Note: Descriptions are shown in the official language in which they were submitted.
CA 02646525 2008-12-11
WIND TURBINE
BACKGROUND OF THE INVENTION
Technical Field
The invention relates to the field of electrical generation and more
specifically to the
use of a wind turbine for generating electricity.
Description of the Related Prior Art
As those skilled in the art are aware, the availability of energy sources such
as coal,
oil and natural gas are limited which has resulted in escalating costs for
such fuels.
This rising cost is significant for residential users and even more
significant for
commercial users such as manufacturers where such costs could mean the
difference
between continued operation and bankruptcy.
As a result of such rising costs, there have been intensive initiatives to
develop
alternate energy sources, a sub-group of which includes renewable energy
sources
which capture their energy from ongoing natural processes such as sunshine,
wind,
flowing water, biological processes and geothermal heat flows. Renewable
energy
sources may be used directly or used to create other more convenient forms of
energy. An example of direct use would include geothermal, while an example of
indirect use would include a wind turbine used to generate electricity.
A wind turbine may be attached to an electrical generator to produce
electricity. Wind
turbines can be separated into two general types based on the axis (either
horizontal
or vertical) about which the turbine rotates. With a vertical axis wind
turbine
(VAWT), the generator is typically placed at the bottom of the tower on which
the
VAWT is mounted so that the tower doesn't need to support it. As shown in
Figure 1,
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VAWT 100 mounted to tower 110 is connected to generator 120 which may store
the
electricity produced, for example, in capacitor or battery 130 or distribute
it directly
to residential or commercial end user 140. Smaller VAWTs have been designed
for
residential and commercial use such as the 2.5 kW VAWT offered by Cleanfield
Energy Corp. of Mississauga, Ontario, Canada. As shown in Figure 2, this
proprietary
VAWT 200 features three narrow, three-metre vertical blades 210 that are
attached to
central shaft 220. Central shaft 220 connects directly to a rotor (not shown)
of
generator 230. Generator 230 is a low-speed direct-connected permanent magnet
synchronous generator that converts the rotational mechanical energy of the
rotor into
electric energy. Wind moves blades 210 and central shaft 220 is rotated
thereby
serving as a drive shaft for the rotor. Operating in conjunction with a stator
(not
shown) integral to generator 230, electricity is produced.
VAWT 200 of Figure 2 is capable of adequately producing electricity, but it is
limited
by design. More specifically, central shaft 220 carries blades 210. If central
shaft 200
rotates too quickly due, for example, to excessive wind speed, the increased
twist or
torque may cause central shaft 220 to break or bearings (not shown) between to
the
shaft and the generator to come apart. In other words, VAWT 200 must operate
at
low blade speeds which in turns results in lower amounts of electricity being
generated. Additionally, even if VAWT 200 could handle higher blade speeds,
the
actual configuration of the blades is limiting. Since blades 210 all operate
on the
same horizontal plane, blades 210 cannot physically disperse the air fast
enough to
generate higher blades speeds.
A VAWT which is able to take advantage of blade configurations which maximize
blade rotation and thus the power generated would be desirable. Further, a
VAWT
which can be readily mounted in a variety of environments would allow its use
in a
wide variety of applications.
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SUMMARY OF THE INVENTION
The present invention seeks to overcome the deficiencies of the prior art by
providing
a fully integrated vertical axis wind turbine (VAWT) which can be mounted on a
cylindrical pole. Rotor blades are disposed on the outside of a permanent
magnet
generator integral to the VAWT of the present invention, the rotor blades
being
coupled directly to a rotating, current inducing set of permanent magnets or
rotor for
rotation about a stationary, current generating stator. At least three rotor
blades are
used which are vertically offset from one another.
Certain exemplary embodiments may provide a wind turbine mountable at or near
an
upper portion of a stationary cylindrical pole, the wind and updraft turbine
comprising: a current inducing rotor comprising a current inducing set of
permanent
magnets rotatable about the upper portion of the cylindrical pole, about an
axis at
least substantially in line with a main axis of the cylindrical pole; a
stationary, current
generating stator comprising at least one wound coil about which the current
inducing
rotor rotates, wherein the current inducing rotor generates a magnetic field
which
passes in close proximity to the at least one wound coil; and at least three
wind-
engaging rotor blades extending vertically from an outer casing associated
with the
current inducing rotor, wherein each of the at least three wind-engaging
blades are
movable upon application thereto of a prevailing wind, and wherein the at
least three
wind engaging rotor blades are vertically offset from one another, and wherein
each
of the at least three wind engaging rotor blades comprises a trough-shaped,
vertical,
wind engaging portion extending from an arm attached to the outer casing
associated
with said current inducing rotor.
In one aspect, the current inducing rotor comprises a circular array of
permanent
magnets, the current generating stator comprises a circular array of wound
coils, the
circular array of wound coils extends around a circumference of the
cylindrical pole
and is rigidly attached thereto, and the circular array of permanent magnets
extends
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around a circumference of the stator and is rotatably attached thereto,
thereby
avoiding a torsional force on the cylindrical pole when the at least three
wind-
engaging rotor blades attached to the outer casing associated with the current
inducing rotor begin to move.
In another aspect, the current generating stator comprises a horizontally
disposed
circular array of wound coils, the current inducing rotor comprises a
horizontally
circular array of permanent magnets positioned above, and in close proximity
to the
circular array of wound coils, the circular array of wound coils extends
around a
circumference of the cylindrical pole and is rigidly attached thereto, and the
circular
array of permanent magnets extends around a circumference of the cylindrical
pole
and is rotatably attached thereto, thereby avoiding a torsional force on the
cylindrical
pole when the at least three wind-engaging rotor blades attached to the outer
casing
associated with said current inducing rotor begin to move.
Alternately, a plurality of the horizontally disposed circular arrays of wound
coils are
layered above and in close proximity to a plurality of the horizontally
disposed
circular arrays of permanent magnets and the at least three rotor blades are
removably
attached to a top surface of an uppermost circular array of permanent magnets.
The advantages of the invention are now readily apparent. The compact VAWT of
the
present invention can efficiently generate electricity through its integrated
design and
ability to be mounted on any available cylindrical pole. The VAWT may be
mounted
on existing infrastructure e.g. a cylindrical pole extending from a
residential building
or a communications tower. The compact integrated VAWT allows wind turbine
owners to be at least partially self-sufficient for their supply of
electricity, producing
and storing electricity locally instead of relying on power produced by large,
remote
commercial stand alone generators.
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BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in relation to the following drawings in
which:
Figure 1 depicts a prior art electricity generation system using a vertical
axis wind
turbine;
Figure 2 depicts a prior art vertical axis wind turbine which may be used in
the
system of Figure 1;
Figure 3 depicts a functional block diagram of an alternator;
Figure 4(a) depicts a cylindrical pole housing a VAWT in accordance with a
first
embodiment of the present invention mounted thereon;
Figure 4(b) depicts in greater detail the stator of the first embodiment of
Figures 4(a);
Figure 4(c) depicts in greater detail the rotor of the first embodiment of
Figures 4(a);
Figures 5(a) depicts a cylindrical pole housing a VAWT in accordance with a
second
embodiment of the present invention mounted thereon;
Figure 5(b) depicts in greater detail the stator of the second embodiment of
Figures
5(a);
Figure 5(c) depicts in greater detail the rotor of the second embodiment of
Figures
5(a);
Figure 5(d) depicts the stator and rotor of Figures 5(b) and 5(c) in assembled
form
with the cover removed;
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Figures 6(a) to 6(e) depict a blade used in both the first and second
embodiments;
Figures 7(a) and 7(b) depict the present invention mounted to a communications
tower.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As understood by those in the art, in a VAWT the electrical generator produces
electrical energy from a mechanical energy source i.e. the rotation of the
blades. An
alternator is a generator that converts mechanical energy to alternating
electrical
current. When the magnetic field around a conductor changes, current or energy
is
induced in the conductor. Referring to Figure 3, in a typical alternator
(labeled
generally as 300), a rotating magnet or rotor 310 turns within stator 320, a
stationary
set of conductors wound in coils on an iron core. When rotor 310 rotates, its
magnetic
field cuts across the conductors (or windings) of stator 320, generating
electrical
current or energy, as the mechanical input causes the rotor to turn. The
magnetic field
of rotor 310 may be produced by a rotor winding energized with direct current
(i.e. a
field current) through slip rings and brushes (not shown). If a direct current
output is
desired (e.g. to charge a battery 330), the alternating current voltage is
converted by
output diodes 340 into pulsating direct current voltage. Additionally, to
regulate the
field current delivered to rotor 310, diode trio 350 may be used to provide
field
current to a regulator 360 with a control voltage input from the battery being
used to
determine if more or less field current is required to increase or decrease
the magnetic
field strength of rotor 310.
Figures 4(a) to 4(c) depict a first embodiment 400 of the present invention.
In this
configuration, a ring-shaped permanent magnet generator 410 is integrated with
cylindrical pole 420. In this embodiment, vertical rotor blades 430 are
coupled
directly to an outer casing associated with a rotating, current inducing set
of
permanent magnets or rotor 440 (see Figure 4(c) for greater detail) for
rotation about
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a stationary, current generating stator 450 (see Figure 4(b) for greater
detail) which is
rigidly affixed to cylindrical pole 420. The outer casing of rotor 440
includes bearings
(not shown) positioned at the top and bottom which allow rotor 440 to rotate
smoothly about stator 450 (i.e. cylindrical pole 420 does not rotate). Similar
to a
traditional generator, the permanent magnets produce a magnetic field.
However,
rotor 440 rotates around stator 450. When the magnetic field of rotor 440 cuts
through
the conductors of stator 450, a voltage is induced in the conductors. Stator
450 may
be wound for single phase or three phase alternating current generation as is
well
known in the art. Current produced by generator 410 can be used immediately in
a
device requiring electricity or stored in a battery pack (not shown).
The key advantage of this configuration is that the need for linkages and/or a
driveshaft between rotor blades 430 and generator 410 is avoided and blades
430 do
not need to be attached to cylindrical pole 420 (as discussed in relation to
Figure 2 of
the prior art). As a result, there is no rotational torque on cylindrical pole
420 thereby
eliminating the possibility that cylindrical pole 420 will shear off, one of
the
disadvantages discussed in relation to the prior art. Further, because rotor
440 with
attached rotor blades 430 rotates around stator 450, there are only two long
life
bearings which are subject to wear. Due to the limited number of moving parts
lower
vibration and noise levels are achieved. As will be appreciated by those in
the art,
ring-shaped permanent magnet generator 410 can be retrofitted to encircle any
cylinder i.e. it can make use of existing infrastructure, thereby making it
extremely
versatile for a wide variety of commercial or residential applications.
Figures 4(b) and 4(c) depict in greater detail the rotor and stator of the
embodiments
shown in Figure 4(a). More specifically, the current generating stator 450 is
depicted
in Figure 4(b), while the current inducing set of permanent magnets or rotor
440 is
depicted in Figure 4(c). As will be discussed in more detail below, Figures
6(a) to
6(e) depict in greater detail rotor blades 430 which are removably attached to
rotor
440 with arms 460.
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Figures 5(a) to 5(c) depict a variation of the embodiment of Figures 4(a) to
4(c). In
this embodiment 500, the permanent magnet generator 510 is comprised of a
horizontally disposed circular array of wound coils 540 (see Figure 5(b) for a
detailed
view) and a horizontally disposed circular array of permanent magnets 550 (see
Figure 5(c) for a detailed view). The circular array of wound coils 540 is
rigidly fixed
to cylindrical pole 520, while the circular array of permanent magnets 550 is
positioned above, and in close proximity to, wound coils 540. Vertical rotor
blades
530 are coupled directly to an outer casing associated with the top surface of
the
circular array of permanent magnets 550. The circular array of permanent
magnets
550 rotate about cylindrical pole 520 on bearings (not shown). Figure 5(d)
depicts the
circular array of wound coils 540 and circular array of permanent magnets in
assembled form with the outer casing removed. As highlighted in Figure 5(d),
the
circular array of wound coils 540 is horizontally disposed and affixed to
cylindrical
pole 520. The circular array of permanent magnets 550 are also horizontally
disposed
for rotation about cylindrical pole 520 in close proximity to the circular
array of
wound coils 540. The circular array of permanent magnets 550 are magnetically
coupled to the circular array of wound coils 540. More specifically, when the
magnetic field associated with the circular array of permanent magnets 550
cuts
across the windings of the circular array of wound coils 540, an electrical
current is
generated which can be used immediately in a device requiring electricity or
stored in
a battery pack (not shown).
Similar to the embodiments of Figures 4(a) to (c), the key advantage of the
configuration of Figure (5(a) is that the need for linkages and/or a
driveshaft between
rotor blades 530 and generator 510 is avoided and blades 530 do not need to be
attached to cylindrical pole 520. As a result, there is no rotational torque
on
cylindrical pole 520 thereby eliminating the possibility that cylindrical pole
520 will
shear off.
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Figures 5(b) and 5(c) depict in greater detail the circular array of wound
coils 540 and
the circular array of permanent magnets 550 integral to the embodiments shown
in
Figure 5(a). More specifically, the circular array of wound coils 540 is
depicted in
Figure 5(b), while the circular array of permanent magnets 550 is depicted in
Figure
5(c). As will be discussed in more detail below, Figures 6(a) to 6(e) depict
in greater
detail rotor blades 530 which are removably attached to the top surface of the
circular
array of permanent magnets 550 with arms 560.
A variation in the aforementioned embodiment comprises rows of horizontally
disposed circular arrays of wound coils 540 which are layered with and in
close
proximity to rows of horizontally disposed circular arrays of permanent
magnets 550.
Similar to the embodiment of Figure 5(a), the horizontally disposed circular
arrays of
wound coils 440 are attached to cylindrical pole 520. Rotor blades 530 are
removably attached to the top surface of the uppermost circular array of
permanent
magnets 550 and the circular arrays of permanent magnets 550 are coupled
together.
Upon movement of rotor blades 530, the horizontally disposed circular arrays
of
permanent magnets 550 rotate together.
Figures 6(a) to 6(e) depict the configuration of rotor blades 600 reflecting
rotor blades
430, 530 shown in the embodiments of Figures 4(a) and 5(a). Figures 6(a) and
6(b)
are perspective views which highlight the trough-like feature 610 which is
designed
to catch the wind and maximize rotation of the rotor. Rotor blades 600 may
span ten
feet in height and cover more than 5 feet in diameter but they are not meant
to be
limited in this regard. As highlighted in figure 6(b), rotor blade 600
includes a bracket
620 for removable attachment to generator 410, 510 using arms 460, 560.
Notably, whether associated with the embodiment of Figure 4(a) or 5(a), rotor
blades
600 are vertically offset from one another. In the presence of a horizontal
wind, with
the rotor blades 600 configured as depicted in Figures 4(a) or 5(a), the
rotational
speed of rotor blades 600 is greater than blades configured in a more
traditional
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configuration i.e. the same horizontal plane. As those skilled in the art will
appreciate,
increased rotational speed translates directly to increased horsepower (hp) in
generator 410, 510. As wind speed increases, the horsepower (hp) generated by
generator 410, 510 increases with a multiplier effect e.g. if the wind speed
doubles,
more than eight times the power becomes available.
Figure 7(a) and 7(b) depict a typical installation of the embodiments of
Figures 4(a)
and 5(a). As previously discussed, the embodiments of Figures 4(a) and 5(a)
can be
retrofitted to any cylindrical pole in either an industrial and residential
application.
For example, it can fitted on any building from which a cylindrical pole can
be
extended, or, as depicted in Figures 7(a) and 7(b), wind turbine 700 can be
mounted
on the top end of a communications tower 710 such as a microwave tower used in
a
wireless network. The use of existing infrastructure to accommodate the
present
invention is a key advantage, along with the wind turbines efficient
generation of
electricity.
Although the present invention has been fully described by way of the examples
with
reference to the accompanying drawings, it is to be noted that various changes
and
modifications will be apparent to those skilled in the art. Therefore, unless
such
changes and modifications otherwise depart from the spirit and scope of the
present
invention, they should be construed as being included therein. For example,
although
the present invention may be preferably mounted on cylindrical pole 80, it
could also
be mounted on square tubing or the like which extends vertically.
