Henrik Stiesdal: From scrapyard to wind industry prizewinner

The birth of the 20MW offshore wind turbine, it may one day be said, can be traced to a scrapyard outside the town of Brande in Denmark.

Here in 1978, Henrik Stiesdal, now chief technology officer of Siemens Wind Power, salvaged the parts that would be retooled to fashion his first wind turbine.

This wind-power pioneer’s early “Danish concept” designs went on to energise Vestas’ transformation from a farm machinery manufacturer into the largest wind turbine maker in the world.

His vocation came to him in a rush. The year before, Stiesdal had taken a cycling tour of the UK. One of his abiding memories of the trip was seeing clouds forming downwind of a Lincolnshire power station’s cooling towers — a symbol, as he read it, of the way “man’s attempts at power generation impact on the climate”.

“When we started out that morning it has been a brilliant blue sky, but by the time we travelled beyond the power station the sky had grown overcast because of the cloud cover created,” Stiesdal recalls.

“Thinking back, it has struck me that it is one of those events that makes you stop and recognise the extent to which we impact our environment and how the environment then impacts on us. It was a real eye-opener.”

Not long after his return home, his father read in the local newspaper about a group of students at a nearby teachers’ college who were attempting to erect a 2MW wind turbine. The two drove out to see it. The experience was formative for Stiesdal, galvanising him to attempt to engineer and build one of his own.

“I found it really fascinating to see young men and women not much older than me welding and drilling and machining with a vision,” he says. “It really switched something on in me.”

Mark 1, a machine with a one-metre-diameter rotor devised by Stiesdal and his father, was hand-built — and hand-held. “When you held it in the air you could actually feel the power of the wind in your hand,” he remarks. Mark 2, a two-bladed model with a three-metre rotor diameter, had to be transported by wagon into the fields of his family farm for testing.

Blades made of wood

Stiesdal then immersed himself in books — including Englishman EW Golding’s Generation of Electricity by Wind Power, aircraft engineering manuals, and republished sections of a UN report on wind power and turbine design — while keeping up with work by other “self-builders” who were growing in number in Denmark in the late 1970s.

“In some ways it might have seemed a little naive but what was more important was the core message: ‘You can do it if you want — why not?’

"The technology was difficult, but no more difficult than a science-minded college student could manage. It was complex in that it brought together many different technologies, from generator systems to gearbox control systems to towers and so on.”

Standing 12 metres tall and topped with a nine-metre-diameter rotor, Stiesdal’s first grid-connected turbine was a chimera: a tower previously used as an electricity pylon, a generator set from a chalk-manufacturing plant, and a control system made “out of things found at the junkyard”.

He adds: “The only thing you really had to make from scratch were the blades — which were eventually made of wood — and the rest could be salvaged from other industries.”

In 1978, Stiesdal met Karl Erik Jørgensen, who was to become his partner. Backed by a DKr50,000 ($9,500) government grant, they inaugurated their first 15kW prototype in June that year — and in 1979 delivered to their first customer: the company that would become Vestas.

Series production of a 30kW machine started that year. Stiesdal went back to university, bankrolled by a licence fee arranged with Vestas, a company he worked with until 1986.

“I quit because my studies had suffered somewhat during this time and I wanted to concentrate on my education. But it was only a few months before I missed the wind industry too much.”

This passion carried him through a nearly ten-year collaboration with Vestas, during which Stiesdal helped design its first pitch-regulated wind turbine. Moving to rival turbine developer Bonus in 1987, he set about exerting an almost revolutionary influence on technologies from blade tip through to drivetrain and down the tower.

Among his contributions are the blade manufacturing concept now known as IntegralBlade, the Combistall regulation systems used in Bonus megawatt-range machines until the company’s acquisition by Siemens in 2004, and the variable-speed turbine still used by the German outfit today. Stiesdal, most recently, has spearheaded Siemens’ progress in direct-drive transmission.

Prize-winning year

Stiesdal was this year’s winner of the prestigious Poul La Cour prize, awarded for outstanding achievements in the field of wind power by the European Wind Energy Association.

“The blades and direct-drive are the two areas where I have had the greatest joy of having a vision and seeing it materialise,” he says.

“Particularly now direct-drive, because it is something that I had thought about for years — removing the gearbox — but that took a long time to come about. I have the greatest respect for Aloys Wobben [founder of direct-drive turbine maker Enercon] for his work; he has been a shining example.”

Since joining Siemens after it took over Bonus, Stiesdal has been laurelled with the industrial group’s various innovation prizes.

He was one of those who established the company as a leader offshore, devising “marinised” turbine solutions for the Vindeby and Middelgrunden wind farms, and managing negotiations and execution of the first bona fide offshore wind farm, Vindeby.

“Offshore is clearly where we must go, but it is equally clear that what we are missing is the industrialisation of the infrastructure that will support development of this campaign,” he says.

“This is the legacy of our oil-and-gas-based, project-orientated industry. Go to a yard and look at the jackets — each is going to a specific project. We need to get to the point where wind turbines are standardised products ready to go wherever they are needed.”

6MW will not be the limit

Stiesdal won’t be drawn on what size of turbine he thinks will eventually become the norm.

“I have a terrible track record with my predictions,” he explains. “Back in 1985, I publicly stated no turbine larger than 250kW would be commercial, and in 1990 I repeated the error and stated that 500kW would be as big as we could go. I have stopped making predictions.

“I will venture that the 6MW will not be the largest ever built. And there will be double-digit megawatt machines from companies including ours.

“It has always been the case that what first looks grotesquely large soon begins to feel familiar.”

Stiesdal doesn’t expect vertical-axis wind turbines to join the offshore skyline, as “it would be like starting to design cars with three wheels rather than four”.

He concludes: “I have been doing this for the better part of 35 years now and what is clear is that when I think about the world’s needs with regards to clean power I can’t find any other disciplines that have the same feeling of potentially providing the answer in the way we have in wind power.”