Prime-mover dynamo plants – Fluid-current motors – Wind
Reexamination Certificate
2000-02-05
2001-08-21
Ponomarenko, Nicholas (Department: 2834)
Prime-mover dynamo plants
Fluid-current motors
Wind
C290S054000
Reexamination Certificate
active
06278197
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a wind energy conversion system and, more particularly, to the design and manufacture of a jet assisted contra-rotating wind turbine system.
2. Prior Art
In recent years, it has become apparent that conventional methods of generating electricity will soon be insufficient to meet the world's ever-growing need for electric power. Several factors, including the pollution which results from the combustion of fossil fuels, the dangers associated with the operation of nuclear reactors, and the limitations inherent in the traditional hydroelectric as well as the more modern solar energy approaches to the generation of electricity, have encouraged the development of alternative sources of electric power, such as the wind turbine generator.
In recent years, wind energy projects have included the installation of large numbers of wind turbine generating systems at locations having favorable wind conditions. Several of these so-called “wind farms” have been located in the state of California. However, during the 1980s, it became apparent that the various wind energy projects using wind turbines to generate electrical energy suffered from a major problem in that the turbines were not receiving the amount of wind energy that was projected based on the initial wind studies that were conducted. Many reasons have been advanced for this shortfall of wind energy. Little can be done about the wind itself, with the exception of understanding the available resource better by using direct measurement and analysis. However, a new rotor blade system according to the present invention, designed to take better advantage of the available wind resource, provides an opportunity for a significant energy increase.
As noted, then, wind turbines are renewable energy devices that are currently useful but not able to optimally extract energy from the wind. According to Albert Betz, a German engineer, pioneer in optimizing wind energy utilization, and author in 1926 of “Wind Energie und Ausnutzung durch Windmuehlen”, an ideal rotor disk can deliver to a selected task 59% of the total wind energy generated. For example, an ideal rotor disk is expected to yield 797 watts per square meter at 13 m/sec of wind speed. In contrast, a practical wind turbine, according to Paul Gipe, a more recent well known promoter of wind energy technology in the United States, author of many books on the subject, his most recent contribution being “Wind Energy Comes of Age”, John Wiley & Sons, Inc., New York, 1995, can only deliver less than 20% of the available power which is about 100 to 250 watts/m
2
. Even the most acclaimed Bergey's BWC EXCEL wind turbine yields only 260 watts/m
2
. Michael Bergey is a small wind turbine manufacturer in the United States whose BWC EXCEL model is generally considered to be the most efficient wind turbine machine in the United States. The reason for such a significantly low energy conversion efficiency may be attributed to the downstream velocity (V
2
) being greater than one half of the upstream velocity (V
1
). Thus, a wind turbine comprising of a single rotor system cannot possibly extract the amount of power suggested by Betz. Consequently, more than 60% of the usable energy is swept away in the downstream wind. Another drawback of a single rotor system is that it experiences a large power loss resulting from drag associated with high tip speed of large diameter rotor. Then too, single rotor renewable energy devices are limited in their use since a high torque is necessary to self start the system and therefore can be installed only in regions with consistently high wind speeds.
A small number of patents are typical of the known prior art attempting to improve on earlier efforts to harness wind energy. For example, U.S. Pat. No. 5,456,579 to Olson discloses a wind turbine blade with a governor to maintain optimum rotational speed. The governor positions an aileron for varying wind speed and includes a lead weight positioned at the wing tip and connected to a mechanism that deploys the aileron to achieve the maximum lift to drag ratio at all wind speeds. U.S. Pat. No. 5,419,683 to Peace discloses a method of installing a plurality of wind turbines on chimneys, towers or the like. Two rotors having their horizontal axes are mounted back to back on a ring that turns about the chimney. The primary concept of this invention is to utilize existing structures to mount a plurality of wind turbines and to eliminate the need for wind farms. U.S. Pat. No. 4,976,587 to Johnston et al. discloses a method for manufacturing composite blades having highly improved aerodynamic efficiency. The blades employ the NASA airfoil section LS(1)-04XX having 29 per cent thickness at {fraction (3/10)} radius and 18 per cent at the blade tip. The airfoil section comprises two spars which terminate into a circular section at the hub. U.S. Pat. No. 4,648,801 to Wilson discloses a method of compressing air by means of a wind turbine. The air is drawn from the low energy region of the downwind stream. The compressed air is connected to the intake of a prime mover (such as a diesel engine, a gasoline engine, or a gas turbine) to boost its output power and drives an alternator.
It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.
SUMMARY OF THE INVENTION
The present invention relates to wind turbine apparatus which includes an upright mast with support bearings underlying and rotatably supporting a hub assembly having inner and outer coaxial shafts telescopically related but radially spaced to permit independent rotation about a generally horizontal axis. An armature winding is provided on the outer shaft and a plurality of dielectrically separated magnets are mounted on the inner shaft at a plurality of circumferentially spaced locations. A first set of rotor blades is mounted on the inner shaft at a plurality of circumferentially spaced locations, the rotor blades extending radially away from the axis of rotation and positioned on the inner shaft for rotating the inner shaft in a first direction about the axis of rotation when subjected to wind-induced air flow. A second set of rotor blades is similarly mounted on the outer shaft axially spaced from the first set of rotor blades for rotating the outer shaft about the axis of rotation in an opposite direction. The hub assembly may be selectively positioned in azimuth so that the first set of rotor blades is relatively closer to the wind-induced air flow, or windward, and the second set of rotor blades is relatively farther from the wind-induced air flow, or leeward. Electrical power is generated as the armature winding on the outer shaft and the plurality of magnets on the inner shaft rotate in opposite directions and power transfer apparatus is provided for drawing off the electrical power from the hub assembly to a distant receiver.
To circumvent the deficiencies of a single rotor turbine, a jet assisted, contra-rotating wind turbine system is proposed to extract almost twice the amount of wind power at half the cost of known devices. The proposed wind turbine system involves three distinct innovations. In a first instance, the turbine design of the invention comprises a pair of rotors directly mounted on a pair of co-axial shafts having airfoil shaped bearing supports. The turbine rotors are set to rotate in opposite directions. The co-axial shafts play the dual role of an alternator as well as a torque-transmitting device. The outer surface of the inner shaft is imbedded with permanent magnets, while the inner surface of the outer shaft is wound with armature coils. Thus, the dual-use direct drive concept reduces the weight and cost of the turbine unit. More importantly, a twin rotor system extracts a substantially increased amount of power from the wind. It also provides increased relative speed in the magnetic field that improves electrical performance and results in alternators o
Hilburger Albert W.
Ponomarenko Nicholas
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