Dr. Steve Mitchell presented on investigating the viability of wireless charging technology for mining applications. He discussed the motivation to move away from diesel vehicles due to health hazards and high ventilation costs. Current electric vehicle technologies have limitations like limited range, cable damage, and battery change-out overhead. Wireless charging could enable electric vehicles to charge while in operation without cables or battery swaps. The technology uses magnetic resonant coupling between transmitting and receiving coils, with efficiencies over 80% demonstrated. While not yet suitable for explosive atmospheres, it shows potential for metalliferous mining like block caving where automated vehicles could be wirelessly charged.

1. Wireless Charge
Electric Mine Vehicle
Dr. Steve Mitchell
26th Mechanical Engineering Safety Seminar : 3 - 4 August 2016

2. Presenter Background
• Presently : Engineering Manager at Ampcontrol CSM
• Formerly: Academic at the University of Newcastle
• Research focus on electric power systems for power,
mining and heavy industry sectors
• Investigated the viability of wireless charge technology
in mining applications on behalf of CRCMining in 2014

3. 3
ENERGY AND POWER RESEARCH PROGRAM
• A key program within CRCMining
• Mission: The electric mine
• Electric machines provide:
• High operating efficiency
• High reliability
• Zero particulate emissions
• Therefore the electric mine will facilitate:
• Reduction in emissions
• Reduction in energy consumption
• Reduction in mining costs

4. WIRELESS CHARGE ELECTRIC MINE
VEHICLE
• Project sponsors were:
• Anglo American
• Barrick Gold
• Caterpillar
• Joy Global
• Sandvik
4

5. Background – Underground Mining
• Hard rock => Metalliferous
– Drill and blast
• Soft rock => Coal
– Long wall mining
– Continuous mining
– Explosive atmospheres

6. Today’s Underground Mining Vehicles
• Diesel powered vehicles
– Load Haul Dump (LHD)
– Trucks
– …
• Trailing cable
– Shuttle car
– Drill
– ..
– Utility (e.g. Land Cruiser)

7. Today’s Underground Mining Vehicles
• Battery Change-out
– Battery hauler
– Coal Scoop
– …
• Connector brushes
– Dump truck
– Train
– …

8. Today’s Underground Mining Vehicles
• Range of trade-offs associated with power
systems and their application in U/G vehicles

9. Diesel powered vehicles
• Highly mobile and versatile
• High energy density fuel
– 36MJ/litre
– Long range/duty between refueling
• Poor energy efficiency
– Typical energy efficiency of 37%
• High routine maintenance cycle
• Diesel particulate emissions
– 2012 diesel exhaust classified as Group 1
carcinogen

10. A problem with diesel…
• The key motivation to move away from diesel
powered vehicles is health
• Epidemiological studies specific to U/G mining
demonstrated an increased risk of lung cancer
due to DPM exposure
• Legal precedent in Canadian Superior Court
– 2013 recognised the lung cancer of deceased miner
as an occupational disease despite no evidence to
prove that the mine had exceeded exposure
regulations

11. In addition…
• A second motivation to move away from diesel
powered vehicles is ventilation costs
• Ventilation in underground mines is required for to:
– Dilute and remove dust and noxious/explosive gases
– To regulate temperature due to geothermal inputs and
machinery operation
• Ventilation currently accounts for up to 40% of a
mine’s energy needs
• Infrastructure costs for ventilation are significant

12. Ventilation requirements for diesels
Jacobs 2013

13. Hydrogen Fuel Cell Power System
• Generating significant interest as a potential
replacement for fossil fuels
• Polarising technology with as many proponents
as opponents
– Nissan and Tesla are stanch critics
– Toyota released the fuel cell hybrid “Mirai” in 2014
• Very enticing properties of high energy density
with zero emissions
• Significant energy cost with each stage in the
process

14. Fuel Cell versus Electric
Bossel 2006

15. Hydrogen Fuel Cell Power System
• Introduces challenge of maintaining safety
whilst importing hydrogen into confined
space.
• Fuel cell powered LHD and U/G Locomotive
projects utilised metal hydride storage in
order to chemically lock up the hydrogen
• Significant complexity, cost of the fast fill
metal hydride storage system, poor
conversion efficiency

16. Electric vehicle - Trailing cable
• No refuel/recharge
• High efficiency electric machines
• No emissions
• Range limited
• Limit to the number vehicles/section
• Vulnerable to cable damage due to impact,
abrasion, tensile stress, fatigue
– Arcing incidents in hazardous areas
(average 1 per year, per mine in NSW 2008-2012)
• Logistics to shift machine between sections
– Diesel vehicle tow between sections

17. Electric vehicle - Battery interchange
• High efficiency electric machines
• No emissions
• Battery change-out overhead leads to reduced
availability
– 3 Battery carousel (Battery/shift)
• Very large battery system to maximise kWhr
– Typically lead-acid
– Long-Airdox CHA818 Un-a-Hauler = 7880kg…
• Battery change-out not readily conducive to
future automation

18. Electric vehicle - Connector brush
• High efficiency electric machines
• No emissions
• Significant infrastructure costs
• Vulnerable to damage due to impacts
• Brush sparking => not suitable for explosive
atmospheres
• Multi-vehicle use challenges (ie passing)

19. Electric vehicle - Connector brush
• Eg. Kiruna electric truck

20. Proposal:
Wireless Charge Mining Vehicle
• Promote the development of a wirelessly
charged underground mining vehicle system
• Create technology to charge U/G mining
vehicles dynamically whilst they are in
production

21. Wireless charge benefits
• No battery change-out
• No trailing cables
• No connector brushes
• No particulate emissions
• Immunity to dirt and water
• Electrically isolated
• Significantly reduced battery requirement
• Ideal for future automation

22. The technology…
• Magnetic Resonant Coupling
• Basic premise is similar to that of a
transformer
• Power delivered between a coupled
transmitting and receiving coils
• Poor transformer since in air (not iron core)
• To maximise power transfer efficiency the
transmission is at a tuned resonant frequency

23. Technology origins
• The origins of this approach => Nikola Tesla
• Tesla was fascinated by all types of resonance
• Tested the resonance of steel buildings in the
1890s resulting in “panic stricken steel-
workers…”
• His electrical resonant transformer circuit
(Tesla Coil) was invented around 1891

24. The technology…
• Both the transmitter and receiver coils are
capacitively loaded to form tuned LC circuits with a
common frequency
– Efficient energy transfer over distances up to a
few coil diameters
• The magnetic field is shaped with ferrite cores to
maximise energy transfer efficiency
• Faraday’s Law
– Higher frequency
– Higher the induced voltage
– Better transfer efficiency.

25. The technology…
• However … in the MHz range
– Skin and proximity effects become problematic
=> losses
– Inverter IGBT switching efficiency dramatically
decreases
• Human EM Exposure Limits
– Passive shielding used to keep the magnetic field
exposure to international limits
– Example: < 2 μT (KAIST Campus bus)

26. The technology…
The All-Electric Car You Never Plug In - IEEE Spectrum 2013

27. Current state of the art
• Typically 20kHz – 120kHz range
• In the past decade there has been significant
advances in wireless charging
• Efficiencies of >80% demonstrated with 20cm
air gap (and continuing to improve)
• Power transfer to buses of 180kW (suitable
for loaders/scoop vehicles)

28. KAIST campus bus
• 2012 Korea Advanced Institute of Science and Technology
(KAIST) introduced Online Electric Vehicle
• 3.7km circuit around the campus
• Charging whilst in motion
• Dynamic charging stations 5 - 20% of journey

29. KAIST Fast train
• KAIST are also currently working on wireless
charge fast train
• Train would require MW transfers
• Current fast trains are speed limited by the
pantograph
• This limitation and brush wear are eliminated
by wireless charge inductive coils

30. Eg: Mining wireless charge concept

31. Limitations/Applications
• Currently would be restricted from use in
explosive atmospheres
– AS/NZS 60079.0 => 6W for 9kHz – 60GHz
– However generated interest with mine safety
bodies both in the US and Australia..
• Suitable for many metalliferous applications
– An ideal solution for Block Cave mining
=> Automated wireless charge LHDs….

32. Wireless charge technology
• World Economic Forum listed wireless
electromagnetic transmission as one of the 10 most
promising technologies of 2013
• Road Embedded Rechargers was listed by Time
Magazine as one of the 50 best inventions of 2010
• Toyota, Nissan and Honda scheduled to release
wireless charge technology cars in 2016
• Currently exponential growth in wireless charge bus
and tram projects in Europe, USA and Korea
• Multiple technology vendors with 1MW systems at
planning stage (for light and heavy rail projects)

33. Conclusion
• Significant advances within the past 10 years…
Where will it be in another 5 years?
• The technology has now reached a tipping point
and may have significant potential for mining
applications
• No one in the mining space yet…

34. Questions?
Thank you