Modeling wake effects in large wind farms in complex terrain: the problem, the methods and the issues

Politis, E. S.; Prospathopoulos, John; Cabezón, D.; Hansen, Kurt Schaldemose; Chaviaropoulos, P.; Barthelmie, R.J.

doi:10.1002/we.481

Cited by 158 publications

(100 citation statements)

References 13 publications

(27 reference statements)

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“…(4) is used. However, in (Ishihara et al, 2004;Mittal et al, 2011;Politis et al, 2011) it is demonstrated that this equation is not so reliable because only the ambient turbulence level is considered. In fact, the wake decay is influenced by a lot of factors.…”

Section: Wake Turbulence Modelmentioning

confidence: 99%

Development and validation of a new two-dimensional wake model for wind turbine wakes

Tian

Zhu

Shen

et al. 2015

Journal of Wind Engineering and Industrial Aerodynamics

131

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a b s t r a c tA new two-dimensional (2D) wake model is developed and validated in this article to predict the velocity and turbulence distribution in the wake of a wind turbine. Based on the classical Jensen wake model, this model is further employing a cosine shape function to redistribute the spread of the wake deficit in the crosswind direction. Moreover, a variable wake decay rate is proposed to take into account both the ambient turbulence and the rotor generated turbulence, different from a constant wake decay rate used in the Jensen model. The obtained results are compared to field measurements, wind tunnel experiments, and results of an advanced k À ω turbulence model as well as large eddy simulations. From the comparisons, it is found that the proposed new wake model gives a good prediction in terms of both shape and velocity amplitude of the wake deficit, especially in the far wake which is the region of interest for wind farm development projects.

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Section: Wake Turbulence Modelmentioning

confidence: 99%

Development and validation of a new two-dimensional wake model for wind turbine wakes

Tian

Zhu

Shen

et al. 2015

Journal of Wind Engineering and Industrial Aerodynamics

131

View full text Add to dashboard Cite

show abstract

“…There has been considerable research into optimising the power output of a wind farm via the placement of the wind turbines themselves (Chowdhury et al 2012;González et al 2011;Husien et al 2013;Magnusson & Smedman 1999;Meyers & Meneveau 2012;Politis et al 2012;Røkenes & Krogstad 2009) and most notably the work carried out from Risø National Laboratories in Denmark on the European Wind Atlas, providing comprehensive wind statistics (Troen & Petersen 1989). The issue of wind turbine siting is important for overall energy yield and relies heavily on how each turbine is placed with respect to its surroundings and more importantly, other turbines.…”

Section: Energy Yield As a Developer Responsibilitymentioning

confidence: 99%

Engineering and energy yield: The missing dimension of wind turbine assessment

2014

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The goal of optimising the energy yield of renewables sits uneasily with the politics and processes of planning for wind turbines. In countries such as the UK the land-use planning consent regime is not concerned with the energy yield of proposed wind developments. This is a matter for the developer rather than the regulator, which might seem curious given the policy commitment to maximising the potential for renewable energy generation and the need to weigh up local environmental impacts with emissions reduction. In this paper, we highlight and investigate the implications of the exclusion of energy yield from wind turbine regulation. The case is made for increasing the weight given to energy yield within Environmental Impact Assessment and the landuse planning process.

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“…Once the model has proved to be valid for an isolated wake case, a first result is obtained for a small wind farm like the ECN test farm [17][18][19], located at flat coastal terrain and composed by 5 wind turbines Nordex N80 of 2.5 MW in a row. Separation between wind turbines is 3.8D.…”

Section: Validation At the Ecn Test Farmmentioning

confidence: 99%

A semi-parabolic wake model for large offshore wind farms based on the open source CFD solver OpenFOAM

Cabezón¹,

Migoya

Crespo

2014

ITM Web of Conferences

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Abstract. Wake effect represents one of the main sources of energy loss and uncertainty when designing offshore wind farms. Traditionally analytical models have been used to optimize and estimate power deficits. However these models have shown to underestimate wake effect and consequently overestimate output power [1,2]. This means that analytical models can be very helpful at optimizing preliminary layouts but not as accurate as needed for an ultimate fine design. Different techniques can be found in the literature to study wind turbine wakes that include simplified kinematic models and more advanced field models, that solve flow equations with different turbulence closure schemes. See the review papers of Crespo et al. [3], Vermeer et al. [4], and Sanderse et al. [5]. Purely elliptic Computational Fluid Dynamics (CFD) models based on the actuator disk technique have been developed during the last years [6][7][8]. They consider wind turbine rotor as a disk where a distribution of axial forces act over the incoming air. It is a fair approach but it can still be computationally expensive for big wind farms in an operative mode. With this technique still active, an alternative approach inspired on the parabolic wake models [9, 10] is proposed. Wind turbine rotors continue to be represented as actuator disks but now the domain is split into subdomains containing one or more wind turbines. The output of each subdomain is mapped onto the input boundary of the next one until the end of the domain is reached, getting a considerable decrease on computational time, by a factor of order 10. As the model is based on the open source CFD solver OpenFOAM, it can be parallelized to speed-up convergence. The near wake is calculated so no initial wind speed deficit profiles have to be supposed as in totally parabolic models and alternative turbulence models, such as the anisotropic Reynolds Stress Model (RSM) can be used. Traditional problems of elliptic models related to the estimation of the reference wind speed at each rotor position are mitigated due to the semi-parabolic algorithm. The model has been validated at the ECN test farm and at the offshore Horns Rev wind farm with significant results and also have been compared to other wake models. Description of the semi-parabolic modelThe semi parabolic wake model is an in-house code based on the open source CFD solver OpenFOAM [26] and specifically designed for offshore wind farms. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Modeling wake effects in large wind farms in complex terrain: the problem, the methods and the issues

Cited by 158 publications

References 13 publications

Development and validation of a new two-dimensional wake model for wind turbine wakes

Development and validation of a new two-dimensional wake model for wind turbine wakes

Engineering and energy yield: The missing dimension of wind turbine assessment

A semi-parabolic wake model for large offshore wind farms based on the open source CFD solver OpenFOAM

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