December 9, 2023

Windkeeper facing modern challenges of offshore maintenance

The French shipyard CNIM has designed the Windkeeper, a new type of maintenance craft, specifically to meet the challenges brought by the appearance of the offshore wind farms industry.

Offshore wind farms are a bit of a game-changer, despite their inconspicuous appearance. It brings major shifts in the maintenance world, which shipbuilders must now take into account. The number of turbines has been on the constant rise for the past decade, with constant improvement on their power output, reliability, but also increase in complexity and size. The maturation of the market means that the operators can no longer be content with the maintenance solutions which have filled the market until now.

Wind power was expected to be the all-time riddle-cracker, with eternal clean energy to harness from generous Mother Nature. The real-life implementation of the dream came with a few complications of its own, but the train is rolling. When turbines started becoming efficient enough to actually produce large-scale power, running on wind, many projects spouted of the ground, only to be met with local opposition, sometimes fierce against them. Wind currents vary in strength according to their altitude, with the strongest layers within reach being between 90 and 200 feet above ground. Because they aren’t mobile, they must be strategically placed in the path of currents, or choking points. Their relatively high altitude and large dimensions make them visible for miles around, and the number of locations they can be placed in are just not that many. Quickly, promoters realized that the business was getting too complicated on land and started looking out at sea.

Today, 22 of the 25 largest wind farms in the world are in Northern Europe (Northern and Easter Seas, Channel, mostly), and range up to 630 MW. The Offshore Wind toward 2020 report forecast the market to reach 130 billion dollars by that year. “But power prices for offshore wind have remained stubbornly high, leaving regulators and developers alike searching for ways to lower costs any way possible.”, says Silvio Marcacci in his June 2014 article for Clean Technica. He indicates that, today, most maintenance operations are performed with boats which have modified from their original states, and fitted with tethering devices to enable workers and their equipment to transfer from one structure to the other. Because the makeshift solution is slow, this increases down-time, hinders efficiency and therefore keeps the energy from becoming more competitive.

Windkeeper is designed specifically for this task, which is a lot newer than it seems. Most maintenance operation until now were performed from surface to surface (one boat scanning another or operating on it) or from fixed structure to fixed structure (from the docks to a tethered boat – or an offshore platform maintaining itself). In the case of wind turbines, the whole difficulty comes from stabilizing the vessel onto the mast, in order to let workers transfer, transport or simply move safely between one and the other. The ship’s architecture and the position of its propulsion system will enable it to remain immune to large swell, thus keeping it operational and seaworthy for longer every year. The ship is fitted with a mechanized and stabilized walkway, which will let workers operate safely in the most critical part of the maintenance: transfers. Once on the structure, or still on the boat, workers are safe, and most accidents occur when transferring from one to the other. The Windkeeper therefore focused its safety on the tip of the bow.

As for the new-generation efficiency it promises to bring wind turbine operators, CNIM also tackled the other peculiarity of the market: operational blindness. Given that turbines operate by themselves, out at sea, all year, there are no on premise maintenance teams to shed light on the areas or devices which require maintenance. The ship has therefore been equipped with all the electronics and communication equipment needed to keep in touch with ground structures and offshore turbines, perform remote diagnosis, and anticipate preemptive maintenance. The two biggest challenges maintenance units have to face are down-time and damage. Inability to detect and replace failing pieces before they actually fail will result in either the turbine not producing for the time of the replacement, or even causing disastrous damage to the general structure. The Windkeeper is built to stay out at sea, most of the year. Its communication capacity enables it to detect maintenance needs off from a distance, and communicate them to the base of operations or surrounding ships, to suppress supplying delays.

The reliability of the ship enables it to spend 300 days per year, yet another factor to cut down costs. The French market is expected to need 20 to 40 ships over the next 20 years.  Current ships, with only 200 to 250 days of annual availability, would therefore need to be 5 or 10 more for the same job, with all the purchasing, operation, insurance and maintenance costs ensued.  All of that would wind up in the end price of the kilowatt per hour, also.

The challenges the Windkeeper will have to face are not to keep turbines running: they already do. The immature market hasn’t yet received specialized equipment to maintain its mills, but it is making do with makeshift industrial solutions. But how smoothly maintenance goes impacts cost and therefore selling prices. Every time a turbine fails, it affects the annual yield of the unit.  If an average maintenance boat needs to return to shore often, then additional boats must be purchased to maintain capacities, the costs of which will also wind up in the end price. The Windkeeper wasn’t built to maintain wind turbines. The Windkeeper was built to make wind energy competitive.

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Sarah Jackson