wireless charge - steven mitchell
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Wireless Charge Electric Mine Vehicle
Dr. Steve Mitchell
25th Electrical Engineering Safety Seminar – 5 November 2015
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
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• 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
ENERGY AND POWER RESEARCH PROGRAM
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• Project sponsors were: • Anglo American • Barrick Gold • Caterpillar • Joy Global • Sandvik
WIRELESS CHARGE ELECTRIC MINE VEHICLE
Background – Underground Mining
• Hard rock => Metalliferous – Drill and blast
• Soft rock => Coal – Long wall mining – Continuous mining – Explosive atmospheres
Today’s Underground Mining Vehicles
• Diesel powered vehicles – Load Haul Dump (LHD) – Trucks – Utility (e.g. Land Cruiser) – …
• Trailing cable – Shuttle car – Drill – ..
Today’s Underground Mining Vehicles
• Battery Change-out – Battery hauler – Coal Scoop – …
• Connector brushes – Dump truck – Train – …
Today’s Underground Mining Vehicles
• Range of trade-offs associated with power systems and their application in U/G vehicles
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
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
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
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
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
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
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
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)
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
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
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
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
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.
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)
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)
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
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
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….
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)
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…
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