French offshore wind turbine project: NIRAS adviser on future dismantling

Even before the first of 124 wind turbines off the west coast of France has been set up, a detailed plan has been set for how they will be taken down again at the end of the wind farm’s operation.

01. Nov 2017

The developer of two 496 MW wind farms in France has chosen the consulting engineering company, NIRAS, to set a plan for decommissioning even before final investment decision has been made.

NIRAS has previously assisted the developer, Les Eoliennes en Mer Services (LEMS, owned by Engie, EDP Renewables and La Caisse des Dépôts) in the phase of de-risking regarding the issue of future dismantling. And precisely knowledge about decommissioning, which also includes the physical dismantling of offshore wind turbines, is an area NIRAS a few years ago chose to invest heavily in.

This investment has now resulted in NIRAS being selected as owner’s engineer at the two French offshore wind farms:

“We have now been chosen to assist in making intelligent design of the future dismantling already in this very early planning phase. LEMS takes their job seriously and has chosen to think years ahead when they include the full life cycle of the turbines, from birth to last breath, and thus also wish for help with the retirement and clever dismantling", says Johan Finsteen Gjødvad, project manager in NIRAS, who will help to make the final strategy for decommissioning.

Investment in decommissioning tool a success

NIRAS' investment a few years ago included an innovation project, ODIN-WIND, which resulted in a tool to keep track of the processes from A to Z in relation to retire offshore wind turbines. ODIN has made decommissioning a key competence in NIRAS and also explains the entry on the French market. Only few offshore wind farms worldwide have been scrapped so far, but the world's very first of its kind, Vindeby northwest of Lolland, has been taken down with help from NIRAS. And by assisting DONG with this, NIRAS has verified its knowledge in the field of decommissioning of offshore wind turbines:

"When it comes to taking down offshore wind turbines, NIRAS has the right know-how. By using known methods and actual data, we are able to think backwards", Johan says, adding that the decommissioning market is traditionally operating with an uncertainty of up to 50% when it comes to calculate what it would cost to take down a wind turbine down:

"But we can reduce the uncertainty to 15% because we base our knowledge on what things have actually costed and which methods have already been tested earlier regarding installing, maintenance and dismantling. We have specific knowledge about what can be sold, which metal parts and cables can be recycled, and which stones from the foundation around the mills that can be used elsewhere. So not only is it about optimal waste management and a reduced environmental impact, but we also reduce costs in relation to the dismantling", says Johan Finsteen Gjødvad.

Dismantling has an impact on profitability

NIRAS experience with decommissioning of offshore windfarms is that the project as a whole will be more profitable when the strategy includes the full lifecycle of the offshore turbines. It is about healthy economy, but also concerns for example, law, environment, recycling and safety for the people who are going to perform the actual work.

According to Johan Finsteen Gjødvad, there is a growing demand if the developer of a wind turbine project is to succeed:

"As a developer you have to look at the entire life cycle. From instalment to dismantle. And that is our expertise in NIRAS. We look at the design before the turbines are installed and can therefore plan how we can optimise how to take down the turbines many years later. And it goes without saying that it is an advantage for the customer to include in their plan from the start - coupled with the fact that the authorities naturally intensify on the statement of the retirement of offshore wind farms”.

Intelligent decommissioning tool

• The tool from the ODIN-WIND project is realised in corporation with Vattenfall, Maersk Broker, DTU-Wind and the British The Welding Institute (TWI)
• ODIN is short for “Offshore, Decommissioning of Installations NIRAS”