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Wind turbines: is vertical or horizontal best?

Posted by Graham Eastwick on 24 August 2009 at 12:05 pm

There are two main categories of small wind turbines you will see as you travel around the UK today. Horizontal axis turbines look like traditional wind turbines and typically have two or three blades. Vertical axis turbines come in a number of designs, a spiral or some paddles blowing around in the wind.

I am often asked about the relative merits of the two fundamental designs and unfortunately neither the recent Energy Saving Trust field trial or the earlier Warwick Wind Trial study was able to monitor the performance of these turbines.

The key parameter of a wind turbine that determines its maximum theoretical output is the swept area of the blades. For both types of turbine this is easy to calculate from the dimensions provided in the data sheets.

The other important factor is the start-up wind speed. High wind speeds will generate more energy, as the output increases with the cube of the wind speed. Most wind speeds are low, so the lower the start-up speed the longer the turbine will run.

The effectiveness of all wind turbines is reduced in locations where the wind is turbulent and often changes direction. These problems are worst close to buildings so are a big problem in urban environments.

A horizontal turbine needs to face into the wind to extract power, so it has to change direction as the wind changes. A vertical axis turbine does not have this problem so the consensus feeling is that they  should be more suited to an urban environment. If you have any data to back this up please post a comment.


About the Author: Graham Eastwick is a director of Encraft, and manages renewable energy installations for home owners, community organisations and small businesses across the UK.

More information about wind turbines from YouGen

Wind power information page

How to choose the best turbine for your site

Will shadow flicker affect a wind planning application?

About the author: Graham Eastwick is a director of Encraft, and manages renewable energy installations for home owners, community organisations and small businesses across the UK.

If you have a question about anything in the above blog, please ask it in the comments section below.

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5 comments - read them below or add one


tparnell39Comment left on: 21 February 2012 at 10:21 am

I have heard of wind turbines over heating and catching fire if the wind is too much! I'm sure a hurricane would be more severe, there are many considerations you should bear in mind:

Wind Turbine Considerations

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Urban Green EnergyComment left on: 16 November 2010 at 10:44 pm

In Response to D & M Economy Development co. ltd's Question:

" can wind turbines and LED light combine as a streetlamp?"

The answer is YES! Urban Green Energy offers a Hybrid Street Lamp that has a 600w wind turbine as well as two photo voltaic panels all incorporated into one unit. It has a 5 day battery backup, and the lamp has 60 one watt LEDs.

I encourage you to take a look

let me know what you think. 

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D & M Economy Development co. ltdComment left on: 29 September 2010 at 2:56 am

can wind turbines and LED light combine as a street light? I wonder it works.

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Cathy Debenham

Cathy DebenhamComment left on: 4 November 2009 at 1:02 pm

For the non engineers among you the following might make the comment below easier to understand:

hawt: horizontal axis wind turbine

vawt: vertical axis wind turbine

vsd - probably variable speed drive

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scott nangle energyComment left on: 25 August 2009 at 4:00 am

hawt are mature technology 1000s of years of developement

tried and trusted designs

no real change in designs for a long time

vawt are new boys on the market , many new & novel designs

on rotor and generator types , eg floating bearings and rotors maglev types

hawt rule the roost at higher power expecially MW utilty

although vawts are made to quite large sizes these days 200kw +

vawts do have the following benefits

omni-directional work with winds from any direction

very compact ,  very low noise,  low vibration

special versions to fit direct to flat/angled roofs without towers

should offer good reliabilty smaller component count

vawts are very common on micro hybrid on & off grid systems

combination of wind & pv fitted to many modern designs

led street lighting , cctv , telecom masts , road signs 

china telecom recently announced taking all there mobile phone

masts off grid by fitting vawt/hybrid to top of the towers

over 1 million , there are a lot of mobiles in china 

good vawt turbines will have start up speeds from 1.5m/s

good ouputs from 3.5 to 12m/s

and have flat output curves from 14 to 25m/s

hawts generally above 14m/s have dropping power curves

modern regen direct ac single conversion  inverters on new vawts

offer very good outputs and effciencies

adapting from industrial motor vsd drives

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