Urban micro wind turbinesKent Hogan
Onslow College
Fellowship goals:
1. Investigate micro wind turbines to determine the practicality of their use for domestic energy production.
2. Investigate the current uses, engineering, effects & possible future directions of micro wind turbines.
3. Learn computing skills such as Java programming and webpage design.
What is micro-wind?
Why micro-wind?
• Cheaper than other alternatives (solar, larger scale wind)
• Less intrusive
• Smaller rotational inertia means faster response to wind gusts & more power
Why Wellington?
• Lots of wind (obviously)
• Urban environment
• Strong gusts on top of high average wind speed
Warning: Statistics content
Real data (histogram) and simulated Weibull distribution (black line) for Kelburn wind speeds 2004-2008
Available Power
Rotor swept areaA
v1 v2
Warning: Calculus content
Wellington Wind Energy Distribution
Model Weibull distribution of wind speed and available energy for Wellington wind distribution
Continuous power extraction
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Power ratio extracted
Optimum speed ratio
Optimum speed ratio
Betz Limit
Vertical Axis Wind Turbine (VAWT)
• Wind direction− No wind seeking mechanism needed
• Tower loading− Generator, etc can all be placed near the ground, placing less stress on tower
• Not self-starting− Darrieus need a ‘push’ at start-up
• Efficiency− Generally not as efficient as horizontal axis turbines
Darrieus VAWT
Savonius VAWT
Horizontal Axis Wind Turbine (HAWT)
• Upwind / downwind rotor− Wind shadowing by tower− Wind tracking mechanism− Blade flex
• Fixed tip speed / tip speed ratio− Stresses on blades− Output frequency− Power at varying wind speeds
• Number of blades− Size of aerodynamic surface− Turbulence in rotor plane− Torque on rotor hub
Typical uses
• Typically used off-grid to charge battery banks (yachts, isolated cabins).
• Batteries need ‘continuous’ charging, so turbines are optimised for average wind speeds.
Batteries vs grid-tied
Battery charging:Optimised for average wind speed, low total energy
Grid tied:Free to optimise for high wind speeds to maximise total energy
Grid tied turbines
3 phase rectifier
Turbine
Wild A.C. –variable voltage
variable frequency
D.C.–D.C. voltage
converterInverter
240 V 50 Hz synchronous A.C.
To Grid
Feedback loop
Measurement & Control
3 phaserectifier
Dump load
MeasurementControl
AnemometerWind vane
Turbine
Measurement & Control
Teething problems
Burnout (the turbine, not me)
Data mining
Data mining
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Wind Speed Distribution
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Wind Direction - Relative Frequency
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Average & Peak Power
Data mining
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Relative wind power - direction
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Relative turbine power - direction
Load matchingP
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Voltage
Power at varied wind speed
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Constant Voltage LoadP
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Voltage
Power at varied wind speed
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Constant load
Smart LoadP
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Power at varied wind speed
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Smart load
Where to from here?• Second horizontal axis turbine
• Vertical axis turbine
• Smart load
• Cheaper inverter
• Immersion water heater
• Gusting hysteresis
• Data live to the web
Data live to web (well, liveish)
csv data file saved every 15 min
Labview measurement software Graph images produced & saved by Java program
Latest saved images uploaded by website
ABSURDLY TRICKY
Micro-wind – is it worth it?
PROS• Wind is free
• Wind is renewable
• Can harness increased power in wind gusts
• Excess power buy-back
• Wind turbines look cool
• Great conversation topic at cocktail parties
• ‘Feel-good’ / Green factor
CONS• Local council by-laws vary
• Currently downstream electronics required for grid-tying are expensive
• …this & low power produced make micro turbines economically iffy
• May annoy the neighbours
• May annoy the neighboursDepends on the
neighbours I guess
What I’ve gained…
Evaluating the potential of the wind resource at the King
of Tonga’s house
Time to learn new skills
Opportunities:Working with RPNYC to plan education centre
Time to get my head around stuff
Played with lots of fun toys
Flexibility to see what goes on in other parts of the
education sector
Sorry, what?
The ability to ask the important questions
‘Achieved’… What does that mean?
Experience what its like from the other side of the fence
Huge thanks to:
Chris Bumby, John Hannah, Tim Exley, Howard Lukefahr, Alan Rennie,
Manu Pouajen-Blakiston, David Stead, Peter ‘Pondy’ Andreae…
James Capper & Roy Godkin
Joseph Lawrence
Thanks Especially to Gill & Miki
The New Zealand Science, Mathematics and Technology Teacher Fellowship Scheme is funded by the New Zealand Government
and administered by the Royal Society of New Zealand
www.kenthogan.blogspot.com