Project Kelpie

Group CEnergy Harvesting

Module Task

• Project Kelpie is a long term marine exploration project to monitor and record weather and environmental conditions in the ocean and inland waters. The task of this module is to design and implement a drift buoy to complete these requirements.

Task for Group C

• To generate power for the drift buoy and supply this power safely to the battery.

• This involves an energy harvester and a power rectifier.

Possible Solutions

Small wind turbine, custom mounted to the exterior of the buoy or on a following raft.

The “shaky” torch, or faradays torch, uses faradays law of electromagnetic induction to generate electrical power. Could be adapted for use in the buoy.

Through the use of natural water injection, a turbine could be turned to generate electrical power.

Final Choice

• The idea of the Faraday’s Torch was chosen to be designed and implemented.

• It could generate power from waves.• This was because other ideas were too bulky, and

potentially could have caused a water leak into the buoy.

Voltage Rectification

• The voltage generated would need conditioning to satisfy the needs of the system.

Block Diagram

Division of Tasks

• We decided to split the group into two subgroups

• The first was the Harvesting group, set the task of designing the energy harvester

• The second was the rectifying group, set the task of designing the voltage rectifier

Harvesting Rectifying

Kieran Bell Lebari Zerubbabel Dumka

Andrew Elliot Michael Cross

Andrew Bisset Douglas Sparling

Andrew ElliottHarvesting Subgroup

Coil theory • The thickness of coil• The material of the coil• The number of turns of the coils• Separation of coils to suit the Faraday torch

design• The direction the coils were to be wound on

the design

Coil Thickness• The thickness of the wires is 0.4mm• The coils had to be a practical thickness so

they would fit into the design effectively • Too thin could come loose and too thick

could overlap other coils on the design causing it too fail

Material of coils• Copper is a cheap and conductive material

that is very suitable for the task• Silver and Gold were also considered but were

deemed too expensive• The material used for the coils is Copper

Number of turns• The number of coils per section was 200 turns.• This was to suit the equation

• 1200 turns total

Coil Design• The coils were 200 turns per winding• The coils were separated in accordance with

the magnets• They were wound in opposite directions to the

coils adjacent to them• They were separated using 3D printed discs

Andrew BissetHarvesting Subgroup

What is a magnet?

A magnet is a material that exhibits a magnetic field due to its arrangement of atoms.

Why we need magnets

• We need magnetic flux to cut through the coils of wire and generate a potential.

North & South Poles

Power of Magnets

Magnets come in different strengths which depend on the flux density (B). The more lines of flux there are in a meter squared the stronger the magnet is.

Size

Due to the measurement of flux density being in meters squared then the larger the surface area is the more lines of flux it produces.

Shape

The shape of the magnet plays an important roll in how the magnetic flux can be used.

The Bar, Rod, Rectangle and Disc magnets have the same flux lines

Ring Magnet

The ring magnet loses lines of flux due to its smaller area

SphereThe sphere magnets shape is too difficult into put into practical use.

Repulsion

We have used repulsion in the project to force the lines of flux out to right angles of the coils.

Conclusion

We have selected the disc magnet with the largest surface area and the largest flux density measured in Gauss (G/cm2) that was available

Kieran BellHarvesting Subgroup

Initial Research

• A magnet passing a coil can induce a current in the coil

• (Faradays Law)• The negative denotes the voltage

is opposite in direction to the motion of the magnet. This is Lenz’slaw

Initial Prototype

• Single core 0.4mm insulated cable• Magnet 9mm dia x 25mm long, 3.8kg force• Tube • 50 turns

Further Research

• Increase the flux density• Can be achieved by repulsively

stacking magnets.• This causes the flux to push

perpendicular, in a stronger density

• To increase generated voltage, a larger number of turns in the coil can be used

• However, due to the repulsively stacking magnets, if two magnets passed a coil they would induce opposing currents.

• Therefore, each magnet will have a corresponding coil to pass

• The diameter of the magnets can be increased, along with an increase in strength.

• This would result in a greater flux.

• A is the area of the loop of coil, where a greater diameter would increase area.

• Furthermore, the magnets could be decreased in length, created a shorter distance to pass and ultimately a quicker time taken to pass.

• Finally, the winding wire could be changed to enamel coated wire. This would use less area in the coils than insulated wire, allowing for more turns in the same area.

Improved Prototype

• Used the further research conducted• 0.275V, 0.1 volt/division

Final Design and Implementation

• Housings were to be 3D printed:– Coil housing, and lid– Magnet housing, and lid

The Printed Design

Assembly

• During first assembly, a desgin flaw was noted.• The magnets spun inside the magnet house,

smashing together and breaking themselves.• Spacers were designed and printed to combat

this.

The completed Design

• 200 turns per coil• 6 coils, totalling 1200 turns• 6 magnets (25mm dia x 5mm thick, 9.3kg pull)• 5 spacers• 6 disks• Coil housing, and lid• Magnet housing, and lid

Mounting

• Epoxy Resin can be used to mount the harvester anywhere in the buoy.

• On a shelf or on the shell.

Testing

1V per division

Michael CrossRectifying Subgroup

Half Wave Rectifier• Rectification is an application of transforming

AC and DC Currents• A Half wave rectifier uses a single SCR

Half-Wave Operation• Positive-Half Cycle: Current Passes through the

diode in forward Bias• Negative Half Cycle: Polarity Reverses and the

diode blocks the flow of current

Full Wave Rectifier

• Full Wave Rectifier

Full-Wave Operation• AS before, the positive half cycle flows

through the first diode but the second diode in reverse bias blocks the current.

• The Negative-Half Cycle flows in the opposite direction, through the second diode in forward bias and is blocked by the first diode in reverse bias.

Full-Wave Operation• This gives an extra wave per cycle at the

output

Douglas Sparling

Lebari Zerubbabel DumkaRectifying Subgroup

Background Theory

• The load used in the project is a rechargeable battery which would need to be supplied with a DC power supply. Therefore the output of the electromagnetic harvester which is unregulated needs to be rectified and filtered

Working Principle of the Circuit• Positive half diagram of the rectifier

(http://www.electronics-tutorials.ws/diode/diode_6.html)

• Negative half of the rectifier

(http://www.electronics-tutorials.ws/diode/diode_6.html)

Minimising Ripple

• Capacitor

• Reason for choice

• Functions

ANALYSIS OF CIRUIT • Peak current of the rectifier

• Output current

• DC output of the bridge•

Simulation on Multisim

Result of Multisim Simulation

Implementation of Design

• PCB Design

• Building of the circuit

Interfacing Circuit with Harvester and Buoy

• For the circuit to be interfaced with the harvester, I have labelled the output of the circuit board to show the point from which the load would be connected and I have also labelled the input known as the harvester were the input from the harvester would be connected to the rectifier through an electrical connector.

The System

Testing• By hand shaking the harvester to simulate the

ocean waves, the capacitors charge increase.• The capacitor charges when the voltage across the

rectifier is greater than that of the capacitor.

Analysis and Discussion

• The circuit was designed and observed to function properly when tested. A voltage was generated and stored in the capacitor.

• Through manufacturing more energy harvesters, the desired voltage could be generated and supplied to the battery.

Future Work

• Research into suspending the magnet housing by spring. This would incur the magnets to make more passes per wave.

• Control system, to monitor charging, could be implemented.

• A step up transformer to maximise the voltage.

Conclusion

• The designed system was constructed from conceptualisation to implementation.

• Through the use of Faradays Law, the system generates electrical power and a means of increasing this generated power are noted.

• The system rectifies the generated power to DC in order to charge the battery.

Thank you for listening…

… any questions?