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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Data mining

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Relative wind power - direction

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Load matchingP

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Power at varied wind speed

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Smart LoadP

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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