When Gustav Kristensen makes a single change in his calculations, it can mean a difference of several hundred tons of steel.

On a daily basis, he calculates how much load a foundation for offshore wind turbines must withstand—the part that ensures the turbines remain stable on the seabed.

“How strong the wind is, how high the waves are, and how severe a collision it must endure—that’s what we’re talking about,” he explains.

Today, offshore wind turbines can reach the height of the Great Belt Bridge, and the structures therefore require advanced engineering.

As a civil engineer at the global firm WoodThilsted, Gustav Kristensen optimizes every element of a foundation to reduce the amount of steel used—and even small changes make a huge difference when a pile containing 1,800 tons of steel must be driven 30 meters into the seabed.

“There are rarely standard solutions in my work. An order might be for 100 units, and while that could be called mass production, each foundation is unique,” he says.

They must be installed hundreds of meters apart in open sea, in water depths of either 15 or 60 meters. Optimizing a foundation weighing as much as 1,000 cars therefore requires extreme precision.

“We’re constantly developing to save resources, and I really enjoy this optimization process, which forces us to focus on the details,” says Gustav Kristensen, explaining:

“We’re not building a single lighthouse or 50 identical row houses. We’re constantly working with custom solutions and advanced materials.”

From School Assignments to Major Offshore Wind Projects

It’s not just for the sake of enjoyment that Gustav Kristensen gets to delve deeply into the details—there are clear environmental and economic benefits.

Steel for a single foundation can cost around 30 million Danish kroner—and that’s before you factor in installation, transport, welding, fabrication, design, quality assurance, corrosion protection, and everything else.

“For us, it’s more important to spend extra time on the details if it saves several tons of steel. We put a lot of effort into reducing costs, but also the amount of resources we use,” he says:

“I have to think carefully and meticulously—not quickly.”

When Gustav Kristensen makes his calculations, he uses the same software and methodologies he learned during his civil engineering studies at the Department of Civil and Architectural Engineering.

“It’s been very plug-and-play for me. I work with the same programs I was taught, and I often go back to my study notes,” he explains.

With a bachelor’s degree in load-bearing structures and a master’s in Structural Engineering, the transition from theory to practice in complex offshore wind projects has been seamless.

A strong theoretical background can indeed be applied in practice in a highly specialized industry, Gustav Kristensen believes.

“As students, we learn how to acquire knowledge. If you stand on a solid academic foundation, the practical side comes quickly once you start working,” he says.

Today, he is employed as a graduate engineer in the primary steel department. While newly graduated engineers are usually offered rotation through various departments, he has been allowed to stay in the steel department.

Here, he benefits from knowing the programs and coding language so well from his studies that he is allowed to further develop the tools behind them.

“I spend a lot of time developing the tools and software behind the programs we use for our calculations, which I find extremely exciting,” he says.

Turning Advanced Theoretical Knowledge into Concrete Solutions

It’s also motivating to be part of an innovative industry, Gustav Kristensen explains.

“Just ten years ago, offshore wind turbines could only generate half the electricity they can today,” he says, adding:

“Really significant scientific steps are being taken right now. The technological development is being pushed so we can produce more green energy.”

He is currently working on a project that includes 64 Siemens SG236 wind turbines, each with a capacity of 15 MW.

Their blades have a diameter of 236 meters—equivalent to the length of two football fields. The turbine tower itself measures 150 meters above sea level, taller than a lighthouse.

The piles are driven into the seabed with a massive hammer delivering 5.5 megajoules per blow—the equivalent of a 1,150 kg car crashing into a wall at 350 km/h.

It takes thousands of such “impacts” to fully drive a pile into the seabed.

“I analyze whether the piles can withstand the extreme forces they are subjected to during installation,” says Gustav Kristensen.

The project is expected to cost approximately 34 billion DKK, of which the foundations are only a small part of the total. For comparison, the total cost of the Great Belt Bridge was 21.4 billion DKK.

The East Anglia Two project is planned in the southern North Sea, off the east coast of the UK. When completed, it will have a capacity of up to 960 MW—enough to supply green electricity to around 1 million households.

“I think it’s great to contribute to a greener transition, both by reducing resource consumption and increasing the production of wind energy efficiently,” he says.

Gustav Kristensen is part of the first cohort to graduate with a master’s degree in civil engineering from the Department of Civil and Architectural Engineering at Aarhus University.

[Translate to English:]

Om Wood Thilsted

Wood Thilsted er et rådgivende ingeniørfirma med speciale inden for offshore vindenergi.

De tilbyder ingeniør- og rådgivningstjenester gennem hele livscyklussen for havvindmølleprojekter.

En central opgave er udvikling af fundamenter til offshore vindmøller, hvor der arbejdes for at optimere fundamenterne, fx ved at minimere materialeforbrug (mindre stål). Det gør installationerne billigere og mere bæredygtige. 

Virksomheden har global rækkevidde og leverer løsninger til store havvindprojekter verden over.