Patent Application
20100276937
This description relates to generating electricity using wind.
The swaying of a tree in the wind is driven by its leaves. The structure of the tree inherently aggregates the small individual energy contributions of the large number of leaves into enough energy to sway even a very large tree.
For centuries, windmills have been used to extract energy from the wind and apply it to tasks such as milling wheat between rotating stones and more recently generating electricity for broad distribution to users.
Some considerations in the design and operation of electricity generating windmills (sometimes called wind turbines) are efficiency, cost and practicality of construction, safety (to birds, animals, and humans), environmental impact, aesthetics (some people think wind turbines are ugly), and energy storage (e.g., using batteries).
One measure of efficiency of a wind turbine is the percentage of the total energy of the wind that could be potentially captured in the geometrical area that is swept by its rotating blades, that is actually captured. Efficiency is maximized when the blades rotate fast enough to scoop all of the wind passing through that area, but not so fast as to cause the blades to cavitate (lose traction because air cannot flow fast enough through that area).
Yet the blades of a typical wind turbine rotate much more slowly than this ideal speed, and much of the available wind energy is lost as it blows through that area without doing work on the blades. In addition, wind turbine blades tend to operate at high efficiency only along about two thirds of their length; their efficiency is lower in blade segments that are near the center of rotation (where they move more slowly for a given wind speed) and also near their outer ends.
Wind turbine blades and the structures that support them must be carefully designed and built because they are large, heavy, subjected to large stresses and vibrations, must last a long time, must be stabilized at the ground, and need to rise high above the ground to catch winds that are steady rather than unpredictable and random.
An elegant way to derive value from even small amounts of generated electricity is to use it to drive the electricity distribution grid negatively to offset the cost of electricity that would otherwise be drawn from the grid.
In general, in an aspect, a wind catching surface is supported to face an oncoming wind and not to rotate continuously in one direction under the influence of the oncoming wind, and an energy converter converts motion, caused by the surface catching the oncoming wind, into electricity.
Implementations may include one or more of the following features. The wind catching surface is fixed at one edge and at least some other portions are free to move in response to the wind. The wind catching surface is supported to face the oncoming wind directly. The wind catching surface is arranged to alter its configuration in response to the oncoming wind. The wind catching surface is arranged to billow in response to the oncoming wind. The wind catching surface is generally rectangular. The wind catching surface includes a stem. The stem is coupled to the energy converter. The wind catching surface is fixed at one edge and is coupled at another location to the energy converter. The motion caused by the surface catching the oncoming wind includes linear motion of the energy converter. The wind causes a distance between the fixed pitch and the coupled location to vary.
The energy converter includes an electromagnetic device. The energy converter includes a magnet and a coil that move relative to one another. The energy converter includes reciprocating elements.
Implementations for restoring force may include one or more of the following features. An element applies a restoring force in response to the motion. The element that applies a restoring force includes a spring. The element that applies a restoring force includes a mass that is acted on by gravity, which may be the weight and elasticity of the wixel itself.
There is a support for the wind catching surface. There is at least one additional wind catching surface on the support. The support is stationary relative to the wind. The support has nodal points of resonance to impart a randomized elasticity to the support. The support is movable to orient the wind catching surface relative to a direction of the wind. The wind catching surface and the additional wind catching surface are mounted to prevent interference with one another in the wind.
In general, in an aspect, at a wind catching surface, an oncoming wind is received that varies unpredictably in speed and direction over time. Motion, which is caused by the surface catching the unpredictably varying wind and is not continuous rotational motion in one direction, is converted into electricity.
In general, in an aspect, a wind catching surface is supported to face an oncoming wind and not to rotate continuously in one direction under the influence of the oncoming wind, and a linear electromagnetic energy converter converts back and forth linear motion, caused by the surface catching the oncoming wind, into electricity.
In general, in an aspect, two or more independently movable wind catching surfaces are supported in common to face an oncoming wind and to exhibit different motions at a given time in response to the oncoming wind. An energy converter converts the different motions into electricity.
Implementations may include one or more of the following features. There is an array of the wind catching surfaces. The array includes rows and columns of generally rectangular wind catching surfaces. There is a supporting structure for the wind catching surfaces, the supporting structure and the wind catching surfaces comprising a wind screen. There are additional such wind screens, and the wind screens are coupled to provide electricity to electricity distribution grid.
In general, in an aspect, at least two wind catching surfaces are supported to face and to move in response to an oncoming wind. An energy converter converts the motion into electricity. Text, colors, and/or images are arranged on the wind catching surfaces and are configured to provide visual effects that depend on motion of the surfaces in response to the oncoming wind. The text and/or images include advertising. The visual effects embody artistic creativity and individual satisfaction and are capable of changes of design over time.
These and other features and aspects, and combinations of them, can be expressed as methods, apparatus, systems, components, means and steps for performing functions, business methods, and in other ways.
Other aspects, features, and advantages will be apparent from the following description and the claims.
As shown schematically in
As shown schematically in
Electric energy storage devices 28 (such as batteries) can store the generated electric energy temporarily or over a longer term to smooth variations in energy generation as the wind varies. With batteries to even out the electricity supply, it should be possible to use wind screens to supply the needs of, for example, an average house 29 at modest cost, instead of or in addition to returning the power to the grid.
A baffle 30 in front of and a vane 32 behind the array can help to randomize the impact of the wind on the wixels. If the wind screen is movable, the vane can cause the wind screen 14 to face the wind as the wind direction changes. The baffle helps to mix the wind and to deflect it in quasi-random directions toward the wixels.
Each of the wind screens 14 may contain one, a few, a dozen, hundreds, or even thousands of wixels. A small or large (or very large) number 33 of wind screens can be arranged to form a wind farm 34.
Aesthetic features 36 can be imparted to individual wixels, to parts of wixels, to wind screens containing wixels, to groups of such wind screens and in combinations that span multiple wixels or windscreens. Colors, shapes, sizes, patterns, texts, advertising, textures, surfaces, images, and other aesthetic features can be used to enhance small or large installations, say, and also for commercial advertising or other purposes. The varied movements of the wixels and the wind screens that contain them can produce intriguing visual effects, much as do colored flags dancing in the wind. Very low power lights (although they would be energy drains) could be selectively attached to the wixels or the wind screens to add visual interest, especially at night. Different wixels may be colored differently to present attractive visual impressions. Wixels may also be patterned selectively, including using shiny portions (for example, silver, gold, or copper colored, but not metal). The images or text of signs may be attractive as the pattern moves with the wind, seductively or teasingly, so that the viewer sees the text or picture at times and at other times does not.
As shown in
In general, the design of the flap, its attachment to the support, and the operation of the energy converter should be directed to producing the smallest possible amount of friction and chance of jamming. A Teflon antifriction coating or element may be helpful.
The motion of the wixel back and forth 53 in the wind is translated to back and forth motion 55 of the electromagnetic transducer, generating electricity. In some implementations, the coil may be similar to those used in solenoids; in other examples, the coil could be formed integrally in the flap or the stem of the flap.
In some examples, when the wind strikes the flap of a wixel it causes a flexing, billowing, or other reconfiguration of the flap which causes the effective length 57 of the flap between the end that is attached to the wind screen and the end that is connected to the energy transducer to vary, thus inducing the generation of electrical energy.
As shown in
The coil of wire 46 is mounted on another cross bar 69, parallel to the cross bar 62, so that the flap is suspended between the two rods and is separated by small spaces 71, 73 from the adjacent wixels 75, 77. The spacing helps to assure that adjacent wixels will not strike or otherwise interfere with one another, which would dissipate energy from the wind uselessly. Each support rod (cross bar) may have thicker nodules spaced along its length to provide multiple nodal points of resonance thereby providing a randomized elasticity function, which may aid in making the wind appear more random to the wixels.
Although the flap of the wixel is generally rectangular, as shown in
By attaching a relatively long edge of the flap along the rod 62, that edge is stabilized and twisting of the flap out of its original orientation (e.g., plane) is dampened in favor of motion and reconfiguration of the flap surface generally at right angles to its original plane. For example, the flap of the wixel moves forward and backward 53 preferentially. As the flap surface moves forward and backward and the contour of the flap changes, the distance 57 between the edge that is attached to rod and the stem 54 varies causing the magnet to move in and out of the coil which is attached to the next adjacent cross bar 70 of the wind screen.
In this example, the wixel is arranged so that the wind moves and reconfigures the flap somewhat like a billowing sail, blowing it into a temporarily more concave shape, with some twisting allowed, and pulling the stem and magnet in a direction parallel to the axis of the coil. The farther the magnet moves back and forth away from a central normal position 72 (at which it rests when there is no wind, for example), the larger is a restoring force that is arranged to tend to pull the magnet back to the normal position. The restoring force can be the produced by elasticity of the wixel flap material, the gravitational force on the magnet and wixel flap if the coil is so angled to the vertical, or by a non-ferrous coiled spring held within the electrical coil, as commonly used in solenoids, or a combination of these.
The randomness and the variability of the strength of the wind (and its direction) as it strikes each of the wixels moves the electromagnetic transducer to and fro and enables energy to be extracted. In some examples, the generation of electricity depends on this variability of the wind and would not work as well or at all in a steady wind (as do conventional wind turbines). To the extent that the to and fro movement causes electricity generation there will also be a natural electromagnetic damping action on the movements of the flaps.
A double rectifier arrangement 90 can be provided inexpensively for each wixel to capture energy generated during both forward and backward motion of the wixel in the wind and to provide a natural braking action in both directions. The braking action can be electrically adjusted using resistive elements in the circuitry 22 (
The coupling 24 (
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When multiple wind screens are deployed together in a wind farm, they can be placed in a pattern to reduce the negative effect of the wind-shadow cast by each of the wind screens on the ability of each of the other wind screens to catch the wind.
It is desirable for different wixels of a given wind screen to move randomly but not so that the flaps knock against one another. Mechanical interference from one flap to another would diminish the output and cause unnecessary wear.
In some examples, each of the flaps could be about 5 inches wide and 7 inches long. The screen could be rectangular and on the order of five feet on a side. There could be 12 wixels in each row and 15 wixels in each column of the array, for a total of 180 wixels. Pairs of rods spanning the wind screen would provide support for the static ends of the flaps and the coils associated with the movable stem ends. Each coil could have 200 turns of wire.
The amount of electricity that can be generated depends on a wide range of parameters, including the characteristics of the wind, its speed and variability, the mechanical configuration of the coil and magnet in the energy converter. The performance of a wixel or a wind screen or a farm of wind screens will depend on optimizing the relevant parameters in its manufacture. Each wixel could generate an average 10 watt hours per day in smaller installations of eight or ten wind screens or about 2 kilowatt hours per day for a wind screen when the average wind speed is in the range of 10-15 mph. (a small installation might have 8-10 screens). In a larger installation (say with screens sized 15 feet by 21 feet each), ten times as much energy, or more, per wixel, may be generated, depending on wind. Actual performance may be better or worse then these projections.
Elasticity is an important consideration in designing the frame of the wind screen, especially for larger installations. It may be useful to consider the branches of trees as they move along with the smaller branches and leaves, in a dance that is intriguing and protective. The branches provide multiple center of masses each having eigenfunctions that result in movements that have many natural frequencies of damped oscillation. The total effect is rather unpredictable, but has a stable and strong organic aspect.
Other implementations are within the scope of the following claims.
For example, a very wide range of shapes, sizes, configurations, materials, weights, elasticities, orientations, and other parameters could be used for each of the flaps. In determining a good size for a particular application, the following considerations are pertinent: Larger installations could generally have larger wixels, but the maximum size may be determined by the strength and life span of the plastic or other material used for the flaps. Sail design considerations may be relevant. Sails are subject to similar but not identical stresses. Fluttering of sails is suggestive of some of the behavior of wixels (but in wixels is less pronounced). The wind encountered by a flap is proportional to its area, and the impact of the wind is proportional to the cube of wind velocity. So a steep increase in wind force can be implied by larger flap size.
The flaps that form part of a given wind screen can respectively exhibit two or more different shapes, sizes, configurations, materials, weights, elasticities, orientations, or other parameters, as well as different aesthetic features. These different features can be selected to serve functional purposes, to improve the generation of electricity, the durability of the pieces, and to serve other functions. The modes of motion that characterize different flaps within a given wind screen can also be different.
The orientation of each flap could be different than in the examples. For example, in some implementations, the stem could point up instead of down. Then the weight of the magnet would reinforce (rather than oppose) the effect of the wind. In some examples, a mechanism could be provided so that the stem would be tilted at different angles to vertical depending on the strength of the wind. Although, when the weight of the magnet is used as a restoring force, pointing the stem of the flap upward may produce more friction and lose the advantage of a cleaning motion congruent with the action of the wixel as it is being pulled forward.
A wide variety of different energy conversion techniques can be used. Other electromagnetic conversion modes, not limited to linear motion, may be useful. Conversion to electricity through other mechanisms than electromagnetism may be fruitful.
The speed of the movement of the magnets on the stem of a flap past the coil within which it rides is an important factor in how much electricity can be generated. While the speed will be much slower than in typical rotating generators of power plants, it is still effective, at a smaller scale. Electrical generation is proportional to relative velocity. In any case, it may be possible to enhance the speed of motion of the magnet within the coil by a speed leveraging mechanism.
The restoring spring may be weaker or stronger and may even be omitted depending on whether and how the rectifiers are used. Since the voltages generated at each wixel are small, rectifiers may not work as efficiently as desired in light winds. In most existing wind energy installations, a wind of 5 mph is considered as a low cutoff point. With the use of wixels, a lower cutoff point may be possible.
Wind screens and groups of them can be deployed in a wide variety of contexts, environments, locations, and in many different ways for a broad range of purposes.
They can be used on roof tops and in back yards of houses and in public places, without danger to birds, animals, or humans, for example. An entire wind screen could be mounted high in a tree, and in forested areas on many trees, perhaps about two thirds up the tree on moderately large trees to catch the wind. In such a deployment, a cylindrical swivel mounting could be used together with a vane to permit the wind screen to swivel freely into the wind.
Other implementations are within the scope of the following claims.
