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WIND TECHNOLOGY SUPPLEMENT - MAY 2011

David Appleyard, Chief Editor, Renewable Energy World

FROM THE EDITOR

According to BTM Consult’s International Wind

Energy Development – World Update 2010, the

wind sector is still one of the world’s fastest growing

energy-related industries.

With record installations of 39.4 GW over the year, market

value is expected to grow from an estimated €66.8 billion in

2011 to €111.7 billion in 2015.

Total cumulative global installed wind generation capacity,

meanwhile, has now grown to approximately 200 GW. This

represents a staggering 25% increase over BTM’s 2009

market assessment.

Perhaps inevitably these gures are dominated by Asia

and more specically the Chinese market which, with some

18,928 MW of new capacity, recorded the highest volume

ever by one country in a single year. This boom is, of course,

tempered to a certain extent by a falling market in the US

and Europe.

In the US, only 5115 MW of new capacity was installed

in 2010 – about half that of 2009 – while Europe continues

to lose market share, dropping from more than half of the

global market to nearer a quarter over the space of four

years. Nonetheless, Europe does still lead in the offshore

wind stakes with nine new projects racking up a total of

more than 1.4 GW of additional capacity, the majority in the

UK, but with Denmark and Belgium also contributing.

Given that we are still only just emerging from the worst

recession in more than 50 years, what does this imply

for the future of the wind technology sector? All things

considered, wind power is expected to deliver 1.92%

of the world’s electricity in 2011 and current indications

are that it may be able to meet 9.1% of global electricity

demand by 2020. Looking forward, the report projects

an average global growth rate of 15.5% per year for new

annual installations through 2015, resulting in a total

global capacity of 513.6 GW by 2015.

In the less predictable ve-year period 2016–2020,

the expectation is for an average annual growth rate of

approximately 11.5%, closing in on the 1000 GW milestone

by the end of 2020. By then, based on the International

Energy Agency’s prediction of overall demand, wind power

is expected to supply 9.1% of the world’s electricity, the

analysis concludes.

BTM’s 2010 report followed an equally buoyant view

released by the Global Wind Energy Council (GWEC).

‘The continued rapid growth of wind power despite the

nancial crisis and economic downturn is testament to the

inherent attractiveness of the technology, which is clean,

reliable and quick to install. Wind power has become

the power technology of choice for a growing number of

countries around the world,’ said Steve Sawyer, GWEC’s

secretary-general.

Sawyer’s comments aside, what role does technology play

in this incredible success story? Clearly, by establishing an

impressive track record of reliability, commercial viability

and continued technological advancement, the industry has

succeeded in securing signicant long-term and ongoing

investment. It is by securing this investment – effectively

shorthand for building market condence – that such

impressive growth rates can be achieved and maintained.

This condence, ultimately, is built on the technology.

Several articles in this edition of our Wind Technology

supplement consider issues that reect this current of

development with a look at the design limits of wind

turbines in the drive to manufacture a 20 MW machine. In

our feature starting on page 21 we delve into the EC-backed

UpWind project, which is tackling the many issues that must

be overcome to achieve such a goal.

A signicant step in that direction is explored in our lead

feature on the latest developments to emerge from the wind

technology sector. This article details new turbines, such as

Vestas’ 7 MW V164 dedicated offshore machine with its

proposed 164 metre rotor diameter.

Another key, and ongoing, trend among the major

manufacturers is the development of existing series machines

with adaptations to lower wind speeds or more turbulent

regimes. This activity continues to expand the operational

range of commercially viable machines. The issue is explored

further in our article starting on page 11, which features a

report from TÜV SÜD Industrie Service. This article considers

the expanding range these new machines can reach by

opening previously unsuitable areas of woodland. Larger,

taller machines can exploit such areas, opening the prospects

for lucrative onshore installations, even in regions that may

have previously been considered uneconomic.

Looking still further ahead we also review a forecast from

DNV, which has considered the likely developments in wind

technology, in particular advances in T&D, that will enable

large volumes of wind capacity to be effectively distributed

to demand centres.

The future is never certain, but it is more than evident that

wind technology will be with us for a long time and,

as always, the best technology will come out on top.

ANOTHER KEY AND ONGOING

TREND IS THE ADAPTATION OF

EXISTING SERIES MACHINES TO

SUIT LOWER WIND SPEEDS OR

MORE TURBULENT REGIMES

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WIND TECHNOLOGY SUPPLEMENT - MAY 2011

TECHNOLOGY TRENDS

By David Appleyard

SPRING GROWTH

FOR TURBINES

A series of new, larger turbines with longer blades have been launched into the market recently as manufacturers strive to

deliver the lowest cost of energy with the next generation of designs. Here we take a look at some of the more prominent

launches of recent months.

A NEW GENERATION OF LARGER TURBINES

A trend towards larger capacity turbines with longer blades and larger

rotor diameters has been long established, with OEMs continuing to

offer existing machines with a range of rotor diameters. But now, a

new generation of still larger machines has been unveiled.

Among those companies unveiling new models REpower Systems

AG, introduced its 3.2M114. Optimised for low-wind locations, the

3.2 MW turbine has a 143 metre hub height and a 114 metre rotor.

A hybrid tower made of concrete and steel is to be used. At the

end of 2010, two 3 MW turbines were erected on 128 metre hybrid

towers in Germany. A second 3.2M114 prototype, with a hub height

of 93 metres and a steel tube tower is due to be erected late 2011.

Matthias Schubert, REpower Chief Technology Ofcer (CTO) says:

‘Especially in the European market, greater hub heights allow new

sites to be developed. In southern Germany, for example, signicant

unexploited potential still exists in hilly terrain and forested areas.’

REpower majority-owners Suzlon, meanwhile, has also launched

a low-wind version of an existing platform recently with its new S9X

suite of machines.

An evolution of Suzlon’s platform, the upgrade is built around

doubly fed induction generator-based technology. New blade designs

with rotor diameters of 95 and 97 metres offer power production from

moderate to low wind speeds, the company says, and tower heights

of 90 or 100 metres are available for the 2 MW machine.

Serial production of the S95 turbine is scheduled to begin in Q2

of the 2011–2012 nancial year, followed by the S97 in Q4.

Similarly, Alstom has revealed an upgrade to its existing 3 MW

ECO 100 platform to specically address low wind speed sites with

a new (IEC Class III-A) turbine, the ECO 11X, with a larger rotor

diameter. The exact rotor diameter, in the range of 115-125 metres,

will be released in the second half of 2011, when the turbine will be

offered for deliveries starting in 2013.

Earlier the company had announced a new partnership with

Spanish generator manufacturer Converteam in a move that will bring

the company’s direct drive permanent magnet generator to Alstom’s

under-development 6 MW offshore wind turbine.

Under the terms of the alliance, Converteam will supply Alstom

with its Advanced High Density (AHD) direct drive PMG. Pierre

Bastid, CEO of Converteam, commented: ‘The generator will have

the largest torque of any PMG built to date, and with this project,

we are making a big step in commercialising very large direct drive

wind generators.’

The rst two turbines are scheduled for installation off the coast

of Belgium during the winter of 2011–2012 in collaboration with

developers Belwind as part of a roughly 40 MW demonstrator project

Full commercialisation and series production of the turbine is

anticipated in 2014. In January Alstom and EDF Energies Nouvelles

(EDF-EN) announced that they would jointly bid using the 6 MW

machine for projects under the recently launched French offshore

wind tender for 6 GW by 2020.

CONVERTEAM’S NEW PMG WILL BE

USED IN ALSTOM’S UNDER

DEVELOPMENT 6 MW TURBINE

Converteam itself has recently been the subject of an acquisition

by GE, which at the end of March announced that it had entered

into a roughly US$3.2 billion agreement to acquire some 90% of the

equity in Converteam from a controlling shareholder group.

GE’s announcement followed a similar move from American

Superconductor Corporation (AMSC), which has signed an agreement

to acquire Finland-based The Switch Engineering Oy.

Revealing the €190 million ($265 million) acquisition, AMSC

said it expects The Switch’s background in advanced synchronous

generators to help commercialise superconductor generators for its

direct drive 10 MW SeaTitan turbine.

Direct drive systems

A number of new direct drive and hybrid systems have also been

launched onto the market recently. For example, GE has introduced

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WIND TECHNOLOGY SUPPLEMENT - MAY 2011

its 4.1-113 wind turbine, a 4 MW-class machine which it says is

optimised for offshore use.

The company has signed a contract to supply one of the machines

to Göteborg Energi for installation in Gothenburg harbour, Sweden,

in the second half of 2011. The project is supported by the Swedish

Energy Agency through its technology programme.

Earlier, in June 2010, GE revealed plans to install up to ve

offshore demonstration wind turbines through separate partnerships

with Norwegian rms Statoil and Lyse and featuring a 4 MW machine

with a 110 metre rotor diameter. Subject to successful completion

of feasibility studies and the appropriate investment and funding

decisions, the installation of the wind turbines is due to start in 2012.

This new machine builds on the 3.5 MW direct-drive design which

GE obtained through its September 2009 acquisition of Norwegian

rm ScanWind and which has been operating since 2005 on a coastal

site in Norway.

Siemens has also revealed its new direct drive gearless wind

turbine for low to moderate wind speeds. The core features of the

new SWT-2.3-113 wind turbine are its permanent magnet generator

and a rotor diameter of 113 metres when tted with the new Siemens

B55 Quantum Blades. This new blade design is lighter than previous

models but retains the strength of earlier generations, Siemens says.

Each blade is 55 metres long and features a redesigned tip and

root section. Meanwhile, the blade tip has also been redesigned to

minimise loads and reduce noise levels to a claimed 105 dB, which

Siemens says makes it one of the quietest on the market. The top

head mass of the new machine is estimated at 114 tonnes, with the

rotor comprising some 66,700 kg of that.

With a prototype of the new machine installed in the Netherlands

in March, the SWT-2.3-113 is the second gearless wind turbine

launched by Siemens following on from the SWT-3.0-101, the 3 MW

direct drive wind turbine it launched in April 2010.

To date, Siemens has installed and commissioned a total of ve

direct drive SWT-3.0-101 wind turbines in Denmark and Norway with

further projects planned in the US, Denmark and Germany.

‘The rst prototypes of our SWT-3.0-101 have been running for

more than a year and fullling all expectations in terms of reliability

and performance,’ said Henrik Stiesdal, CTO of the Siemens Wind

Power Business Unit.

‘This year we’ll launch our 6 MW direct drive wind turbine, which

will be particularly suitable for large offshore wind power plants,’ he

added.

Meanwhile, Northern Power Systems Inc has announced the

introduction of a 2.3 MW permanent magnet direct drive wind turbine

designed for the onshore market.

At the same time, the company said it had installed and

commissioned its rst prototype machine, owned by Heritage

Sustainable Energy at the Stoney Corners wind farm in McBain,

Michigan, in the US.

The prototype turbine, shipped from the new Northern Power

factory in Saginaw, Michigan, is the largest such direct drive machine

currently in commercial operation in North America, the company

claims, adding that the Northern Power 2.3, features a superior power

curve and a lower cut in speed than competing wind turbines.

New entrants, new technologies

A new entrant to the offshore sector, Doosan Power Systems, part of

the Korean industrial conglomerate Doosan Heavy, has unveiled plans

to develop a 6 MW offshore specic turbine. It plans to develop the

turbine in order to enter the European market, where the company

says it has identied a signicant opportunity by 2020.

Furthermore, the company says that its clients have expressed

an interest in seeing new competitive entrants to the offshore wind

arena. It currently offers a geared 3 MW wind turbine product, rst

developed in 2004 and commercially launched towards the end

of 2010, although currently this is mainly for its domestic market.

In September 2009, Doosan installed a prototype machine in

Gimnyeong, Jeju Island.

Doosan Heavy Industries & Construction also recently announced

that it had acquired type certication for its 3 MW offshore wind

turbine from DEWI-OCC in Germany.

Doosan says it has decided to aggressively step up its campaign

to industrialise its wind power business. The company also says it

plans to co-develop core parts, including blades, with local small and

medium-sized enterprises.

While the conceptual specication of the new 6 MW machine

is complete, Doosan says it is currently nalising both the technical

details of the system as well as options for manufacturing and

assembly – Scotland is one option being favourably considered with

groundbreaking anticipated in 2012. Technical specications – rotor

diameter, and whether it is geared, hybrid or gearless – are due to

TECHNOLOGY TRENDS

GE Energy has launched a new 4 MW

offshore platform

GE Energy

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LM WindPower’s innovative Lightning Protection System,

SafeReceptor, takes the sting out of lightening strikes, reducing

the potential costs of blade damage and the subsequent loss of

generation capacity for the owner.

SafeReceptor’s tungsten alloy lightning receptors have been

high voltage tested and deliver industry leading protection

which complies with the new IEC 61400-24 standard.

Innovation is born out of the experience of producing more than

80,000 blades with lightning protection systems. We’ve put that

knowledge to work to offer operators the very best protection

they can get.

For further information please contact us at:

safereceptor@lmwindpower.com

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WIND TECHNOLOGY SUPPLEMENT - MAY 2011

TECHNOLOGY TRENDS

A graphic showing Vestas’ 7 MW giant

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be released as Wind Technology goes to press with the company still

working with its design partners.

An on-site pilot prototype is due to be installed by the end of 2013

and this will be followed in 2014 by prototype and demonstration

units offshore, likely comprising three to four machines. Currently, the

company foresees commercial series production in 2015. However,

it is also in discussion with its partners with a view to exploring an

option to accelerate the development programme by a full year. In

addition, it is open to the concept of jointly developing pilot schemes

with utility partners, it says.

In a related move, the company has also said it expects to invest

up to £170 million (around $255 million) in wind power in Scotland

over the next decade.

Following positive discussions, Doosan and Scottish Enterprise

have agreed to enter into a Memorandum of Understanding (MoU)

that will likely see the company locate its R&D Centre of Excellence

for Renewables at its current site at Westway in Renfrew, near

Glasgow. A second phase will advance a further proposal for the

establishment of assembly and manufacturing facilities in Scotland

– now the company’s favoured location for wind turbine prototype-

build and manufacturing.

Jean-Michel Aubertin, Doosan Power Systems’ CEO, said: ‘We

hope to develop cutting-edge wind power technology that will

enhance the role of renewables in the energy mix. This also is great

news for Scotland’s economy in terms of jobs and inward investment.

Doosan’s current wind power portfolio and position with the industry

will continue to grow strongly over the coming years.’

Elsewhere, Germany’s Winergy presented a new 3 MW drive train

concept in April 2011, the so-called ‘HybridDrive’, which combines

the gearbox and generator in a single compact drive train concept.

Winergy says that the HybridDrive uses only 20% of the quantity of

rare earth elements required for direct driven wind turbines.

The new HybridDrive combines a two-stage gearbox with a

permanent-magnet generator

in a design that allows for

a signicant reduction of the

nacelle size and minimisation of

the overall weight, Winergy says.

Direct connection of the gearbox to

the generator enables the length of the

drive train to be shortened by about 35%.

Furthermore, Winergy says, its compact

dimensions present various advantages for

the design of a wind turbine.

For example, if the HybridDrive is used

to replace an existing wind turbine design, it

is possible to utilise the space that has been

saved for the converter and transformer,

instead of locating these in the tower. This

choice of location for the transformers

reduces the low-voltage cable losses, which

subsequently improves efciency, it says.

A modular design that allows assembly/

disassembly of single elements through

the internal service crane also represents an advantage over other

existing integrated solutions, Winergy claims.

The company offers the HybridDrive optionally with journal

bearings or conventional bearings for the planetary bearings.

According to Winergy, the product distinguishes itself through

its small product dimensions and the highest power density in the

industry. Furthermore, the company adds, the concept can be easily

implemented for the 6 to 7 MW power range of turbines.

Offshore entries

Germany’s Nordex SE has revealed its new platform, the N150/6000,

which has been developed specially for offshore. With a 150 metre

rotor diameter, it has a nominal output of 6 MW and is a direct

drive machine with a permanent magnet generator and a full

power converter, a move the company says has enabled it to keep

the, undisclosed, top head mass low. Nordex says it is currently

engineering this drive train design in conjunction with its suppliers.

Explaining the move, Thomas Karst, CEO of the Offshore division,

said: ‘Out at sea in particular, we must do everything we can to

optimise the technical reliability of the turbine. With cost structures

differing to those in the onshore market, we are able to implement a

more complex drive system, namely a direct drive.’

Nordex has participated in a reference project in the German part

of the Baltic Sea and says that up to 70 machines are to be installed

in Germany from 2014–2015 onwards.

‘Our strategy is being driven by the development of a competitive

product. For this purpose, we are acting on the trend towards third-

generation wind turbines, which are characterised by a substantially

greater nominal output and lower specic weights,’ said Thomas

Richterich, Nordex CEO.

Nordex also recently launched its onshore 2.4 MW N117/2400

machine. The so-called Gamma Generation turbine has been specially

developed for inland locations with a 117 metre rotor diameter and

is the highest-yielding IEC III turbine in its class, with a capacity factor

of 40%, its manufacturer claims. The N117/2400 is scheduled to enter

series production in July 2012.

Nordex says it has also

implemented a second

efciency package,

which boosts the

yield of its 2.5 MW

series of turbines

by 2.6% with its

Nordex AP control

module, which

measures wind speed,

direction and air density.

Using this, the management

system adjusts the generator to

optimum effect, resulting in greater

yields at low and medium wind speeds.

Vestas has also marked a new move back into

offshore with a 7 MW machine boasting a massive

164 metre rotor diameter.

WIND TECHNOLOGY SUPPLEMENT - MAY 2011

This new geared machine, at 7 MW, is signicantly larger than

previously announced plans for a 6 MW machine. The V164-7.0 MW

features a swept area of more than 21,000 m

Finn Strøm Madsen, president of Vestas Technology R&D,

explained the philosophy behind this particular design choice,

saying: ‘We actually kept all options open from the start, running two

separate parallel R&D development tracks: one focusing on direct

drive and one on a geared solution. It soon became clear that if we

wanted to meet the customers’ expectations about lowest possible

cost of energy and high business case certainty, we needed a perfect

combination of innovation and proven technology and so the choice

could only be to go for a medium-speed drive-train solution.’

Construction of the rst V164-7.0 MW prototypes is expected in

Q4 2012. Serial production is set to begin in Q1 2015, provided,

Vestas says, a rm order backlog is in place to justify the substantial

investment needed to pave the way for the V164-7.0 MW.

THE MAJOR PART OF OFFSHORE

WIND DEVELOPMENT WILL HAPPEN IN

THE NORTHERN PART OF EUROPE

Commenting on the expected deployment of the machine,

Anders Søe-Jensen, President of Vestas Offshore, said: ‘We expect

the major part of offshore wind development to happen in the

northern part of Europe, where the conditions at sea are particularly

rough… we have specically designed the V164-7.0 MW to provide

the highest energy capture and the highest reliability in this rough

and challenging environment.’ Based on the potential market

size, the business case for the machine is based on Europe and

primarily the Northern European markets, Vestas says, though its

adds that in due course it would take the machine to other regions,

given demand.

DONG Energy and Vestas subsequently announced the signing

of a letter of intent regarding testing of the new turbine. According

to the letter of intent, DONG Energy will perform a design review of

the V164-7.0 MW. Additionally, it is the intention that one or more

could be installed at one of DONG Energy’s test sites for research

and demonstration purposes. The companies are investigating the

possibility of Vestas supplying a number of machines for DONG

Energy’s Danish onshore Kappel test site, for example. The move

could enable DONG to be one of the rst to acquire this next

generation turbine for a future commercial offshore project.

Author Details

David Appleyard is chief editor of Renewable Energy World

e-mail: rew@pennwell.com

This article is available on-line. To comment on it or forward it to a

colleague, visit: www.RenewableEnergyWorld.com

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WIND TECHNOLOGY SUPPLEMENT - MAY 2011

WIND DEVELOPMENT

By Peter Herbert Meier

WOODLAND

WIND ENERGY

As developers look to expand the opportunities available onshore, new generations of turbines with higher towers and

longer blades are opening up previously unobtainable sites to development. Here some of the key issues are explored,

along with the challenges of an environment that can offer a host of attractive locations.

ADAPTING TO FOREST CONDITIONS

With more than 27 GW of installed wind capacity, Germany is Europe’s

leading wind producer and has plans to increase its capacity further

still. Commercial forests in particular offer new potential locations –

but what are the challenges faced by operators and investors?

Estimates by the European Wind Energy Association (EWEA)

anticipate installed onshore wind capacity in Europe will increase from

the current 83 GW to 190 GW by 2020. As well as producing the lion’s

share of renewable energy in Europe, onshore wind will continue to

be the most cost-effective of all renewable energy sources.

In Germany, the development of land areas for potential new

sites is increasingly focusing on inland southern Germany. Within

the scope of option contracts, experts are currently assessing about

100 locations on land owned by the Bavarian state forest enterprise,

Bayerische Staatsforsten, for their suitability as wind farm sites. Areas

of monoculture forestry, especially, offer the opportunity for protable

and environmentally compatible wind farms.

Overall, the development of onshore wind power continues

undiminished across Germany, offering major opportunities for

planners, investors and operators. The German government aims to

increase electricity from renewable sources to 25%–30% by 2020. The

most recent amendment of Germany’s Renewable Energy Sources

Act (EEG) in 2009 further increased feed-in tariffs for wind.

Germany’s Renewable Energy Sources Act is based on a clean

energy cash-back scheme, guaranteeing wind-farm operators xed

feed-in tariffs for the generated power over a period of 20 years. The

act places grid operators under the obligation of giving a purchasing

preference to electricity produced from renewable sources. The EEG

has proved to be one of the most successful legal acts of its kind at

international level and has been used by over 40 countries as a role

model for developing their own tools promoting renewable energy.

Forests as wind farm sites

Firstly, inland sites offer the possibility of injecting power at many

different locations, generally permitting direct use of the existing grid

infrastructure. Unlike offshore wind farms in the Baltic and the North

Sea, they do not require massive expansion of existing grid capacities

or the addition of new ones. Secondly, installation and maintenance is

far less technically challenging for onshore turbines than for offshore

projects, which, in turn, cuts investment costs.

Suitable wind-energy regions in commercial forests are generally

far from residential areas, which therefore minimises adverse

effects on residents from noise emissions and shadow icker. The

forest also reduces the visual impact of the wind farm. Impacts

on residents and the environment can be further reduced by

strategically selecting wind farm sites along existing infrastructure

routes, including national roads, railway lines, overhead power lines

and motorways.

Wind farms may be of considerable economic signicance

for the region, particularly in the rural areas of southern Germany.

During construction, for example, wind farm operators generally

commission regional planning ofces, experts, electrical engineers

and contractors for road and foundation building. Operating wind

farms also creates jobs with regional service providers, suppliers and

servicing companies. In addition, local administrations, municipal

utilities, energy co-operatives and residents may have the possibility

of investing in the wind farm.

A fresh breeze for inland areas

Locating wind farms in forest areas was only made economically

feasible in recent years by rapid progress in wind turbine technology.

Turbine hub heights and rotor diameters are particularly crucial

for forest areas, because the wind prole in a 15 to 40 metre-wide

layer of air directly above the tree tops is massively inuenced by

the trees acting as obstacles to the wind. This zone is characterised

by considerable turbulence and low wind speeds, and is therefore

unsuitable for protable exploitation of wind energy.

Above this zone, at heights of between 30 and 60 metres, the

inuence of the trees becomes increasingly negligible. Wind speeds

rise while turbulence decreases. Modern wind turbines with hub

heights of over 100 metres, which only became the standard some

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WIND TECHNOLOGY SUPPLEMENT - MAY 2011

years ago, now extend into these high-wind, low-turbulence layers of

air high above the tops of the trees. Mean wind speeds reach up to

5.8–6.7 metres/second at a height of 120 metres, even in Bavaria and

Baden-Wuerttemberg.

At higher altitudes, wind speeds tend to be both greater and more

consistent. Taller towers enable longer rotor blades to be used that

further increase energy yield. As a general rule of thumb, doubling

the rotor diameter quadruples the rated capacity. Thanks to this

advance in turbine technology, even wind turbines in low mountain

ranges can now achieve yields that had only been feasible in coastal

and high-mountain areas a few years ago.

Ideal assessment tools

The assessment of a forest site calls for interdisciplinary know-how.

In this case, information and experience from a host of disciplines

including plant engineering, measuring systems, landscape and nature

conservation, logistics and pollution control need to be combined and

integrated in a reliable manner. In addition, the interests of operators,

investors, nature conservationists, residents, forest owners and forest

authorities need to be taken into consideration.

A reliable assessment of the potential site rst necessitates a

survey of the forest stand structure with a focus on diversity, average

stand height, tree density and the width of the tree tops. German

forests consists mainly of spruce, pine, beech, oak and Douglas r

with average heights of between 15 and 30 metres and a density of

between 400 and 1000 trees/hectare. The tops of the trees are 4–20

metres wide and the trees have a mean age of 45–65 years. Wind-

relevant parameters can be determined efciently with the help of

modern laser instruments. A factor that must be taken into account is

variance, in particular with respect to the densities, stand heights and

distances between trees.

Comprehensive wind measurements deliver indispensable data

based on one or several measurement stations.

Using a quasi-3D model, it is possible to predict annual mean

energy generation and the wind speeds for various project

congurations. These data form the basis of ‘bankable wind reports’

and detailed analyses of wind potential, and can also be used for

determining the most suitable type of wind turbine for a specic site

and the ideal hub height and distances.

Reliable reports reduce risk

Reliable wind reports are of particular signicance for successful

wind-farm operation. They form the basis of the protability analysis,

reecting the feed-in tariffs for the generated energy and thus the

projected income. Incorrect assessments may affect the protability

of the wind farm and jeopardise the funding of the entire project.

Energy yield predictions in Germany are frequently based

on the ‘IWET index’, a value determined and published by IWET

The impacts on residents and the environment can be further reduced by

strategically selecting wind farm sites along existing infrastructure routes

WIND DEVELOPMENT

RENEWABLE

ENERGY

WORLD

RENEWABLE

ENERGY

WORLD

Renewable Energy World - magazine - 5/6-2011

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