Transcript microstructured guided-wave devices for applications in optical

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
1.
–
–
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”,
Pop’n and Environ.,24, 193 (2002).
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PROBLEMS WITH FOSSIL FUELS
2.
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+
1. 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”,
Pop’n and Environ.,24, 193 (2002).
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ENERGY OPTIONS TO 2050+
2.
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 req’d 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_What_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 lithiumion as a
function of
charge and
discharge
rates.
http://www.mpoweruk.com/performance.htm
A moderate
charge and
discharge
puts less
stress on
the battery,
resulting in
a longer
cycle life.
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/rollers1.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 x’fer
• 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 !
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