Growth through Research, development & demonstration in Offshore Wind


Monopiles dismantle themselves with water pressure

4 June 2020, Cobouw

At the end of their service life, monopiles used for the foundation of offshore wind turbines can be removed from the ground by sealing them and pumping water into them under pressure. Scale tests conducted in the Deltares laboratory have shown this. The remarkable experiment requires a follow-up. Using this concept can save hundreds of tons of steel.

Read the full article in Cobouw (in Dutch)


Two pre-proposals submitted under MOOI-call

25 May 2020

Monday 18 May was the first deadline for submitting pre-proposals for the MOOI call for tender. MOOI stands for Mission-driven Research, Development and Innovation and is a subsidy scheme that supports projects and/ or programs applying a more integral approach. The integral approach should be reflected in a multi-disciplinary composition of the consortium and/ or in the themes being addressed. This scope is significantly broader than the HER (Renewable Energy Regulation) scheme that is used for most GROW projects. Within the HER, only research and development on specific technological innovations are  supported.

Two pre-proposals were submitted by consortia with GROW partners in the lead, both addressing the theme of sustainability:

An advisory committee will review the pre-proposals. With feedback given after review, consortia can prepare a definitive proposal that needs to be submitted before 6 October 2020. The overall subsidy budget for offshore wind projects is 10.1 million euro.

Sustainable Installation of XXL Monopiles (SIMOX)

About a quarter of the total wind turbine investment is spent on the turbine foundation. Monopiles are by far the most commonly used foundations for offshore wind turbines in the North Sea and it is expected to remain like this in the near future. Monopiles are straightforward to fabricate, relatively inexpensive to manufacture, use less space on deck on transport vessels, and are reliable.

Currently, the dominant method used to drive monopiles into the seabed is the so-called hydraulic impact piling (hammering). Wind turbines with electrical capacities up to 10-15 MW (or higher) will require the use of even larger monopiles (XXL monopiles with diameters up to 12 m). Conventional installation by hammering presents challenges in terms of noise reduction measures, the limited installation time during the year due to the environmental regulations, and the expected heavier design of the monopile. Innovative and integrated installation solutions are therefore required, both in terms of cost-effectiveness as well as for planning, to be able to roll-out large number of wind turbines to adhere to the Netherlands’ energy transitions plans as stipulated in the Dutch climate agreement (Klimaatakkoord, missie A).

The SIMOX project should lead to the following results:

The research in a laboratory and field tests will cover the following installation methods: the Gentle Driving of Piles, the conventional vibro-hammering (axial vibration), the BLUE Piling Technology, and fluidisation (jetting), considered separately or in addition to one of the technologies above. Further, these technologies will be tested for their capability for end-of-life full decommissioning of the monopiles.

The 3-year project – if and once the subsidy is granted – is coordinated by the TU Delft together with 15 project partners, 12 of those are GROW Partners.

SolUtions for offshoRe wind FArms with a Circular Economy (SURFACE)

SURFACE focusses on the overall balance of reduction in raw/ waste materials and emissions by design and optimisation of the fabrication, installation, operation and decommissioning processes during the full life cycle of an offshore wind farm.

The overall goal of the project is to increase the circularity of offshore wind farms. It is well recognised that wind energy emits far fewer greenhouse gases compared to fossil fuel power generation. However, the vast growth expected for the industry requires us to find solutions to its increasing emissions and environmental impacts.

SURFACE will achieve this and focuses on impactful topics where pragmatic system solutions are within reach for both operating (before 2030) and also new to be built wind farms. 

Offshore wind energy has moved rapidly from a young aspiring renewable energy source to a cornerstone of our energy transition. For offshore wind energy by 2050, 26 times the additional capacity needs to be installed than the current install base to meet our targets. Not only the number of wind turbines will increase, but also larger turbines will be installed with vast composite and steel structures. The largest turbine today in the market is already rated at 12 MW with a rotor diameter of 220 meters. The scale and speed at which wind farms are going to be built are unprecedented. Vast quantities of raw materials will be needed. For context, the amount of composite material used for one 12 MW wind turbine is in the order of 160 tonnes, and the amount of steel 2,845 tons (including monopile). Scaled up to a typical 750 MW wind farm this equates to over 10,000 tonnes of composite and almost 180,000 tonnes of steel respectively. Operating such a wind farm with fossil fuel-based vessels for installation and maintenance equates to a CO2 emission of more than 7,000 tonnes-eq per year.

Our energy transition ambitions can be realised; however, we also need to recognise quickly as a sector that we must become even more sustainable. Only by thinking and acting circularly, a truly sustainable and socially thought-leading industry can be realised. 

The project will explore various solutions for different aspects of the offshore wind value chain: circular blades and remanufacturing, sustainable operations and decommissioning, and integration with nature.

The 4-year project – if and once the subsidy is granted – is coordinated by TNO and has currently 22 project partners, of which 7 GROW partners.

offshore wind farm installation, source innogy
offshore wind farm installation, source innogy
source Sif
source Sif

To develop a proven methodology for the improved design of monopiles under environmental cyclic loading

11 May 2020

The GROW partners Deltares, Eneco, IHC, innogy, Shell, TU Delft, Van Oord and associate partner Siemens Games kicked-off the MIDAS project. The project "Monopile Improved Design through Advanced cyclic Soil modelling" targets to develop a fundamental understanding of the interaction between monopile and soil under cyclic loading by combining advanced experimental and computational modelling.

Offshore wind turbines are getting bigger and more powerful. In the next decade, project developers will install turbines in increasingly harsh marine environments and deeper waters. This will present significant challenges for the design and installation of supporting structures.

MIDAS focuses on sandy soils, especially relevant for the North Sea. The project partners Van Oord and Siemens Gamesa will use the acquired knowledge to improve their technical models. Optimization of monopile design will further reduce the cost of foundations and ultimately lead to lower electricity costs.

Please, find out more about MIDAS

source Eneco
source Eneco

World’s first full-sized submerged Slip Joint successfully installed

25 April 2020

On 25 April, Van Oord installed successfully the first foundation with a Slip Joint at the Borssele Wind Farm Site V. SIF has made the Slip Joint and DNV GL has certified it. This step was made possible due to the innovation realized by the GROW consortium. Last year, DOT successfully completed the GROW project 'Slip Joint Offshore Research (SJOR)'. In close collaboration with Heerema and the GROW partners Eneco, SIF, Van Oord, TU Delft and TNO, DOT tested this innovation for the first time under offshore conditions. The test was carried out in Eneco's Amalia wind farm on the North Sea.

The Slip Joint is an alternative connection between a monopile and a transition piece. It consists of two conical sections placed on top of each other. The Slip Joint is based on friction, with the weight ensuring firmness and stability. Installation takes place by sliding the wind turbine’s foundation elements over the monopile, without having to use grout or bolts. Unlike standard solutions, the Slip Joint makes a submerged connection possible, allowing for a more balanced weight distribution between monopile and transition piece.

It therefore opens up the possibility of manufacturing larger foundations for the next generation of wind turbines with existing manufacturing facilities and installing them at deep-sea locations using existing vessels. The (conical) sections that make the connection are produced using standard manufacturing methods. The Slip Joint provides a rapid, simple and safe installation solution in combination with reduced maintenance for the duration of the project.

Find out more about SJOR

Installation transition piece Borssele Wind Farm V, Source photo:  Van Oord
Installation transition piece Borssele Wind Farm V, Source photo: Van Oord

New project: Bubbles JIP

1 April 2020

To achieve more efficient and effective use of bubble curtains for noise mitigation in offshore installation projects

In April 2020, GROW partners start the Bubbles JIP project. This Joint Industry Project researches the sound propagation of piling noise through water and soil and the physical mechanism of noise attenuation by air bubbles. The Dutch maritime institute MARIN leads the project and is supported by six GROW partners (Boskalis, Royal IHC, Seaway7, TNO, TU Delft and Van Oord) and by two visiting partners (Heerema and Wageningen Marine Research). The expected results of the project are:

GROW expects to complete the project in the spring of 2022.  
Find out more about Bubbles JIP

Bubble curtain
Bubble curtain
Bubbles JIP chart
Bubbles JIP chart

Video: HyPE-ST

2 March 2020

Sustainable monopile decommissioning, one step closer to circularity

TKI Wind op Zee produced and released an informative video about The Hydraulic Pile Extraction - Scale Tests (HyPE-ST) project. The aim of the project is to increase the fundamental understanding of the hydraulic extraction of monopiles from the seabed. The project was carried out by the GROW consortium and coordinated by Innogy and Deltares.

This video informs about the technique and the scale tests. The project team conducted tests in the test basins of Deltares to better understand the interaction between the pile and the ground during extraction. The test provided essential understanding on the breakout pressure of the pile. This knowledge is necessary before the sector can apply safely and efficiently this extraction technique on a full scale.

Find out more about HyPE-ST


Video: Gentle Driving of Piles

Twist the cork and it becomes thinner

24 december 2019

TKI Wind op Zee released an informative video about a promising new installation technique. The Gentle Driving of Piles (GDP) method aims to make the pile installation process faster, cheaper and more efficient than current methods. GDP is based on simultaneous application of low-frequency and high-frequency vibrators exciting two different modes of motion on the monopiles. By doing this, the monopile gets a little bit thinner. This makes it easier to drive the pile into the soil. 

The traditionally used method of impact hammering leads to the opposite: monopiles expand a bit when hammered, leading to increased resistance to drive the pile into the ground. The GDP method is called “gentle” for its envisaged capability to reduce the driving loads and the emitted installation noise which is harmful for the environment, e.g. to mammals and fish. We expect that the advantages of the GDP method becomes even more profound by the anticipated increasing size of monopiles.

Get an impression of the technique here:

The TU Delft is coordinator of this project and supported in the execution by CAPE Holland and eleven GROW partners Boskalis, Deltares, DOT, Eneco, IHC, innogy, Seaway 7, Shell, SIF, TNO, and Van Oord.

Find out more about this GROW project Gentle Driving of Piles

GDP DEMO Day Successful

7 November 2019

On Friday the 1st of November the Gentle Driving of Piles (GDP) project hosted a demonstration day of the field tests at the second Maasvlakte in the Netherlands. On that day the use of a newly developed pile installation method based on simultaneous application of low-frequency and high-frequency vibrations was demonstrated. Over 100 visitors witnessed a successful test installation and attended the symposium in the afternoon with technical presentations about GDP and other related subjects within the Offshore engineering research group of the TU Delft.

The field tests are part of the GDP research project that aims to develop a novel pile driving technique that simultaneously improves drivability, reduces noise emission, and ensures that the soil bearing capacity stays intact. In this experimental campaign that is executed from October to December 2019, the newly developed GDP shaker is tested and compared to traditional vibratory and impact hammers. In total eight piles were installed of which four were driven with the GDP shaker, three by impact hammering and one by vibratory driving. At the end of this year the field test finishes, and the piles will be removed.

In the next 2 months the installed piles will be laterally loaded and the behavior of the soil around the piles is monitored. The highly instrumented pile and soil monitoring will provide a unique set of data which will be used to validate three new prediction tools. These numerical models will provide the required tools to be able to predict the drivability of offshore monopiles, the state of the soil during and after driving the piles, and the noise generated during gentle driving of piles. Next step is the development of the GDP shaker in an offshore full-scale test and in stiffer soil types.

GDP is a project within GROW, the joint research program in offshore wind that initiates research and accelerates innovations. Delft University of Technology (TU Delft) is coordinating the project with the following project partners; Boskalis, Cape Holland, Deltares, DOT, Eneco, IHC IQIP, Innogy, Seaway7, Shell, SIF, TNO and Van Oord. This project is funded by RVO and supported by TKI Wind Op Zee. 

Find out more about GDP

Gentle Driving of Piles Demoday
Gentle Driving of Piles Demoday
Demonstration of Gentle Driving of Piles
Demonstration of Gentle Driving of Piles

Video of successful decommissioning slip joint connection

19 September 2019

Find out more about the SJOR project and the slip joint connection


After a year of successfully testing the Slip Joint connection, the DOT wind turbine is decommissioned

16 August 2019

With the removal of the DOT wind turbine all phases of this concept’s lifetime are investigated and successfully put to the test. 

Friday morning the 16th of August 2019 the wind turbine, outfitted with a Slip Joint connection, was successfully removed from its monopile foundation. 

The DOT wind turbine was located in Eneco’s Princes Amalia Wind Park off the coast of IJmuiden, the Netherlands. The complete wind turbine was picked up in a single lift from its monopile foundation to be transported towards and backloaded on the quay of Sif Rotterdam for further onshore decommissioning. Same as during the installation, the offshore removal of the wind turbine was executed by Heerema’s DCV Aegir being operated on its Dynamic Positioning System. This way of working in combination with the use of a slip joint connection is noticeably faster than current industry practice.

With the removal of the wind turbine all necessary data regarding the Slip Joint connection is successfully gathered and is now being processed and used for validating by the project partners.

Find out more about the project and the slip joint connection

DOT Wind Turbine
DOT Wind Turbine

GROW side-event at the WindDays - Foundation Innovation: Presentations are available now

13 June 2019

Did you visit our side event on foundation innovation at the WindDays and do you want to have an other look at the presentations? Or were you not in the possibility to attend and want to know more about foundation innovation?

During this side-event, GROW presented several new developments in the field of offshore foundations. The first (intermediate) results of three GROW projects were presented;

Find the presentations here

GROW side-event at the WindDays - Foundation Innovation

12 June 2019, 11.15 – 12.45, WTC Beursplein 37, Rotterdam, Leeuwen Room II

Interested in the developments in offshore wind foundations?

Please be welcome at our side-event on foundation innovation at the WindDays in Rotterdam on 12 June 2019.

During this side-event, GROW presents several new developments in the field of offshore foundations. David the Jager, director of GROW, will lead you through the program. The first (intermediate) results of three GROW projects will be presented;

The presentations will be followed by a discussion.

Find out more about the presentations


Let us know that you want to visit the GROW side-event by registering here.

Please note: You also need to purchase a WindDays Exhibition ticket to enter the GROW side-event. You can buy ticket to the WindDays exhibition here.

Maxim Segeren, Reinder Jorritsma and Ahmed Elkadi
Maxim Segeren, Reinder Jorritsma, Sander Suur and Ahmed Elkadi

Innovation doesn’t stop with subsidy-free tenders

22 March 2019

In the coming years, offshore wind energy in the Netherlands will get a big boost. By 2030, the total installed offshore wind capacity is planned to be 11.5 GW. Where a few years ago, offshore wind was seen by the general public as the most expensive climate solution, it has now become one that needs almost no financial support from the Government. Technological and non-technological innovation have contributed significantly in bringing the cost of offshore wind energy down. With offshore wind being more competitive, do we still need to invest in innovations in this area? The answer is YES!

Wind Energy Magazine spoke to David de Jager, director of GROW, a consortium of about 20 players in the Dutch offshore wind energy industry that work towards bringing down the cost of offshore wind and increasing the role in the energy system by exchanging knowledge and intensive cooperation. 

You can find the complete interview with David de Jager here.

David de Jager
David de Jager

First offshore wind turbine using the Slip Joint connection successfully installed

30 September 2018

SJOR project tests innovative connection offshore: ready-to-use installation within an hour.

This morning the DOT wind turbine was successfully installed on its previously installed monopile using a Slip Joint connection. The Slip Joint is an alternative connection between an offshore wind turbine and its foundation. It works and looks like two paper cups upside down stacked on top of each other. The connection is based on friction, where the weight ensures a firm and stable connection. Installation is done by simply sliding the wind turbine over the monopile without the use of grout or bolts. This simple mechanism allows for cost reduction in material, equipment & personnel as well as allowing for a shorter installation time. It is the first time a slip-joint connection is deployed offshore. 

The DOT wind turbine is located in Eneco’s Princes Amalia Wind Park off the coast of IJmuiden, the Netherlands. The complete wind turbine was picked up in a single lift by Heerema’s DCV Aegir from the quay of Sif Rotterdam and transported towards its designated location. The installation of the wind turbine took within an hour in total, which is noticeably faster than usual installation. Jan van der Tempel, Director of DOT BV: “This offshore installation is a major milestone in the commercialisation of the Slip Joint.” The wind turbine will stay offshore for a year to test and collect data regarding this innovative connection after which the gathered data will be processed and used for validating lab tests by both TU Delft and TNO.

Find out more

Installation slip joint connection magnify
Installation slip joint connection
Installation of turbine with Slip Joint connection

GROW and the Ministry of Economic Affairs and Climate Policy sign collaboration agreement to strengthen innovation in offshore wind energy

22 March 2019

Offshore wind energy is a key technology in the transition of our energy system towards sustainability. This is demonstrated by its dominant position in several energy agreements and reports on the energy transition. Also the draft Climate Agreement is heading in that direction. GROW, the consortium of leading Dutch offshore wind industry and research partners, is working hard on the required innovations to fulfil this important role. The Ministry of Economic Affairs and Climate Policy fully supports GROW. “The Dutch offshore wind sector represented in GROW is leading the way.” said Sandor Gaastra, Director General Climate & Energy at the Ministry of Economic Affairs and Climate Policy. “That is why my ministry signed a collaboration agreement with GROW. With this agreement we will further strengthen the position of offshore wind energy and of the Dutch wind sector.”

GROW is contributing to the energy transition by working on the societal task of making the energy supply more sustainable. It carries out a coherent program of Research, Development & Demonstration (RD&D), ranging from more fundamental research to the demonstration or rollout of offshore wind energy innovations. Research questions within the program include: How can the wind turbine installation process be improved further, at lower costs? How can the environmental impact of noise, for example, be limited or even be prevented? How can maintenance activities be carried out as effectively and efficiently as possible?

Sandor Gaastra: “Due to the intensive cooperation and knowledge sharing within GROW, with parties representing the entire offshore wind value chain, successful innovations can be realised relatively fast. GROW is therefore an interesting discussion partner for us and we are happy to formalise this cooperation.”

Chairman of GROW Peter Terium: “To achieve the energy and climate goals, the government, industry, knowledge institutions and civil society organizations must work together even more. That starts with innovation. This agreement helps us to keep up the pace of innovation. "

Signing of the collaboration agreement
Signing of the collaboration agreement
Signed collaboraton agreement a magnify

David de Jager is GROW’s new Director

15 May 2018

As of today David de Jager succeeded Ernst van Zuijlen as Director of GROW. After being responsible for the programming of RD&D on offshore wind energy for about ten years (as Director of FLOW, TKI Wind op Zee, and GROW) Ernst will pitch into both product- and project development in the same area.

David de Jager comes from consultancy firm Ecofys and has almost 30 years of experience in renewable energy, notably on the interaction of technology development, policy design, and finance. Over the past decade he acted as Operating Agent for the IEA-RETD, an international research program of the International Energy Agency.

David de Jager
David de Jager

GROW consortium officially launched at Wind Days 2016

The GROW consortium was officially launched at the WindDays 2016 conference held in Rotterdam, the Netherlands. This consortium of leading Dutch companies and knowledge institutes involved in the offshore wind industry has created an innovation programme that aims to reduce the costs of offshore wind energy.

GROW launch during WindDays 2016
GROW launch during WindDays 2016