The making of Borssele offshore wind farms

Before it was named one of the backbones of energy transition and saw multiple new projects announced worldwide, and in more countries than ever before, offshore wind had one main quest – cost reduction. While this is, to some extent, also true today – the industry has long passed the price thresholds set several years ago and a few of the sector’s firsts in this regard happened in the Netherlands.

Back in 2016, the Dutch government announced the winners of its first two Borssele tenders, first in July when Ørsted (then DONG Energy) crossed the mark of € 100/MWh by bidding 7.27 Eurocents per KWh, and then five months later when the Blauwwind consortium made headlines with a new record price – 5.45 Eurocents per KWh – thus brining the sector close to its aim of reaching levelized cost of energy (LCoE) of EUR 50 per MWh.

This led to the cost of building and operating the Borssele 1 & 2 offshore wind farm to be some € 2.7 billion cheaper than previously estimated and Borssele 3 & 4 to have even higher subsidy savings – needing a subsidy of only € 0.3 billion instead of the originally anticipated subsidy of € 5 billion. And to top it all, the Netherlands saved some room in the Borssele Zone to support offshore wind innovation to bring the costs further down and to facilitate novel approach to building sustainable offshore wind farms. At the Borssele V innovation site, the Dutch government is backing demonstration projects with € 15 million and the electricity produced by the two

wind turbines installed there with a maximum subsidy of € 35 million.

So, how did the Netherlands reach the point where the country would pay less in subsidies while also keeping the developers interested in building and operating wind farms off its coast? According to the Dutch government, setting up a tendering process based on competitive bidding – under which the developers are awarded both subsidies and permits – and the government taking care of all conditions for building offshore wind farms were the key reasons for the low strike prices offered.

Before the competitive procedure was implemented, companies had to receive consents before they could compete for a grant. Moreover, installing the export cables to connect the offshore wind farms to the grid on land was also the developers’ responsibility. Now, the Netherlands sets the stage for the construction of offshore wind farms, including siting, consents, as well as the connection to the electricity grid which is now being taken care of by TenneT. The government also makes an operating grant available and the projects receive subsidies for the renewable energy they generate.

Looking at the developers who won the rights to build the Borssele 1 & 2 and Borssele 3 & 4 projects – which are now fully operational – financing the construction and operation of the world’s cheapest offshore wind farms at the time also did not appear as much of an issue.

Ørsted as the leading offshore wind developer already had a portfolio of both operational projects that were producing electricity and those under development, and vast experience with offshore wind technology, construction, operation, and supply chain. And the Blauwwind consortium behind the second Borssele project is a partnership between the investors Partners Group, Diamond Generating Europe, the oil and gas giant Shell, offshore construction specialist Van Oord, and the Dutch offshore wind developer Eneco. Van Oord is also part of the Two Towers consortium that won the Borssele tender for the innovation site, which also comprises Investri Offshore and Green Giraffe Holding.

“We have overcome [a number of] challenges…” This notion appeared in announcements of the wind turbine installation completion at both Ørsted’s Borssele 1 & 2 and Blauwwind’s Borssele 3 & 4 offshore wind farms last year, as the teams working to bring the projects to their completion were fighting the COVID-19 pandemic and everything that came with it. Still, offshore construction works on both wind farms were finished on schedule.

Van Oord installed both the wind turbines and the monopile foundations at Borssele 3 & 4. Photo Flying Focus

DEME installed the first of the total of 94 Siemens Gamesa 8 MW wind turbines on Borssele 1 & 2 in April 2020, shortly after which the project delivered its first power. Using its jack-up vessel tandem Sea Installer and Sea Challenger, the company erected all the Siemens Gamesa units in five months, announcing the completion of the work at the beginning of September 2020.

“Achieving this milestone has been made possible due to the collaborative and tireless efforts of countless individuals from Ørsted, DEME, SGRE and our subcontractors. Together we have overcome the unique challenges of executing turbine installation during these difficult times and delivered a fantastic result”, said Ben Beardsmore-Rust, Ørsted’s project manager for the turbine package.

“While installing turbines at Borssele III/IV, we have overcome a number of challenges arising from COVID. Not only have we needed to adjust our way of working on the installation vessel, but even the transport of technicians to the project has been an international challenge”, said Laurens van Pijkeren, Project Director at the now former MHI Vestas (now Vestas), as Van Oord’s installation vessel Aeolus installed the final of the 77 9.5 MW turbines at the Borssele 3 & 4 site some three months after the same work was completed on Borssele 1 & 2.

Along with challenges related to the global pandemic, project construction was also impacted by significantly more adverse weather than what could have been statistically expected. Aeolus installed the first turbine on Borssele 3 & 4 at the end of May 2020, with the wind farm producing its first power in August and having all the turbines in place in around six months.

On Borssele 1 & 2, all the foundations, cables and wind turbines were installed in only nine months, after the first foundation was put in January last year. Wind turbine installation started just as DEME, using its jackup Innovation, put half of the project’s foundations in place.

The monopiles for Ørsted’s 752 MW wind farm were supplied by EEW SPC and Sif, each delivering 47 units, while Bladt Industries and EEW OSB manufactured the transition pieces. The Innovation vessel was loading the foundation components at Sif’s facility on Maasvlakte 2 in Rotterdam before transporting and installing them at the offshore construction site some 22 kilometres off the coast of Zeeland in the Netherlands. Van Oord’s Aeolus, which installed both the wind turbines and the monopile foundations at Borssele 3 & 4, was also using Sif’s terminal at

DEME installed the first of the total of 94 Siemens Gamesa 8 MW wind turbines on Borssele 1 & 2 in April 2020. Photo Van der Kloet

Maasvlakte 2 for foundation installation, as Sif produced all the TP-less monopiles for the project. The vessel installed the first monopile at the end of October 2019 and completed the work in April 2020.

Van Oord was also contracted to install inter-array cables on both Borssele offshore wind farms. The company used its cable-laying vessel Nexus to transport and install the inter-array cables supplied by Nexans on Borssele 1 & 2 and Prysmian’s cables on Borssele 3 & 4.

The Borssele 1 & 2 went into operation in November 2020. Borssele 3 & 4 started officially operating in February of this year.

The Borssele V offshore wind farm in the Netherlands has been producing electricity since February of this year, with its two turbines being able to power as many as 25,000 households – and the project’s contribution to a sustainable, clean energy future does not stop there.

While investigating the offshore wind areas and preparing the Borssele Wind Farm Zone tenders years ago, the Dutch government earmarked the Borssele V area as a place where the industry could test and demonstrate novel, cost-effective, and sustainable solutions.

For the testing of innovations, the government had secured a subsidy of up to EUR 15 million, along with a subsidy for the electricity supplied of a maximum of EUR 35 million. A consortium between Van Oord, Investri Offshore, and Green Giraffe won the tender for the innovation site in April 2018, with Van Oord also being the Balance of Plant contractor. The consortium, called Two Towers, installed two Vestas 9.5 MW wind turbines on top of two monopile foundations manufactured by Sif in 2020 and later entered into a partnership with Dutch energy company Vandebron to enable the power consumers to purchase their renewable electricity directly from the project.

One of the two wind turbine foundations features Van Oord’s Slip Joint connection, making it the first time anywhere that a submerged slip joint was used on a full-sized offshore wind turbine on a fully commercial basis, according to the company.

The Slip Joint is an alternative connection between a monopile and a transition piece, consisting of two conical sections placed on top of each other. This solution makes a submerged connection possible, allowing for a more balanced weight

Borssele 1 & 2 offshore wind farm in the Netherlands. Photo by Ørsted

Borssele Beta, the platform connecting offshore wind farms Borssele III & IV, and Borssele V to the Dutch grid. Photo by TenneT

distribution between a monopile and a transition piece. The installation is done by sliding the wind turbine’s foundation elements over the monopile, without having to use grout or bolts. Along with the Slip Joint foundation, the technologies being demonstrated at Borssele V include Thermally Sprayed Aluminium (TSA), Impressed Current Cathodic Protection (ICCP) optimisation, oval cable entry holes, eco-friendly scour protection, and oyster beds.

The eco-friendly scour protection and oyster beds are an integrated approach to demonstrating the performance of the scour protection and testing different outplacement methods for live European flat oysters on the two scour protections of Borssele Site V.

The project involves installing eight different reef structures with oysters underwater at the offshore wind site to determine which method works best for the long-term establishment of oyster reefs on scour protections. On the structures, oysters will be placed in various ways such as contained, loose and pre-settled.

Within the project focused on oval cable entry holes, the team at Borssele is working on the optimisation of both the entry hole dimensions for cable pull-in and the cable protection system (CPS) to minimise stress concentration in the monopile wall, which leads to reduced steel usage in the section of the foundation.

A novel coating technology, Thermally Sprayed Aluminium (TSA), which is said to be more hard-wearing, is also being demonstrated at the innovation site, together with an automated application system that could cut the coating costs in the industry. The offshore wind farm is also featuring the Impressed Current Cathodic Protection (ICCP) system to mitigate internal corrosion of foundations by supplying a controlled direct current to the underwater surface. The ICCP system, whose current is being monitored by zinc reference electrodes, is automatically adapting to the existing conditions to provide the suitable level of corrosion protection.

Now that all three Borssele offshore wind projects are up and running, the next Dutch move in offshore wind is materialising with the world’s first subsidy-free offshore wind farm – the 1.5 GW Hollandse Kust Zuid – now under construction. Undoubtedly powered by the cost reductions achieved in the Borssele tenders.

Adrijana Buljan