POWER MANAGEMENT FOR SUSTAINABLE ENERGY SYSTEMS

1. POWER MANAGEMENT FOR SUSTAINABLE ENERGY SYSTEMS Graham Town Electronic Engineering Macquarie University.

2. 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

3. 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.

4. ENERGY 2010 CO2 emissions are mainly from burning fossil fuels for: Electricity generation (coal) Transport (oil)

5. 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”, Pop’n and Environ.,24, 193 (2002).

6. 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

7. 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”, Pop’n and Environ.,24, 193 (2002).

8. 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).

9. 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.

10. 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)

11. 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, orMPP http://www.innovativesolar.com/images/File/BSE_What_is_MPPT.pdf

12. 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)

13. 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

14. GREEN TRANSPORT This? ……….. or this? http://www.gizmag.com/lexus-hybrid-bicycle-concept/14938/

15. GREEN TRANSPORT http://www.gizmag.com/lexus-hybrid-bicycle-concept/14938/

16. 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

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

18. “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

19. 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 !