Expert Risk Articles

Risk Consulting for an Offshore Wind Project

Wind energy is found where the fierce gales blow. Risk Consultant Reinhold Schaar visited an offshore wind project in Germany to see how it handles the challenge.

It's already midday. And they still have a long way to go. Upwards. To the very top of a 150-meter high windmill on the northern German coast near the town of Emden. Reinhold Schaar looks up at the rotor against the breezy, partly cloudy sky, so tiny at a distance. "It looks cute from down here," he chuckles to himself. "But when you're up there it's amazing."


The view from the bottom: the rotor towers overhead

The project is also headed upwards, which now means seawards. BARD, a wind energy pioneer, has reached a critical phase in its development on the German North Sea coast. It is about to go from its on-shore test site to its first "near-shore" units before they expand to the grand off-shore wind park envisioned that should produce 400 MW of power. When the project goes in the water, the Allianz Center for Technoloy (AZT) Risk & Technology will be in charge of risk monitoring. Today, Schaar and his team are there to check how the prototype rotors and towers are holding up.

The team has spent the morning at the nearby factory, especially built to produce the unique parts for these towers. "Large as an Oktoberfest tent," Schaar joked, giving a hint of his Bavarian origins. Jokes aside, he is always awed by the sight of car-sized spools of fiberglass, unwinding and wrapping around the leg-thick shafts for mounting the rotor blades.

But even that sight doesn't distract the team from checking all the safety details and making their recommendations. Schaar, ever the analyst with a bright and curious look in his eyes, comments: "This is interesting for us," and never "This is risky." Everything is interesting. There is always something to be considered, something to be discussed.

An enormous joint vision

Schaar, a trained engineer, is in charge of welds and nondestructive materials testing. Further team members are electronics expert Rudolf Fischer and fire safety man Christian Wittenzellner. It's a holistic, integrative collaboration.
Each of them has his own specialty, but each aspect of the wind turbine, from the layout of the cables to its structural integrity, is "interesting" for the whole team.

Now to the top: An elevator takes Schaar and the two other Allianz consultants along with a two-man team from BARD up inside the tower. They get out and climb another 10-meter ladder to the top, passing resting platforms for tired climbers, a recently installed innovation Schaar happily notes. Finally, there it is, the nerve center: a room the size of a small house that gives access to the control panel, the nose cone, the gearing, the generator and all the other sensitive gear. Very interesting.

As Schaar gazes through a window he sees the long coast, the now tiny looking towns and the vast gray sea. He also watches the rotor blades whip past the window, each one 59.4 meters long, as the floor sways and shakes beneath him. "I've been up here three times", he says, "but this experience is something I never get used to."

Here he can feel the enormous power of the winds, and ultimately, their energy too: nature and technology in grand dimensions. There is also a way to get outside, the top of the tower is secured with ropes and clips, but his eyes are on the insides. All he would get out there on top would be a wraparound panoramic view.


The view from the top: the North Sea coast stretches off in the distance.

A focus on every detail

There are gigantic forces at work, but monitoring the smallest details is just as important. Schaar and other members of his team, Thomas Gellermann and Ferdinand Wikidal, have already set up a system of remote monitoring that allows them to keep track of the minutest changes. About 90 sensors are based in the test towers measuring everything from tower warping to cog tooth shape. The results can be read in real time on computers in Munich on the other side of the country.

But nothing beats on-site inspection. Together with the 2-man team from BARD, they examine the condition of the driveshaft, generator and electronic devices exhaustively, both during operation and at a standstill.

All of the windmill's parts are, of course, important for general operation, but some of its equipment is designed for extreme situations. In case of a storm, for example, it is important that the rotor blades can stop immediately just before wind forces become too powerful. A malfunction of the pitch system designed to regulate rotation frequency can result in a rotor speed that creates pressures strong enough to rip the blades apart. This mustn't happen.

Yet another peculiarity of offshore facilities is critical in case of a storm: their remoteness makes them inaccessible in case of emergencies. Maintenance and repair, which is done by boat under normal circumstances, is impossible in stormy seas. In this situation, the engine has to be able to operate, change its settings and shut down autonomously. "You can compare this to a robotic probe operating on Mars," Schaar explains. With this thought in mind, his team member Wittenzellner carefully looks at the electronics and controls the automatic fire protection system.

Feasible solutions

The Allianz consultants talk to their BARD counterparts about all the various known and unknown risks. Deriving feasible solutions for "interesting" things through dialogue is one of the things Schaar likes best about his job. Now, they are discussing the risks of lightning. The facility is well prepared: Lightning rods are installed on the rotor blades. Transition current lines lead off potential hits and ground them. Otherwise, the heat could melt the gearbox parts or worse.

But the fact is, the risk of lightning on the North Sea is not well known. Together the teams decide to install lightning monitoring cards on the first near-shore towers that will record more detailed information on how often and with what intensity lightning strikes.

Another critical issue is salt water. It is highly abrasive and can corrode the steel construction. Three pylons in the water have to support the 1200-ton towers as well as withstand the massive forces of wind and waves. And entire towers will later go up at a speed of 1-2 a week. It is not so much the pylons and the towers that concern Schaar, it is more the welds, the connections. How are they made? How are they sealed? "The connections," he observes, "are always interesting. It's a marriage of the parts. When you have two solid pieces joined together, the joint is what has to hold up to the strain."

The connections count

It is the same with organizations, he points out philosophically in the discussion. When different departments and different partners have to work together, the areas of their collaboration become the most important in terms of risk management. From manufacturing and mounting to operation and risk engineering, Schaar stresses that the key to their success is always how they interface.

Back on the ground, Schaar and his colleagues recapitulate their impressions. Their conclusion is affirmative: the large investments BARD is making in monitoring and consulting are worth their effort. One last time Schaar looks up at the rotor. He will be back soon. The project is more than interesting.

Download "Global Risk Dialogue" fall 2008 (1 MB)

  1. Expert Commentary

    Knowing the engineers involved and their work I am very impressed by their risk assessment based on damage and prototype validation experience. Offshore wind technology has been undergoing rapid development and there are a lot of associated challenges. Interdisciplinary teamwork is therefore crucial.

    In order to be ahead of the competition you need to understand the technical risks and you need to be out there. This is what they are doing.

    In addition to the technological challenge going up on a wind turbine can become a personal challenge due to the height of the towers, especially when weather gets rough. The size of these installations is stunning and only when you see it with your own eyes you understand what a power output of 5 MW really means.

    As a turbomachinery engineer I remember a similar experience when I stood close to a 240 MW gasturbine that tripped. The vibrations and noise were overhelming... But this is what made it a day to remember.

    /assets/Global%20offices%20assets/Germany/agcs.momentum/Ausgabe%20Mai%202014/Thumm%20Stefan_1.jpg Stefan Thumm

    Stefan Thumm has a degree in mechanical engineering. Starting his career he worked with a turbine manufacturer (Gas Turbine Development, Steam Turbine Development and Commissioning) for six years. In 2000 he joined the Allinaz Zentrum für Technik (AZT) specializing on technical loss analysis of turbomachinery. Since 2008 he is a team leader within ARC Germany, including running of associated AZT business.