Badger, Jake

Hahmann, Andrea N.

Volker, Patrick

Online Research Database In Technology

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Dec 20, 2017Shadowing effects of offshore wind farms - an idealised mesoscale studyVolker, Patrick; Badger, Jake; Hahmann, Andrea  N.Publication date:2013Link back to DTU OrbitCitation (APA):Volker, P., Badger, J., & Hahmann, A. N. (2013). Shadowing effects of offshore wind farms - an idealisedmesoscale study [Sound/Visual production (digital)]. Danish Wind Power Research 2013, Fredericia, Denmark,27/05/2013Shadowing effects of offshore wind farms -an idealised mesoscale studyPatrick Volker, Jake Badger & Andrea HahmannDTU Wind Energy1Wind Farm InteractionWind Farm (WF) interaction is already an issue (e.g.):• Hornsrev I – Hornsrev II• Rødsand 2 – NystedLarge scale effects on the WF wake advection are not negligible anymore⇒ Mesoscale Models are a suitable solution.Drawback: Single turbine wakes cannot be resolved! (D0  ∆x)Possible solutions:(1) WF from microscale model & Mesoscale model as a wake transport medium(2) WF “parametrised” inside mesoscale model2Mesoscale ModelHorizontal scale: ∆x ∼ kmVertical scale: ∆z ∼ 10m (Boundary layer)Time step: ≤ ∆x/|U |Unresolved processes to be parametrised:RadiationMicro physicsVertical mixing (turbulence & convection)... Wind turbines3Wind Farm ParametrisationFrom the diffusion equation, one can obtain the typical length scale `:(1) `2 =2KmU0x+ `20Km is the turbulence coefficient for momentum`0 the initial length scaleU0 background hub-height velocityAssumption: In the far wake the ensemble average will be Gaussian. then Ubecomes:(2) U(z)︸ ︷︷ ︸Wake velocity= U0(z)︸ ︷︷ ︸Upstream velocity− Usf(z)︸ ︷︷ ︸Velocity deficitwhere f = e−12(z`)2.Using (2) we can obtain Us from the thrust equation:Us`12ρCtA0U20 = W ρzmax∫0U0(U0−U) dzCt is obtained from the thrust curveW is the width of the wakezmax is the height of the domain4Evaluation for Horns Rev I (80× 2MW)Model resolution: ∆x = 1.12k˙mLongitudeLatitude6° E 8° E 10° E 12° E 14° E54° 30' N55° 30' N56° 30' N57° 30' N58° 30' NDenmarkSchwedenHorns Rev ILongitudeLatitude7° 45' E 7° 54' E 8° 03' E 8° 12' E55° 27' N55° 29' N55° 32' N55° 34' Nl l l l l l l l l ll l l l l l l l l ll l l l l l l l l ll l l l l l l l l ll l l l l l l l l ll l l l l l l l l ll l l l l l l l l ll l l l l l l l l lM2M6 M7Rows 1 to 8Columns 1 to 105 kmU (m/s) θ (◦)Obs: 8± 0.5 270± 15Model: 8 270Plot: Velocity deficit Uh/U0h VS downstream distance (Volker et al. 2013)U0h is the upstream and Uh the downstream hub wind velocity.MastTurbineM6M740 Layers0.60.70.80.91.00 4000 8000 12000Distance [m]Uh/U0hVolker, P. J., Badger, J., Hahmann, A. N., Ott, S. Implementation and evaluation of a wind farmparametrisation in a mesoscale model. To be submitted.5Wind Farm Interaction - and idealised case studyHorizotal resolution ∆x = 1.12 km. U = 8m/s and θ = 270◦. WF size 80× 2MWRun WF Separation (km) Pdown/PupWF08 8×1.12 0.80WF15 15×1.12 0.86WF22 22×1.12 0.91Velocity Deficit: U/U0 Power Production: P =12ρCP pi R20U300.800.850.900.950102030 0.85  0.85  0.9  0.9  0.95  1  1  1  1 y [km]x [km]WF1min = 0.82WF2min = 0.80WF220 20 40 600102030 0.8  0.85  0.85  0.9  0.9  0.95  1  1  1  1 y [km]WF1min = 0.82WF2min = 0.79WF150102030 0.8  0.85  0.85  0.9  0.95  1  1  1  1 y [km]WF1min = 0.82WF2min = 0.78WF080.300.350.400.450.500.550.60 0.3  0.3  0.3  0.3  0.3  0.3  0.35  0.35  0.35  0.35  0.35  0.35  0.4  0.4  0.4  0.4  0.4  0.4  0.45  0.45  0.45  0.45  0.45  0.5  0.5  0.5  0.55  0.55  0.6 x [km]P = 40.9MW P = 33.2MWP = 40.9MW P = 35.3MWP = 41.3MW P = 37.1MW0 10 20 30PT(MW)6

Shadowing effects of offshore wind farms - an idealised mesoscale study

http://orbit.dtu.dk/ws/files/55644784/Shadowing_effects_Patrick_Volker.pdf

Shadowing effects of offshore wind farms - an idealised mesoscale study

Abstract

Similar works

Full text

Available Versions

Online Research Database In Technology

Online Research Database In Technology