GB2494119A

GB2494119A - Coil arrangement harvesting energy from vehicle motion

Info

Publication number: GB2494119A
Application number: GB1114848.3A
Authority: GB
Inventors: Gerard Paul Connolly
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-08-28
Filing date: 2011-08-28
Publication date: 2013-03-06
Anticipated expiration: 2031-08-28
Also published as: GB2494119B; GB201114848D0

Abstract

The time-varying magnetic fields generated by vehicles in motion, predominantly emanating from the vehicle tyres and the alternator as well as all other circuits that have current flowing therein, interact with generating coils mounted in the vehicle path. The coils comprise a non conducting base carrying multiple àCâ shaped loop conductors, adjacent conductors being separated by loops of magnetic shielding material. These coils can be placed on roads, motorways, bridges and other vehicle carrying structures and will generate electricity in the vicinity of any time-varying magnetic field of sufficient strength and angle to induce an electroomotive force in the conductors. The base may additionally carry solar panels or additional circuit try.

Description

Introduction

This invention (referred to as the C-loop) generates &ectricity by using the time-varying magnetic helds generated by vehides (e.g. cars, buses, trucks etc) in motion. These time varying magnetic fields predominantly emanate from the vehcie tyres (when in motion) and the alternator as well as all other circuits that have current flowing when the vehicle is in motion, The C-loop comprises muitiple loops of conducting mat.eriai, muWple loops of magnet!c srueldng matenal uf.ted onto a non conducting base.

The C-loop uses inductance to generate electricity. The time varying magnetic Field oF the travelling vehicle induces an Ectromoflve Force (EMF) in the Gloop. This EMF is used to produce electrical currentThese loops can be placed on roads, motoiways, bridges and other vehicle carrying structures but will generate electricity in the vicinity of any time-varying magnetic field of sufticJent strength to induce EMF.

Figure 1 -The C-Loop There are two primary sources of magnetic field emanating from a travelling vehicle Alternator -. While the vehicle is stationary electricity is provided by the battery and while travelling by the alternator.. The alternator produces a low-frequency magnetic field in the cables and components that conduct the electricity. Since the chassis is used as a neutral conductor, electricity flows through it as well, producing a low-frequency magnetic field.

Tyres -Magnetic fields emanate from radial tires due to the presence of reinforcing belts which are made of magnetized steel wire. When these tires spin, they generate alternating o magnetic fields of extremely low frequency (ELF), usually below 20 Hz. The fundamental frequency of these fields is determined by tire rotation rate and has a sinusoidal waveform with a high harmonic content. The static field of radial tires can exceed 500 microT at the CO tread. [1] The steel beads and belts in tyres are "magnetised, possibly as a result of a manufacturing process. Such magnetic tyres emit a static magnetic field when the vehicle to which they are fitted is stationary and a low-frequency magnetic field while it is in motion.

The FOPH commissioned a study in which the magnetic fields produced by vehicle tyres were measured. Since the low-frequency magnetic fields are produced when the magnetic tyres rotate, measurements were made in vehicles travelling at 80 km/h. The magnetic fields were measured at frequencies of 5 to 2,000 Hz in 12 different vehicles [2].

Page lot 4 Magnetic Total Mew tyres Used Aluminium dma Steel rims e1dipT) (n2) (n13 tyrè5 fn19) (n25) n7.} Averaoe 252 224 292 2t5 381 Sandard ?fl 78 J40 18 299 devaton Maxnuntva&e 970 330 970 9iC 7 9 1T Mrmrmvahe 08 01 08 08 64 Table 1: Peak values of spectral magnetic fields of vehicle tyres, measured on a balancing machine at 2 cm from the lyre's surface. Source [3] In addition to the fundamental frequency, magnetic fields with higher harmonics (multiples of the fundamental) also occur.

Figure 2 -Magnetic Field vs Frequency Source [3]

In two cars tested, the fields were roughly sinusoidal; frequencies were about 6Hz at 48.3 km/h (30 mi/h) and 12 Hz at 96.6 km/h with high harmonic content. Although frequency I'" increased with tire rotational speed, the magnetic field intensity remained nearly constant at o all speeds. [4] F" The C-loop primarily uses the magnetic fields generated by the tyres, however any varying co magnetic field will add to the induced voltage and hence, the induced current produced by the C-loop.

Proof of Concept Figure 3-A Single Loop To simplify the concept, we shall consider one loop in the C-loop.

In general, a time varying magnetic flux can pass through a circuit due to its own or nearby time varying current or by the motion of the circuit through a magnetic field.

For any ioop, Faraday's iaw is = E,d1 (1) dt d r ThdS cit cit The above is Faraday's law of electromagnetic induction. The reference direction along the contour, by convention, is connected with the reference direction of the normal to the surface S spanning the contour by the right-hand rule.

Page 2 of 4 For a stationary loop (the C-loop) in a time-varying B-field i.e. a stationary conducting loop in a time varying magnetic B field. Equation (1) becomes = 4) E.dl= -j 4ds Now consider a vehicle passing over a stationary loop of wire that lies in the xy plane. As the wheels pass over the loop, a time-varying magnetic field due is generated in the loop. We shall pick an instance in time whereby the flux is vertical (although as stated earlier, the flux is almost sinusoidal) Figure 4-Induced EMF

The magnetic field generated is given by

IT.'..

B(rt) = B cos(----) cos(ot') a.

-Lb -The magnetic flux that is enclosed within the "closed" loop is given by r = cosotu1.frtthu2' Integrating by parts gives cos42i* --Hence the induced voltage in a single loop is given by dP1t) _ $b.(IT -

-cit

Generic Example

Consider a vehicle travelling at 70 km/hr with one wheel passing over a single loop where the amplitude of the magnetic flux density is B =0.25 jiT the radius of the loop is b = 0.3m the angular frequency of oscillation of the time-varying magnetic field is w = 221f where I = 9 Hz = (time spent in the loop based on a car travelling at 70 km/hr) =0.ls The centre of the loop is at the point r = 0.

Page 3014 Solving for the above variables will induce a voltage of 1.9 1W in a single loop as the single wheel passes over the loop The resistance P of the loop is given by R = pL/A Where p = resistivity of copper L = Length of material A = Cross Sectional Area In accordance with ohms law, the current produced is = V/P Hence as a single wheel passes over a single loop, a current is generated.

Now consider a series of concentric loops separated by a magnetic shielding material to prevent mutual induction.

Figure 5-The C-Loop Each individual loop will generate a current.

C-loops could be placed on motorways and linked directly into new/existing electrical infrastructure.

00 Figure 6-Possible C-loop Placement References [1] Bioelectromagnetics. 1999 Oct;20(7):440-5.

Magnetic fields from steel-belted radial tires: implications for epidemiologic studies.

[2] Federal Office of Public Health (FOPH) http://www.bag.admin.ch/themen/strahlung/00053/00673/02377/index. html?lang=en [3] Stankowski S et al. Low frequency magnetic fields induced by vehicle tire magnetization.

Health Phys 2006;90:148-53

[4] Milham S, Hatfield JB, Tell R.

http://sammilham. com/Magnetic%2Ofields%2Ofrom%2osteel-belted%2Oradial%2Otires.pdf Page 4 of 4

Claims

<claim-text>Claims What is claimed is 1. This invention (referred to as the C-loop) generates electricity by using the time-varying magnetic fields generated by vehicles in motion. These time varying magnetic fields predominantly emanate from the vehicle tyres (when in motion) and the alternator as well as all other circuits that have current flowing when the vehicle is in motion. The C-loop comprises multiple loops ot conducting material and multiple loops of magnetic shielding material fined onto a non conducting base.</claim-text> <claim-text>2. The C-loop uses inductance to generate electricity. The time varying magnetic field of the travelling vehicle induces an Electromotive Force (EMF) in the C-loop. This EMF is used to produce electrical current.</claim-text> <claim-text>3. The C-loop is designed to be placed on roads, motorways, bridges and other vehicle carrying structures but will generate electricity in the vicinity at any time-varying magnetic field of sufficient strength and angle to induce EMF.</claim-text> <claim-text>4. The C-loop will generate EMF when vehicles travelling over, or in the vicinity of it.</claim-text> <claim-text>5. The length, breadth, number of loops, radius of loops and thickness of loops affects the amount of EMF produced. These variables can be altered at the manufacturing stage depending on the amount of EMF required and the anticipated placement location.</claim-text> <claim-text>6. The C-loop has an output cable that can be wired into existing or new electrical infrastructures and circuitry depending on what the generated electricity is to be used for.Optionafly, additional circuitry or green power sources such as solar panels can be added to increase the electrical output of the C-loop.</claim-text>