In December 2016, emeritus professor Gijs van Kuik gave his final lecture at the Delft University of Technology (TU Delft) in the Netherlands.
"Wind expected: brace yourself," was the title of his reflections on offshore-wind development, one of his specialist research fields, and seen through the prism of a long and successful academic career in wind energy.
The lecture started by highlighting the unexpectedly low bids for the Borssele 1 and 2 wind projects. (The even lower bids for Borssele 3 and 4 were announced a few days after the lecture.)
Until then, offshore wind was generally perceived as offering plenty of potential, but still burdened by high generating costs and slow progress in cost-reduction. The Borssele bids made offshore wind (almost) instantly cost-competitive with fossil-fuel generation.
Van Kuik calls the latest 7-9MW offshore turbines "the largest rotating machines on earth", and stresses that further upscaling will continue to represent huge scientific and technological challenges. "It makes me proud to see what has been achieved technologically," he says.
"At a wind conference early this century, I expressed my fear that the pace of turbine scaling was too fast and lacked scientific validation in intermediate stages. I am happy that these fears proved unjustified, and I compliment the industry for having proven capable of successfully conducting these benchmarks themselves."
The small-step bottom-up approach of product development from a semi-artisan base proved the right one for the wind industry, he says.
"These pioneers made steady progress, while government-supported contracts typically awarded to large aerospace companies following the 1973 oil crisis proved largely unsuccessful," he argues.
"They grossly underestimated the technological differences and challenges linked to wind-power application. Simply copying helicopter-rotor technology to turbine rotors, for example, was soon found not to work.
"But it led to a growing acceptance that wind energy must be treated as a fully new technology discipline requiring unique approaches and solutions, besides learning from associated disciplines."
Although critical of early large-scale projects in general, Van Kuik acknowledges that some served useful purposes. The MOD 5 research turbine in the US, for instance, performed well for many years, and many of those large early turbines featured slender blades and operated with pitch-controlled variable speed.
This is semi-standard practice now, but was far from common for the kilowatt-rated commercial turbines of the mid-1990s when Danish pioneers still favoured "the best control is no control".
Early development programmes
In the early days, industry and specific institutions were deployed for EU-supported technology development programmes. Examples include four 1.5MW turbines developed in the mid-1990s, while the more recent Upwind and latest Innwind research programmes have explored the feasibility of building 10-20MW turbines.
"Research efforts at universities and scientific institution in the late 1970s and 1980s contributed a lot to developing essential engineering know-how, which was then passed on to turbine suppliers. This knowledge transfer was nicknamed 'design by certification'," he says.
"Today, the key role of academics is generating fresh knowledge on engineering and scientific disciplines, while the design of wind turbines by academics has become a near relic of the past. Dedicated EU-supported research programmes like Upwind and Innwind fit well into that new role and should at aim at leading the way in offering future direction to industry."
The scaling of rotor blades provides a good example of the huge technological progress achieved in the past decades. Van Kuik demonstrates with the mass increment of the 7-metre blades fitted on early 65kW Bonus turbines, with the 75-metre blades of the 6-7MW Siemens offshore platform.
"Conventional scaling rules following the square cube law (SQL) dictate that the Siemens rotor mass should have been 92% higher if it had been built by scaling the original Bonus design. One could argue that science has beaten SQL here by 92%," he says.
The continued growth in turbine and project size justifies speaking of power plants rather than wind farms, he says.
The turbine is one element, albeit key, that must fit into the overall plant package. Furthermore, wind power covers all major scientific disciplines above and below sea level, from multiple engineering fields to materials science, hydro-dynamics and marine biology.
"Wind-flow turbulence is another complex phenomenon and the least understood," says Van Kuik. "In fact, turbulence represents one of the greatest fundamental challenges to the wind industry, and wind energy is a main user of turbulence-related knowledge.
"It is characterised by many different scales, from meso-level, up to hundreds of kilometres, to micro-scale levels of millimetres. The same holds for aerodynamics: computational fluid dynamics analysis, wind-tunnel experiments and full-scale testing supplement and reinforce each other in achieving better in-depth understanding. An example is dedicated research into the stability of vortices behind turbine rotors."
The North Sea space is currently mainly dedicated to oil and gas exploration, shipping, fishery, military and other conventional maritime uses. But Van Kuik's lecture includes a video with a grand vision of gradually converting the North Sea into a powerhouse of offshore wind by 2050.
This process has started, and a completely new infrastructure design, consisting of multiple-use functions and smart-grid linkages between countries, is now envisaged.
"At an ever wider and more comprehensive scale, I could imagine the creation of large artificial islands in the middle of oceans where wind turbines produce electricity. This power would then be converted into hydrogen or synthetic fuels, to enable the re-bunkering of ocean-going vessels with clean fuels," he says.
"Such major projects have never been done before, but history offers many examples where 'the impossible' has been realised. Curiosity is, apart from boldness and determination, crucial for accelerating fundamental science to the benefit of future generations."
A LIFE IN WIND — GIJS VAN KUIK
Gijs van Kuik's involvement with wind energy goes back to the early 1970s, when he studied aerospace engineering with a specialisation fundamental aerodynamics at Delft University.
After graduating in 1976, he joined the university as a researcher, earned his PhD, moved into industry and was in 1988 appointed full-professor of wind energy and wind technology.
His first main task was to establish a dedicated wind-energy institute, cross-linking multiple faculties, and boost cooperation between participants.
DUWIND was founded in 2001, initially with three technical faculties, while the academic research programme started up with five PhD students. When Van Kuik retired, this number had grown to more than 40, and many former students have taken senior industry roles and wind professorships at leading universities.
The number of students taking the introductory wind-energy course rose from the first intake of just 10 students to over 250 today, with an increasingly international flavour. "In 2004 DUWIND organised the first scientific wind conference, 'the science of making torque from wind', which has since been held every other year," he says.
"Another milestone at this first event was the founding of the European Academy for Wind Energy (EAWE)."
EAWE is a registered body of research institutes and universities in Europe working on R&D projects and education on wind energy, and aiming to maintain the continent's pre-eminent position in wind-power technology and innovation.