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What I know about ‘Small’ Wind Turbines
March 25, 2009 · 2 comments


Gazelle Wind Turbine at MSC (UK) Ltd Ipswich
Last year one of Barefoot & Gilles Architects’ new buildings became the first in Suffolk to have a Gazelle Wind Turbine, to comply with Ipswich Borough Council’s new 10% Renewables Policy. The building is the New 30,000 sft Headquarters for MSC (UK) Ltd, the agents of the world’s second largest shipping line, Mediterranean Shipping Company. You can see the 20Kw wind turbine from the A14, just along from the new office building which I like to think looks a bit like a big black crow.

Last week I had the opportunity to visit the elegant turbine at Ransomes Europark as a guest of the Suffolk and Essex Environment and Energy Group and Bower Fuller, who installed the turbine. A demonstration and talk was given by the MD of Gazelle Wind Turbines, Ken Chaplin.
Here are some of the things I learned from Ken, and some of my thoughts about it.

How much energy does a turbine Generate?
In ideal conditions the Gazelle will generate 60,000 kWh a year, displacing 20 tonnes of CO2. Note the caveat. What are ideal conditions?

The turbine will cut in and generate electricity between wind speeds of 2.5m/s (10mph) and 20 m/s (45 mph which is Gale Force). Ideal wind speed is 6.5m/s. At the maximum wind speed the turbine cuts out for self preservation. Below the minimum speed it also cuts out, otherwise the turbine starts to suck energy from the grid – effectively becoming a rather large fan. Whilst you can find out about the general wind conditions in your postcode by visiting the BERR website, it is recommended that windspeed is monitored in the proposed location for 3 years to identify the likely conditions on your particular site.

Location and Height
Location and height is everything for a wind turbine. The higher the turbine the more winds it is likely to benefit from, and the more energy it can generate. The Gazelle has a nacelle (hub) height of 13.5 – 20.5m depending on what height you can get planning permission for. Ken pointed out that local authority planners can insist on the shortest possible turbine height, for example to avoid distracting passers-by, only to find that this can make the turbine dramatically less efficient.

Ideal conditions to locate your turbine are near the top of a gentle hill on the windward side. Too close to buildings, trees and clifftops and turbulence will break up the wind and dramatically reduce efficiency. Ken told us some sad stories about some retail clients who had chosen the turbines on wholly inappropriate sites as a statement of their eco-credentials, something that they may live to repent at leisure.

There are just 22 Gazelle Turbines in the UK so far and the most efficient ones are on Southport seafront in Lancashire and in the Welsh countryside. The turbines are often erected for dairy farms, industrial units and rural schools, where they can generate electricity pretty efficiently.

Lifetime costs are very difficult to calculate because each location is different, but in ideal conditions the Gazelle has a 14 year payback time and a 25 year lifespan. Dover Council was able to obtain grants for 95% of the construction cost of their Gazelle, clearly this reduces the payback time somewhat!

Are they Noisy?
Turbines make noise, but when we saw it demonstrated (and stood underneath and at various distances) I was surprised at how quiet it was. Research suggests noise levels are 36dB at 180m which is the minimum distance they should be installed from houses, and for comparison 30dB is the noise level of someone whispering 1.5 meters away. The sound one can hear is the turbulence caused by the blades, which very much depends on where you are standing.

When you see one it does appear to spin rather fast – the Gazelle has an 11m rotor diameter and a rotation speed of 106rpm. I think our collective consciousness automatically compares it to the huge offshore ones one often sees in advertising.

As the turbines need to be such a distance from buildings in any event (research advises distances between 10x and 60x the height of the buildings) I couldn’t imagine that noise would be a major problem. The MSC turbine is at the far end of a car park, next to the busy A14, so traffic noise is more of an issue.

Ken has supplied a Gazelle Turbine to a site in North Wales just 60 metres from a riding school, where the owners report no adverse effects on the horses, and commented on how quiet the turbine was.

What about Bird Strikes?
Apparently wind turbines do kill birds – on average one or two per year per turbine. In comparison, cars kill 10 million birds a year. And don’t mention cats.

So are Wind Turbines a good idea?
Last year the East of England Plan Policy ENG1 advised that

… new development of more than 10 dwellings or 1000m2 of non-residential floorspace should secure at least 10% of their energy from decentralised and renewable or low-carbon sources, unless this is not feasible or viable;

With the pressure to meet a renewables target like this you might be tempted to install a wind turbine on your development project. They make a very clear statement about your organisation’s philosophy to the general public. They can be an educational tool and certainly draw attention to your project.

However their effectiveness in generating electricity which is their main role, is dependent on the site conditions. Make a proper site evaluation and use the results used to inform your decision, otherwise you may just end up with an expensive, if attractive, outsize table fan.

Turbine erected in a morning
Would you like to see the MSC building’s Gazelle Wind Turbine being erected? You can view a time lapse video of the installation on the Bower Fuller website. Scroll half way down and click on the image of the crane.



Tagged as: Construction, Developer, Planning Permission, Property, Sustainability

{ 2 comments… read them below or add one }

1 Christian A. Wittke March 25, 2009 at 3:38 pm
Very well put and analyzed. Su. You described very well my own experience and trouble with a 7.5kWe turbine, producing about 500kWe/year; an output I would be better to generate by sitting on a bicycle while getting a workout. The even worse difference is the fact that our 13m cast iron turbine mast is grounded into 70 tons of concrete – which we had to do twice as an “expert” advised that the second location would boost its production of electricity.

Well, it did boost the footprint, kill any sustainability and delayed efficiency into 2109, or close to it.

Indeed, renewables’ evaluation – as anything else – requires looking at the complete picture and thinking things trough in their entirety.

Christian