U.S. patent application number 10/909324 was filed with the patent office on 2005-01-13 for sky turbine that may be mounted on top of a city.
Invention is credited to Brueckner, Manfred Karl.
Application Number | 20050008488 10/909324 |
Document ID | / |
Family ID | 36262140 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050008488 |
Kind Code |
A1 |
Brueckner, Manfred Karl |
January 13, 2005 |
Sky turbine that may be mounted on top of a city
Abstract
A sky turbine, having impeller blades with a plurality of panels
that can telescope inward and outward. The pitch of the panels can
be adjusted, and the pitch of each panel on a blade, passing from
the innermost panel to the outermost panel, differs from the pitch
of the previous panel by a certain adjustable amount. The sky
turbine is preferably mounted above a city at a sufficiently high
elevation that air current will be generally faster than just above
the ground. In the preferred embodiments, a wing with two pods is
pivotally mounted on a tower. Each pod has front and rear shafts,
from which four blades extend. Servomotors cause the wing to turn
so that the shafts are approximately parallel to the direction the
wind is blowing, cause the pitch of the panels of the blades to
change, and cause the panels of the blades to move
telescopingly.
Inventors: |
Brueckner, Manfred Karl;
(Milwaukee, WI) |
Correspondence
Address: |
STEPHEN CHRISTOPHER SWIFT
SWIFT LAW OFFICE
SUITE 200
1940 DUKE STREET
ALEXANDRIA
VA
22314-3451
US
|
Family ID: |
36262140 |
Appl. No.: |
10/909324 |
Filed: |
August 3, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10909324 |
Aug 3, 2004 |
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10051521 |
Jan 18, 2002 |
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Current U.S.
Class: |
416/132B |
Current CPC
Class: |
F05B 2240/2021 20130101;
F03D 1/02 20130101; F03D 80/40 20160501; Y02B 10/30 20130101; F03D
1/0633 20130101; F05B 2240/911 20130101; Y02E 10/728 20130101; Y02E
10/72 20130101; F03D 1/0608 20130101; F03D 13/20 20160501; F05B
2240/313 20130101 |
Class at
Publication: |
416/132.00B |
International
Class: |
B63H 001/06 |
Claims
I claim:
1. A sky turbine, comprising: at least one shaft; and blades
extending from the shaft, each blade having at least three
telescoping panels.
2. The sky turbine according to claim 1, wherein pressure of air
current against the blades causes rotation of the shafts, which is
used to generate electricity.
3. The sky turbine according to claim 2, mounted at a sufficiently
high elevation that air current will be generally more rapid than
on the ground.
4. The sky turbine according to claim 3, mounted above a city.
5. The sky turbine according to claim 4, mounted at the top of a
tower containing the city.
6. The sky turbine according to claim 1, wherein the angles of the
panels of the blades are adjustable.
7. The sky turbine according to claim 6, wherein there are two
parallel pods, with each pod having two opposite ends containing
one of the shafts, with the blades extending radially outward from
the shaft in each end.
8. The sky turbine according to claim 7, wherein the pods are
retained on a wing that can pivot on a vertical axis.
9. The sky turbine according to claim 8, wherein wind speed and
direction are detected by sensors that communicate with a computer,
and servomotors controlled by the computer cause the wing to turn
so that the shafts are approximately parallel to the direction the
wind is blowing, and minimize changes in the speed of rotation by
causing the angles of the panels of the blades to change and the
panels of the blades to move telescopingly.
10. The sky turbine according to claim 9, wherein when the blades
telescope inward, the panels of the blades nearer to the shaft are
nested within the panels of the blades further from the shaft.
11. The sky turbine according to claim 10, wherein the angles of
the panels of each blade are such that the blade forms a helix.
12. The sky turbine according to claim 11, wherein one end of each
pod is a front end, and the other end of each pod is a rear end,
and the shafts in the front ends of the pods rotate independently
of the shafts in the rear ends of the pods.
13. The sky turbine according to claim 12, wherein the shafts and
blades on the front ends of the pods intermesh and counter-rotate,
and the shafts and blades on the rear ends of the pods intermesh
and counter-rotate.
14. The sky turbine according to claim 13, wherein each panel of
the blades is equipped with electrical deicing and a moisture-proof
seal, and is strengthened by a light structural lattice.
15. The sky turbine according to claim 14, wherein planetary gears
increase the speed of the shafts.
16. The sky turbine according to claim 15, wherein each of the
panels of each of the blades is a symmetrical airfoil having: a. a
chord (C) as its length, b. a width (B), c. a dimension (A) which
is, 6 A = 2 C 3 d. a leading edge radius (r), 7 r = B 2 2 A e. a
line (M) perpendicular to the chord (C) and located at the
dimension (A) from a trailing edge, f. a dimension (X), 8 X = A 3 -
3 AB 2 + 2 B 3 4 B ( A - B ) g. a radius (R) centered on the line
(M), 9 R = X + B 2 and h. a straight portion, tangent to the radius
(R) and the trailing edge.
17. A symmetrical airfoil comprising: a. a chord (C) as its length,
b. a width (B), c. a dimension (A) which is, 10 A = 2 C 3 d. a
leading edge radius (r), 11 r = B 2 2 A e. a line (M) perpendicular
to the chord (C) and located at the dimension (A) from a trailing
edge, f. a dimension (X), 12 X = A 3 - 3 AB 2 + 2 B 2 4 B ( A - B )
g. a radius (R) centered on the line (M), 13 R = X + B 2 and h. a
straight portion, tangent to the radius (R) and the trailing edge.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on Regular Utility patent
application Ser. No. 10/051,521, filed Jan. 18, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to turbines for generating
electrical power from wind, which may be mounted on top of a
city.
[0004] 2. Description of the Prior Art
[0005] Mankind's history began in the stone age, then continued in
the bronze age and the iron age, to our present age, the industrial
revolution. At the present time, electricity is produced by
hydroelectric dams, atomically or by the burning of hydrocarbons.
Production of electricity by hydroelectric dams is limited and is
also destructive to the environment. The burning of coal deposits
mercury and acid rain into the environment. Toxic ash must also be
disposed of. Nuclear power production is plagued with the problem
of long term storage of radioactive waste. In 1954, Lewis Strauss,
Chairman of the Atomic Energy Commission, said that atomic reactors
might someday produce such an abundance of energy that electricity
would become "too cheap to meter". What nuclear power failed to do,
wind power using the present invention may accomplish. It will be
the backbone of our next age, the solar age, in which all our
energy needs are satisfied by power derived from the sun.
[0006] U.S. Pat. No. 1,757,667, issued on May 6, 1930, to Erich
Hesse, discloses a device for regulating wind wheels to obtain a
uniform rotational speed, by changing the pitch of their vanes with
rods in the arms on which the vanes are located. The instant
invention is distinguishable, in that the blades of the turbine can
be telescopically extended or retracted to regulate their
speed.
[0007] U.S. Pat. No. 4,065,225, issued on Dec. 27, 1977, to William
D. Allison, discloses a multivane windmill, in which the pitch of
the vanes can be changed in response to wind speed, to keep the
speed of rotation constant. Again, the instant invention is
distinguishable, in that the blades of the turbine can be
telescopically extended or retracted to regulate their speed.
[0008] U.S. Pat. No. 4,257,736, issued on Mar. 24, 1981, to Dennis
Jacobs, discloses a governed propeller type wind motor arrangement,
in which the pitch of the blades is changed, but the blades do not
telescope, as in the instant invention.
[0009] U.S. Pat. No. 4,500,259, issued on Feb. 19, 1985, to
Berthold W. Schumacher, discloses a fluid flow energy converter,
with several screws (or "helicoid structures") rather than
propeller-like blades, as in the instant invention. It is disclosed
in column 8, lines 45-49 that, "an ideal location for a wind mill
is, for instance, the roof of a high-rise building in a city. Of
course, a special tower may also be built for carrying the
helicoids." But its structure in completely different from that of
the instant invention.
[0010] U.S. Pat. No. 4,710,101, issued on Dec. 1, 1987, to Peter M.
Jamieson, discloses a wind turbine, with each blade having a fixed
inner portion and an outer portion that can move outward to
lengthen the blade, to increase drag and slow down rotation of the
turbine. The instant invention is distinguishable in that it has
several panels, not just two, that can telescope inward or outward,
and it can reduce its speed of rotation by telescoping inward.
[0011] U.S. Pat. No. 4,878,807, issued on Nov. 7, 1989, to Keith G.
Baker, discloses a device for producing electricity from wind,
having a vertical belt and interspaced hydrodynamic foil members.
Its use in high rise buildings is disclosed in column 8, lines
13-21, but its structure is different from that of the instant
invention, e.g., it has no telescoping blades.
[0012] U.S. Pat. No. 5,313,103, issued on May 17, 1994, to John J.
Hickey, discloses an auger shaped fluid medium engaging member. Its
use "on tops of roofs of a high rise building" is suggested in
column 1, lines 66-67, but its structure is readily distinguishable
from that of the instant invention, e.g., it has no telescoping
blades.
[0013] U.S. Pat. No. 5,609,472, issued on Mar. 11, 1997, to
Masahiro Obukata and Masaaki Nakadate, discloses a rotor blade for
a rotary wing aircraft (such as a helicopter) having a different
shape from the impeller blades of the instant invention.
[0014] U.S. Pat. No. 6,361,279, issued on Mar. 26, 2002, to Anne
Marie Rodde, Joel Reneaux and Jean Jacques Thibert, discloses a
blade profile for an aircraft rotor, again having a different shape
from the impeller blades of the instant invention.
[0015] British Patent No. 252,461, complete specification accepted
on May 27, 1926, inventor Kurt Bilau, discloses improvements in or
related to wind-driven prime movers, including braking action by
producing eddy currents in a slot or slots between displaced
sections of the sail vane or the sail vane and a head piece, but
not by telescoping as in the instant invention.
[0016] Japanese Patent No. 57-32074, published on Feb. 20, 1982,
inventor Teru Matsumiya, discloses a wind mill, with blades having
a fixed inner member and an outer member that can retract inward
into the inner member to reduce the wind receiving area, or extend
outward from the inner member to increase the wind receiving area.
The instant invention is distinguishable in that it has not just
two, but several telescoping panels, which also have an adjustable
pitch.
[0017] Soviet Patent No. 992804, published on Jan. 30, 1983,
discloses a wind motor rotor with telescopic blades, having a fixed
part and a moving part. Again, the instant invention is
distinguishable in that it has not just two, but several
telescoping panels, which also have an adjustable pitch.
[0018] Electric Power from the Wind-II, Electrical World, May 12,
1945, pp. 102-104, discloses the possibility of generating electric
power from wind, which is faster above the surface of the
ground.
[0019] Marks' Standard Handbook, 9.sup.th Edition, 1987, p. 9-173,
FIG. 9.11.18, discloses that the wind speed at an altitude of 350
meters is more than twice that on the ground.
[0020] Handbook of Airfoil Sections, Rice, Michael, 1971, p. 47,
discloses that in a symmetrical airfoil, the center of pressure is
stable for all angles of attack.
[0021] None of the above inventions and patents, taken either
singly or in combination, is seen to describe the instant invention
as claimed.
SUMMARY OF THE INVENTION
[0022] The present invention is a sky turbine, which may be mounted
atop a high rise city. Two main shafts are facing forward and two
are facing aft. Both pairs are intermeshing and counter-rotating.
There is no timing relationship between front and back. In fact,
the front side may be shut down for maintenance while the back side
continues producing power. The sky turbine is able to protect
itself from high wind speeds in the sky. As the wind speed rises,
the impeller blades have panels that can telescope inward, and they
can also change their angle to the wind.
[0023] Accordingly, it is a principal object of the invention to
produce cheap, clean, and abundant electric power for as long as
there are air currents in the sky.
[0024] It is another object of the invention to produce electric
power that is "too cheap to meter".
[0025] It is a further object of the invention to reduce pollution
of the environment.
[0026] Still another object of the invention is to enable dams to
be dismantled and salmon and other migratory fish to return to
running in rivers and streams.
[0027] It is an object of the invention to provide improved
elements and arrangements thereof in an apparatus for the purposes
described which is inexpensive, dependable and fully effective in
accomplishing its intended purposes.
[0028] These and other objects of the present invention will become
readily apparent upon further review of the following specification
and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a perspective view of a sky turbine in the first
preferred embodiment of the invention, with the blades fully
extended.
[0030] FIG. 2 is a detail view of one impeller blade which is
mounted at the left rear spinner.
[0031] FIG. 3 is a perspective view of a sky turbine in the first
preferred embodiment of the invention with panels 2 through 4
telescoped into panel 1.
[0032] FIG. 4 is a detail view of one impeller blade which is
mounted at the left rear spinner, with panels 2 through 4
telescoped into panel 1.
[0033] FIG. 5 is a perspective view of a sky turbine in the first
preferred embodiment of the invention with panels 2 through 7
telescoped into panel 1.
[0034] FIG. 6 is a detail view of one impeller blade which is
mounted at the left rear spinner, with panels 2 through 7
telescoped into panel 1.
[0035] FIG. 7 is a perspective view of a sky turbine in the first
preferred embodiment of the invention with panels 2 through 9
telescoped into panel 1.
[0036] FIG. 8 is a detail view of one impeller blade which is
mounted at the left rear spinner, with panels 2 through 9
telescoped into panel 1.
[0037] FIG. 9 is a detail view of one impeller blade which is
mounted at the left rear spinner, with panels 2 through 9
telescoped into panel 1, with panel 1 having a lower pitch than in
FIG. 8.
[0038] FIG. 10 is a left side elevational view of the turbine of
the first preferred embodiment of the invention.
[0039] FIG. 11 is a top view of the first preferred embodiment of
the invention.
[0040] FIG. 12 is a schematic front elevational view showing one
blade in a first position.
[0041] FIG. 13 is a schematic front elevational view showing the
blade in a second position.
[0042] FIG. 14 is a schematic front elevational view showing the
blade in a third position.
[0043] FIG. 15 is a schematic front elevational view showing the
blade in a fourth position.
[0044] FIG. 16 is a front elevational view of the second embodiment
of the invention.
[0045] FIG. 17 is a left side elevational view of the second
embodiment of the invention.
[0046] FIG. 18 is a top plan view of the second embodiment of the
invention.
[0047] FIG. 19 is a sectional view drawn along lines 19-19 of FIG.
17.
[0048] FIG. 20 is a sectional view drawn along lines 20-20 of FIG.
17.
[0049] FIG. 21A and FIG. 21B are a single sectional view through a
blade in either preferred embodiment of the invention, with the
blade having five panels that are extended.
[0050] FIG. 22 is a sectional view through a blade in either
preferred embodiment of the invention, with the blade having five
panels that are retracted.
[0051] FIG. 23 is a schematic sectional view of the airfoil of the
panel's skin.
[0052] FIG. 24 is a sectional view drawn along lines 24-24 of FIG.
22.
[0053] FIG. 25 is a sectional view drawn along lines 25-25 of FIG.
24.
[0054] FIG. 26 is a perspective view of the inside of the right
hand pod in either preferred embodiment of the invention.
[0055] FIG. 27 is a diagram showing the relative efficiency of
investment capital with respect height H.
[0056] FIG. 28 is a diagram showing the number of panels which are
extended outward (out of a total of nine panels) with respect to
the sky speed.
[0057] FIG. 29 is a schematic map of the Gulf of Mexico.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0058] FIG. 1 is a perspective view of a sky turbine in the first
preferred embodiment of the invention. The invention will have this
appearance when the sky speed is 2.7 meters/second (6 mph) or less.
Each blade may have between five to twelve panels. The embodiment
shown in FIG. 1 has nine panels, 1 through 9.
[0059] FIG. 2 is an enlarged view of one impeller blade which is
mounted at the left rear spinner. The angle (or "pitch") of the
panels 1-9 is controlled by servomotors. The angles between the
panels are such that the blade forms a helix.
[0060] FIG. 3 is similar to FIG. 1 but shows the invention as it
would appear when the sky speed is between 5.8 and 7.6
meters/second (13 to 17 mph). Panels 2 through 4 have been
telescoped into panel 1.
[0061] FIG. 4 complements FIG. 3.
[0062] FIG. 5 shows the arrangement of the invention as it would
appear when it is facing a sky speed of between 14.3 and 21.5
meters/second (32 to 48 mph). Panels 2 through 7 have now been
telescoped within panel 1.
[0063] FIG. 6 complements FIG. 5.
[0064] FIG. 7 shows the invention when facing a sky speed greater
than 21.5 meters/second (48 mph). Also shown is arrow 10 which is
indicating the direction of the wind as it approaches the
invention. Tower 11 contains the stationary portion of the city.
Wing 12 connects the city to the two parallel pods. The right front
spinner 13 is mounted onto the right pod 14. Some of the cities
most luxurious real estate is located just within the skin of the
wing and pods. A weather station 15 located atop wing 12 contains
an anemometer and a sky direction vane or other sensors. A computer
(not shown) located near the weather station 15 communicates with
and commands (via digital radio signals) the various servomotors
located throughout the blades. A pair of wires (not shown) are
strung the length of each spar. Continuity from spar to spar is
maintained by electric brushes. Thus, power is provided to all
servomotors within the blade. Servomotors are also mounted on tower
11 to keep wing 12 facing arrow 10, so that the shafts (32 in FIG.
26) that the impeller blades are connected to will be approximately
parallel to the direction of the wind.
[0065] FIG. 8 complements FIG. 7.
[0066] FIG. 9 is similar to FIG. 8, but shows that the computer has
set the blades to a low angle of attack as the invention faces a
hurricane. This maneuver is merely a pitch change; the invention
continues to produce power.
[0067] FIG. 10 is a left side elevational view of the turbine of
the first preferred embodiment. Dimension H is the height as
measured from the ground.
[0068] FIG. 11 is a top view of the present invention. Dimension D
is the dihedral angle of the blades with respect to the spinner and
dimension S is the skew angle between the spinner and the center of
symmetry. The wind speed above an altitude of 350 meters (1148
feet) is more than two times the wind speed at the ground. (Marks'
Standard Handbook, 9.sup.th Edition, 1987, p. 9-173, FIG. 9.
11.18). (The wind speed at these altitudes is herein referred to as
the "sky speed".) The skew angle subtracts angle of attack at the
top of the swing and adds angle of attack at the bottom of the
swing. With the right front blades rotating clockwise (when viewed
from the front), the skew angle will automatically compensate for
the difference of the sky speed at the various altitudes. When
dimension H is 1.61 kilometers (1 mile) or more the skew angle is
not needed.
[0069] FIG. 12 and FIG. 13 shows the telescoping of panel 1 over
panel 2 in 90.degree. of the blade swing. This is possible because
the blades rotate quite slowly. The speed of the tip of the blades
is about one-sixth of the speed of the wind.
[0070] Or 1 RPM = kS s R
[0071] whereby
[0072] RPM: revolutions per minute of the blades
[0073] k: a constant 57 (84)
[0074] S.sub.S: mean sky speed in M/S (mph)
[0075] R: the total radius of the blades in meters (feet)
[0076] The reciprocal of the RPM is the number of minutes required
to complete one revolution.
[0077] The falling motion is powered by gravity and this fall is
checked by servomotors located inside the blade.
[0078] FIG. 14 and FIG. 15 shows the inverse of FIG. 12 and FIG.
13. Panel 1 extends downward during 90.degree. of blade rotation
and this fall is again due to gravity.
[0079] FIG. 16 through FIG. 20 shows the various aspects of the
second preferred embodiment of the invention. This embodiment
differs from the first embodiment in that the wing 12 is integral
with the city 18. Both are suspended by tower 17. In the version
shown there is no skew angle, therefore, additional dihedral must
be used. Reference 16 is a two channel rotating union allowing
fresh water to enter the city and sewage to exit. FIGS. 19 and 20
are sections taken through FIG. 17.
[0080] FIG. 21A and FIG. 21B are sections through a five-paneled
blade. This blade is shown at maximum extension (or "aspect ratio")
with a zero angle of attack on all panels (i.e., "full feathered").
Each panel is equipped with electrical deicing and a seal 31. This
seal keeps out moisture and strips off any residual ice when the
panels are in relative motion. Planetary gear 34 is a hypocycloid
roller gear with pure rolling contact, that increases the speed of
the main shaft 32 to 25.5 times faster than the spinner 13. (I.e.,
gear 34 is a smaller gear, with rollers in place of teeth, that
rotates inside a larger gear with teeth on its inside.) The main
shaft 32 is held to the stationary structure 35 by bearing 33. A
light structural lattice 36 is provided to give the panels' airfoil
a semi-monocoque strength (i.e., deriving most of its strength from
its skin).
[0081] FIG. 22 is a retracted configuration of FIG. 21 (with the
smallest possible aspect ratio). Typically the number of panels
range between 5 and 12. The difference in aspect ratio of a fully
extended blade to a fully retracted blade is a function of the
total number of panels. Therefore, the more panels that are fitted,
the more the aspect ratio and the size of the wind receiving
surface can be changed, and the better the invention can protect
itself from violent storms. Strobe light 30 warns approaching
aircraft.
[0082] FIG. 23 is the airfoil of the panel's skin. This airfoil is
symmetrical. The center of pressure is stable for all angles of
attack. (Handbook of Airfoil Sections, Rice, Michael, 1971, p. 47).
This airfoil cannot flutter (or "shimmy"). Chord C is the total
length. The maximum width B is located 1/3 of the chord as measured
from the front. 1/3 chord also equals 1/2 A.
[0083] Thus 2 C 3 = A 2 or C 1.5 = A
[0084] And the leading edge radius 3 r = B 2 2 A
[0085] Furthermore 4 X = A 3 - 3 AB 2 + 2 B 3 4 B ( A - B )
[0086] Finally 5 R = X + B 2
[0087] Both the chord C and dimension B may be arbitrarily chosen.
Center 39 is the center of gravity of the airfoil and the axis of
the telescoping octagonal mono-spar.
[0088] FIG. 24 is a section taken through FIG. 22. Each panel is
equipped with two ball screws 19 through 22. (This figure has
distorted proportions for the sake of clarity).
[0089] FIG. 25 is a section taken through FIG. 24.
[0090] FIG. 26 is an isometric view of the inside of the right hand
pod 14. Main shaft 32 is rotating 25.5 times faster than spinner
13. Shaft 40 synchronizes the right main front shaft to the left
main front shaft. The main shaft 32 is supported by pillow block 41
at its back end. Two universal joints 42 remove the skew angle
before providing the nine speed gear box 43 with input. The output
of this gear transmission 43 is fed into a bank of fixed
displacement oil pumps 44 and also into a small bank of variable
displacement pumps 45. The combined oil pumped is fed to a fixed
displacement hydraulic motor 46 through pipe 47 and returned to the
pumps by pipe 48. The motor 46 is directly coupled to A.C.
generator 49. A small sample of electric power is taken from
generator 49 by wires 50 and fed to a synchronous motor 51. The
speed of motor 51 is compared by differential 52 to a clock 53. If
generator 49 is operating off frequency, variable displacement
pumps 45 are readjusted through feedback tube 54. A.C. power from
generator 49 is supplied to all local loads by wire 55. Location 56
contains equipment to convert A.C. to D.C. This D.C. is sent
worldwide by power grid 57. On rare occasions when the sky speed
falls below 4 mph, the sky turbine may no longer have sufficient
strength to supply its designated area with A.C. power. In that
situation, D.C. power is borrowed from grid 57 and converted back
to A.C. by 56 to be used locally through wires 55.
[0091] FIG. 27 shows the relative efficiency of investment capital
with respect to dimension H. Eiffel's tower (in Paris, France) 58
is shown for height comparison. When the H dimension is doubled,
the electric power is increased four times and the city's real
estate is eight times more. Investment capital is largely recovered
by the selling and renting of the city's real estate.
[0092] FIG. 28 shows the number of panels which are extended
outward (out of a total of nine panels) with respect to the sky
speed.
[0093] FIG. 29 is a map of the Gulf of Mexico, depicting
hypothetical locations of my invention 59. Also shown is the
worldwide D.C. power grid 57, including submerged portions 57a. The
local area 60 is supplied with A.C. power from wires 55 in FIG.
26.
[0094] In operation, weather station 15 reports to the computer
that the sky speed has increased over 2.7 meters/second (6 mph).
(See FIG. 28). The computer decides that it is time to retract
panel 1 over panel 2. The computer then instructs panel 1 to align
itself to panel 2, using simultaneously servomotors 27 and 28. (See
FIG. 21B). It then instructs servomotor 37 to relax wedge 38. (See
FIG. 25). Spar 25 is now free to slide down spar 26. (See FIG. 21B
and FIG. 25). As panel 1 falls over panel 2, servomotor 23
decelerates this fall by using ball screw 20 and ball nut 24. Panel
1 then reaches its retracted position gently. Servomotor 37 then
reactivates wedge 38 and a snug fit between spars 25 and 26 is
re-established. All of this action takes place within 90.degree. of
blade rotation as shown in FIG. 12 and FIG. 13 and it is
predominantly gravity driven.
* * * * *