WO2021260711A1

WO2021260711A1 - Energy harvesting from small linear displacement using bobbin shaped core linear generator

Info

Publication number: WO2021260711A1
Application number: PCT/IN2020/050698
Authority: WO
Inventors: Pawan Kumar; Kethan S M
Original assignee: Pawan Kumar; Kethan S M
Priority date: 2020-06-24
Filing date: 2020-08-07
Publication date: 2021-12-30

Abstract

Energy harvesting from small linear displacement using bobbin (3) shaped core linear generator is described to convert mechanical energy directly into electrical energy without presence of any rotational component.

Description

ENERGY HARVESTING FROM SMALL LINEAR DISPLACEMENT USING BOBBIN SHAPED CORE LINEAR GENERATOR

This invention relates to harvesting energy from linear motion using linear generator. The advantage of this invention is, efficient energy is harvested from small linear displacement without any rotational component present in linear generator. More particularly, this invention is about efficient, variable frequency linear generator for harvesting energy from intermittent linear motion and/or vibrations that are abundantly available in our surrounding. Most particularly, this invention is about harvesting energy, where people and/or motor vehicles and/or suspension system and/or rail wagons and/or wave can be the source of linear displacements.

There is currently high focus on the development of new and improved ways to provide sustainable energy sources. There is a great deal of energy that is not profitably used because we have not had satisfying systems for capturing and using this energy. It has been long recognized that the kinetic energy of motor vehicles and/or people and/or suspension system and/or rail wagons and/or wave provides a potential source of input energy for producing electricity and store energy for future use.

A number of methods and systems are present in the prior art to convert energy from human motion and/or motor vehicles and/or rail wagons and/or suspension system and/or wave into electrical energy. Few methods are described in this document.

WO2011138585A1 describes methods for the harvesting of kinetic energy from the movement of people and/or vehicles. A motion converter is discussed which converts linear progression caused by traffic-related impulse forces, to be converted to rotational motion for driving the rotor of an electricity generator. This technique converts linear motion into rotary motion to produce electrical energy, whereas the invention presented in this document uses linear motion directly to produce electrical energy.

CA2715129C describes method for power harvesting from roads, highways and airport runways using piezoelectric generator. This method uses piezoelectric generator to produce electrical energy, whereas the invention presented in this document uses linear generator to produce electrical energy.

US20140027217A1 describes method for power harvesting from shock absorber. This method uses ferromagnetic fluid, whereas the invention presented in this document uses solid ferromagnetic material.

The principle object of the invention is to present efficient method to convert mechanical energy from small linear displacement into electrical energy using bobbin shaped core linear generator. Another objective of the invention is to present methods for energy harvesting directly from linear motion, thereby removal of rotational member as present in many prior art. A further objective of the invention is to present alternatives for arrangement of components that can be used according the application where this invention can be used.

The present invention describes methods to harvest energy using linear generator. The linear generator consists of permanent magnet(s) and bobbin shaped core on which induction coil(s) is wounded. Bobbin shaped core is relatively displaced inside the hollow space of permanent magnet(s), thereby producing the change in magnetic flux with respect to time hence producing electrical energy which can be further stored in storage devices and/or can directly be utilized according to the application.

: Sectional view of assembly of linear generator showing individual components.

: Sectional view of linear generator without showing frame (11).

: Front view of bobbin (3) positioned inside hollow space of permanent magnets (4,6) where south pole of upper permanent magnet (4) faces south pole of lower permanent magnet (6). Here upper permanent magnet (4) is said to be engaged (16).

: Details of Bobbin (3) shown in its front view.

: Isometric view of bobbin (3).

: Front view showing Induction coil(s) (5) wounded on core leg (15) of bobbin (3).

: Magnetic fields shown inside permanent magnet (4,6) and bobbin (3) when linear generator is in rest state. Here, magnetic field direction is downwards in core leg (15) of bobbin (3).

: Front view of linear generator without frame (11) is show in active position.

: Front view of bobbin (3) positioned inside hollow space of permanent magnets (4,6). Here lower permanent magnet (6) is said to be engaged (20).

: Magnetic fields shown inside permanent magnet (4,6) and bobbin (3) when linear generator is in active state. Here, magnetic field direction is upwards in core leg (15) of bobbin (3).

: Front view of Linear generator showing mechanical links to obtain relative displacement bobbin with respect to permanent magnet(s). Both bobbin and permanent magnet(s) are displaced in opposite direction to each other.

: Detailed view of mechanical links of linear generator as marked in Figure 11.

Description of linear generator does not pose any limitation on the scope of the invention otherwise claimed. For example, this invention can be used such that one or more permanent magnet are used with one or more bobbin. The number of permanent magnets may or may not be equal to the number of bobbins used.

This invention is not limited to one grade/type of permanent magnet. This invention is not limited to one grade/type of ferrous material used for bobbin shaped core. This invention is not limited to one grade/type induction coil. Selection of type/grade of permanent magnet, ferrous material of bobbin shaped core and induction coil depends on the application of the linear generator.

This invention is not limited to one geometrical shape of permanent magnet and bobbin core and induction coil. The geometrical shape of permanent magnet may be ring or rectangular, the geometrical cross section the bobbin core can be circular or rectangular and the geometrical shape of induction coil can be circular or rectangular.

This invention describes methods to harvest energy from linear generator due to relative displacement of permanent magnet(s) and bobbin. One method to achieve relative displacement between permanent magnet(s) and bobbin is by fixing any one and allowing the other to displace. Another method to achieve this is to allow displacement of both permanent magnet and bobbin, preferably in opposite direction, using mechanical links.

This invention is not limited to single set of dimensions for components and assembly of linear generator. Suitable dimensions are used according to the application of linear generator.

Linear generator is described in two parts- stator and translator. Sectional view of assembly of linear generator indicating individual components is show in figure 1. Sectional view of linear generator is show in figure 2 without frame (11).

a) Stator: It consists of one or more permanent magnet(s) (4,6) preferably fixed to frame (11). Frame (11) is preferably fixed to mounting base (10) when permanent magnet(s) (4,6) movement is not desired.

b) Translator: It consists of platform (1), upper tube (2), bobbin (3), induction coil(s) (5), lower tube (7), spring plate (8) and compression spring (9).

Permanent magnet(s) (4,6):

Permanent magnet(s) (4,6) used in linear generator are ring-shaped preferably. Magnetization of ring-shaped permanent magnet(s) (4,6) is axial preferably. Number of permanent magnet(s) (4,6) used in linear generator can be one or more depending on the application of linear generator. Various grades of permanent magnet(s) (4,6) are available and type of grade used in linear generator depends on application of linear generator.

Permanent magnet(s) (4,6) are placed such that bobbin (3) of linear generator can relatively displace linearly through the space available inside permanent magnet(s) (4,6). In configuration consisting more than one permanent magnets (4,6), permanent magnets (4,6) are placed such that similar pole faces each other. Figure 3 shows two-magnet configuration of linear generator in which south pole of both permanent magnets (4,6) face each other.

Platform (1):

Platform (1) is a component of linear generator fixed to upper part of upper tube (2) of linear generator. The application of force (21) caused by human motion and/or moving vehicles and/or moving railway wagons and/or suspension system and/or waves results in small linear displacement of platform (1). As platform (1) is a part of translator, small linear displacement caused by force (21) results in progressive linear displacement of whole translator in downward direction.

Upper tube (2) and lower tube (7):

Upper tube (2) and lower tube (7) are components of linear generator. One end of both upper tube (2) and lower tube (7) is placed in the grooves on the bobbin (12). Remaining end of upper tube (2) is fixed to platform (1). Remaining end of lower tube (7) is fixed to spring plate (8). Bobbin (3) tends to displace from required position due to presence of magnetic attractive force. Upper tube (2) and lower tube (7) helps bobbin (3) to remain in required position. Upper tube (2) and lower tube (7) of the translator also helps in guiding small linear displacement of whole translator of linear generator. Advantageously frictional losses are very small as upper tube (2) and lower tube (7) only have contact with the frame (11) of stator.

Bobbin (3):

Bobbin (3) is called core of linear generator. Bobbin (3) description is divided into 3 parts namely upper core (13), core leg (15) and lower core (14) as shown in figure 4. Bobbin (3) is preferably a single piece component of linear generator made up of ferrous material. Bobbin (3) is preferably circular cross section as shown in figure 5. Bobbin (3) can also be of rectangular cross section.

Upper core (13) and lower core (14) consist of grooves (12) for placing upper tube (2) and lower tube (7) respectively. Angles formed in upper core (13) and lower core (14) are θ1, θ2, θ3, θ4 as shown in figure 4. Cogging forces are very high due to presence of permanent magnet(s) (4,6) in the linear generator. Angles (θ1, θ2, θ3, θ4) formed in the upper core (13) and lower core (14) helps in reducing the cogging force greatly.

Various combination of angles (θ1, θ2, θ3, θ4) formed in upper core (13) and lower core (14) reduces the net cogging force present in linear generator. Angles (θ1, θ2, θ3, θ4) in the upper core (13) and lower core (14) vary according to the application of linear generator.

Core leg (15) is in the most delicate part of linear generator. Core leg (15) outer surface is smooth and is in form of cylinder preferably. Core leg (15) radius is varied according to the application of linear generator. Induction coil(s) (5) is wounded on core leg (15).

Induction coil(s) (5):

Induction coil(s) (5) is an electrical conductor with high conductivity. Copper coil(s) is used as induction coil(s) (5) preferably. Induction coil(s) (5) is wounded around the core leg (15). Upper core (13) and lower core (14) provide support to induction coil(s) (5). Figure 6 shows induction coil(s) (5) windings on bobbin (3). Numbers of coils can be used to efficiently harvest energy.

Copper wires are available in different gauges. Selection of gauge depends on the application of linear generator.

Spring (9) and spring plate (8):

Spring (9) used in linear generator can be of compression type or extension type. Various methods to use compression spring can be utilized in linear generator. Figure 1 shows one method of placing compression spring (9) in linear generator. Another method is to use one large compression spring of inner diameter larger than outer diameter of permanent magnet(s) such that permanent magnet(s) and translator sits inside this large compression spring. Another method is to use number of parallel compression springs can be placed along the outer periphery of permanent magnet(s) to form another variant of linear generator.

Spring plate (8) can be used in linear generator if compression spring (9) is used as show in figure 1.

Frame (11) and mounting base (10):

Mounting base (10) of linear generator is fixed. Energy harvesting from linear generator is achieved due to relative motion between permanent magnet(s) (4,6) and bobbin (3). Frame (11) of linear generator is fixed to mounting base (10) when movement of permanent magnet(s) (4,6) is not desired. Frame (11) of linear generator is not fixed to mounting base (10) when movement of permanent magnet(s) (4,6) is desired, and movement of permanent magnet(s) (4,6) is opposite to that of bobbin (3) by using mechanical links (22,23,24,25) as shown in figure 11 and 12.

Platform link (22) is connected to platform (1), frame link (23) is connected to frame (11), connecting link (24) is mounted on hinge (25) and hinge (25) is fixed to mounting base (10). When platform is displaced downwards (26), this results in downward displacement of platform link (22) and this causes the frame link (23) to displace upwards and thereby displacing frame upwards (27). This relative displacement is achieved by using connecting link (24) mounted on hinge (25). The direction reverses when platform (1) is displaced upwards because of spring (9) force.

Working of Linear Generator

Working of linear generator is explained in two states of linear generator namely rest state and active state. Rest state is described when no force (21) is present on platform (1) of linear generator. Active state is described when force (21) is present on platform (1) of linear generator.

Rest state:

Figure 1 shows rest state of linear generator. Upper magnet (4) is said to be engaged (16) during rest state as show in Figure 3. Air gap for magnetic field path between upper magnet (4) and bobbin (3) is less as compared to air gap for magnetic field path between lower magnet (6) and bobbin (3) and thereby upper magnet (4) is said to be engaged (16). More of magnetic field from upper magnet (4) is believed to enter core leg (15) of bobbin (3) as compared to magnetic field from lower magnet (6).

Magnetic field direction in bobbin (3) and permanent magnet(s) (4,6) at rest state is shown in figure 7. Figure 7 shows two-magnet configuration of linear generator and magnetic flux direction in core leg (15) of bobbin (3) is downwards in this configuration. In single-magnet configuration (consisting of either upper magnet (4) or lower magnet (6)) of linear generator, where only upper magnet (4) is present, similar downward direction of magnetic flux direction in core leg (15) of bobbin (3) can be seen in rest state of linear generator as seen in two-magnet configuration of linear generator.

Active state:

Active state of linear generator is when force (21) is present on platform (1) of linear generator. Presence of force (21) causes translator of linear generator to progressively displace downwards. Downward motion of translator of linear generator is proportional to the value of force (21) applied. Figure 8 shows downward displacement of translator (17,18,19) of linear generator in active state.

During progressively downward motion of translator, upper magnet (4) is seen to be disengaging with bobbin (3) and lower magnet (6) is seen to be getting engaged with bobbin (3), as air gap for magnetic path is reducing for lower magnet (6) and air gap for magnetic path is increasing for upper magnet (4). Figure 9 shows lower magnet (6) engaged (20) with bobbin (3).

Due to downward motion of translator of linear generator, bobbin (3) also displaced downwards. As a result, value of magnetic flux in core leg (15) of bobbin (3) changes and reaches zero value and with further downward displacement of bobbin (3) the direction of magnetic flux is reversed. Figure 10 shows magnetic field direction in bobbin (3) and permanent magnet(s) (4,6) at lowest position of translator of linear generator in active state.

In single-magnet configuration (consisting of either upper magnet (4) or lower magnet (6)) configuration of linear generator, where only one permanent magnet (4) is present, upper magnet (4) is seen to be getting disengaged with bobbin (3) with progressively downward motion of translator of linear generator. As a result, value of magnetic flux in core led (15) reduces and reaches zero value. Reversal of direction of magnetic flux is expected when using high grades of permanent magnet (4) in linear generator.

Spring (9) of linear generator absorbs energy as force (21) is applied to platform (1) by moving people and/or moving vehicles and/or railway wagons and/or suspension system and/or waves. Spring (9) stores energy as the translator of linear generator progressively displaces downwards (17,18,19) due to force (21) on platform (1). Spring (9) releases stored energy when applied force (21) on platform (1) is removed. Release of stored energy in spring (9) causes translator of linear generator to progressively displace upwards (17,18,19).

As translator of linear generator displaces upwards (17,18,19) towards end of active state, lower magnet (6) is seen to be getting disengaged with bobbin (3) and upper magnet (4) is seen to be getting engaged with bobbin (3) once again. During upward displacement (17,18,19) of translator of linear generator, magnetic flux in core leg (15) changes again and approaches the value present at rest state.

The upward and downward motion of translator can be continuous or intermittent to harvest energy.

According to Faraday’s law, oscillating electrical current is generated due to change of magnetic flux through induction coil(s) (5) wounded on core leg (15) surface. A rectifier connected to the induction coil(s) (5) of the of linear generator converts oscillating electrical current into direct current. Preferably, in order to obtain a desirable level of electrical output, a plurality of individual linear generator is connected, with each generator being operable for producing an oscillating electrical current from the linear movement. Respective individual rectifiers are connected to each of the linear generator for producing a direct current therefrom, and the outputs of the respecting individual rectifiers are connected together for combining the respective rectified current from the individual linear generator. The thus generated electrical power may be stored in a storage battery or may be directly utilized for electrical loads.

In the preferred form of invention illustrated herein, the linear generator is a self- contained, portable mat like adapted for being either permanently or temporarily mounted on a roadway and/or footpath and/or region where people move. The linear generator includes a mounting base (10) and an overlying platform (1) carried by mounting base (10) and small linear displacement of platform (1) reduces the gap between platform (1) and mounting base (10). Small linear displacement is provided to platform (1) of linear generator caused by moving people and/or moving vehicles when mounted on a roadway and/or footpath and/or region where people move.

This present invention can also be utilized for portable hand-held linear generator where small linear displacement of platform (1) of linear generator is caused by hand.

This present invention can also be utilized for harvesting wave energy. The wave energy provides linear displacement to the translator of linear generator and thereby producing electrical energy.

This present invention can also be used for harvesting energy from small linear displacement of platform (1) of linear generator caused by moving railway wagon when linear generator is placed under railway tracks.

This present invention can also be used for harvesting energy from small linear displacement of platform (1) of linear generator caused by force (21) of shock absorber when linear generator is coupled with suspension system. Oscillating current generated from linear generator can be useful for powering vehicles and accessories and charging batteries.

The power generating system of the present invention can be used to provide electrical power for a variety of different types of devices. For example, it is particularly useful for powering traffic signals, street lights, warning devices and the lighting in remote areas along highways or railroad tracks where power lines are not readily accessible. The power generating system is also quite useful for powering self-powered temporary warning devices for use on highways and the like.

Claims

Linear generator for converting mechanical energy from small linear displacement into electrical energy by displacement of bobbin (3) of linear generator with respect to permanent magnet(s) (4,6) of linear generator. Bobbin (3) is placed inside the hollow space of permanent magnet(s) (4,6), to achieve relative displacement of bobbin (3) with respect to permanent magnet(s) (4,6) through the hollow space of permanent magnet(s) (4,6).
Linear generator as claimed in claim 1, wherein method for relative displacement of bobbin(3) with respect to permanent magnet(s) (4,6) is selected from the group consisting of- linearly displacing only bobbin (3) (or permanent magnet (4,5)) by fixing permanent magnet(s) (4,6) (or bobbin (3)) to frame(11) or displacing both permanent magnet(s) (4,6) ,bobbin (3) in opposite direction using mechanical links (22,23,24,25).
Linear generator as claimed in claim 1, wherein shape of permanent magnet(s) (4,6) is selected from the group consisting of – ring-shaped permanent magnet having hollow space in centre and rectangular-shaped permanent magnet having hollow space in centre.
Linear generator as claimed in claim 1, wherein magnetization direction of permanent magnet(s) (4,6) is parallel to linear displacement of translator of linear generator. Magnetization of ring-shaped permanent magnet is axial and magnetization of rectangular-shaped permanent magnet is along its thickness.
Linear generator as claimed in claim 1, wherein one or more permanent magnet(s) (4,6) is used. For linear generator consisting of more than one permanent magnet (4,6), the permanent magnets (4,6) are arranged so that similar pole of permanent magnet (4,6) faces each other.
Linear generator as claimed in claim 1, wherein permanent magnet(s) is selected depending on the application of linear generator. This does not pose any limitation on the grade/type of permanent magnet selected.
Linear generator as claimed in claim 1, wherein shape of bobbin (3) is selected from the group consisting of – circular cross section bobbin and rectangular cross section bobbin.
Linear generator as claimed in claim 1, wherein bobbin (3) is of ferrous material.
Bobbin (3) of linear generator as claimed in claim 7 and claim8, wherein angles (θ1 ,θ2, θ3, θ4)formed in upper core (13) and lower core (14) results in reduction of cogging force in linear generator There is no limitation on the degree of angles (θ1,θ2,θ3,θ4) formed on upper core (13) and lower core (14). The selection of angles (θ1, θ2, θ3, θ4) depends of the application of linear generator.
Linear generator claimed in claim 1, wherein plurality Induction coil is wounded on surface of core leg (15) of bobbin (3).
Linear generator as claimed in claim 1, wherein spring (9) is selected from the group consisting of – single (or multiple) compression spring, single (or multiple) extension spring. Spring (9) absorbs energy during active state of linear generator and releases this absorbed energy when force (21) on platform (1) is removed.
Linear generator as claimed in claim 1, wherein number of such generator can be used to achieve the desired output required for particular application. Number of permanent magnets (4,6) may or may not be equal to number of bobbins (3) used in group of linear generators.