WEM 2020 01

energy
magazine
#1
Volume 7
March
2020
Rotor blades
Optimisation for improved turbine performance
Interview Pure Energie
The development of wind projects on
land is much more an organic process
than offshore. Renewable energy
developer Pure Energie explains.
u 06 - 09
Rotor blade optimisation
Rotor blades have long been an
undervalued part of a wind turbine.
Their quality, however, impacts the
wind turbine performance.
u 25 - 36
Financing wind
Rabobank - Project Finance shares
their vision on subsidy-free tenders
+ how can citizens participate in
wind?
u 12 - 21

We know which way
the wind blows.
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ENVIR Advocaten creates a fast, efficient and uncomplicated permit process.
We combine our expertise and experience for clear analyses and practical
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ENVIR Advocaten The specialist in environmental law and administrative law
www.envir-advocaten.com

Editor’s note
The ‘weakest
link’
When you attend the many wind
energy related networking events,
you notice how thriving this Dutch
industry is. It is therefore sometimes
hard to imagine that with all our expertise in almost
every aspect of wind energy development and in
technology and innovations, the Netherlands is ranked
last on the list of EU countries when it comes to the
share of energy from renewables.
The Netherlands has a catching-up to do and it knows it by
now. The 2019 Climate Agreement provides a clear strategy to
combat climate change by reducing CO2 emissions with 49% by
2030 compared to 1990. Wind energy, both onshore and offshore,
will contribute significantly in achieving this ambition. The production
of electricity from offshore wind is set to increase to 48 TWh and onshore
to 39 TWh by 2030.
34
Rotor blade
inspection
The Regional Energy Strategies (RES) ensure that it is not just a playing field for
commercial players. Required citizen participation must ensure that the local
community also benefits directly from the renewable energy projects that are being
built in their ‘backyards’. But when you are a developer, what is the best participation
strategy for your project? Or for the politician who is responsible for the RES in his
municipality? Wind Energy Magazine spoke to renewable energy developer Pure
Energie and Leon Pulles, an advisor on this topic.
While onshore wind developers and local and regional politicians are dealing with this
topic, offshore it seems to become less of a necessity as the future wind farms will be
built further from the coast. The timeline and rules for offshore wind projects are quite
clearly defined for the coming years and the cost of offshore wind energy is dropping
beyond expectation, to the point that the last tenders resulted to be subsidy-free.
But, how long will this last? What if the steel and interest rates rise again? We asked the
Project Finance department of Rabobank responsible for renewable energy financing.
A main part of this edition is focused on rotor blades, an essential but at the same time
very sensitive component (or weakest link) of a wind turbine. We have invited a few
Dutch players to share their view in the area of maintenance and inspection, blade to
hub connection, and the afterlife of rotor blades, amongst others. These are just a few
examples of Dutch expertise and innovative entrepreneurship in this area. While the
focus here is on the quality of the rotor blades mainly, there are more activities related to
rotor blades that remain undiscussed, such as the installation techniques.
This, we save for the next edition, out in September!
‘What is the best
participation
strategy?’
Sabine Lankhorst
Editor in Chief
Wind Energy Magazine
presswem@vakbladen.com
01-2020 | 3

Contents
Interview
Pure Energie 06
Rabobank - Project Finance 18
Theme: Rotor blades
We4Ce Root Bushing Solution 26
Boltlife’s blade to hub flange connection methodology 28
Kader - Proper blade maintenance for optimal turbine performance 30
Alternatives on afterlife use of amortized rotor blades 34
Cross-sectoral collaboration for innovation & automation 36
Also in this edition:
Citizen participation in the energy tranistion 12
Winner Offshore Wind Innovation Challenge 2019 38
Cover
The rotor blades for Gemini OWF
© Gemini
Regular features:
Onshore Wind Farm News 10
Wind Statistics 15
Column: ENVIR Advocaten 17
Offshore Wind Farm News 22
Column: ECN 25
General News 40
Agenda 42
24 -36
Theme:
Rotor blades
Colofon
energy
magazine
VOLUME 7 | MARCH 2020 | ISSUE 01
Wind Energy Magazine, a trade magazine for
professionals who are involved or interested in
onshore and offshore wind energy developments
in the Netherlands.
Publication:
Wind Energy Magazine is published twice a year.
Publisher:
Rik Stuivenberg
Publishing company:
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Netherlands
Website:
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www.windenergie-nieuws.nl
Editor in Chief:
Sabine Lankhorst
Contributors to this edition:
Peter Eecen, Benno Boeters, Mischa Brendel,
Erick Vermeulen, Edo Kuipers
Martijn Koelers, Iref Joeman
Cover image:
The rotor blades for Gemini OWF
© Gemini
Advertising:
Archer Media B.V.
Jos Raaphorst, account manager
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Copyright © 2020 Vakbladen.com
The publisher does not necessarily agree with the
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Design:
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Printed by: Veldhuis Media, Raalte
4 | 01-2020

12
Citizen participation in the energy
tranistion
Citizen participation is made a
requirement in the Regional Energy Strategies.
It should help gain more social acceptance for
future onshore wind projects. What are the
best strategies?
06
18
The development of onshore wind projects is an organic process
What started with a single turbine on a farmer’s grounds in Zeewolde, Flevoland,
developed overtime into a mature company that currently owns and operates 70
wind turbines located all over the country, has another 60 granted, and now also
develops solar energy. An interview with renewable energy developer Pure
Energie.
Interview with Rabobank - Project Finance
Rabobank has been a front runner in financing
large wind farms. Pieter Plantinga and Marc
Schmitz of Rabobank - Project Finance look
back on their experience so far.
38
25-36
Rotor blades
Rotor blades are a vital component of a wind turbine. The
quality of a rotor blade has direct impact on the efficiency of the
turbine output. Rotor blades are also one of the most sensitive
components which come with many challenges.
Noise barrier with air bubbles for piling activities
Marine Performance Systems develops a system with air
bubbles that absorb and reduce noise. In December 2019, the
company won with its concept the 2019 edition of the Offshore
Wind Innovation Challenge.
01-2020 | 5

Interview
Sabine Lankhorst
Developing wind onshore is an organic process
In 1995, Dutch entrepreneur Alfons Wispels founded
Raedthuys to develop onshore wind energy. What
started with a single turbine on a farmer’s grounds in
Zeewolde, Flevoland, developed overtime into a mature
company that currently owns and operates 70 wind
turbines located all over the country, has another 60
granted and now also develops solar energy. Last year,
all business activities were united under one single
brand; Pure Energie.
Pure
Energie
6 | 01-2020
De Veenwieken Wind Farm, all photos, courtesy of Pure Energie

Wind Energy Magazine spoke to Pure Energie’s
director wind energy Arthur Vermeulen at the office
in Enschede. In his role, Vermeulen is involved
from the start, when a project is still an idea, up to
the moment financial close is reached and construction can start.
He has been working in onshore wind for 27 years now, of which
16 years at Pure Energie and as such has witnessed from close-up
how the onshore wind industry has developed ever since joining
the company in 2004. Joining him at the table is communication
officer Matthijs Oppenhuizen.
Back in 1995, the type of wind energy development depended on
the policy by each municipality. In Zeewolde there was a
favourable policy for solitary wind turbines on agricultural
grounds, explains Vermeulen. The idea was to finance the wind
turbine with capital from private individuals who would together
own the wind turbine. For farmers this was not their core business
therefore they asked parties like Raedthuys to manage the process
and build the wind turbines. The first wind turbine was installed
two years later, in 1997. In the eastern part of Flevoland, the policy
was more favourable towards clustered wind turbines in line
position and further away from residencies.
Vermeulen: “When the financial participation periods came to an
end, the company started to take ownership of the turbines and
exploit these themselves, thus becoming an utility also.” The
produced power was sold at the energy market (APX). Eight years
ago the company started selling electricity directly to end users
also. This business unit was branded Pure Energie. In 2019 the
decision was made to unite all business activities under this name.
Organic process
Developing wind energy projects in the past was still a pioneering
activity. Vermeulen elaborates: “At the start of this century there
was no real local or provincial land-use planning. We just went out
there and looked for possible locations and started talking to the
local politicians to get their permission. In general we received
more no’s than a yes.”
At some point the objective by the national government was
formulated for 1,500 megawatts of onshore wind energy by 2010.
Provinces slowly started to pay attention. However, it only really
became part of their agenda in 2013, when the Energy Agreement
was formulated, requiring 6,000 megawatts by 2020. The target
was divided amongst the provinces who each started to formulate
their land-use planning policies to facilitate this.
“Our search area became more defined now”, said Vermeulen, “we
would either approach owners of parcels that were identified for
potential wind energy development or the other way round; these
landowners approached us to help them develop.” This does not
mean that it is always easy to start developing projects.
Oppenhuizen explains: “Whereas offshore there is currently one
policy for developing wind and a more clearly stipulated process to
realise it, onshore this can vary with each municipality. Each can
have different requirements with regards to tip height limitations,
minimum distances from the built environment, the type of citizen
involvement and requirements for financial participation. Also,
these requirements can change every four years when new
elections take place.” Vermeulen agrees: “It is much more an
organic process.”
Both men also agree that it is not always easy for local politicians.
Vermeulen: “They need to serve the local interest but at the same
time decide on a project that serves a global interest.”
Oppenhuizen elaborates: “In the eyes of a local community, three
wind turbines might already seem a large project but on a national
or global scale this is just a tiny contribution to the sustainability
targets. This brings along quite a dynamic.”
He provides the example of the wind farm De Veenwieken in the
province of Overijssel where a height limitation of 150 metres was
set to answer to the wishes of the community who wanted turbines
without lights. As a consequence, it was not possible to use the full
production potential for the location. “You are basically moving
the problem to another location as the ‘lost’ capacity would still be
‘We should stop talking
about megawatts. Metres,
that of the hub height and rotor
diameter, not megawatts
determine the output’
installed somewhere”, he says. Vermeulen adds that in Emmen the
company even withdrew a plan for a wind farm. Here the council
also did not allow for wind turbines with tip heights above 150
metres. “With the decreasing trend of the SDE, unfortunately this
meant that our business case would become unviable”, he explains.
Political clarity and consistency
Vermeulen: “For a project to succeed it is very important that the
responsible politician, like the alderman in the municipality, firmly
supports the project and sends a clear message to its community as
to the why. It is okay to take the time to properly prepare the
environmental research before starting the formal process. It is also
a good thing that citizens are given a formal saying, this is part of
our democracy which we should treasure. However, there is too
much time wasted on political bickering and this is in no one’s
interest. It delays the project and creates unclarity.”
“The average lead time is ten years. This could also be four years”,
he continues. He provides the example of the Drentse Monden en
Oostermoer wind farm that has already been going on for twenty
years. “The first ten years the initiative was put on hold due to lack
of political will. Both province and the municipality were looking
at each other”, he explains.
Oppenhuizen agrees: “There should be quicker decision making
and when a decision is made then stick to it.” The Elzenburg-De
Geer wind farm, near Oss, is a good example where the municipal
council has, in his opinion, done everything well. “They were
meticulous and clear and just set out to do it as initially planned.
01-2020 | 7

Interview
This provides more peace for everyone involved. And it worked,
there were hardly any appeals.”
The discussion should also be more qualitative. Vermeulen: “We
can see it with the RES (Regionale Energiestrategie). Often the
ambition for the energy transition is there with the municipal
councils. They set very ambitious targets but then don’t always
know how to proceed. The frameworks in the RES are not always
fitted. When it already goes wrong at the basis, then you are off to a
poor start.”
“They often have never dealt with wind turbines before, and that’s
no blame on them. Most people never dealt with wind turbines
before. We on the other hand have been doing this for 25 years”, he
says, “we know what we are talking about. Come and talk to us.”
Oppenhuizen agrees: “They are often hesitant because we are a
commercial player but in practise sometimes the participating
parties end up contacting us one by one with questions anyway.
Why not invite us at the start, even if it is just over coffee!”
Well-informed citizens
Vermeulen and Oppenhuizen think that if politicians show more
firm support to a project and are better informed then this could
also help the local community to understand wind energy better
and possibly take away some of the objections towards it.
Vermeulen: “It’s a shame that we cannot always use the full
potential of a project location as it also means that the revenue is
lower. Revenue that could have been used for the community.”
He refers to the general thought that bigger turbines mean more
impact. “In practise it doesn’t really matter for your experience
whether you see a wind turbine with a tip height of 150 or 200
metres. In fact, larger turbines are in general more modern and
have less noise impact. For cast shadow the rules dictate a
restriction of 6 hours per year. This remains the same however
many turbines you place or how ever tall they are.”
Another misunderstanding, according to Oppenhuizen, is that one
megawatt solar energy equals one megawatt wind energy. “We
should stop talking about megawatts. In fact, metres, that of the
hub height and rotor diameter, not megawatts determine the
output. And it is the output that is the most important factor now
that the SDE is getting lower!” he says. He illustrates this by
referring to the Kloosterlanden and De Veenwieken projects. “In
both locations we installed 2.35 MW turbines but at De
Veenwieken they are 20 metres higher so the output is higher.”
Citizen participation
Participation of citizens in a project is seen as a way to gain more
social acceptance for the project. In the RES it has even become a
requirement. The Kloosterlanden project in Deventer, consisting of
two wind turbines which became operational in 2015, was Pure
Energie’s first real project with an energy cooperative. Here the
cooperative, Deventer Energie Coöperatie, owns 25% of the
project. Since then, the company always works together with
energy cooperatives when developing new projects. They have a
strict policy on this; the risks should be evenly spread so
participation should take place in all phases.
Having an energy cooperative on your side makes the meetings
with the councils more easy and provides a higher chance of
success, explains Oppenhuizen. “I don’t necessarily believe that
involving an energy cooperative shortens the development process
or makes the project less expensive. However, offering the local
community the possibility to financially participate could, besides
financial gain, lead to an increased feeling of involvement in the
project. Also, as an outsider we have little to none understanding of
the sentiments within the community so working with a local
partner helps.”
The idea of working with other parties is not entirely new to the
company so the switch to the participation model was a swift one.
Vermeulen: “When you look at it, the foundation for citizen
participation was already laid with the first wind project in 1995.
Although, back then, the reason for participation was different,
pure economical, and not yet per se as a means to engage the local
community. The private investors were not yet organised and did
not have to be from the local community.“
The real turn towards this model came when they won a tender for
the development of one wind turbine in Den Bosch, he says. Here
the council required that local citizens could participate financially
and the generated electricity to be used locally. “We offered a wind
bond, something we had already been thinking about for a while.
That was actually the birth of the wind bond in the Netherlands”,
he explains. From that moment on this became the blue print for
developing their wind energy projects and this was copied by the
market also.
2020 activities
In the next few years Pure Energie will add 60 more turbines to its
portfolio. In 2020, the Deil Wind Farm along the A15 will become
operational. Here, Pure Energie owns two of the eleven turbines.
Construction work will start in the wind farms Drentse Monden
en Oostermoer (12 turbines), Weijerswold (2 turbines), Bijvanck
(4 turbines) and Rietvelden (3 turbines), and possibly the company
will receive the definite permit for the Koningspleij project in the
first half of this year. Oppenhuizen: “At the moment we have a 250
GWh/y production volume. We received permits for 9 projects with
a volume of 900 GWh/y, of which 400 GWh/y for the Windplan
Groen wind farm, so we are multiplying our volume four times.”
Just before the end of 2019 the company announced a cooperation
with an energy cooperative; ‘LochemEnergie’. “We will continue to
look for new partnerships throughout 2020”, he adds.
8 | 01-2020

Aerial view on the 2 turbines in Deventer
01-2020 | 9

Onshore
Wind Farm News
Haringvliet Zuid © Eneco
1
Nij Hiddum-Houw
Gooyum Houw BV and
Vattenfall received green light
for their repowering project
near the Afsluitdijk, in the municipality
of Súdwest-Fryslân.
The current wind farm Nij
Hiddum-Houw has been operational
since 1995. The 10
Vestas turbines (7 owned by
Vattenfall and 3 by Brouwer
Windturbines B.V.) with a total
installed capacity of 5 MW, are
being replaced by 9 larger,
more powerful turbines. In
addition, 6 nearby located
solitary turbines are being dismantled.
The new combined
installed capacity is 42 MW.
2
Nij Hiddum-Houw
Waardpolder
All 6 wind turbines in
Waardpolder Wind Farm,
located in the municipality of
Hollands Kroon, are operational.
The wind farm is a project
by WP Energiek. It concerns a
repowering project whereby
the original 19 wind turbines
were replaced by 6 modern,
more powerful models. Until
recently, the wind farm comprised
of 19 Nedwind turbines
with each a rated power of
250 KW/h. The construction
of the six wind turbines was
completed in November 2019.
The new turbines are from
Nordex. These turbines, type
N131, have a hub height of 120
m, a rotor diameter of 131 m,
and a rated output of 3.6 MW.
1
3
De Drentse Monden en
Oostermoer
The 175.5 MW De Drentse
Monden en Oostermoer Wind
Farm reached financial close
at the start of 2020. The
initiators are Duurzame
Energieproductie Exloërmond
BV, Windpark Oostermoer
Exploitatie BV, Pure Energie
and De Windvogel. The wind
farm will feature 45 Nordex
N131/3900 turbines, to be
installed in 6 linear positions.
Each has a rated power of 3.9
MW, axis height of 145 m and
a rotor diameter of 131 m.
Agreements have been made
between the initiators and
ASTRON, the owner of the
nearby located LOFAR telescope,
to reduce the amount
of EMC radiation with 35 dB
compared to the norm. A first
turbine was installed in August
2019 to perform tests. The
tests were successful. The
project in the municipalities of
Borger-Odoorn and Aa en
Hunze will be completed in
2021.
4
Maasvlakte 2
Eneco won the tender for the
Maasvlakte 2 wind farm. With
a capacity of around 100 MW,
this future wind farm will be
the company’s biggest onshore
wind project. The wind farm
will be built on top of a flood
defence in the Maasvlakte 2
industrial area and will generate
around 416 GWh of green
power. Eneco expects to start
the preparatory works for the
construction in 2022 and
complete the wind farm in
2023. Rijkswaterstaat will
purchase the generated electricity
under a 25-year PPA.
5
Westersepolder
Construction activities are
ongoing in the onshore wind
farm Westersepolder, located
near Numansdorp, in the
municipality of Cromstrijen.
The 7 original turbines with a
combined capacity of 3.5 MW
are being replaced by 5
Enercon E-126 EP 3 turbines
with each a capacity of 4.2
MW. Westersepolder wind
farm has been operating for
almost 20 years. The project
is an initiative by Investment
Engineering Projects and is
expected to become operational
this summer of 2020.
6
Energiepark Haringvliet
Zuid
Vattenfall is currently building
a 54 MW energy parc in the
Van Pallandtpolder in
Haringvliet, near the town of
Middelharnis. The energy project
will feature 124,000 solar
panels in an area of around 30
hectares and 6 wind turbines.
Also included are 6 batteries,
combined the size of a sea
container, for energy storage.
In the first half of February the
installation of the first of 6
Nordex N117/3675 wind turbines
was completed. Vattenfall
reached financial close at the
end of 2018. The first preparatory
work started early 2019.
Completion of the full project
is planned for late 2020.
7
Piet de Wit
Early February, De Plaet BV, a
joint venture of Promill BV and
Cooperatie Deltawind, received
green light for the repowering
of a wind farm near
Ooltgensplaat in the municipality
of Goeree-Overflakkee
that has been operating since
2003. The 12 old Vestas V66
wind turbines will be replaced
by 7 more powerful ones that
can have a maximum height of
150 metres. The initiators are
currently in the process of selecting
the turbine supplier.
The wind farm is expected to
become operational sometime
in 2021. By replacing the old
turbines, the capacity will rise
from 24 to 30 MW.
8
6
Egchelse Heide
At the end of January the wind
farm Egchelse Heide, located
in the municipality of Peel en
Maas, received green light.
The wind farm is an initiative
by energy cooperative Peel
Energie and local farmers and
will feature 5 wind turbines
with a maximum height of 210
m. Financial close is expected
in the summer. The turbines
are likely to be installed early
2021 and will start generating
power in Q2 of 2021.
10 | 01-2020
Egchelse Heide© Pouderoyen.nl

1
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3
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6
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Read the full news
on www.windenergymagazine.com
(EN) or
www.windenergienieuws.nl
(NL)
01-2020 | 11

Interview
Sabine Lankhorst
Citizen participation in the energy transition
Finding the right
strategy for
participation
The Netherlands, albeit with a delay, is taking steps in the energy transition.
Wind, both onshore and offshore, is a large driver in the transition and many
gigawatts of it will be needed. Especially onshore, social acceptance is vital in
ensuring that these megawatts will be realised. So vital that local participation
has been included as a requirement in the Regional Energy Strategies.
Wind Energy Magazine spoke to Leon Pulles,
managing partner of Energy Investment
Management BV who advises sustainable energy
developers in setting up participation strategies for
their projects.
Pulles: “The Netherlands has waited for a long time before
starting the energy transition. People were in general not really
engaged in energy matters.” As the pressure grew from the
European Union, something had to be done. That’s when the
government introduced the SDE subsidy scheme. Things started
speeding up and the number of wind and solar farms were rising.
Not long after, the energy transition became a more frequent topic
on the news and people were actually starting to look at their
energy bills. People started to have an opinion on the subject, not
always positive. In addition to the ‘Not in my backyard’ sentiment,
there was also another sentiment growing, that our country was
too small to make a difference. Is it worth spending that much
money on the energy transition?, he explains.
‘With each project you will need
to identify what type of
participation is most suitable’
Topic at birthday parties
“We all benefitted from the industrial revolution, we should now
not walk away from our responsibilities in the energy transition”,
Pulles says. Getting people involved could create broad support
for the energy transition. He mentions Stephanie Platschorre from
the Erasmus University who performed a research on what
motivates people to financially participate in renewable energy
projects through crowdfunding. [1] Her research showed that few
people are really consciously involved.
It is therefore advisable for developers to engage the community in
their project as soon as possible, especially when the project is
planned in a challenging surrounding, he says, “go talk to the local
people, explain them your plans and talk them through the
different phases of the project. When possible, take them to a
comparable project. Let them, within certain set boundaries, have
a saying and ask them how they would like to participate.”
Getting citizens involved in an energy project is not entirely new.
He provides an example of a critical project that was handled
adequately in his opinion. He refers to the case of waste disposal
company HVC in the eighties. In the province of Noord Holland
dioxin was encountered in the milk. The root was traced back to
the waste disposal company of HVC. This was very much a major
issue in those days. In the end, HVC wanted to build a new
factory that would comply to the new regulations imposed. They
went into a dialogue with the people in the neighbouring area in
12 | 01-2020

Stephanie Platschorre, Leon Pulles and Noortje van Heijst
order for them to gain trust in the new factory. Small testing
grounds were created for free to monitor and measure the dioxin
level. These became the ambassadors for the project.
Pulles also provides an example of a wind energy project in
Harderwijk in which he is currently involved. This project is being
developed by the municipality itself. Here the municipality asked
high school youngsters to share their thoughts on setting up a
fund. In this so-called ‘Wind challenge’, three teams of each five
youngsters created interesting concepts. Pulles: “They took their
task very seriously and came up with some good ideas. During the
development of the wind energy project some people actually
stood up and became involved, including influential people in the
community. These people should be involved in the entire process,
as ambassadors!”
Informing and involving people will provide a clearer picture of a
project. In the most positive case, people will get involved or
otherwise become neutral. “Find ambassadors who will share the
message”, he says, “it should become the topic during birthday
parties!” Of course, you will always have people who remain
negative, he adds.
Participation options
Having the local community involved is not only advisable, since
the introduction of the Regional Energy Strategies (RES) as part
of the 2019 Climate Agreement, it is now also a requirement. The
RES dictates that all new renewable projects require 50% local
participation.
There are several options for developers to execute this, directly by
offering shares or loans, or indirectly by setting up a sustainability
fund whereby part of the revenue from the wind farm is reserved
for green initiatives that improve the local community, or
providing other local benefits.
People participate for different reasons. Pulles refers again to the
study by Platschorre. Her research identifies several motivations
for people to participate, one of them being financial return, of at
least a 6, 7 % on the investment. Another motivation is to witness
the social or sustainable impact of their financial participation. In
addition, it is also often seen as a way to learn new things.
“Therefore, with each project you will need to identify what type
of participation is most suitable. Is the project going to be located
in a densely or sparsely populated area? What is the financial
capacity of the local population? How strong is the sense of
community identity?” he explains.
In the Harderwijk case, the community was initially provided four
participation options; shares, loans, sustainability fund or discount
on the energy bill. Here, the collective was given priority over
individual benefits and the choice was made for green initiatives
via the sustainability fund.
In the case of the onshore Krammer Wind Farm, in the province
of Zeeland, participation took place through crowdfunding. This
was a logical step as the initiators of the wind farm were citizen
cooperatives. They already had a large support base through their
members. Within a short period of time ten million Euro was
raised.
Opening Krammer Wind Farm
Pulles was also involved in the Westermeerwind project. Here, the
community participated for a total of more than nine million Euro
01-2020 | 13

in equity and loans. “We were expecting, based on
questionnaires earlier on in the project, that there was
much more interest in shares than loans. This
demonstrates that people only really decide when the
moment is there.”
Financial participation
With regards to financial participation, Pulles thinks
the wind energy industry had to get used to this
becoming part of the business case. “It seems like
players in the solar energy industry are more
entrepreneurial in this field. Perhaps it is because
wind has been there for much longer. In solar, most
players are relatively new and are used to this
concept from day one.”
“In onshore wind
energy development
the main theme is
social acceptance. That
is already an important
driver to make
participation part of
your project. Financial
participation is a good
way to do so. Of course
you need to look at each
individual project but in
seventy percent of the
cases, it works. The
question then rises; what
do you want, as a developer, to share from your business case
point of view?”, he explains.
Participation generally takes place when financial close is reached,
shortly before the construction starts. That is when the definite
financial budget is determined and estimations can be made on
the returns in participation. From a project developer point of
view you would like it to be the sooner the better as the project
development, the period up to financial close, could easily take
between six to ten years for wind energy projects, says Pulles. “In
the case of the Westermeerwind project, the initiators of the
project wanted to have local participation to be introduced sooner
in the project, however the banks involved required the project to
become operational first. “This created a tension field”, he adds.
Participation in an early phase is possible, according to Pulles.
However, it is not possible to determine an interest rate because
there is no definite budget available yet. There is also the risk
factor. “People get their returns when the wind farm is
operational, at an early stage you cannot set that moment in stone.
‘Financial participation
should not be a stand-alone act’
Poster announcements for
financial participation and
sustainability fund
It is however the right time
to already start talking to
the locals because financial
participation should not be
a stand-alone act”, he says.
There is also the discussion
on the height of
participation. Especially
from the point of view of an
Alderman of the
municipality he would ideally wish for people
that are less financially capable to be able to
participate also. In that case, a sustainability
fund in addition to financial participation via
equity and loans would be the best option.
Future outlook
Pulles is convinced that financial participation
will occur more often, especially with the
RES, and developers will be smart enough to do so. People will
also get more used in participating in wind energy projects. Solar
energy projects are less complex than their wind counter parts and
are developed quicker. People tend to understand solar energy
better and are more likely to accept and participate in these
projects, he says. “However, they do not always understand that,
for example, a four megawatt solar project is not the same as a
four megawatt wind project. I also don’t think they quite realise
how many solar fields will be realised in the next few years. The
last SDE+ rounds showed more solar applications than wind
applications, I wonder how they will feel about solar energy when
all these projects are realised”, he explains.
We also have to wait and see how the SDE++ will develop and
how the energy transition will take shape, he thinks. “With the
SDE+ scheme, we were able to look ahead twelve to fifteen years.
In this scheme, banks are generally involved one or two years less
than the SDE period. It is hard to say how this will be with the
SDE++, and possible other future arrangements”, he explains.
And there is the human element, what will happen if people have
been participating for a long period of time. What kind of returns
will they expect? It is very important that the renewable energy
sector tries to involve as many as possible citizens to create
understanding and support for the Dutch energy transition.
1. Research was based on interviews and questionnaires among
Oneplanetcrowd.com en Crowdfundmarkt.nl crowdfunding platforms.
14 | 01-2020

Statistics
Sustainable development made easy
Do you want to make an entry into the Dutch
wind market or are you simply interested in
keeping up to date on what wind farms are being
commissioned in the Netherlands?
!( Commissioned in 2019
2005
2010
2019
Wind energy installed power in the Netherlands
Subscribe to the WindStats database!
Call us for more information: +31 88 22 66 682
or e-mail: presswem@vakbladen.com
441 MW
197 MW
WIND ENERGY in the
NETHERLANDS
2019 in review
ONSHORE
3.552 MW (+192 MW)
OFFSHORE
957 MW
TOTAL
4.509 MW
2.307 wind turbines
!(
!(!(!(!(!(!(!(!(!(!(!(!(!(!(
!(!(!(!(!(!(
!(!(
441 MW
!(
!(!(!(!(!(!(!(!( !(!(!(!(!(!( !(!(!(!(!(!( !(
!(!(!(!(!(
!(!(!(!(!(
341 MW
1147 MW
34 MW
!(
!(!(!(!(
!(!(!(!(!(!(!(
87 MW
!(!(!(
31 MW
!(!(
!(!(!(!(!(!(
67 MW
!(
!(!(!(
!(!(!(
!(!(!(!(
239 MW
516 MW
Commissioned in 2019
MW wind turbines
Drenthe
Flevoland
Gelderland
Noord-Brabant
Noord-Holland
Overijssel
Zeeland
Zuid-Holland
10
14
4
27
91
30
14
110
3
7
1
7
38
13
6
28
SOURCE: WWW.WINDSTATS.NL
WindStats
over windenergie in Nederland
© WindStats.nl 2020
12 MW
e increase in installed power in 2019 was higher than last year,
even though 109 MW was decommissioned.
e largest new wind farms are Slufter 2 (Rotterdam, 50 MW),
Waardpolder (Hollands Kroon, 22 MW), Spui (Hoeksche Waard, 21
MW) and Nieuwe Waterweg (Rotterdam, 21 MW). e end of the
year saw the start of construction of some large wind farms,
notably Wieringermeer, Drentse Monden Oostermoer, Veenwieken
and Deil). ese will be commissioned in 2020 or 2021.
01-2020 | 15

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Column
Erwin Noordover
Lawyer at ENVIR Advocates
Is financial participation the
holy grail for public
acceptance of wind farms?
Now that the spectre of negative interest rates on savings accounts is haunting us,
we are looking for investment opportunities for our savings. The energy
transition provides opportunities for this as various governments offer
frameworks within which citizens must be given the opportunity to participate
financially in wind farms.
One example is the province of Flevoland, which in its environmental regulations has set
requirements for financial participation in wind farms. This includes offering the opportunity
to participate financially in the project on a risk-bearing basis, based on a minimum of 2.5%
of the initial total investment volume in the operational phase. However, this principle may be
deviated from if the developer can demonstrate that there is insufficient interest in
participation. These requirements for financial participation force developers to reach out to
the public. At the same time, the government’s requirements for financial participation should
not jeopardise the business case. Fortunately the Province of Flevoland has included an
exception if insufficient money can be raised from the surrounding area.
Can the
requirement to
offer financial
participation be
taken into
account when
deciding on a
zoning plan?
A great deal is also expected of financial participation for the public acceptance of the energy
transition for which the Regional Energy Strategies are now being drawn up. A guide for
participation in sustainable energy projects has been published with guidelines for
participation in wind projects. Participation is herein tailor-made and the competent authority
checks whether the conditions for participation have been met.
In view of the importance that local authorities attach to financial participation, the question
arises as to whether this participation may be conditional for the cooperation with the
development of a wind farm. Can the requirement to offer financial participation be taken
into account when deciding on a zoning plan? It is doubtful that financial participation is a
spatially relevant aspect, as it does not affect the environment.
But can the municipal council then state that the effects of a wind farm on the environment
are only acceptable if the opportunity to participate financially was sufficient? This seems to
be odd reasoning: the effects of a wind project are no different, but because there is a financial
involvement of (part of) the surrounding area with the project, these consequences have
become acceptable.
If offering sufficient financial participation becomes a criteria for cooperation with a wind
farm, the risk arises that a developer with deeper pockets or a specific business case will be
preferred over other initiatives, even if those other initiatives are a better option for the energy
transition or the environment. Hopefully the focus on financial participation will not lead to
an inappropriate balancing of interests and only helps with the public acceptance of the much
needed development of wind farms.
01-2020 | 17

Interview
Sabine Lankhorst
Interview with Rabobank- Project Finance
‘Do you really want to risk
companies supporting the
industry to go bankrupt and
lose thousands of jobs?’
Financing wind
projects in rapidly
changing times
When the first offshore wind farm was built in Dutch waters, no one at that time
would have been able to foresee how quickly the price per megawatt hour would
drop. Neither did the Rabobank. A conversation with Marc Schmitz and Pieter
Plantinga, managing director and executive director respectively at Rabobank’s
project finance department, responsible for renewable energy financing.
18 | 01-2020

Marc Schmitz
Pieter Plantinga
Prinses Amaliawindpark © Eneco
During the interview at their office in Utrecht it
became instantly clear that both men have been
working together for quite some time, ever since
Plantinga joined the project finance team at
Rabobank in 2009. Schmitz was at that time already working for
the team since 1999. Prior to this, he worked for Vattenfall (back
then Nuon).
Their project finance team handles all large renewable energy
projects in Europe with a debt amount of at least 25 million Euro.
These projects include mainly solar, onshore wind and offshore
wind. Other renewable energy projects, such as biomass, heat, and
bio fermentation, are also dealt with within the team by separate
specialists in this area of expertise.
How do you look back on your cooperation so far?
Schmitz: “Pieter and I built this department in Europe to what it
is today. When he joined in 2009, our renewables team consisted
of seven people, now we have a team of around twenty people. In
addition, Rabobank has teams in India, covering renewable energy
in Asia, and in the US.”
Plantinga: “It was necessary to upscale and create the large, solid
team as we have today. The wind energy market has matured, with
more complicated structures. There is more market price risk
involved now.”
Schmitz: “I remember the first wind project I worked on. These
were 1.65 megawatt turbines near Muiden. Look at the sizes of the
turbines now. We have in the meantime worked on around twenty
offshore wind energy projects, almost thirty if you include the
refinancings. In the Netherlands, we were involved in the first
offshore wind farm to be financed through project financing
globally. In Belgium, we have been involved in all the offshore
wind farms. Furthermore, we have also worked on a large number
of German projects, the first French project, and on one in
Taiwan. The latter, together with our team in India. Many of the
companies involved in Taiwan are European so it made sense.”
Plantinga: “In the onshore sphere we worked or work on several
large wind farms, including, NOP Agrowind, Krammer, Vermeer
and Drentse Monden.”
Schmitz: “We are also active in Spain, the Nordic’s, recently the
UK and Ireland again, and we are currently looking into the Polish
market. Amongst these are more challenging markets due to newer
structures with corporate PPA’s, including some market price
risk.”
The Netherlands is also developing more large onshore
wind farms. Is there a huge difference in the process
between onshore and offshore?
Plantinga: “Although the type of financing is similar, the parties
you work with are different. Offshore is very capital intensive and
therefore there are larger and generally more professional sponsors
in a single project. These sponsors tend to develop multiple similar
projects, they know what we need from them. This market is more
consolidated. Onshore, many of the old projects have been long
term developments by farmers in the Netherlands. These have
generally never developed a project before and will most likely not
do this again. On average, only one out of three onshore projects
being developed will be realised.”
01-2020 | 19

‘Onshore, you also have to
deal with a legacy’
“Onshore, you also have to deal with a legacy. In the early days
developers did not really involve the local communities. You can
see the effect of it now in some parts of the Netherlands like
Drenthe. This is something which needs to be addressed more and
more consciously by developers in the early stages of project
development. The Krammer project in the province of Zeeland is
an example of how it should go, with the right set of shareholders
and local participation.”
Onshore there are already challenges in connecting new
projects to the grid. Does this affect your business case?
Plantinga: “Not in the sense that we simply don’t finance a project
if the connection is not guaranteed. However, we now see private
initiatives coming in who want to realise the grid connections.
We are following this development and are investigating if we
could finance these.”
How is your team positioned in the international playing
field of project financing wind energy?
Schmitz: “Rabobank is a niche player but definitely a front runner
in our field. For a long time we were the largest project financer of
renewable energy projects in the US. In offshore wind we were
involved in one of the first offshore wind farms in 2006, Q7, now
called Prinses Amaliawindpark. In 2007 we helped finance the first
Belgian offshore wind farm C-Power. Keep in mind that offshore
wind only really became popular in 2015, so we were almost ten
years ahead of our time! In Scandinavia we were also one of the
first to accept market price risk. We are involved in eight projects
there.
The project finance department of Rabobank excels in financing
projects with a value between 100 and 500-600 million Euro.
When it comes to project values of two, three billion Euro there
are other players who are better equipped.”
Plantinga agrees: “Another difference between us and the larger
players is that they often use external advisors. We are more used
in serving the entire market, especially in the Netherlands. Here
we work together with the customer to set up the financial
structure for their project, therefore each project is unique.”
Have you ever experienced a situation where a project
went too much over budget?
Schmitz: “Project finance is quite straight forward, you finance a
single asset with clear fund flows. With companies the money flows
in all directions. With projects a technical advisor approves each
drawdown based on actual progress of works. It is therefore easier
to control. We have had an experience once where a project went
way over budget. It then becomes a play between the banks and
shareholders. In practise the shareholders will have to contribute
more to the budget as they can’t risk losing the project to the
bank.”
Plantinga: “In addition, each project has a contingency for
unexpected costs. However, I once worked on a project that went
way over budget. One of the suppliers went bankrupt and could,
as a consequence, not deliver the components. This had a ripple
effect on the entire construction schedule. It required a
tremendous effort from all parties to restructure the project!”
How important is sustainability for Rabobank?
Plantinga: “Sustainability has come higher and higher on the
agenda of the bank over the past years. And we are asked to do
more in this sector.”
Schmitz: ”We actually already tried to push this many years ago
but Project Finance remained under the radar for a while,
amongst others due to the high capital requirements and long
term debt in renewable projects.”
20 | 01-2020

Westermeerwind Wind Farm. © Westermeerwind
The subsidy-free offshore wind tenders of lately are
welcomed by many. Do you share this feeling?
Schmitz: “In 2011, Rabobank, together with Bloomberg,
published a study titled ‘Reaching the ten cents per kilowatt hour’.
The target was 2020. We, and a group of 25 industry experts, were
cautious whether this was possible. Look at the price now, 6 to 7
cents per KwH!”
“However, I don’t think letting go of subsidies is per definition a
good development. Let me put this right, I think the Dutch
government is currently doing a very good job in managing the
development of wind energy in our country, however, I think it
would have been better to keep the subsidy system, albeit
restricted to an acceptable level.”
“How many risks are developers willing to take? What if the
projects will not be realised? Do you really want to risk companies
supporting the industry to go bankrupt and lose thousands of
jobs? That’s to nobodies interest. The problem is, nobody really
knows what the situation is, say, in twenty years. The low interest
rate and steel price have played a positive role in the lower cost of
energy. What if the interest rate would go back to the level we have
seen in 2011 or 2013,14?”
“If you want to move forward with the energy transition then you
probably have to introduce the subsidy scheme again. In the past,
the level of subsidy required was very high, over 100 Euro per
megawatt hour. I personally think a limited subsidy, between 15 to
20 Euro per megawatt hour would be perfectly fine for a project.
Plantinga: “Both the UK and France have indicated not to go
entirely without subsidies. The strong focus on building offshore
wind farms without subsidy remains a surprise to me anyway. One
tends to forget that coal and gas plants have also been supported.”
Turbine sizes are increasing at a rapid speed and new
technological innovations are introduced. As a bank, does
this bring additional risks to the financing of wind
projects?
Schmitz: “The increase in turbine sizes is a continuous natural
process so it is not really a big risk.”
Plantinga: “Our technical advisers would probably say that further
development of existing technologies sometimes pose more risks,
due to things being overlooked. With new technologies, every tiny
detail is tested and checked by certification bodies over and over
again.”
Finally, do you have a favourite wind energy project?
Schmitz: “In general, the projects that were most challenging are
the ones I look back on with most pride. For me these were the
Westermeerwind, Belwind and NOP Agrowind projects. In these
projects we had many challenges which we needed to overcome.
Plantinga: “I agree with Marc’s observation, these projects on
which we worked together have been more challenging but very
interesting to work on, even though they generally tend to take
considerably more time to bring to a financial close. In these
processes you also end up building strong relationships.”
Schmitz and Plantinga agree that this is something that makes
them continue to enjoy this industry; the good relationships that
they have built up over time which has resulted in a lot of
friendships being established within the industry.
01-2020 | 21

Offshore
Wind Farm News
IJmuiden Ver, © TenneT
1
3
4
Ten Noorden van de
Waddeneilanden
The Netherlands Enterprise
Agency (RVO.nl) has granted
Fugro a geotechnical site
investigation contract for the
700 MW Ten Noorden van de
Waddeneilanden Wind Farm
Zone. The activities will take
place from February to May
this year.
The work comprises of a
shallow subsurface
investigation in Phase 1,
followed by a borehole drilling
programme, and standard and
advanced laboratory testing,
in Phase 2. The final
deliverable will be a data
package which can be used to
prepare a detailed integrated
geological and geotechnical
soil model, on which wind
farm developers will base
future tenders.
2
Fryslân
Several construction activities
are currently taking place for
the 382.7 MW Fryslân wind
farm. The section of the cable
route on the Afsluitdijk has
been completed while work
continues on the section of
the cable route on land to the
110kV-station of TenneT in
Bolsward. At the same time,
work on the transformer
station at Breezanddijk is stilll
in progress and a start has
been made on the realisation
of the work island which will
serve as a nature area after
the wind farm has been built.
This area consists of 2
hectares above water level
and a 25 hectares shallow
water zone.
3
IJmuiden Ver
TenneT has initiated a
development process with
HVDC suppliers to help design
an innovative 2 GW 525 kV
HVDC solution which can be
used for the IJmuiden Ver
Alpha and Beta connections
(due in 2030) but also other
future 2 GW high voltage
connections like planned in
Germany.
The partnership includes: ABB
Power Grids, GE Renewable
Energy’s Grid Solutions
(Netherlands), a consortium
of Global Energy
Interconnection Research
Institute Co. Ltd. (GEIRI) &
C-EPRI Electric Power
Engineering Co. Ltd. (C-EPRI)
(China), Siemens (Germany),
and Xian Electric Engineering
Co., Ltd (China). These
suppliers will provide specific
information on this to Iv-
Offshore&Energy b.v., which is
carrying out the Front-End
Engineering Design (FEED)
study on behalf of TenneT. On
this basis, a standardised
platform design will be
developed for all HVDC
solutions.
2
Hollandse Kust (Noord)
The Ministry of Economic
Affairs and Climate Policy
published the Ministerial
Order for permitting offshore
wind energy Hollandse Kust
(noord) Wind Farm Site V in
December 2019. It is one of
three offshore wind zones
identified by the Dutch
government to be developed
by 2023. The tender to
develop the Wind Farm Site V
will run from 2 April 2020 till
30 April 2020, 17:00h CEST.
5
Borssele 1 + 2
In January, foundation
installation work started in the
752 MW Borssele 1 + 2
offshore wind farm, a project
by Ørsted. The wind farm is
planned to be fully operational
by the end of this year. It will
then be the largest Dutch
offshore wind farm. In total,
94 Siemens Gamesa 8 MW
wind turbines will be installed
on monopile foundations
some 22 kilometers off the
coast of the Zeeland, at water
depths varying from 14 to 39.7
meters.
The foundations are produced
by Sif, EEW SPC, EEW OSB
and Danish Bladt Industries.
The installation is performed
by DEME, using their heavy-lift
vessel Innovation. According
to Ørsted, the first turbine
installation activities will start
in April this year.
6
5
North Sea Agreement
In February, the government,
energy sector, fishery, nature
organisations and port
associations presented an
agreement (Onderhandelaarsakkoord)
on the use of the
North Sea. The Agreement
has the theme ‘additional
miles for a healthy North Sea’.
The cabinet has now handed
the Agreement to the
parliament. A consultation
period will take place till 31
March during which the
participating parties can
discuss the Agreement with
their members.
The Agreement outlines the
plans for the next ten years
but also explores the period
following. The government will
sponsor 200 million Euro of
which a large part (119 million
Euro) is destined for the
restructuring and greening of
the cutter fleet. 12 million Euro
will be made available for the
safe passage of vessels during
construction of the wind
farms. Another 14 million Euro
is reserved for enhanced
supervision on the
implementation of the
Agreement and 55 million
Euro is to go to additional
monitoring, scientific research
and nature conservation.
© Windpark Fryslân
22 | 01-2020

1
2
3
4
6
5
Read the full news
on www.windenergymagazine.com
(EN) or
www.windenergienieuws.nl
(NL)
01-2020 | 23

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Column
Peter Eecen,
R&D manager wind energy at TNO
Sophisticated
wind turbine
blades
Looks can be misleading. Ever larger wind turbine blades seemingly look the same
as their smaller predecessors, and not everyone understands the gigantic technical
developments that are required to make these larger blades. Design and
manufacturing of larger blades have to fight the laws of physics. Without
innovations these blades would become too heavy and too expensive to be interesting. Only
the fast innovations in development of design, materials, construction, and manufacturing
have made the up-scaling possible.
New models in aero-elastics are required for the design of these very large blades. The tip
speed of the rotor blades is usually between 80 and 100 m/s, which means that larger rotors,
longer blades, rotate slower. Scaling up the aerodynamic profiles do however result in
different performance compared to the smaller profiles. This is the reason that GE, LM
Windpower and TNO perform an extensive aerodynamic measurement programme on the
Haliade X turbine. The experiments provide the researchers the validation data to check
whether improvements in design modelling are indeed correct.
‘Not everyone
understands the
gigantic
technical
developments
that are required
to make these
larger blades’
To reduce the loading of the very large rotors on the support structure the large rotor blades
become more slender than their smaller counterparts. This results in relatively thick
aerodynamic profiles which have different aerodynamic characteristics than the presently
applied thinner profiles. Reason for increasing the relative thickness of the profiles is that the
height of the profile remains the same to accommodate the loads-carrying structure while the
profile chord length becomes relatively smaller. These profiles are not commonly applied in
other applications while the Reynold’s numbers become larger than in other applications.
That means that the performance becomes uncertain and elaborate airfoil testing is required.
To determine the performance under rotating conditions testing on full-scale wind turbines is
required.
With the increasing rotor sizes, the hub on which the blades are attached becomes a more
dominant weight and cost factor for the rotor. At the same time, the dynamic behaviour of the
rotor is becoming dependent on the flexibility in the hub. The loads carried by the pitch
drives that fix the blades to the hub require increasingly more attention. Within the Dutch
innovation system, a project is carried out by GE, LM Windpower and TNO and addresses
the forces and dynamics of the entire rotor assembly.
Finally, imagine the construction of 107m long blades where the root is 5.4m wide. Laying
fibres along the entire span of the blade is challenging and requires automated and robotised
solutions. Handling these blades requires innovative equipment, which everybody could have
observed when the Haliade X turbine was installed at the Maasvlakte in Rotterdam.
01-2020 | 25

Rotor Blades
Edo Kuipers
We4Ce Root Bushing Solution for Rotor Blades
M.A.R.S.2020
For over 10 years, We4Ce has been providing technology to connect rotor blades
to wind turbines – the We4Ce Root Bushing Solution. The adaptation of more
stringent certification requirements, together with the demand for a reduction in
the main mould occupation time, pushes the launch of the We4Ce M.A.R.S.2020
project. We4Ce’s vision and strategy is clear in this: a convenient, robust and costeffective
blade root connection technology, following the latest DNVGL-ST-0376
ed. 2015 guidelines.
We4Ce was founded in 2008. Its main design offices are located in
Almelo, the Netherlands. We4Ce also has agencies in China and
Russia and a partner in India. Its core business is rotor blade
design, from aerodynamic and structural design to technology
implementation at our customer’s premises, next to
accomplishment of the certification. Parallel to technology
transfers which enables customers to manufacture the bushing
connection in their own factory, We4Ce also provides prefab blade
root parts as well as subcomponents since 2018.
We4Ce Root Bushing Solution
Since its foundation, We4Ce is focused on the development of
bushing solutions for the root part of rotor blades and becoming
‘the company’ in this field. This solution has been widely used with
great success, especially in the Chinese market. Recently, the
European market also showed increasing interest. At present, over
25,000 turbines worldwide are equipped with our bushing
solution.
Our motto is ‘Simplicity is its strength!’. In the design office of
‘We4Ce-The Rotorblade Specialist’, our team is continuously
working on further improvements and finetuning. The We4Ce Root
Bushing Solution has the objective to fulfil at least the following
criteria: easy to build/assemble, exchangeable with T-bolt-blade
root connection, to be built as a prefab component, and to be
strong enough for its application. Furthermore, only a minimum of
activities may be required once the blades are demoulded.
The bushing of We4Ce follows the mechanical locking principle. It
is a connection that finds its strength during the infusion moulding
process of the blade root. The interfaces between the steel bushing
and the surrounding laminate are of great importance. Since the
assembly is done during the resin infusion process, this means that
the connection is secured by the quality of the laminates. This
leads to a higher strength than when using a bonded insert
connection.
In 2008, the development of the We4Ce Root Bushing Solution
started with the M30, directly followed by the M36. In 2018, a
smaller design, the M20, was introduced for the European market.
Having developed and tested these three different sizes, We4Ce
gained valuable knowledge about the scale effect of bushings and
the Critical to Quality (CTQ) effects to be considered.
The blade root bushing connection consists of an assembly of
different sub-components, where the assembly tolerances are key
to assuring quality. Although slight changes occur, a bushing
connection involves the following sub-components: steel bushings,
fibre material wrapped around the bushings, glass fibre elements
between the bushings, core wedges to slope down the bushing
thickness towards the rotor blade tip, and layers of laminate below
and on top of the bushing assembly to integrate to the full rotor
blade.
Sub-component Supply
Since 2018, We4Ce also produces the sub-components of the
bushing assembly in their own workshop. The aim is to provide the
customers with a robust and cost-effective connection technology
during proto building. For We4Ce, this means to have the QA/QC
and material selection at a consistent level, raising the
characteristic strength. As a result, our customers are able to
concentrate fully on the assembly process in the main mould,
which is their core business.
Prefabricated Root 180 Degrees
To help blade manufacturers shortening their mould occupation
time, We4Ce has started to supply 180 degrees prefabricated root
parts. A few sets of relatively smaller roots have been
manufactured and supplied from the east of the Netherlands to
the southern European market. After a successful start-up and
having finetuned the design for production, We4Ce transferred the
technology to India for mass production.
26 | 01-2020

The Launch of M.A.R.S.
In the second half of 2019, We4Ce launched the M.A.R.S. project.
The acronym ‘MARS’ identifies the main characteristic features:
being a Modular and Adaptive Root Solution, where Adaptive
refers to the possibility to extend the number of bushings in a row,
or to increase the loading level by shape adjustment.
Together with research institute TNO in Delft, the Critical to
Quality items within a bushing-root are tackled more
fundamentally, on an engineering level by analysis, as well as on a
practical level by testing. Several material interfaces have been
depicted as being critical for the strength of a bushing system.
Next to the default prescribed materials, it was also decided to
include special pultrusion elements into the test programme to
quantify the effect of material tolerances on the strength by means
of testing.
Offering root segments (modular parts) to our customers as a
hardware product, is the next ambitious goal of We4Ce. For this
purpose, a close cooperation with a Chinese partner will be
explored. The goal of the cooperation is an efficiency improvement
for our customers in terms of main mould occupation time and a
consistent and reliable quality level, taking an attractive cost-level
in mind.
u Edo Kuipers
With more than 22 year of experience in blade design, Edo
Kuipers is one of the founders and co-owners of We4Ce. His
main responsibility is running the engineering department
from the aerodynamic rotor blade design, structural design,
up to accomplishing the certification documentation. His
special interest is to have the in-house developed bushing
connection being applied in as many possible rotor blades
as connection technology between the rotor blade and the
turbine. Edo studied Aeronautical Engineering in the
Netherlands and holds a Bachelor of Engineering degree.
Edo Kuipers, We4Ce - the Rotorblade Specialist
www.we4ce.eu, e.kuipers@we4ce.eu
To impeccably execute the M.A.R.S. project, We4Ce works closely
together with several European certification bodies in a step by
step approach.
The M.A.R.S. project is expected to be accomplished by the end
of 2020, however first results and findings will be applied earlier,
i.e. by the mid of 2020.
For more information, please contact us at:
info@we4ce.eu
01-2020 | 27

Rotor blades
Mischa Brendel
Boltlife’s blade to hub flange connection methodology
Safe upscaling of
wind turbines
Wind turbine generators get bigger and bigger each year. As a result, the dynamic
forces on a rotor blade during its operation become immense. These tremendous
forces are transferred through the blade-to-hub connection, which makes it
imperative that this connection doesn’t have any weak points. This poses
challenges for the designers of wind turbines. But those that can overcome these
design challenges are looking at lower costs of quality and even better revenues.
Boltlife specialises in creating high quality bolted flange
connections in wind turbines, among them blade to hub
connections. In 1996, a blade length of 20 meters was
considered as state of the art; in 2003, 45 meters had
become a standard and today we are working with blades of 107
meters long. In those days the T-bolt connection (IKEA
connection) was the standard method to connect the rotor blade
to the hub of the turbine. The last 15 to 20 years however, a root
bushing connection is the most
commonly chosen method for
connecting the rotor blades.
the bolt preloading procedure. “Current bolt preloading
procedures, like torque-angle or tensioning, have their flaws
due to poorly manageable parameters like friction, lubrication
issues and misalignment,” Joost Prieshof, CEO of Boltlife says.
“The reason is that only a small and unquantified portion of the
applied torque will be converted into actual preload. This leads to
a considerable scattered load throughout the bolted flange
connection.”
One important advantage of a
bushing solution over the T-bolt
connection is the ability to apply
more bolts on the same pitch
circle diameter; about 30 % more
bolts can be placed, which offers
the opportunity to use longer
rotor blades. An increase in size
means an increase in power
capacity and a reduction in
maintenance costs. But it also
means that we are reaching the
limits of what our current
standards can handle when it
comes to design parameters.
High-quality flange
connection
An important aspect for the
quality of the flange connection is
28 | 01-2020

Boltlife has developed a
flange bolting methodology
utilizing ultrasonic load
measurement and custom
sequencing methods, that
create high-quality flange
connections, where all
loads are comfortably over
the minimum required
load, with very little scatter
between the individual
joints. The method used
focusses on load-driventorque,
as opposed to the
conventional torque-drivenload.
Furthermore, each
Measuring WTG flange
bolt in a flange will be
measured and evaluated
during the torqueing or tensioning load application. As a result, a
fully traceable and repeatable load assessment is available at all
times. Boltlife expects the method to be certified by DNV-GL very
soon. The company is also developing an ultrasonic permanent
remote measurement system.
Arnold Timmer, CEO of rotor blade specialist We4Ce, thinks that
Boltlife is on the right track. “The Boltlife technology produces
better connections, which potentially would allow us to design
larger blades, and that enables a higher capacity wind turbine.”
We4Ce is a technology provider; it develops wind turbine rotor
blades but does not build them. The company has over twenty
years of experience, ranging from 50 kW to 14 MW wind turbines.
Timmer: “A rotor blade must be able to absorb the forces from
wind gusts. But at the same time, it needs a certain level of rigidity.
” This means that a lot of force is exerted on the bolts and fringes,
which connect the rotor blades to the turbines. That makes it
imperative to tighten the bolts securely. It is of great importance to
accurately control the bolt preloading procedure. If the design
preload force is not valid on the actual turbine, this will result in
bolt failures and unsafe situations. Variations (or scatter) on the
prescribed preload force will always occur and for this reason, the
We4Ce designers take the expected scatter into account in their
designs. Controlling the preloading procedure in such a manner
that the expected scatter is lowered, will result in more optimised
blade root designs.
Reduction in maintenance costs
Prieshof: “Current bolt preloading procedures have inaccuracies
that can easily get to 30 to 40 % when it comes to torque to load.”
These are inaccuracies in which We4Ce has to make its
calculations.” Boltlife closes the flange comfortably above the
“We are reaching the
limits of what our current
standards can handle”
Blade flange bushing
minimal required load. Together with the lower scatter, this creates
a flange connection that is almost immune to fatigue damage.
Boltlife’s technology also reduces maintenance costs, Prieshof
explains: “We take measurements with a probe, which can be done
very quickly. Within ten seconds I have a re-measurement from
within the blade connection and I can read out the load
immediately.”
Currently, Boltlife is in the process of certifying its methodology
with DNV-GL. “This certification will guarantee that bolted
flanges meet the highest traceable quality standards and they can
expect considerable improvements in their Maintenance Plan.”
Whether certification alone is enough, remains to be seen; the
wind turbine market is a conservative one. Timmer: “I can imagine
that the market is careful to release another approach. Companies
are used to certain procedures and a new methodology could give
some challenges, which need time to settle in.”
But when it does, the biggest advantage is clear: safe upscaling of
wind turbines, which means more capacity and a big opex
reduction.
01-2020 | 29

Rotor Blades
Sabine Lankhorst
Interview with Redak
Proper blade
maintenance for
optimal turbine
performance
Blades have been the so-called ‘underdog’ in wind energy for a long time. Its use
was practical but not seen by definition as a vital element. Only later did the
industry became aware of its importance in the energy production of a wind
turbine. Dutch blade inspection and repair specialist Redak has witnessed this
process from the start.
Kader Benali is the owner of Redak, based in Noord-
Scharwoude. His professional experience in wind
energy dates back almost 30 years. After graduating
from high school he worked on several jobs before
joining Nedwind, a Dutch manufacturer of wind turbines. “At that
time I didn’t know that much about wind turbines and actually
thought they were built from wood, but as I have a passion for
technique I decided to give it a try.” This decision would dictate
his future career path.
Nedwind was at that time one of the main wind turbine
manufacturers in the world with an international customer base.
At some point the company was split. Nedwind continued with
the mechanical activities while the rotor blade manufacturing
activities were placed under a new entity, Rotorline. This enabled
Rotorline to also sell blades to other turbine manufacturers. Benali
joined Rotorline. It didn’t take long before the management of
Rotorline noticed his quality and asked him to specialise in
maintenance and repair of blades. For Rotorline he worked in the
Netherlands, the USA and Germany.
When Rotorline was sold in 1999 to LM Windpower, Benali
joined this company. He worked for LM for two years before
deciding to found his own company, Redak, in 2000, offering
blade service and inspections.
International reach
Even though a small company at first, he continued to work on
international projects. In fact, his first assignment was in Curacao.
Having Vestas as a regular client certainly helped but he was also
asked by other companies to perform blade inspection work on
projects all over the world. Countries where Redak worked include
South Africa, Australia, Jamaica, Thailand, Curacao, Chile,
Uruguay and Costa Rica. Benali: “Half of the time during my
career I spent abroad.”
In the Netherlands he is involved in both onshore and offshore
wind. Offshore, his company has performed inspection and repair
activities on the Noordzeewind project, also known as Egmond
aan Zee. Onshore, he is working for Vattenfall at their Haringvliet
wind farm where 6 Nordex 117 turbines are currently being
installed. Last year he signed a contract with Vattenfall for
maintenance work on 36 wind turbines at the Prinses Alexia wind
farm. His company is also performing inspections in the Deil wind
farm which is currently being built in the province of Gelderland.
Underestimated
Regular wind turbine blade inspections are nowadays part of the
operation and maintenance budget for a wind farm. This was not
always the case, explains Benali. For a long time, blades were not
seen as important. The focus was more on the mechanical part of
30 | 01-2020

Blade damage
Benali performing blade repair
‘When the leading edge starts to wear
it affects the aerodynamics, resulting
in a decrease in performance’
u Blade inspector requirements
Full GWO
VCA
Blade B Repair and Inspection Course
English in spoken and written
Medical G41 test (for offshore)
VOP
Irata
01-2020 | 31

the turbine. The industry was not aware yet that the quality of the
blades also has an influence on the production efficiency of the
wind turbine. He elaborates: “When the leading edge starts to
wear it affects the aerodynamics, resulting in a decrease in
performance.”
Therefore in the early days, his job consisted mainly in repairing
damaged blades and in the inspection of blades before
transportation and before being installed on site. Blades often get
damaged during transport. Not so much in the Netherlands, he
stresses. Here the transportation companies are more experienced
and transportation is bound to certain rules and regulations. In
countries that are new to wind energy this can be different. He
provides the example of South Africa where the government
dictates that local input is used. “Transportation companies were
not used to moving blades and often a lamp post or traffic light
was hit when making a turn”, he says. It is therefore important to
check the blades during transportation, for example when arriving
in port.
Blades, and the leading edge in particular, are prone to several
elements that can cause wear and tear like salt, lightning and the
wind itself, he continues, “In several cases I was called out for an
inspection overseas to find out that the blades were damaged
beyond repair. This could have been prevented with regular
maintenance.” He takes pride in his first project in Palm Springs,
USA. Here he performed planned maintenance on twenty turbines
over a period of 26 years. “In general, blade manufacturers provide
a 20-year warranty but they can last longer when taken care for
properly. In Palm Springs the turbines are now being replaced by
more modern turbines, however, the blades were still in good
shape”, he says.
It was only later on that the industry started to realise how the
blade quality affects the turbine performance and regular
maintenance was introduced. Benali: “Insurance companies also
started to require maintenance to take place, in general once every
two years.”
Inspection & Repair
“On land, first we make a preliminary observation of the state of
the blades from the ground, using a camera or sometimes drones.
Nowadays the cameras are of enough quality to do so. Based on
the results we decide whether repair is needed”, Benali explains.
Repair work can be performed in 99% of the cases with the blade
still connected. This is done by using rope access, a sky climber or
boom truck. “It is only occasionally that a blade is damaged to
such an extent that we need the blade to be dismantled and lifted
down to perform the repair work on the ground. In those cases the
damage is most of the time to the interior laminating. “To repair
this we would need to do new laminating. The epoxy that is used
needs to dry. This is done by means of a type of heat blanket
which exposes the epoxy laminate to a temperature of 60 degrees
Celsius during two hours”, he elaborates.
There are some limitations to doing repair work on site. When
using epoxy it is important that the air humidity is below a certain
level, less than 70 to 80%, says Benali. Ideally the temperature
Roos and Cerri Ann of Redak during offshore inspections
should be above 15 degrees Celsius. New, modern blades now also
require a vacuum system when performing repair work, he adds.
Offshore is a different story, both the inspection and repair are
being performed using rope access. There are exceptions he says.
“Once I was asked to perform repair work offshore on a blade that
was hit by lightning. In this case the damage was too big to repair
using rope access. We had to rent a platform which could be
installed on the transition piece and lifted up by cables.”
When asked whether he thinks drones will fully take over
inspections of blades offshore in the future he is doubtful.
“Drones, currently being used, can only picture the external
surface, they cannot provide a view on the internal layering of the
blade so you won’t be able to see when delamination is taking
place. The internal layering are the carriers of the blade. Do you
really want to risk making decisions based purely on the results
from drone images?”, he wonders.
Manpower
Since the start of the company in 2000 his company witnessed a
strong growth. He started to scale up a few years ago when he
realised he was growing too quickly to manage every single detail
himself. “I realised I had to transfer my knowledge and let others
do some management tasks. I also started to use a software system
for reporting and digitalising.”
Currently he has a fixed team of four people and around forty
persons working for him on-call. He can look back on a very busy
year in 2019, even to the point that he had to say no to a new
project. This has mainly to do with limited manpower. “It is very
hard to build an experienced, qualitative team”, he explains. “It
really took me a lot of time and effort to get the team I have now.
There are simply not enough experts in the Netherlands so I had
to attract people from other countries like Latvia and the UK.
With this team I know that I can deliver quality.”
His team also includes two women. Not enough to his liking.
“These women are amazing, they are not afraid to go out there
offshore and take on the activities that men have always done. In
fact, they are actually more meticulous than men!”, he admits.
One of his wishes is to get more Dutch professionals interested but
the fact that youngsters seem to prefer digital work rather than
using their hands worries him.
32 | 01-2020

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AWS_A5_Windmolenpark 190x135.indd 1 19-02-20 14:15

Rotor blades
Iref Joeman
Alternatives on
afterlife use of
amortized
rotor blades
Despite the many advantages of wind energy, there are also several
challenges this fast expanding industry is facing. One of these is the
recycling of the turbines at the end of their life cycle. The rotor
blades in particular are difficult to recycle. Much more research
will need to be conducted on this topic.
Superuse Studios considers
reclaimend rotor blades as an excellent
building material for urban furniture.
©Superuse Studios
u Iref Joeman
Iref Joeman completed his Bachelor in Mechanical
Engineering on the topic Recycling PET-bottles in Suriname.
He came to the Netherlands in the summer of 2016 in
pursuit of his Master degree. Initially at the Technical
University of Delft, but later on at the University of Twente.
In September 2019 he successfully obtained his Master degree
in Environmental and Energy Management. His thesis
treated on the recycling of wind turbine rotor blades.
34 | 01-2020

Wind energy, together with solar energy, are the main
drivers for reducing CO2 emissions globally. Their
share in the energy production will rapidly grow as
many countries have set ambitious targets to reach
a reduction in emissions or even a carbon neutral energy industry.
But what happens when these turbines reach the end of their life
cycle? Currently in the Netherlands, many of the first generation
wind turbines are being dismantled, making place for the new
much more powerful, improved generation turbines. This poses a
problem that is the same for the solar industry; namely the
recyclability.
Iref Joeman, while following a master in Environmental and
Energy Management at the University of Twente, one day came
across an article that discussed the challenges of recycling wind
roto blades after their lifecycle. At that time he was not aware of
this challenge and it aroused his curiosity. When it came to
choosing a topic for his thesis, he did not have to think twice. His
supervisor, who instantly approved his choice, got him in contact
with a consultancy who offered him an internship. Over a period
of five months he learned a lot from his colleagues and his
company supervisor. Last year he successfully completed his
master.
Main challenges
Of the wind turbine components, the rotor blades are the most
challenging to recycle as they are non-biodegradable. Normally,
a blade has a life expectancy of approximately 25 years when it is
kept in good conditions through adequate maintenance. This life
expectancy of 25 years may seem like a long period, but with the
growing size and number of rotor blades and wind turbines
globally will lead to disposal challenges in the future.
In his research, Joeman discussed four methods for the afterlife
treatment of rotor blades: pyrolysis, refurbishment, pavement
application, and landfilling.
His research consisted of data acquisition from comparable
research reports, articles and publications, complimented with
data from interviews he conducted with several parties that are
related to the topic of rotor blades. The interviewed parties varied
from researchers, companies involved in dismantling, refurbishing
and reselling end of life rotot blades, and parties active in
landfilling and or recycling parts of wind turbines.
Research results
With their robust size and weight and their non-biodegradable
characteristics, it will become more of a problem to dispose of the
rotor blades in landfills. Especially since many EU nations are
phasing out landfills.
One of the conclusions Joeman drew was that, although
challenging, recycling of rotor blades can be improved and
realised. The current technical state of the art of the afterlife
application of rotor blades is still in its development stage but
progress is already being made. Though limited, a few of the fore
mentioned applications can be used currently.
One of these applications is pyrolysis in which the blade is
decomposed in separate materials. Another application is
shredding the rotor blades into granulates which can be used as a
resource for pavements and other building applications or to
manufacture furniture, skateboards, decorative lamps, amongst
other things. This is done, for example, by Demacq in the
Netherlands and is currently the most viable option. Yet another
option is refurbishing end of life rotor blades in good conditions
and reselling them. This is currently done in the Netherlands,
around 20% of the amortized rotor blades are refurbished and
resold to countries like Italy, Greece, Asia, eastern Europe and
North Africa.
These options, however, pose their own challenges as the
incineration and transportation produces quite a lot of CO2
emissions.
Replacing the thermoset epoxy material with the thermoplastic
recyclable Elium is another viable option. Elium has been applied
to and successfully tested on rotor blades with lengths of 8 m and
25 m recently. There is no certainty on the performance and
application of rotor blades larger than 25 m regarding the use of
Elium. Regardless of the infancy of this application, the
application shows to have prominence in the near future.
The design and choice of material for the rotor blade is very
crucial considering the rising trend of wind turbines being
installed in the coming years. Rotor blades manufactured from
recyclable material like thermoplastics and polyester can be a
solution, but the mechanical and aerodynamic properties should
not be compromised only because of their recyclability.
Next steps
The reseach performed by Joeman and the outcome of his report
is the first step of many to come as this topic is still in its early
stage. Fortunately, technological research and development is still
in progress. Time and public awareness may be an issue and has to
be dealt with carefully.
Recommendation
In order to improve the whole recycling process, the following
should be further researched: the dismantling, transportation, and
location of the refurbishing or recycling facility need to be
improved to reduce transportation costs, CO2 emissions and the
time delay in getting all the necessary permits. This can be done
by either better planning and or technical innovation. Technical
innovation can be designing and choosing better recyclable
materials for the rotor blades, facilitating/improving the reverse
engineering process.
There should also be more research into further development of
available recycling methods. This can be achieved by making more
funds available for NGO’s, researchers and universities.
01-2020 | 35

Martijn Koelers
Rotor blades
Cross-sectoral collaboration
for innovation & automation
in rotor blades
Wind is a powerful renewable energy choice to
sustain the planet we all know and enjoy.
Competition in the wind industry has never been
fiercer. Reliable rotor blades are essential to
bringing down the costs of wind energy.
Technology plays a central role
in each wind turbine blade
(WTB), taking factors such as
materials, aerodynamics, blade
profile, and structure into consideration.
These factors define the performance and
reliability of the blade and require a high
degree of precision. Excellent craftmanship,
uniform processes, and flexible and
responsive manufacturing set-up are
needed to produce high-quality blades.
Innovation & automation
To get ahead in the competitive wind
industry, innovations are needed. Higher
efficiency in current processes and
introducing automation are key to ensure
decreasing LCOE. But it is not only
automation that will help. Along with these
developments, material research is
necessary as well as design, assembly and
logistic innovations.
Key to these different topics is the need to
collaborate with and learn from other
industries. The composites industry will be
one of the more prominent partners, they
have experience in automation of
production lines, albeit with smaller parts,
but this kind of innovation involves more
than simply implementing a new
technique.
Simultaneously, innovation in one step of
the value chain opens the door to further
innovation in a linked process. Automation
may lead to different ways of assembling
the blade, which can lead to the use of
different materials, and this then opens
new ways of designing the blade or vice
versa.
That said, all of this must not interfere with
current processes. There can be no
disruptive innovations in a live production
line.
Official support
These challenges can’t be solved by the
separate industries, rather external and
more formal nudging into the right
direction is needed. Sector clusters and
governments can pave the path into crosssectoral
collaboration. Help is needed to
facilitate these collaborations, the
industries have their role, but governments
could speed up the process by supporting
or demanding cross-sectoral initiatives.
An important factor in this kind of support
is the objective or the end result. Serious
investments are needed for the
implementation of new technologies on an
operational scale and come with big risks.
It would be highly beneficial for crosssectoral
collaborations if initiatives in this
area would get official support beyond any
technology readiness level and into a
mature phase of manufacturing readiness.
CompositesNL.nl is the Dutch Composites
Association
36 | 01-2020

Duurzame energie voor en door iedereen
Veiligheid als
sluitstuk
Ynso Suurendonk
en Jesse Don
www.duurzameenergie.org
Probeer WindNieuws nu vrijblijvend met een
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ontwerpstructuurVisie
coöperaties
wind op Zee stomen door!
Ad. Littel
Siward Zomer
energie-
nr.3 | 2014
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Duurzame energie voor en door iedereen
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EEn goEdE basis dE wind
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Van woorden
naar daden
Mirjam Tielen
GedraGscode
onder de
juridiscHe loep
Aaldert ten Veen
en Derek Sietses
de waarde
Van een
onafHankelijk
windrapport
Erik Holtslag, Bob
Schulte, Rolf de Vos
nr.1 | 2015
wind op land
en de proVinciale
staten
Verkie ZinGen
Ad. Littel
VRIJDENKEN
OVER HET
ELEKTRICITEITS-
NET
VERMINDEREN
VAN EFFECTEN
VAN WIND-
TURBINES OP
VLEERMUIZEN
PARTICIPATIE
BIJ WIND OP ZEE
WINDDAGEN
2018
BEURS EN
PRESENTATIES
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Event
Benno Boeters
Offshore Wind Innovation Challenge 2019
Noise barier with air
bubbles for piling
Marine Performance Systems (MPS) develops a system with air
bubbles that absorb and reduce noise. On 9 December 2019, the
company won with its concept the Offshore Wind Innovation
Challenge, organised by Innovatielink and Offshore Wind Innovators.
Driving wind turbine
monopiles in the seafbed
results in a large amount of
noise underwater and in the
seabed. The hammering by the pile driver
can produce 170 to 180 dB of sound; that
is comparable with the sound produced by
a firing cannon. Should you swim nearby
in the sea during the pile driving, you
would turn instantly deaf. Moreover, in
the future monopile diameters will
increase, and therefore there is a growing
demand for technological solutions that
reduce the underwater noise. After all,
authorities around the North Sea and
elsewhere enforce strict limits in order to
minimise damage to nature, fish and sea
mammals.
For this purpose, Marine Performance
Systems (MPS) develops a system with air
bubbles that absorb and reduce noise.
When the company won with its concept
the Offshore Wind Innovation Challenge,
Van Oord and other large offshore
contractors responded immediately and
already in January, a month later, meetings
were planned to discuss cooperation and
carry out experiments in Wageningen at
the Marin (Maritime Research Institute
Netherlands).
There were three other finalists in the
Challenge. Two of them were focussed on
the design of new oyster cages that must
enable the growth of oysters on the seabed
near offshore wind farms in the North Sea.
The fourth contestant was a company that
uses sound to measure friction, tension
and wear in jointed bolts and thus
increases the efficiency of the maintenance
management of wind turbines. (see Boxes)
“We know a lot about bubbles”, says Pieter
Kapteijn, Chief Technology Officer at
MPS, in his presentation in the Oude
Bibliotheek in Delft. He mentioned an
additional reason for his evident selfconfidence;
he found himself back on
familiar territory because once in this
building he was cramming to complete his
study as civil engineer.
His company, with facilities in Rotterdam
and Copenhagen, started in 2014 with the
development of Air Lubrication, an air
bubble drag reduction system for vessels.
By emitting air bubbles along a vessel’s
hull, the drag of a vessel can be reduced
with 30 to 40 percent. In that case it is of
paramount importance that the air bubbles
are emitted in the boundary layer between
hull and water, that the bubble size is kept
constant and that the bubbles can have
their effect along the whole length of the
vessel.
Kapteijn’s colleagues and co-founders at
MPS, Frode Lundsteen Hansen and Fulko
Roos, made contact with Van Oord, and
that company encouraged them to work
out the idea of a noise barrier with air
bubbles.
“Sound forces an air bubble to vibrate and
that resonance supplies energy or heat to
the bubble”, explains Kapteijn. “At the
same time, that bubble spreads the sound
pulses around to other bubbles, that will in
turn absorb the vibration. It reflects in all
directions. Thus, it is about absorbing –
from vibration to heat – and scattering.
That results in noise reduction.”
During the piling of the tubular monopile
in the seabed the hammering of the pile
driver causes sound waves that propagate
from up to down and back up through the
pipe. A part of the noise is radiated to the
surrounding water, and another part
causes a low frequency vibration in the
seabed, that will also be reflected upwards
to the water surface.
“For the noisiest part of the sound
spectrum, between 30 and 3000 hertz, we
introduce air bubbles with a specific size, 7
to 0,3 millimetre diameter. It is essential
that we continuously tune the diameter of
the bubbles to the changing frequencies,
because when the monopile is driven
deeper into the seabed, the sound
frequencies change”, explains Kapteijn.
“Noise mitigation is all about control.”
38 | 01-2020

Monopile installation by Van Oord at Gemini OWF, © Gemini Windpark
“We are now working on an active system
in which continuously performed
measurements and feedback result in the
oscillators producing air bubbles with the
optimal diameter. For instance, when the
strongest noise is around 400 Hz, the
oscillator will create bubbles with a
diameter of 1 to 2 millimetres.”
“We know how it works in theory, we are
all in agreement about that. Now we have
reached the engineering phase in which we
continue the development with other
partners, such as Van Oord, towards a
practical, working system. We are confident
that this approach will offer a solution and
mitigate the underwater sound
explosions”, according to Kapteijn.
u Oyster reefs
Ecological values were the focus for two other contestants in the Innovation Challenge.
The British ARC Marine (not to be confused with the Dutch company of the same name,
producer of teak shipping and yachting equipment) makes concrete reef cubes, that can
be combined modularly to make every desired shape of oyster reef.
The two representatives of the Brixham, South East England based company, were
wearing dark grey T-shirts advertising their goal: ‘accelerating reef creation’. Director Tom
Birbeck showed the audience a map dated 1890 that depicted north of the Wadden Sea
an area of 20,000 km2 that was covered by oyster beds. Those have disappeared by
‘destructive fishery’; bottom trawling with nets that are weighted with chains can wreak
havoc on the seabed.
The hollow reef cubes, with sizes of 1, 0.5 or 0.25 m3, do not only offer an inviting habitat
for oysters and other marine life, but can also offer protection to submarine cables and
pipelines, Birback demonstrated. And the cubes can be used for coastal protection as well.
Annemiek Hermans of engineering and consultancy firm Witteveen+Bos demonstrated a
different design to enable oysters to grow below wind farms, the O-float. This is a new type
of oyster cage as well, but it does not rest on the seabed, as it floats thanks to a balloon
above it and an anchor beneath it. That prevents the oyster bed getting covered by sand.
u Sound measures stress
Tribosonics, a company in Sheffield, UK, reached the final of the Innovation Challenge with
a technology that uses sound to determine the tension in already mounted bolts.
Pieter Kapteijn (L) and Frode Lundsteen
Hansen (right), resp. CTO and CEO of Marine
Performance Systems
A wind turbine contains thousands of bolted joints that are fastened with a precise force
and lubrication. Determining the condition of the connections and the possible wear after
an installation has been in operation for a while, is a very labour-intensive operation,
especially in the case of offshore turbines. Christina King of Tribosonics (“We are very
good at measurement systems”) showed how the tension in a bolt can be measured
without turning the bolt or the nut. Tribosonics (tribology is the science of friction) sends a
sound pulse through a bolt, along the entire length. The echo of the ultrasonic pulse forms
an indication of the (surplus of) tension. The technology is also capable of evaluating the
bearings in the gearbox of a turbine.
01-2020 | 39

General news
MOOI innovation scheme
In February, a new 2020 subsidy
scheme MOOI (stands for Missiondriven
Research, Development and
Innovation) was officially announced
in the Goverment Gazette. The new
scheme, with a budget of 65 million
Euro, is offered by the Topsector
Energie and TKI Wind op Zee
organisations, together with RVO.nl
(Netherlands Enterprise Agency).
The MOOI subsidy scheme supports
integral solutions that contribute to
the energy transition. It is based on
the long-term mission-driven
innovation programmes (MMIP’s) by
the Topsector Energie and aims to
speed up the process for innovations
to market entry.
The scheme is intended for projects in
the area of offshore wind (10.1 million
Euro), onshore renewable energy
(10.9 million Euro), built environment
(27 million Euro), and industry (17
million Euro). The submission period
is divided in two phases, a preliminary
round and the final submission. All
projects must first be submitted before
20 April 2020, 5 PM. The submitted
applications are then evaluated by an
advise committee. This has been
introduced to provide applicants the
opportunity to improve their
applications. The deadline for the final
submission is 8 September 2020, 5
PM. The projects need to meet certain
criteria. More info can be found at
rvo.nl/mooi.
SDE++
The tender round for the first SDE++
subsidy scheme will open on 29 September
and close on 22 October 2020. There is 5
billion Euro available in this round.
SDE++ is the succesor of the SDE+ scheme.
It builds further on some of the features
from the SDE+ but is expanding the
categories of technologies that can apply for
subsidies. A new principle in the SDE++ is
the ranking based on expected subsidy per
tonne of avoided CO2 emissions.
The Minister of Economic Affairs and
Climate Policy, Wiebes, aims to publish the
SDE amendment decision in April this year.
The publication of all underlying regulations
concerning the opening of the SDE++ is
expected this Spring. For the decision and
regulations an approval from the European
Commission is also required.
KenzFigee launches
new rope actuated
knuckle boom subsea
crane
Crane and lifting specialist KenzFigee
launched their new knuckle boom subsea
crane. This new generation rope actuated
crane builds on proven technology but with
improved features for optimized daily
operations, safety and operability, without
compromising to lifting capacity from
approximately 400 tonnes up to 2,000
tonnes.
For the new design, KenzFigee
incorporated their clients’ requirements.
These were mostly related to improvement
of operational safety and workability.
Plan for further cost
reduction in wind and
solar on land
The Dutch associations NVDE and
Energie-Nederland have presented an
action plan to further reduce the cost of
electricity generated by wind and solar
farms in the Netherlands. The associations
worked together with companies from the
wind sector, united in NWEA, the Dutch
wind energy association, and the solar
industry, united in Holland Solar.
4 areas of improvement
Several agreements have been made in the
Climate Agreement to reduce the cost of
electricity from solar and wind.
The plan focuses at measures that can be
taken or already taken by the industry itself
to lower the cost of electricity. The wind
and solar sector have identified 4 areas of
improvements, to be achieved by
cooperation; more efficient management
through standardisation, improvement in
© KenzFigee
The new knuckle boom subsea crane
includes improvements including a high
safe working load-up of up to 2,000
tonnes, a decreased hook weight and
pendulum length, full deck coverage
including reach at minimum radius and a
lifting height and reach for tall objects.
the eligibility of the projects, optimalisation
of the production process by improved
predictability and monotoring, and an
optimalisation in grid connection.
When successful, these measures could
achieve a cost reduction of several Euros
per MWh. Additional reductions can be
achieved by technological developments
and other agreements stated in the Climate
Agreement. These measures combined
should make it possible to develop wind
and solar on land without the aid of
subsidies by 2025.
40 | 01-2020

Haliade-X: World
record holder on
Maasvlakte II
Recently, the world’s most powerful wind
turbine, the Haliade-X of GE Renewable
Energy, started operating on the most
western point of Maasvlakte II. The blades,
with a length of 107 metres, are good for a
capacity of 12 MW and an estimated gross
annual energy production of 67 GWh,
enough energy to power 16,000 European
households. During a festive inauguration
on 17 December 2019, the wind turbine
was deployed.
The owner of this world record holder is
Future Wind, a consortium consisting of
General Electric Renewable Energy,
Pondera Consult, and Sif Netherlands.
The Haliade-X is built on the site of Sif, a
producer of turbine foundations, bordering
FutureLand, the information centre of
Maasvlakte II. In the coming years, the
owners and TNO will perform extensive
testing on the 12 MW mega turbine for
certification. To give an idea of the size: the
8 M turbines of Borssele I and II have a
rotor diameter of 164 metres, whereas the
rotor of the 12 MW turbine of GE has a
diameter of 220 metres.
The Haliade-X could as easily have been
built in Denmark or France, but thanks to
a smooth issuing of permits and a
logistically favourable location, Maasvlakte
II was chosen. The location is just onshore,
but enjoys a steady wind blowing in from
the sea, and of course the turbine is
intended for offshore wind farms. GE
Managing Director Ward Gommeren
expects that in 2022, Ørsted will install ten
to fifteen 12 MW Haliade-X’s at the East
Coast of the United States, the Skip Jack
Project near Rhode Island. “Though for
the tender procedure for the Hollandse
Kust (Noord) Wind Farm Zone, the
Haliade-X offer also an opportunity”,
Gommeren says. The tender submission
will be in April 2020, the construction
phase is planned for 2023-2024.
LM Wind Power produces the hybrid
carbon blades that exceed the length of a
football field. Their flexibility and relatively
low weight contribute to the power of 12
MW, allowing the Haliade-X to exceed a
limit that a few years ago wind turbine
constructors deemed unsurmountable.
The blade length also leads to higher
energy production at low wind speeds.
They are made in the LM Wind Power
production facility at Cherbourg, France.
The nacelle is produced in the GE factory
General news
in Saint Nazaire (France). Contractor GRI
in Seville, Spain builds the tower with a
height of 135 metres. Two brand new 1350
tonnes Liebherr cranes (‘the biggest you
can find’) were needed to build the
Haliade-X. The tips of the blades reach a
height of 244,4 metres; that is in
accordance with regulations, higher is not
allowed. Next to the Haliade-X will arise a
measuring tower built by Extentruder in
France. That tower will supply all desired
information on wind, temperature and
humidity.
TNO will play a major role in the tests that
are planned during the next years. Sensors,
strain gauges and accelerometers in and on
the turbine components, already installed
during the construction phase, will submit
data on the performance of the
construction in wind and weather.
According to TNO/ECN, this is the first
time a wind turbine will be tested in such a
manner.
The Haliade-X will also be equipped with
instruments that ‘see’ approaching squalls
and turbulences. Reflecting laser pulses of
the ‘light radar’ will warn against all too
heavy strains, so the blades can react in
time and change their angles. The
aeroelasticity, that is the extent of bending
and twisting of the blades, and the
prevention of resonation of the blades, are
main issues during the tests. Also the yaw
system (that steers the blades and the
nacelle into the wind) can in the event of
approaching strong winds be set to a larger
resistance, thereby keeping the rotation
speed and the temperature within the
nacelle within limits.
© Pondera
At the inauguration, Ward Gommeren
emphasized again that the 12 MW turbine
will make it possible to take another step in
reducing the Levelized Cost of Energy
(LCoE), the price per MWh. The more
power wind turbines produce, the less there
are needed in a wind farm. That will
reduce the costs of installing the
monopiles, the nacelles and the blades, and
later on the number of maintenance
inspections at sea.
According to Gommeren, there are already
five or six installation vessels in service that
are capable to install the Haliade-X. He
expects that ‘within a few years’ globally a
large number of these heavy lift vessels will
be available for the setting up of these
mega turbines.
Benno Boeters
01-2020 | 41

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