The disclosure generally relates to energy generation devices and, more particularly, the disclosure relates to energy scavenger devices.
Wearable and other small, portable devices commonly use battery power. More recently, energy scavenger devices (also known as “energy harvesters”), which generate energy from the environment, have become more widely used to power small devices. Kinetic energy scavenger devices have become particularly popular due to their broad applicability to various energy sources, such automobiles, buildings, and human bodies.
Many kinetic energy scavenger devices, however, rely on high frequency and predictable motion. For example, automobile tires often have energy scavenger devices to capture the kinetic motion of the moving automobile wheels. This energy powers MEMS pressure sensors that transmit tire pressure readings to the central computer of the automobile. As such, energy scavenger devices in tires typically capture the energy at relatively high frequencies and with generally known directions/motion.
The random, low frequency motion of a person (e.g., a person jogging) or object, however, presents certain challenges that such noted energy scavenger devices have difficulty addressing.
In accordance with one embodiment of the invention, an electric energy scavenger device has a housing forming an internal chamber with an internal wall, and a movable element contained within the internal chamber. The movable element is freely movable and unconnected to any other movable element within the internal chamber. Within the internal chamber, the device also has a plurality of piezoelectric charge conversion elements positioned along the internal wall. The plurality of piezoelectric charge conversion elements are positioned side-by-side to contact the movable element when the movable element moves within the internal chamber. In addition, the movable element is configured to simultaneously contact at least two of the plurality of side-by-side piezoelectric charge conversion elements. During use, the movable element is freely movable within the internal chamber in response to movement of the entire housing.
Among other configurations, the housing may form a toroid. As a consequence, the internal chamber is in the shape of a toroid. Moreover, the internal wall may include a first internal wall and a second internal wall that is parallel with the first internal wall. The plurality of piezoelectric charge conversion elements may include first side-by-side charge conversion elements and second side-by-side charge conversion elements. The first internal wall has the first of side-by-side charge conversion elements, while the second internal wall has the second side-by-side piezoelectric charge conversion elements. The movable element is configured to simultaneously contact at least one of the first side-by-side charge conversion elements and at least one of the second side-by-side charge conversion elements.
In a similar manner, the internal wall may include a first internal wall, a second internal wall, and a third internal wall. The first and third walls are substantially parallel, while the second internal wall is substantially normal to the first internal wall. The plurality of charge conversion element may include a first charge conversion element on the first internal wall, a second charge conversion element on the second internal wall, and a third charge conversion element on the third internal wall.
The movable element may have specified surface features, and the internal chamber may have complimentarily shaped surface guide features to guide the movable element in one dimension along the internal chamber. Such features can alleviate the direct pressure that the movable element applies to the charge conversion element and, therefore, improve the device durability. The movable element preferably is configured to traverse along and rotate within the internal chamber in response to movement of the housing.
Among other things, the internal chamber may be configured so that the movable element is constrained to movement in no more than one dimension, relative to the internal chamber, in response to movement of the entire housing. Alternatively, the internal chamber may be configured so that the movable element can move in two or three dimensions, relative to the internal chamber, in response to movement of the entire housing.
In accordance with another embodiment of the invention, an electric energy scavenger device has a housing forming an internal chamber with an internal wall, a stationary element fixed on the internal wall within the internal chamber and including a first material, and a movable element within the internal chamber. The movable element includes a second material and is freely movable within the internal chamber so that it slides along the stationary element in response to housing movement. The first material and second materials have different properties for gaining and losing electrons so that they exhibit a non-negligible triboelectric phenomenon when the first material slides along the second material. The device also has a pair of electrodes (or multiple pairs of electrodes) in contact with the stationary element. The charge in the pair of electrodes changes as the moveable element slides over the stationary element.
In accordance with other embodiments, an electric energy scavenger device has a housing forming an internal chamber having an internal wall, and a plurality of triboelectric charge conversion elements within the internal chamber and positioned along the internal wall. The plurality of triboelectric charge conversion element includes a first material. The device also has a movable element contained within the internal chamber. The movable element is freely movable within the internal chamber and includes a second material. The first and second materials have different properties for gaining and losing electrons so that they exhibit a non-negligible triboelectric phenomenon when the first material contacts and separates from the second material. The plurality of triboelectric charge conversion elements are positioned side-by-side to contact the movable element when the movable element moves within the internal chamber. Moreover, the movable element is freely movable within the internal chamber in response to movement of the housing (e.g., the entire housing).
Those skilled in the art should more fully appreciate advantages of various embodiments of the invention from the following “Description of Illustrative Embodiments,” discussed with reference to the drawings summarized immediately below.
In illustrative embodiments, an energy generating/capture device attached to a person or object efficiently scavenges kinetic energy generated by low frequency motion directed in random directions. To that end, the energy generating device has a movable element that freely moves within an internal chamber when the device itself moves (e.g., due to gravity or inertia). Specifically, the internal chamber has a plurality of elements that, when contacted by the movable element, generate energy. Details of illustrative embodiments are discussed below.
People tend to move in random manners at low frequencies (e.g., a few Hertz). For example, a person may walk, run, play a sport, ride in an automobile, ride a bicycle, etc. To augment or power its underlying functionality, the wearable device 10 has its built-in energy scavenger device 12 that converts this random, low frequency kinetic energy into electrical energy that at least in part may power the wearable device 10. Among other things, the energy scavenger device 12 may store this converted energy in a local battery, and/or immediately use this energy to at least in part power the underlying electronic technology.
Moreover, although not shown, the person may wear more than one wearable device 10, with integrated energy scavenging capabilities, to more efficiently capture the once lost kinetic energy. For example, the person may wear one or more energy portable devices 10 with integrated scavenger devices 12 (with or without the underlying wearable device 10) on each of their different limbs, on their torso, hands, feet, etc. The converted energy may be wirelessly transferred to the application device, or transferred via a wire.
The energy scavenger devices 12 need not be integral or a part of another device, such as an MP3 player. Instead, the energy scavenger device 12 may take on the form of a wearable device itself with no substantial function other than capturing the person's kinetic energy. For example, the energy scavenger device 12 may be mounted on the person's arm, as shown in
Of course, discussion of people using energy scavenger devices 12 is illustrative and not intended to limit a number of other embodiments—illustrative embodiments also apply to movable inanimate objects.
Discussion of the automobile 14 and door 15 is illustrative only, however, and not intended to limit various embodiments of the invention. Indeed, those skilled in the art can couple energy scavenger devices 12 to any of a wide variety of other movable objects, such as roller coasters, bicycles, mobile computing devices, and exercise machines.
The energy scavenger device 12 can have any of a wide variety of form factors.
As shown, the housing 16 has a pair of spaced apart sidewalls 18 that are substantially parallel to each other, and a cylindrical wall 20 that is generally normal to the two sidewalls 18. Accordingly, the cylindrical wall 20 forms right angles with the two sidewalls 18. Other embodiments, however, may form the housing 16 to have one substantially continuous wall, eliminating seams and angles.
Discussion of a cylindrical form factor is but one example. Those skilled in the art can select any of a wide variety of other form factors, such as a rectangular form factor, a wider form factor, a random form factor (e.g., customized to the space in which it is to be mounted), etc.
Illustrative embodiments implement the energy scavenger device 12 using one or both of piezoelectric elements and triboelectric elements. Both types of energy scavenger devices 12 are discussed in detail below. To that end, FIGS. 3A-3D schematically show partial cross-sectional views of exemplary implementations of the energy scavenger device 12 of
The charge conversion elements 24 may include any of a wide variety of well-known piezoelectric materials. For example, each charge conversion element 24 may be formed from a stack of three layers of material. The top layer and bottom layer may be formed from piezoelectric material, while the middle layer may be formed from an insulator. When the charge conversion element 24 deforms from its flat configuration, one of the outside layers stretches to some extent while the other of the outside layers compresses to some extent. This causes a potential difference, generating energy that can be captured.
Indeed, the charge conversion elements 24 can be in any of a number of forms.
The internal chamber 17 also contains a movable element 26, such as a rolling element (e.g., a ball or rolling cylinder), that moves freely within the internal chamber 17. In illustrative embodiments, the movable element 26 is unconnected to any other element within the internal chamber 17 and has a mass that is sufficiently high enough to respond to movement of the entire housing 16. Among other things, the movable element 26 may be formed from metal or plastic.
During use, the person or object may move the entire energy scavenger device 12. For example, a person jogging may move the energy scavenger device 12 in three dimensions. This causes a number of different forces to act on the movable element 26 so that it moves within/relative to the internal chamber 17. Specifically, when the entire housing 16 moves, the movable element 26 reacts to gravity and/or inertial forces. As such, the movable element 26 moves, relative to the internal chamber 17, in one (e.g., Figure C), two (e.g.,
The embodiment shown in
As shown, the movable element 26 contacts the piezoelectric charge conversion elements 24, thus generating energy that can be captured by external circuitry (e.g., a battery and/or other circuitry). In illustrative embodiments, the size of the movable element 26, and the pitch or spacing between the charge conversion elements 24, ensures that the movable element 26 can simultaneously contact at least two side-by-side charge conversion elements 24. Other embodiments may be spaced so that the movable element 26 only contacts one charge conversion element 24.
Free movement of the movable element 26 in two or three dimensions, however, can damage or degrade performance of the energy scavenger device 12.
It should be noted that the movable element 26 of
To more efficiently capture the kinetic energy of the movable element 26, illustrative embodiments may position charge conversion elements 24 on walls other than the cylindrical wall(s) 20 and 20A. Specifically, the embodiments of
In some embodiments, the internal chamber 17 has more than one movable element 26. One benefit of having multiple movable elements 26 is the corresponding increase of the total mass of the movable elements 26 within the same housing 16. Specifically, the mass of movable element 26 is typically proportional to the harvestable kinetic energy (and thus converted electrical energy). Accordingly, to a certain degree, the device can generate more electrical energy with a higher movable member mass.
To that end,
The embodiments of
The movable element 26 can strike any of the charge conversion elements 24 with great force, consequently damaging both elements and the overall device. This even can happen to the embodiment shown in
To that end,
In the embodiment of
In both cases, the grooves 30B act as a guide for directing the movable element 26 along the internal chamber 17 in a more controlled manner. In fact, the movable element 26 of
As noted above, the energy scavenger device 12 uses one or both of piezoelectric elements and triboelectric elements.
In fact, various materials are considered to form a so-called “triboelectric series,” in which materials range from more positive to more negative.
It should be noted that
Unlike prior embodiments, however, this embodiment has a stationary element 32 coupled to or otherwise flush against the cylindrical wall 20 (the “main cylindrical wall 20”) of the internal chamber 17. Electrodes 34 (discussed below) couple with this wall 20. In fact, the housing 16 itself may form this stationary element 32. In the embodiment shown, the stationary element 32 extends a full 360 degrees about the internal chamber 17—it extends along the entire main cylindrical wall 20 without a break. Alternative embodiments may use a plurality of stationary elements 32 that are spaced apart, while others may position the stationary element(s) 32 about just a portion of the total circumference of the internal chamber 17.
To take advantage of the triboelectric effect, the stationary element 32 is formed from material that, in the triboelectric series, is spaced from the material included within the movable element 26. For example, the movable element 26 may be formed from polyester (PET), while the stationary element 32 may be formed from polydimethylsiloxane (PDMS).
In a manner similar to the piezoelectric embodiments described above, illustrative embodiments also may form the stationary element 32 on second or third internal walls within the internal chamber 17. For example,
To take advantage of the triboelectric effect in this embodiment, the movable element 26 slides along the stationary element 32. In illustrative embodiments, the movable element 26 is a unitary structure formed by a plurality of segments. In the example of
The outer face of each triboelectric segment 1, 3, and 5 preferably has a surface area, shape and size corresponding (e.g., the same) to that of the surface of the electrodes 34 facing inwardly. In a similar manner, the inner face of each triboelectric segment 1, 3, and 5 preferably has a surface area, shape, and size corresponding to (e.g., the same) that of the surface of the electrodes 34A facing outwardly. Other embodiments, however, may not have such a correspondence with one or both sets of the electrodes 34 and 34A.
Preferred embodiments also maximize the surface area of face of the movable element 26 sliding against the stationary element(s) 32. Accordingly, illustrative embodiments form the movable element 26 as an arc that has one or more slidable interface(s) with the stationary element(s) 32. For example, in the embodiment having stationary elements 32 on the sidewalls 18 and both cylindrical walls 20 and 20A, the arc-shaped movable element 26 has an outer surface that slidably contacts the stationary element 32 on the main cylindrical wall 20, a smaller inner surface that slidably contacts the stationary element 32 on the secondary cylindrical wall 20A, and front and back surfaces that respectively contact the stationary elements 32 on the interior sides of the front and back sidewalls 18.
To gather energy, the energy scavenger device 12 of
As an example,
Accordingly, during use, the housing 16 moves, causing the movable element 26 to slide over the stationary element 32. This movement causes the two elements 26 and 32 to interact, causing charge to transfer between two electrodes 34 and 34A. Specifically, the charges in two electrodes 34, and that in two electrodes 34A, changes as the moveable element 26 slides over the respective stationary elements 32.
Of course, those skilled in the art may use any of a wide variety of techniques to cause the two members to slide over one another. For example, the energy scavenger device 12 may be formed to have other form factors, such as a rectangular form factor or irregularly shaped form factor. As another example, the movable element 26 may be in the form of a rotor that rotates about an axis over the stationary element 32, which, in this latter example, acts as a stator.
Other embodiments may implement the triboelectric effect in another manner. For example,
Specifically, this embodiment forms the stationary elements 32 from a conductive/metallic core 38A, such as aluminum or copper, at least partially covered with a covering 40A that, when in contact with another appropriate material, will react with a triboelectric effect (a “triboelectric material”). In a similar manner, the movable element 26 has a conductive/metallic core 38B, such as aluminum or copper, and is at least partially coated with a covering 40B including a second triboelectric material. As with other embodiments, the movable element 26 may be in the form of a rolling element, such as a cylinder or ball.
During use, the movable element 26 contacts the stationary elements 32. Since only a portion of the movable element 26 contacts the stationary element 32, both elements preferably are coated with the triboelectric coverings 40A and 40B primarily (or only) where they make contact. Moreover, during use, the movable element 26 contacts and moves past a given stationary element 32. Indeed, although there may be some negligible amount of sliding between the two members, this embodiment is not considered to have the movable and stationary elements 26 and 32 slide against each other. This is in direct contrast to the triboelectric embodiment of
The metal core 38B of the movable element 26, and the metal core 38A of the stationary element 32, respectively function as one of the pairs of electrodes 34 of
The metal core 38A of the stationary element 32 may extend through the housing 16 for more direct contact with an external circuit. Accordingly, the metal core 38B of the movable element 26 acts as one electrode 34 for each of the stationary elements 32 within the internal chamber 17. In other words, the core 38A of each stationary element 32 forms an electrode pair with the core 38B of the movable element 26.
Those skilled in the art can form the energy scavenger device 12 at a wide variety of manners. To that end,
It should be noted that this process is substantially simplified from a longer process that normally would be used to form the energy scavenger device 12. Accordingly, the process of forming the energy scavenger device 12 has many steps, such as testing steps, coupling and possibly deposition steps, which those skilled in the art likely would use. In addition, some of the steps may be performed in a different order than that shown, or at the same time. Those skilled in the art therefore can modify the process as appropriate. Moreover, as noted above and below, many of the materials and structures noted are but one of a wide variety of different materials and structures that may be used. Those skilled in the art can select the appropriate materials and structures depending upon the application and other constraints. Accordingly, discussion of specific materials and structures is not intended to limit all embodiments.
The process of
The flat layer of material 42 preferably is formed from a flexible material, such as plastic or other inert/insulative material. The side of the flat layer of material 42 that is opposite to the charge conversion elements 24 also has a metal routing layer 44 that electrically connects with the charge conversion elements 24. This metal 44 ultimately forms electrodes 34 for accessing the energy produced by the device.
The process continues to step 902, which rolls the flat layer of material 42 into a cylinder, and positions the rolled element into a supporting framework. For example, the supporting framework may include a mold for receiving molten plastic material.
Next, the process adds the movable element 26 to the internal chamber 17 (step 904
Accordingly, illustrative embodiments make use of piezoelectric and/or triboelectric techniques to more efficiently capture low frequency, random kinetic energy from a person or an object.
Although the above discussion discloses various exemplary embodiments of the invention, it should be apparent that those skilled in the art can make various modifications that will achieve some of the advantages of the invention without departing from the true scope of the invention.
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