ture fabrication processes. WEP technology is loW in
19773 proposed a vaneless ion Wind generator that produces maintenance, highly durable and very cost effective.
electrical energy directly by using the Wind to pump charged Robust and Light Weight: All the materials used are light
aerosols (Water droplets) from one electrode to another, With and strong, such as the air jet tunnel, the frame and case
no moving parts. It is obvious that most of the Wind’s kinetic materials.
energy is lost in order to move the charged aerosol from one 40 These advantages are made possible by the folloWing
electrode to another. Daniel Y KWok, et al, “Electrokinetic unique innovations:
microchannel battery by means of electrokinetic and microf Application of small air jet tunnels With side cantilever
luidic phenomena”, Journal of Micromechanics and arrays;
Microengineering, 13, 964-970, 20034 proposed a micro?u Incorporation of a PVDF-brass-PVDF sandWich pieZo
idic approach to extract energy from a pressure driven liquid 45 electric cantilevers as kinetic-electric conversion
How in a microchannel. devices;
HoWever, this approach also exhibits loW ef?ciency and Integration of a cascading phononic structure speci?cally
high cost because it requires an additional energy-absorbing designed and constructed for an air jet tunnel and sand
process to drive the liquid How in the microchannels Where Wich cantilever array.
only a Weak electric current is induced due to the presence of 50 Market Potential: The present invention represents a major
an electrical double layer in the interface betWeen the liquid advance in the conversion of Wind energy to electric poWer
and microchannel Walls. and Will lead to more ef?cient, less costly Wind generators.
These generators Will provide bene?ts in a Wide variety of
SUMMARY OF THE DISCLOSURE applications because, compared to existing Wind turbine sys
55 tems, they can be less noisy, more e?icient, less costly and
The present invention is a neW approach to converting Wind more adaptable. The systems may Well represent the future of
motion to electrical poWer. The approach is based on an Wind energy converters since they may be able to loWer the
adaptation of the pieZoelectric effectia Well knoWn property cost of Wind poWer to a level more competitive With fossil
of certain materials to produce electrical poWer When they fuels. As such they Will compete in the fast groWing World
undergo strain and stress. For example, in devices such as 60 Wide market for Wind poWer generators Where they are
microphones, sound vibrations can create enough stress and expected to have many advantages over current systems,
strain on pieZoelectric crystals to generate electric current. including higher electrical conversion e?iciency, loWer cost
Based on recent breakthroughs in nanotechnology, neW, loW of manufacture, loWer maintenance cost due to the lack of
cost, micro-siZed crystals can noW be assembled to create mechanical moving parts, longer life, and greater adaptability
more e?icient pieZoelectric materials. 65 due to the modular design. These advantages open up the
A ?rst embodiment of this invention incorporates pieZo possibility for these systems to make reneWable, non-pollut
electric materials as components inserted into the side Walls ing Wind poWer more competitive With fossil fuels in the
 US 8,067,878 B1
3 4
electric power markets WorldWide. As such, this new technol FIG. 1C illustrates a perspective vieW of the ?rst embodi
ogy Would have enormous positive social, environmental and ment of the present invention.
energy impact. FIG. 1D illustrates a perspective vieW of an air jet tunnel of
Wind poWer currently produces about 1 .5% of World-Wide the ?rst embodiment of the present invention.
electricity, and has become one of the leading electricity FIG. 1E illustrates a perspective vieW of a set of air jet
producing poWer sources in various countries. In 2008 the tunnels used in a modular poWer unit of the ?rst embodiment
WorldWide neWly installed capacity of Wind poWer Was of the present invention.
27,000 megawatts (MW),8 an increase of 29% compared to FIG. 2A illustrates a perspective vieW of a cantilever of the
2007. The total generated capacity WorldWide at the end of ?rst embodiment of the present invention.
2008 Was 121,188 MW, generating 260 teraWatt hours FIG. 2B illustrates a cross section of the cantilever of FIG.
2A.
(TWh). The World Wind Energy Association (WWEA)
FIG. 3A illustrates a perspective vieW of an air jet tunnel of
expects the installed capacity to keep increasing at a very fast
the ?rst embodiment of the present invention.
rate, and to be around 190.000 MW in 2010 and 1.5 million
FIG. 3B illustrates a perspective vieW of a detail of FIG.
MW in 2020 equaling around 12% of global electricity con 3A.
sumption.9 According to Clean Edge, capital costs of neW FIG. 3C illustrates the de?nition of an angle-of-attack.
installations are projected to expand from $51.4 billion in FIGS. 4A through 4C illustrate an air jet tunnel Without
2008 to $139.1 billion in 2018.8 This is expected to be the case cantilevers.
even With the current ?nancial crisis, as Wind poWer is attrac FIGS. 4B and 4C illustrates alternate con?gurations of the
tive to investors due to its relatively loW-risk character, it’s 20 air jet tunnel.
societal and economic bene?ts, and the groWing need for FIG. 5A illustrates multiband acoustic energy Waves ema
clean and reliable energy sources. In 2008, Europe accounted nating from the air jet tunnels of a modular poWer unit of the
for 32.8% of the Worlds Wind market, North America for ?rst embodiment of the present invention.
32.6%, and Asia for 31.5%. Latin America’s share Was 0.6% FIG. 5B illustrates a typical 2-dimensional phononic crys
and Africa’s share 0.5%.9 Since the WEP technology is 25 tal lattice acoustic dispersion pattern.
expected to have the advantage of loW-cost, high e?iciency, FIG. 6 illustrates an assembly ?oW diagram for construct
and modularity compared to competitor Wind turbine sys ing a modular poWer unit of the ?rst embodiment of the
tems, it can potentially make strong inroads into this Wind present invention.
energy market. FIG. 7A illustrates a poWer regulation circuit of the ?rst
30 embodiment of the present invention.
LIST OF PART NUMBERS FIG. 7B illustrates a poWer storage system of the ?rst
embodiment of the present invention.
1024cantilever
104iframe DETAILED DESCRIPTION
106iair jet tunnel 35
1084case The term cascaded frame, in this detailed description,
110imodular poWer unit means that the frame has cross-sections that decrease in siZe
112iair outlet WindoW moving from the air intake opening 122 to the air outtake end
114ipanel 124. The term air ?oW energy is interpreted as Wind energy. If
116ipedestal 40 a part number in the ?gures refers to multiple parts, only one
1174cantilever array or tWo parts may be assigned the part number, and the same
118iphononic array part number may be used for the singular part and the same
119imodule tunnel grouping multiple parts in the ?gures. The same part number may be
120iside Wall used for a generic term such as the pieZoelectric material 128
122iair intake opening 45 and a speci?c implementation such as polyvinylidene ?uo
124iair outtake end ride (PVDF).
125iair intake ?oW FIGS. 1A through 1E illustrates an overvieW and the use of
1264electrode the air jet tunnels of a ?rst embodiment of the present inven
127ilongitudinal axis tion. FIGS. 2A and 2B illustrate a proprietary design of a
128ipieZoelectric material 50 cantilever 102 used in the embodiment. FIG. 3A illustrates
129iangle-of-attack the con?guration of the air jet tunnel 106 With cascading
130imetal layer cantilever array 117 on the side Walls 120 shoWing the path of
1314exit air ?oW air ?oW through the air jet tunnel 106. FIG. 3B, a detail of
132ifront grid FIG. 3A in expanded scale illustrates tWo cantilevers 102 and
133iair outtake ?oW 55 the air ?oW around them. FIG. 3C, a second detail of FIG. 3A
134iback grid in expanded scale, illustrates the angle-of-attack 129 betWeen
136itunnel circuitry the air intake How 125 and the air jet tunnel 106 for the ?rst
137i?rst cantilever edge embodiment. Referring to FIGS. 1A through 3B, the ?rst
138*?I‘SIW1I1dOW edge embodiment is comprised of a group of trapezoidal shaped
140imodule circuitry 60 cantilevers 102 (see FIGS. 2A and 2B) With the cantilevers
142ipanel circuitry 102 mounted in a cascaded frame 104 that forms an air jet
tunnel 106 (see FIG. 1D). In other embodiments, the cantile
BRIEF DESCRIPTION OF THE DRAWINGS vers 102 can have the shape of an approximate trapeZoid (i.e.
a trapeZoid With curved sides, or more generally an approxi
FIGS. 1A and 1B illustrate front and back perspective 65 mate polygon. In the ?rst embodiment, the air jet tunnel’s 106
vieWs of a modular poWer unit of the ?rst embodiment of the air intake opening 122 is positioned at the air intake How 125.
present invention. The frame 104 has a plurality of air outlet WindoWs 112 that
 US 8,067,878 B1
5 6
permit the air How to exit (air outtake How 133) the air outlet as an electrode-PVDF -brass-PVDF electrode (electrode 126,
WindoWs 112, and optionally to exit the air outtake end 124 PVDF 128, brass 130) sandWich as shoWn in FIGS. 2A and
(exit air How 131). Each cantilever 102 is ?rmly mounted on 2B. When the cantilever is comprised of multiple layers, the
the cascaded frame 104 of the air jet tunnel 106 at the larger positive and negative surfaces of the piezoelectric materials
parallel edge (?rst cantilever edge 137) of the trapezoidal used in each layer may be aligned in series, parallel, or a
shaped cantilever 102. combination thereof depending on the application. Referring
A number of air jet tunnels 106 (see FIG. 1E) are mounted noW to FIGS. 3A and 3B, the area ratio of cantilevers 102 to
in a case 108 to form a modular poWer unit 110. The case 108 the side Walls 120 of the air jet tunnel 106 is larger than 90%
has a front grid 132 and a back grid 134 (See FIG. 1E for the to ensure high conversion e?iciency. The ratio of the air
mounted unit Without the case 108.) FIG. 1A illustrates a front outtake end 124 to the air outlet WindoWs 112 is larger than
vieW of a modular poWer unit 110 mounted in a case 108; FIG. tWo to maintain the effects of lateral forces generated by the
1B illustrates a rear vieW of modular poWer unit 110 mounted air How and exert required pressures on the cantilevers 102.
in a case 108; and FIG. 6 illustrates the front grid 132 and the The aspect ratio (the average cross section to the length of air
back grid 134. Note that FIG. 1A shoWs 36 air jet tunnel air jet tunnel 106) also may be optimized in terms of maximum
intakes openings 122 in a front vieW of modular poWer unit sandWich cantilever area, maximum conversion e?iciency,
110. FIG. 1B shoWs 36 air jet tunnel outtake ends 124, each and maximum coef?cient of performance. In alternate
surrounded by rectangular spaces Where air ?oWs out from embodiments, the cantilever 102 can be made using virtually
the many air outlet WindoWs 112. FIG. 1C shoWs the modular any type of existing piezoelectric material (polymers such as
poWer units 110 attached together to form a large panel 114 polyvinylidene ?uoride (PVDF), ceramics such as Lead zir
that is mounted on a pedestal 116 and positioned on a hill to 20 conate titanate (PZT), crystals such as quartz, etc.). The can
generate energy from Wind. The system in FIG. 1C may also tilever 102 can also contain one or more layers of brass or
have a motor and other mechanisms to rotate the panel into the other metals bonded to the piezoelectric material 128. In
Wind. In other embodiments, any number of air jet tunnels addition, the piezoelectric material for a cantilever 102 of
106 can be contained in each modular poWer unit 110 and any higher ef?ciency can be fabricated by using standard nano
number of modular poWer units 110 can be contained in a 25 technology thin ?lm fabrication processes, such as coating,
panel 114 comprising the Wind energy conversion system. In etching, deposition, and Langmuir-Blodgett processes, to
alternate embodiments, the front grid 132 and back grid 134 form a non-central symmetric thin-?lm of piezoelectric par
may be designed With various patterns of openings, and the ticles on a metal or other type of substrate surface.
grids may be designed to be positioned either on the outside or The electrode-PVDF-brass-PVDF-electrode cantilevers
the inside the case to hold the air jet tunnels 106 ?xed so as to 30 102 of the ?rst embodiment Will vibrate and generate AC
keep effective air ?oWing inside and outside the air jet tunnels output poWer When the air ?oWs through the air jet tunnel 106.
106. PVDF is a piezoelectric polymer that has high piezoelectric
Again referring to FIGS. 1A through 1E, 2A and 2B, the stress constants (g3l~240 mV-m/N)5 indicating it has excel
modular poWer units 110 of the ?rst embodiment can be lent kinetic-to-electric conversion properties. The sandWich
assembled to form a large panel With a loW volume, small 35 design not only improves the conversion ef?ciency but also
ground contact footprint and loW Weight capable of delivering prevents noise generation because PVDF is a soft polymer
large amounts of poWer With a range of Wind resources. The that is able to effectively absorb acoustic vibration energy.
Wind Energy to PoWer (WEP) system operates With mini These cantilevers 102 inside the modular poWer unit 110 are
mum noise. The modular poWer units 110 can be assembled assembled in a periodic manner that generates a phononic
into various shapes such as rectangular or approximately 40 array 118 structure With a bandgap frequency Within the
circular or oval to form a large panel 114 that is adaptable to human perception range. HoWever, the sound is absorbed by
the physical site conditions and poWer demands. The WEP the materials employed resulting in nearly silent operations.
system is highly durable, requires little maintenance, and is The modular poWer unit 110 is integrated into a protection
easy to transport and assemble. case 108 that Will further eliminate any residual sound. The
Referring to FIGS. 1A through 1E, 2A and 2B, and 3A, the 45 cantilevers 102 can be connected to one another via a com
modular poWer unit 110 of the ?rst embodiment is comprised bination of series and parallel Wiring into tunnel circuitry 136,
of a number of identical air jet tunnels 106 (see FIG. 1E) that module circuitry 140 and panel circuitry 142 (circuitry not
form a cascade type module tunnel grouping 119. The shape shoWn in the ?gures) to effectively tune the output voltage and
of the cross section of each air jet tunnel 106 in the ?rst current exiting the panel. The speci?c circuitry in general
embodiment is rectangular. In alternate embodiments, the air 50 depends on the application, and designing appropriate cir
jet tunnel 106 can take on various 3-dimensional shapes such cuits for e various alternate embodiments is straightforWard
as rectangle, trapezoid, pyramid, cylinder, etc. or contain by experts in the ?eld.
curved surfaces With different cascaded shapes, a feW possi The materials used in the ?rst embodiment are light and
bilities are shoWn in FIGS. 4A through 4C. Furthermore, in robust, such as the air jet tunnel 106, cascaded frame 104 and
alternate embodiments, the air jet tunnel 106 can be designed 55 case 108 materials made of polymers in the ?rst embodiment.
With virtually any size and shape in order to optimize perfor The entire Weight of a modular poWer unit 110 is less than 400
mance e?iciency for various applications and environmental g (4.1 1 oz) making the larger assembledpanel <300 kg (661 .4
conditions. pounds) and able to deliver >3 k W of poWer With a Wind
The actual dimensions and con?guration of the modular resource of 10 meters per second (32.8 feet/second). The
poWer unit 110 is determined to optimize the aerodynamic 60 modular poWer units 110, each With a volume of0.2><0.2><0.l
performance and for obtaining a large internal surface to cubic meters, can be readily assembled in a building block
volume ratio. The side Walls 120 of the air jet tunnel 106 have manner to form virtually any shape and size. A large ?at panel
many air outlet WindoWs 112 that are ?lled With correspond With a volume of less than 2.8 cubic meters (3 .66 cubic yards)
ing cantilevers 102 (see FIG. 3A), such that the kinetic energy and a ground contact footprint of less than 1 square meter
of the moving air Will be largely absorbed and converted to the 65 (1.20 square yards) Would be able to deliver >3 k W of poWer
electrical poWer by the piezoelectric cantilever structures. In With a Wind resource of 10 meters per second (32.8 feet/
the ?rst embodiment, the cantilevers 102 are each structured second. The WEP system is modular, durable, and very easy
 US 8,067,878 B1
7 8
to transport and assemble. The technology associated with the tric polymer PVDF as the building block materials for the
WEP has signi?cant military and commercial applications. kinetic-to-power conversion application; however, other
The approach makes harvesting large quantities of wind embodiments using piezoelectric materials including but not
energy feasible by avoiding the high cost, intolerance to dam limited to ceramic, quartz can be used in various applications
age, low e?iciency, environmental and safety drawbacks of of the technology.
current wind turbines. WEP is a potentially disruptive break The most commonly used geometrical con?guration in
through technology that is highly scalable and couldtherefore piezoelectric power harvesting is the rectangular cantilever
provide both large and small amounts of power in many types beam. The cantilever beam harvester has been well
of wind energy applications, wherever a continuous wing researched and has proven to be easy to implement and effec
energy source exists such as for shipboard and airborne elec tive for harvesting energy from ambient vibrations. The ?rst
tronics, as well as in various residential and commercial sys embodiment uses different sizes of trapezoidal shaped canti
tems. Scaled up to their maximum potential, WEP systems levers 102 (FIG. 2A) for different applications so that the
could potentially reduce the cost of wind power substantially, strain can be more evenly distributed throughout the structure
allowing it to become an even more viable source of clean,
leading to more than twice the energy generation than a
renewable energy for the national power grid. rectangular beam. Other embodiments may use uses different
Piezoelectric Cantilever: The use of piezoelectric materials sizes and shaped cantilevers such as rectangles, triangles, etc.
FIG. 2B illustrates the electrode-PVDF-brass-PVDF-elec
yields signi?cant advantages for energy harvesting systems.
The energy density achievable with piezoelectric devices is trode piezoelectric cantilever structure. When the cantilever
potentially greater than that possible with electro-kinetic, bends during the vibration generated by air ?ow, it will effec
electrostatic or electromagnetic devices. Since piezoelectric tively produce a strain and corresponding stress on the PDVF
materials convert mechanical energy into electrical energy layers that in turn will effectively convert the energy of the
strain to electric current. A cantilever 102 has a unique reso
via stress and strain in the piezoelectric material, they lend
themselves to devices that operate by bending or ?exing, nant frequency. By properly selecting the length, thickness,
which brings signi?cant design advantages. shape, elasticity and mass of the beam, the overall device is
25 designed to have a wide band of resonant frequencies to
achieve a maximum kinetic-to-electric conversion e?iciency
TABLE 1
CE and CE>50%.
Property comparison of standard piezoelectric polymer and ceramic State of the art Air Jet Tunnel Design and Fabrication: In
a a
order to effectively convert the kinetic wind energy to
(131 g3l 30 mechanical movement of the electrode-PVDF-brass-PVDF
Piezoelectric Materials (pm/V) (mV — m/N) k31 Salient Feature
electrode cantilevers 102 for electric power generation, the
Polyvinylidene?uoride 28 240 0.12 Flexible, light ?rst embodiment of the present invention includes an air jet
(PVDF) Weight, low tunnel 106 for optimal aerodynamic performance that can
acoustic and
mechanical
effectively generate air ?ow turbulence and convert the air
impedance 35 ?ow to pressure on the side walls 120 of the air jet tunnel.
Lead Zirconium 175 11 0.34 Brittle, heavy, FIGS. 3A and 3B illustrate the con?guration of the air jet
Titanate (PZT) toxic tunnel 106 and the path of the air intake ?ow 125 through the
“Values shown are absolute values of constants.
air jet tunnel 106. The side walls of the air jet tunnel 106 have
many trapezoidal shaped air outlet windows 112 that are
Piezoelectricity is a property of many non-central symmet 40 covered with corresponding piezoelectric PVDF-brass
ric ceramics, polymers, and other biological systems. The PVDF sandwich cantilevers. As the turbulent air intake ?ow
properties of organic polymers such as PVDF are so different moves through the outlet windows, it creates stresses and
in comparison to inorganic ceramic materials such as PZT strains on the corresponding piezoelectric cantilevers that
(see Table 1) that they are uniquely quali?ed to ?ll niche areas effectively absorb and convert the kinetic energy of the mov
where single crystals and ceramics are incapable of perform 45 ing air to electrical power. The ?rst cantilever edge 137 is
ing as effectively. As noted in Table 1, the piezoelectric strain mechanically ?xed on the corresponding trapezoidal shaped
constant (d3 1) for the PVDF polymer is lower than that of the ?rst window edge 138 and the other sides of the cantilever 102
ceramic. However, piezoelectric polymers have much higher are left free.
piezoelectric stress constants (g3 1) indicating that they are FIGS. 3A through 3C shows the angle between the air
much better kinetic-to-electric converters than ceramics. In 50 intake ?ow 125 entering the air intake opening 122 and the
addition to their high strength and high impact resistances, longitudinal axis 127 of the air jet tunnel 106 for the ?rst
piezoelectric polymeric materials also offer the advantage of embodiment. The air intake ?ow 125 passes through the air
processing ?exibility because they are lightweight, tough, outlet window 112 as air outtake ?ow 133. The angle-of
readily manufactured into large areas, and can be cut and attack 129 between the air intake opening 122 and longitudi
formed into complex shapes. Other notable features of poly 55 nal axis 127 of the air jet tunnel 106 can vary signi?cantly
mers are low dielectric constant, low elastic stiffness, and low with optimal angles being between —20 and +20 degrees. In
density, which result in high voltage sensitivity (excellent the ?rst embodiment, as indicated in FIGS. 3A and 3B, the
sensor characteristic), and low acoustic and mechanical ?rst window edge 138 and the ?rst cantilever edge 137 are
impedance (crucial for medical and underwater applications). joined and positioned towards the air intake opening 122. In
Polymers also typically possess a high dielectric breakdown 60 alternate embodiments (not shown in the ?gures), the ?rst
and high operating ?eld strength, which means that they can window edge 138 and the ?rst cantilever edge 137 are joined
withstand much higher driving ?elds than ceramics. Poly and positioned towards the air outtake end 124. In various
mers offer the ability to pattern electrodes on the ?lm surface, embodiments, the air outtake end 124 may be open, closed or
and pole only selected regions. Based on these features, throttled so that the air outtake ?ow 133 may be controlled.
piezoelectric polymers possess their own established area for 65 Due to the ?ow shape of each air jet tunnel 106 and the
technical applications and useful device con?gurations. The optimal ratio of the air intake opening 122 to the air outlet
?rst embodiment of the present invention uses the piezoelec windows 112, the air?ow pressure on the side walls is uni
 US 8,067,878 B1
9 10
formly dispersed on the cantilevers 102 resulting in cantilever vibration kinetic energy localiZes in the form of an oscillatory
vibration. The area ratio of side WindoW cantilevers 102 to the motion of the internal structural elements (the vibration of the
inside surface Walls of the tunnel is larger than 90% to ensure cantilevers), rather than being transferred across the materi
high conversion e?iciency of the overall device. The aspect al’s propagating Waves. In other Words, the substructures
ratio (the ratio of the average cross section area to the length behave as Wave dampers and dynamic energy absorbers. The
of air jet tunneIiAISWg/L) is optimized in terms of maxi idea is to exploit the pieZoelectric effect featured by the
mum cantilever area, maximum conversion ef?ciency, and electrode-PVDF-brass-PVDF-electrode cantilevers 102 and
maximum coe?icient of performance. convert its vibration energy into electrical poWer localiZed in
The con?guration of each tunnel can be adjusted to achieve the resonators at frequencies of excitation falling near the
optimal aerodynamic performance for speci?c applications. bandgaps. The cascading phononic ?ltering effect can not
The ratio of the air intake opening area to the air outlet only dramatically improve the kinetic-to-electric poWer e?i
WindoWs area (XISM/SOM is larger than tWo to maintain the ciency but also make the overall system nearly silent.
effects of lateral forces generated by the air How and to exert The band gap density and its resulting ?ltering effect are
the required pressures on the cantilevers. The ratio A and ratio dramatically enhanced through the introduction of the cas
0t affect the coe?icient of performance C. By selecting the cading array structure Which resonates at speci?c frequencies
proper ratios for A and ot, a high coe?icient of performance and produces signi?cant strain and energy localiZation. The
(>0.50) can be obtained. enhancement of energy harvesting is achieved as a result of
FIG. 4A illustrates a cascaded frame of a quadrilateral air the conversion of the localiZed kinetic energy into electrical
jet tunnel 106 (AIZ and (F1 .5) With four trapeZoidal shaped energy through the electrode-PVDF-brass-PVDF-electrode
open side WindoWs on each Wall. It does not include the 20 cantilevers 102 sitting in the lattice frameWork.
cantilevers 102. FIG. 4B illustrates its complete structure Modular and Quiet Wind Generator Unit: The WEP sys
With trapezoidal electrode-PVDF-brass-PVDF-electrode tem, as illustrated in FIG. 6, is constructed With an array of air
cantilevers. FIG. 4C illustrates an air jet tunnel 106 With A:9 jet tunnels 106, a circuit board and an electric coupler to
and (F5 respectively, and With 13 trapeZoidal side WindoWs smooth or regulate output poWer, a poWer panel generator
and electrode-PVDF-brass-PVDF-electrode cantilevers 102 25 receiving quantities of poWer from the modular poWer units
on each side Wall 120. 110, front and back grids and protection case that Will also
Air Jet Tunnel Array and Cascade Phononic Structure: The absorb acoustic Waves to further eliminate system sounds.
air jet tunnels 106 are assembled to form a tWo dimensional FIG. 6 illustrates an assembly ?oW diagram of the modular
(2D) array for extracting a large amount of Wind energy as poWer unit 110. FIG. 6 does not shoW the module circuitry
illustrated in the left ?gure of FIG. 5A. This array forms not 30 140 of the modular poWer unit 110.
only a modular panel but also a cascading phononic lattice Necessary Electronic Circuits: The plurality of layers
structure. Due to the cone-like structure of the air jet tunnels, Within the cantilever 102 canbe interconnected to one another
the cantilevers at different levels create different 2D phononic via a combination of series and parallel circuitry to effectively
crystal effects due to the different periodic lengths as illus capture the pieZoelectric output voltage and current generated
trated in the four layers of the right side of FIG. 5A. The 35 by each layer. The poWer directly from the cantilevers 102 is
combination of these four 2D phononic crystal lattice patterns non-regularAC poWer that needs to be regulated to either DC
creates a cascading phononic structure capable of absorbing current or to a required voltage and frequency via the appro
the multiband acoustic energy Waves and prohibiting their priate transformers, recti?ers, and control circuits. The can
propagation through the structure. tilevers 102 comprising the cantilever array 117 are intercon
Referring again to FIG. 5A, 2D phononic crystal lattice can 40 nected via additional series and parallel circuitry. The
be made by creating an array of air-?lled cylinders in a solid circuitry Which is standard in the ?eld may be implemented in
material (see insert) so that the speed of sound varies periodi various Ways in alternate embodiments to match the electrical
cally. The dispersion relationsiplots of frequency, 00, versus output to the application requirements.
Wave vector, kifor different phonons in this structure FIGS. 7A and 7B shoW tWo examples of the basic circuit
(dashed lines) reveal that Wave propagation is not supported 45 diagram With necessary electronic components for the ?rst
for certain ranges of frequencies (yelloW region). This is a embodiment. The circuit board is designed as part of the ?rst
phononic band gap. In a homogeneous material, (1):C'k, embodiment of the present invention, While the electronic
Where c is the velocity of sound, and the dispersion relation components and rechargeable battery are commercially avail
Would appear as a straight line on this graph. The directions able. AC poWer from the cantilevers 102 is input to a circuit
With the highest symmetry in this structure are F-X and F-M 50 board to regulate and smooth the output DC voltage and
(see insert)6. current for a rechargeable battery (FIG. 7A). For some appli
Phononic lattice structure crystals make use of the funda cations, the current Will be converted to a required AC poWer
mental properties of Waves, such as scattering and interfer by a static inverter that has no moving parts and is used in a
ence, to create “band gaps”iranges of Wavelength or fre Wide range of applications, from small sWitching poWer sup
quency Within Which Waves cannot propagate through the 55 plies in computers, to large electric utility high-voltage direct
structure. The bandgap in a phononic lattice crystal is created current applications that transport bulk poWer (FIG. 7B).
by a periodic variation in the refractive index of an arti?cially More generally, each cantilever 102 has its oWn indepen
structured material. In a phononic crystal lattice, the density dent electrical circuit that connects its generated AC electrical
and/or elastic constants of the structure change periodically. output to a bridge recti?er before connecting it to the other
This changes the speed of sound inside the structure, Which, 60 cantilevers in the system. In various alternate embodiments,
in turn, leads to the formation of a phononic band gap. FIG. the bridge recti?er can be a full Wave recti?er, half Wave
5B shoWs a typical 2-dimensional phononic crystal lattice recti?er, single phase recti?er, or multi-phase recti?er. These
acoustic dispersion pattern and its relations With the band gap. all Work, but the ef?ciency and cost Will vary. In the ?rst
The existence of a phononic bandgap in the band structure embodiment, the recti?ed electrical output of all the cantile
implies the availability of ?at regions in the propagation 65 vers in the system is combined together in a series circuit. In
modes immediately beloW and above the gap itself, in Which alternate embodiments, the recti?ed electrical output of the
the Wave group velocity goes to Zero. In these regions, the cantilevers is combined together in a series circuit, parallel
 US 8,067,878 B1
11 12
circuit or combination thereof depending on the application. structures as Well as employment of materials in the cantile
Alternate embodiments can also include electrical circuits vers different from brass and PVDF. For example, the canti
With capacitors, charge pumps, rechargeable batteries, regu lever structure could be comprised of multiple electrode/
lators and other electrical components depending on the PVDF layers folloWed by a brass layer folloWed by multiple
application. PDVF/electrode layers. In addition, any elastic metal or com
Ef?ciency Evaluation of the WEP System: BetZ’ laW and bination of elastic metals could be substituted for the brass
coe?icient of performance: Wind energy comes from mass layer and any pieZoelectric thin ?lm, including pieZoelectric
?oW that obeys conservation of mass and the laWs of aerody polymer, pieZoelectric ceramic, pieZoelectric crystal, and so
namics. The ef?ciency of extracting Wind energy by any Wind on, could be substituted for the PVDF layers.
generator With cross section S Will be constrained Within
In the ?rst embodiment, each cantilever 102 contains a
these natural laWs. The more kinetic energy a Wind generator
brass layer sandWichedbetWeen tWo pieZoelectric layers With
pulls out of the Wind, the more the Wind Will be sloWed doWn
as it leaves the generator. If We tried to extract all the energy
electrode coatings. HoWever, other embodiments may
from the Wind, the air Would move aWay at speed Zero, i.e. the employ cantilevers 102 With pieZoelectric material and elec
air could not leave the generator. In that case We Would not trodes on only one side of a brass layer or no brass layer at all.
extract any energy at all, since all the air Would be prevented Furthermore, different embodiments could include cantile
from entering the generator. Therefore, it is obvious that no vers of virtually any shape provided one side or section of the
Wind generator can achieve 100% e?iciency. A German cantilever 102 is ?xed to the air jet tunnel frame 104 WindoW
Physicist, Albert BetZ, identi?ed the so-called BetZ laW that edge. The trapeZoid shape is used in the ?rst embodiment to
states that a maximum of 16/27 (or 0.59) of the kinetic energy 20 folloW the contours of the air jet tunnel and increase the
of Wind can be converted to mechanical energy7. This e?i surface area and ef?ciency of the cantilevers 102 Without
ciency is called the Coe?icient of Performance and denoted reducing the structural integrity of the air jet tunnel cascaded
as CPJMX. All Wind generators use a tWo step process to frame 104. HoWever, cantilevers 102 can take any shape. The
convert Wind kinetic energy preferred to mechanical energy cantilevers can also be single layer or multilayer, With elec
then from mechanical to electrical energy. Therefore, accord 25 trodes in betWeen layers.
ing to BetZ laW, the overall Coef?cient of Performance Will Still other embodiments can include air jet tunnels of many
alWays be less than 0.59. siZes and con?gurations and they can be made from many
Ef?ciency and corresponding siZe of WEP system: materials including metals, plastics, Wood, carbon ?ber,
Because air has mass and it moves to form Wind, it has kinetic acrylic and others. The ?rst embodiment incorporates certain
energy as folloW: 30
air jet dimensional ratios to improve aerodynamic perfor
Kinetic energy (joules):1/2><m>< V2 mance and increase electrical conversion ef?ciency. HoW
Where: mImass (kg); Vq/elocity (meters/second). Usually, ever, other embodiments With different dimensions and ratios
Were more interested in poWer than energy. Since can be constructed to produce electrical poWer under various
energyrpowerxtime, and density is a more convenient Way to 35
Wind conditions.
express the mass of ?oWing air, the kinetic energy equation
can be converted into a How equation: REFERENCES
Power in the area ofa Wind generator panel P:0.5><
DAXAX V3
REF. 1: Scott Lux and Roch Ducey, Non-rotating Wind
40 Energy Generation, Army SBIR 2010.2iTopic A10-111,
Where Prpower in Watts; DAIair density (about 1.225 kg/m3 2010.
400 g at sea level, less higher up); A:area of Wind generator REF. 2: Of?ce of the Director of Defense Research and Engi
panel exposed to the Wind (m2); Vqvind speed in meters/ sec. neering, “The Effect of Windmill Farms On Military
This equation yields the poWer in a free ?oWing stream of
Readinessi2006,” REPORT TO THE CONGRES
Wind. Of course, it is impossible to extract all the poWer from
SIONAL DEFENSE COMMITTEES.
the Wind because some ?oW must be maintained through the
panel. Therefore, some additional terms need to be included REF. 3: Marks, A. “Wind PoWer ChargedAerosol Generator,”
to get a practical equation for the Wind generator panel. Final Report Subcontract XH-9-S128-1, Solar Energy
Wind panel PoWer: Research Institute (SERI) of DOE, 1980. Marks, A,
“Charged aerosol generator With uni-electrode source”
50 US. Pat. No. 2,406,396, 1977.
Where: Prpower in Watts; DAIair density (about 1.225 kg/m3 REF. 4: DanielY KWok, et al, “Electrokinetic microchannel
at sea level, less higher up); Arpanel area, exposed to the battery by means of electrokinetic and meicro?uidic phe
Wind (m2); CpICoef?cient of performance (0.59 {BetZ limit} nomena”, Journal ofMicromechanics and Microengineer
is the maximum theoretically possible, 0.5 for a good design ing, 13, 964-970, 2003.
of air jet tunnel); Vqvind speed in meters/sec; 55 REF. 5: G. T. Davis, “Piezoelectric and Pyroelectric Poly
CE:Conversion ef?ciency of the cantilever array panel (the mers”, Polymers for Electronic and Photonic Applications,
estimated value of WEP is 50%). With a good design, this C. P. Wong, ed., Academic Press, Inc.: Boston, Mass., p.
equation can be expressed as: 435, 1993.
REF. 6: T. Gorishnyy, M. Maldovan, C. Ullal and E. Thomas,
60 “Sound Ideas”, Physics World, pp. 24-29, December, 2005.
If We Want a 3 kW generator With a Wind resource of 10 meters REF. 7: Albert BetZ, Introduction to the Theory of FloW
per second (32.81 feet/second) and 50% ef?ciency (CE), the Machines. (D. G. Randall, Trans.) Oxford: Pergamon
panel area “A” should be 3000/ 1 53:1 9.6 m2 that Will require Press, 1966.
a volume of 2 cubic meters (2.616 cubic yards) because the REF. 8: Clean EdgeiMakoWer, 1., Pemick, R., Wilder, C.,
thickness of the WEP panel is only 10 cm (3.84 inches). 65 Clean Energy Trends 2009.
Other embodiments are consistent With the inventive con REF. 9: WWEA, World Wide Energy Report 2008, WWW.W
cept presented herein. These include multilayered cantilever Windea.org.
 US 8,067,878 B1
13 14
We claim: intake opening 122 being larger than the air outtake end 124
1. An air ?oW energy to power conversion system com and the ?rst cantilever edge 137 of a plurality of the cantile
prised of: vers 102 being positioned toWards the air outtake end 124.
a plurality of cantilevers 102, each cantilever 102 being 6. The air ?oW energy to poWer conversion system of claim
comprised of electrodes 126 and at least one pieZoelec 2 Wherein the air jet tunnel 106 is designed so that a ratio of
tric material 128, each cantilever 102 having a ?rst can the area of the air intake opening 122 to the area of the air
tilever edge 137; outtake end 124 is larger than 2.
an air jet tunnel 106 having a frame 104, the frame 104 7. The air ?oW energy to poWer conversion system of claim
having an air intake opening 122, and a plurality of air 2 Wherein the air outtake end 124 of the air jet tunnel 106 is
outlet WindoWs 112, each of the air outlet WindoWs 112 throttled to adjust the quantity of air alloWed to pass through.
having a ?rst WindoW edge 138 Wherein each of the air 8. The air ?oW energy to poWer conversion system of claim
outlet WindoWs 112 is siZed and con?gured to receive 2 Wherein the air intake How 125 is Wind.
one of the cantilevers 102, the ?rst cantilever edge of 9. The air ?oW energy to poWer conversion system of claim
each cantilever 102 being attached to the ?rst WindoW 2 Wherein the frame 104 has a cross section selected from the
edge 138 of one of the air outlet WindoWs 112; group consisting of an approximate polygon, a circle and an
the air jet tunnel 106 con?gured so that When an air intake ellipse.
How 125 ?oWs in the direction toWards the air intake 10. The air ?oW energy to poWer conversion system of
opening 122, a portion of the air intake How 125 then 20 claim 2 Wherein a plurality of the cantilevers 102 and the air
passes through the plurality of air outlet WindoWs 112 outlet WindoWs 112 have a shape selected from the group
creating air outtake ?oWs 133, the air outtake ?oWs 133 consisting of an approximate polygon, a circle, and an ellipse.
causing stress and strain in each of the cantilevers 102 11. The air ?oW energy to poWer conversion system of
thereby generating poWer in each of the cantilever 102. claim 2 Wherein the pieZoelectric material 128 is selected
2. An air ?oW energy to poWer conversion system com 25 from the group consisting of polymers, ceramics, crystals,
prised of: polyvinylidene ?uoride, lead Zirconate titanate, and quartz.
a plurality of cantilevers 102, each cantilever 102 being 12. The air ?oW energy to poWer conversion system of
comprised of electrodes 126 and at least one pieZoelec claim 2 Wherein a plurality of layers of pieZoelectric material
tric material 128, each cantilever 102 having a ?rst can 128 and electrodes 126 is used to form each cantilever 102
tilever edge 137; 30 Wherein the positive and negative surfaces of the pieZoelectric
an air jet tunnel 106 having a frame 104, the frame 104 materials 128 are aligned in series, parallel or a combination
having an air intake opening 122, an air outtake end 124 thereof Within the cantilever 102.
and a plurality of air outlet WindoWs 112, the air outlet 13. The air ?oW energy to poWer conversion system of
WindoWs 112 each having a ?rst WindoW edge 138 claim 2 Wherein the tunnel circuitry 136 collects electrical
35
Wherein each of the air outlet WindoWs 112 is siZed and poWer in an additive manner.
con?gured to receive one of the cantilevers 102, the ?rst 14. The air ?oW energy to poWer conversion system of
cantilever edge of each cantilever 102 being attached to claim 2 Where the pieZoelectric material is fabricated by using
the ?rst WindoW edge 138 of one of the air outlet Win a thin ?lm fabrication processes to form at least one layer of
doWs 112; 40 non-central symmetric thin-?lm of pieZoelectric particles on
the air jet tunnel 106 con?gured so that When an air intake a solid substrate surface to form the pieZoelectric material.
How 125 ?oWs in the direction toWards the air intake 15. The air ?oW energy to poWer conversion system of
opening 122, a portion of the air intake How 125 then claim 14 Wherein the thin ?lm fabrication processes is a
passes through the plurality of air outlet WindoWs 112 Langmuir-Blodgett process.
creating air outtake ?oWs 133, and optionally a portion 45 16. The air ?oW energy to poWer conversion system of
of the air intake How 125 pass through the air outtake end claim 2 further comprising a modular poWer unit 110, the
124 as exit air How 131, the air outtake ?oWs 133 thereby modular poWer unit 110 comprised of a plurality of air jet
causing stress and strain in the cantilevers 102 covering tunnels 106 con?gured such that the plurality of air jet tunnels
the WindoWs 112; 106 generates a phononic array 118 Whereby the air intake
tunnel circuitry 136 attached to each cantilever 102 that 50 ?oW travels through each of the air outlet WindoWs 112, and
collects from each cantilever 102 electrical poWer gen the air outtake ?oWs 133 induce and intensify a vibration of
erated due to stress and strain of the pieZoelectric mate the cantilevers 102 Which generate the electrical poWer that is
rials. passed by the tunnel circuitry 136 to a module circuitry 140.
3. The air ?oW energy to poWer conversion system of claim 17. The air ?oW energy to poWer conversion system of
55
2 Wherein each of the cantilevers 102 is further comprised of claim 16 Wherein the modular poWer unit 110 further com
one layer of an electrode 126 folloWed by at least one layer of prises
pieZoelectric material 128 folloWed by a metal layer 130 a case 108;
folloWed by at least one layer of pieZoelectric material 128 a front grid 132 and a back grid 134, the front grid 132 and
folloWed by a layer of electrode 126. the back grid 134 positioned to hold the air jet tunnels
4. The air ?oW energy to poWer conversion system of claim 106 ?xed While alloWing free How of air inside and
2 Wherein the frame 104 has a cascaded shape With the air outside the air jet tunnels 106; and
intake opening 122 being larger than the air outtake end 124 the tunnel circuitry 136 and the module circuitry 140
and the ?rst cantilever edge 137 of a plurality of the cantile together employing a plurality of electronic components
vers 102 being positioned toWards the air intake opening 122. 65 Wired such that the electrical poWer generated by the
5. The air ?oW energy to poWer conversion system of claim cantilevers 102 are additive When collected via the mod
2 Wherein the frame 104 has a cascaded shape With the air ule circuitry 140.
 US 8,067,878 B1
15 16
18. The air ?oW energy to power conversion system of 125 generates a quantity of poWer at each of the modular
claim 2 Wherein the tunnel circuitry 136 is selected from the poWer units 110, the quantities of poWer transmitted through
group consisting of bridge recti?ers, rechargeable batteries, the module circuitry 140, the panel 114 and panel circuitry
voltage controllers, capacitors, charge pumps and any com 142 thereby forming a poWer panel generator.
binations thereof. 20. The air ?oW energy to poWer conversion system of
19. The air ?oW energy to poWer conversion system of claim 19 Where the panel 114 is rotatable into the Wind.
claim 17 further comprising a plurality of the modular poWer
units 110 mounted in a panel 114 Wherein the air intake How * * * * *