POWER MANAGEMENT FOR SUSTAINABLE ENERGY SYSTEMS

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POWER MANAGEMENT FOR SUSTAINABLE ENERGY SYSTEMS

• Graham Town
• Electronic Engineering
• Macquarie University.

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OVERVIEW

• The need for
• decreasing reliance on fossil fuels
• increased reliance on sustainable sources of
  energy
• efficiency in energy conversion and use
• Sustainable energy systems
• source, storage, load, power management
• Efficiency in sustainable energy systems
• solar cells, wind turbines, batteries, converters
• Integrated circuits for
• power conversion management
• energy harvesting

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ENERGY 2010

• Fossil fuels (oil, coal) are main source of
  energy in modern society.
• Advantages high energy density (45MJ/kg, approx.
  twice ethanol) relatively easy to transport
  safely, easy to use.

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ENERGY 2010

• CO2 emissions are mainly from burning fossil
  fuels for
• Electricity generation (coal)
• Transport (oil)

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PROBLEMS WITH FOSSIL FUELS

• A finite (non-renewable) resource esp.
  oil/petroleum
• maximum rate of production - peak oil -
  occurred in 2008
• current rate of usage greater than rate of
  production
• at current rates oil will run out around 2050

Campbell, Petroleum and People, Popn and
Environ.,24, 193 (2002).
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PROBLEMS WITH FOSSIL FUELS

• CO2 emissions causing environmental change
• Global warming caused by greenhouse gases in
  atmosphere
• ? climate change, extreme weather events, etc.
• Ocean acidification caused by absorption of CO2
• ? potential threat to marine food chain

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ENERGY OPTIONS TO 2050

• Reduce fossil fuel usage
• i) for the environment, ii) to make resource
  last longer
• To use less energy (esp. for transport,
  heating/cooling).
• reduce population and/or living standards
• increase energy efficiency

Campbell, Petroleum and People, Popn and
Environ.,24, 193 (2002).
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ENERGY OPTIONS TO 2050

• Replace fossil fuels with sustainable energy
  sources (i.e. no compromise to the needs of
  future generations)
• Nuclear energy
• Renewable (naturally replenished) sources of
  green (unpolluting) energy
• solar
• wind
• wave tidal
• hydropower
• biomass
• geothermal
• Energy harvesting

International Energy Agency, Key World Energy
Statistics, p6 (2009).
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PRACTICAL ENERGY MATTERS

• Available on demand?
• e.g. solar power not available at night, wind
  power often variable
• Storage? (if not available on demand)
• e.g. thermal, mechanical, chemical, electrical
• Transport? (if source and load not colocated)
• e.g. electrical, chemical
• Efficient conversion (for storage, transport)
• e.g. chemical ? electrical (e.g. battery)
• e.g. thermal ? mechanical (e.g. steam turbine)
• e.g. mechanical ? electrical (e.g. wind turbine)
• e.g. electrical ? electrical (e.g. DC-AC, DC-DC
  converters 95 efficient)
• conversion efficiency particularly important for
  harvesting small amounts of energy from the
  environment (ambient light, vibrations) for
  mobile devices.

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POWER SYSTEM MANAGEMENT

• Any electric power system has a source, load, and
  usually storage
• Each of the components have a preferred operating
  point
• e.g. maximum power point (V and I for max. power
  transfer)
• e.g. charge/discharge rate for max. lifetime
• Power management is reqd to maximise system
  performance, especially in energy harvesting
  (ambient sources small, variable)

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SOLAR CELL ARRAY CHARACTERISTICS

• For a given irradiance, the power extracted from
  a solar cell (or uniform array) depends on the
  voltage across it, up to a maximum the maximum
  power point, or MPP

http//www.innovativesolar.com/images/File/BSE_Wha
t_is_MPPT.pdf
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SOLAR CELL ARRAY CHARACTERISTICS

• The MPP varies with irradiance, temperature, etc.
• Arrays of cells are often used to boost voltage
  or current
• BUT shadowing of any cells in array can cause
  large reduction in avail. power
• Need smart and efficient power conversion
  combining

Organic (polymer) solar cell array fabricated and
characterised by the author at St Andrews
University (2009)
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ENERGY STORAGE TECHNOLOGY

• Many different technologies available, different
  characteristics

Longevity of lithium-ion as a function of charge
and discharge rates. A moderate charge and
discharge puts less stress on the battery,
resulting in a longer cycle life.
http//www.mpoweruk.com/performance.htm
http//www.batteryuniversity.com/parttwo-34.htm
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GREEN TRANSPORT

• This?
• .. or this?

http//www.gizmag.com/lexus-hybrid-bicycle-concept
/14938/
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GREEN TRANSPORT
http//www.gizmag.com/lexus-hybrid-bicycle-concept
/14938/
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ENERGY HARVESTING

• e.g. wireless switch technology
• The effort made in pushing the switch powers a
  small and efficient wireless transmission system
  to activate remote equipment
• e.g. power generators in your shoes
• The act of walking generates electricity by
  flexing a piezoelectric material embedded in a
  shoe, e.g. to charge a battery for mobile
  communication, etc.

http//www.inhabitat.com/wp-content/uploads/roller
s1.jpg
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POWER TECHNOLOGY

• Will follow same evolutionary path as wireless
  communication technology (i.e. to smaller, more
  mobile systems)

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POWER SUPPLY ON A CHIP

• Research sponsored by local company, Sapphicon
  Semiconductor
• Only IC manufacturer in Australia
• Silicon-on-sapphire CMOS platform
• Transparent sapphire substrate ? low loss, high
  speed, efficient heat xfer
• Better than standard CMOS for power management
  and energy harvesting

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CONCLUSIONS

• We need to change energy usage patterns
• develop different sources of energy
• use available energy more efficiently
• Integrated electronics provides reliable, low
  cost, and compact technology for
• efficient energy conversion and utilisation
• smart management of power systems
• and the battery on your mobile phone will last
  longer !