June 2013

Valuable wind science

A commercially applicable product that can reduce the cost of wind energy, thorough, fundamental-scientific publications and a cum laude PhD; these are the results of a successful partnership between ECN and the Centrum Wiskunde & Informatica (CWI). Michiel Houkema of ECN and Barry Koren of CWI explain how they found each other in the modeling of air flows of wind farms.

Barry Koren, currently professor at Eindhoven University of technology and advisor at CWI:


Photo Minnie Middelberg

‘Several years ago when I was still working for Delft University of Technology, I supervised the graduation of Benjamin Sanderse on a calculation method for aerodynamic problems. At that time, ECN was looking for more fundamental depth. I, on the other hand, was looking for more practical applications of our research. That is where we found each other.

After graduating, Benjamin joined ECN to work on PhD research. He spent part of the week at ECN, and another part at CWI. He focused on the modeling of air flows behind wind turbines. This is a complex, mathematical problem for which he developed a new calculation method.

It is no coincidence that Benjamin belongs to the five per cent of cum laude PhD graduates. He has delivered excellent fundamental work and brought this all the way to practise. Going through the entire chain during one’s promotion research is seldom done. Not only did his research yield a thesis, it also brought about a concrete product: a computer code that ECN can now start exploiting commercially.

Four PhD researchers will continue working on Benjamins calculation method. This method is already able to accurately predict laminar and turbulent flows. Now we will conduct some reverse calculations: how should one build a wind farm to realise optimal flow? Optimal here means that a farm delivers a maximum yield at a minimal cost as a result of minimal maintenance.

I am very satisfied. It has been a fruitful cooperation. It is not without reason that, with new PhD students, we are continuing the course we embarked on with ECN.’

Michiel Houkema, senior manager at ECN:

‘At ECN we are researching optimal wind turbine configurations for wind farms. There needs to be sufficient distance between the turbines to prevent them from affecting each other's performance. Rotating rotors influence the wind direction as well as wind speed. They can, for example, catch wind for a turbine that is placed too nearby. At the same time, the turbines need to be placed as closely to each other as possible: this reduces the amount of cable needed and prevents the farm from taking up too much space.

Another important cost pertains to maintenance. If you are able to influence the wind load on turbines, you can arrange that all turbines need maintenance at the same time.  Particularly for offshore wind farms, this may result in huge cost savings.

Benjamins PhD research was fundamental mathematically sound and practically oriented as well. The CWI fed him with fundamental knowledge, whereas we provided him with experiences and wishes from practise.

In follow-up projects, we will further validate his calculation method with practical cases, among other things by means of measurements at our own test site. The code ultimately needs to be good enough to enable calculations of all kinds of flows, including the most difficult turbulence. This will enable us to reduce the cost of wind energy and increase the yields, which will make wind energy increasingly more competitive. And that is our goal.’

Are you interested in the developed computer code or in opportunities to collaborate with ECN in this field? Michiel Houkema will gladly to talk to you about it. Give him a call at +31 (0)224 56 4599.