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Faculty of Engineering
Department of Energy and Process Engineering

PhD position within Wind turbine wake interactions (IV-4/18)

The Faculty of Engineering at the Norwegian University of Science and Technology (NTNU) has a vacancy for a 100% position as a PhD Research fellow at the Department of Energy and Process Engineering. The described PhD is part of a joint PhD research project between NTNU and TU Berlin aiming to deepen the connections between TU Berlin and NTNU as well as the internal research infrastructures within each institution.

Both universities investigate similar research topics in the field of renewable energy, particularly dealing with the extraction of mechanical/electrical energy from the environmental wind. The candidate will work in close collaboration with the TU Berlin counterpart, and will have an opportunity to do a part of his/her PhD research at TU Berlin.
Information about the department

The Department of Energy and Process Engineering (EPT), a part of the Faculty of Engineering, is organized into six sub divisions - or research groups - for both teaching and research purposes:

Research Groups: Energy and Indoor Environment, Fluid Mechanics, Industrial Ecology Programme, Industrial Process Technology, Renewable energy and Thermal Energy (the present position is organized with the Fluid Mechanics group).

The Department of Energy and Process Engineering has a total of 200 employees, including approx. 90 doctoral students (PhD). We have an extensive contact network, and graduates from our master's programmes are employed by both industry and public administration. Our research is applied to both offshore and onshore industry, by consulting companies, energy advisory services, engineering companies, and public administration. At the department, we work with systems based on natural gas as well as renewable energy. Pollution problems both in relation to the external environment and the indoor environment in buildings is a key part of our activities. We work with industrial process engineering in the broadest sense, with processing Norwegian raw materials for high-quality and competitive products.

Project description: “Wind turbine wake interactions”

Clustering wind turbines as a wind farm to share the infrastructure is an effective strategy to reduce the cost of energy. This leads to aerodynamic interaction among the turbines. As a turbine extracts energy from the wind, a velocity deficit and increased turbulence occur in its wake. Wind turbines located downstream inside such a wake produce less power and experience altered structural loading. This couples the power production and loading of upstream and downstream turbines. The significance of such coupling depends on the topology of the wind farm, wind direction and wake recovery time. Since traditional control strategies aim to maximize the power production of the individual wind turbines, the total wind farm power production is suboptimal. Control strategies that take into account the wake effects are capable of mitigating this problem.

A recent approach is to redirect the wake of upstream turbines away from downstream turbines using yaw-misalignment. As the literature shows, yaw-misalignment has the potential to increase the power output of a wind farm. While the loads of upstream turbines may benefit from yaw-misalignment, downstream turbines can potentially experience increased loads due to partial wake overlap. To decrease the cost of wind energy, it is important to increase the power production without significantly reducing the lifetime of a wind turbine. Therefore, any application of control algorithms should not negatively impact the wind turbine loads.

In order to be able to come up with holistic control approaches for optimizing a wind farm, well-performing prediction tools for the wake flow behind a wind turbine are needed. This motivated the development of wake models in the early 1980s. Early analytical wake models by e.g. Jensen (1983), Ainslie (1988) or Crespo et al. (1988) were calibrated with empirical parameters. Most of the state-of-the-art software used for industrial wind farm planning is still based on these engineering wake models. In recent years, however, a number of improvements for existing models have been proposed and new wake models developed. Promising models are proposed by Ishihara et al. (2004), Larsen et al. (2008) or Bastankhah and Porte-Agel (2015).

Recently, an extensive set of experimental wake measurement data has been produced at the wind tunnel laboratory at NTNU (see references below). These experiments investigated the influence of turbine control parameters such as tip speed ratio, pitch angle or yaw angle on the wake flow behind a model wind turbine of D=0.90m. Furthermore, wake development was analyzed dependent on ambient parameters, such as turbulence intensity and shear in the inflow.

The objective of the proposed PhD work is to further assess the accuracy of existing analytical wake models by comparing them to experimental data measured at NTNU and with wind farm field data. In particular, wind tunnel measurements in the far wake of a model turbine will be performed.  The next step is to measure and analyze the turbulence parameters and scales that are important for the dynamical load characteristics on wind turbine rotors – with a goal to come up with correlations that will be used for the design of the wind turbine rotors.

Pierella, Fabio and Sætran, Lars. (2017). Wind tunnel investigation on the effect of the turbine tower on wind turbines wake symmetry. (2017) Wind Energy. Vol 20, pp 1753-1769. DOI: 10.1002/we.2120
Bartl, Jan and Sætran, Lars. (2017). Blind test comparison of the performance and wake flow between two in-line wind turbines exposed to different atmospheric inflow conditions. Wind Energy Science. Vol 2, pp 55-76
Hearst, R. Jason, and Ganapathisubramani, Bharathram (2017). Tailoring incoming shear and turbulence profiles for lab-scale wind turbines. Wind Energy. Vol. 20(12).
Krogstad, P-Å; Sætran, LR; Adaramola, MS. (2015) “Blind Test 3” calculations of the performance and wake development behind two in-line and offset model wind turbines. Journal of Fluids and Structures. Vol 52, pp 65-80
Pierella, F; Krogstad, P-Å; Sætran, L R. (2014) Blind Test 2 calculations for two in-line model wind turbines where the downstream turbine operates at various rotational speeds. Renewable Energy. Vol 70.

We seek a highly-motivated individual:
• Holding an excellent Master degree in Mechanical Engineering or Physics with a specialization in Fluid Mechanics
• Creativity and willingness to work in an inter-disciplinary project
• Familiar with experimental methods using e.g. Hot Wire Anemometry, Particle Image Anemometry or Laser Doppler Anemometry
• Ability and motivation to conduct high-quality research, including publishing the results in relevant journals and presenting at conferences
• Analytical skills
• Good programming skills and knowledge of quality evaluation methods (experience with MATLAB and/or LabVIEW).
• Very good communication skills (both written and oral) in English
Applicants are asked to provide a research statement (max 3 pages) in their application, describing research interests and initial plans with regards to the above project description. The statement should also provide details on how the project relate to previous education, research and competence.
Applicants who do not master a Scandinavian language must provide evidence of good written and spoken English language skills. The following tests can be used as documentation: TOEFL, IELTS, Cambridge Certificate in Advanced English (CAE), or Cambridge Certificate of Proficiency in English (CPE). Minimum scores are:
- TOEFL: 600 (paper-based test), 92 (Internet-based test)
- IELTS: 6.5, with no section lower than 5.5 (only Academic IELTS test accepted)
- CAE/CPE: grade B or A.

PhD Candidates are remunerated in code 1017, and are normally remunerated at gross NOK 436 900 before tax. There will be a 2 % deduction to the Norwegian Public Service Pension Fund from gross wage.

Engagement as a PhD Candidate is done in accordance with “Regulation concerning terms and conditions of employment for the posts of post-doctoral research fellow, research fellow, research assistant and resident”, given by the Ministry of Education and Research of 19.07.2010. The goal of the positions is to obtain a PhD degree. Applicants will engage in an organized PhD training program, and appointment requires approval of the applicants plan for a PhD study within three months from the date of commencement.

The appointment has a duration of 3 years as a researcher towards the degree of PhD. Depending on the candidate’s preferences and qualifications, the position duration could be changed to 4 years with a 25% teaching duty for the Department throughout the employment period.

For further information about the position, please contact Prof. Lars Sætran, Department of Energy and Process Engineering, NTNU, Trondheim. Email: lars.satran@ntnu.no

See http://www.ntnu.edu/ivt/doctoral-programme for more information.

The engagement is to be made in accordance with the regulations in force concerning State Employees and Civil Servants. The positions adhere to the Norwegian Government's policy of balanced ethnicity, age and gender. Women are encouraged to apply.

The application
The application must contain information of educational background and work experience. Certified copies of transcripts and reference letters should be enclosed. Applications with CV, grade transcripts and other enclosures should be submitted via this webpage at www.jobbnorge.no  Mark the application with IV-4/18.

Start-up date is as soon as possible, but may be discussed with the Department

Application deadline is 1 February 2018.

According to the new Freedom of Information Act, information concerning the applicant may be made public even if the applicant has requested not to be included in the list of applicants.

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Om stillingen

  • Søknadsfrist
    1. februar 2018
  • Arbeidsgiver
    NTNU - Norwegian University of Science and Technology
  • Nettside
  • Kommune
  • Arbeidssted
    Energy and Process Engineering
  • Jobbnorge-ID
  • Intern-ID
  • Omfang
  • Varighet

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