Simulasi Numerik Wake Effect Terhadap Perfoma Turbin Angin Pada Ladang Angin Susunan Non Staggered Near Wake dan Far Wake

AZHIM ASYRATUL AZMI, Prof. Ir. Samsul Kamal, M.Sc., Ph.D.

2017 | Tesis | S2 Teknik Mesin

Turbin angin yang dibangun satu atau lebih kemudian membentuk sebuah ladang angin menghasilkan wake pada daerah downstream. Wake yang dihasilkan oleh turbin angin sangat berpengaruh terhadap performa dari sebuah ladang angin yang memiliki keterbatasan area. Salah satu metode penelitian wake effect pada ladang angin adalah menggunakan pedekatan simulasi numerik menggunakan bantuan perangkat komputasi atau biasa dikenal dengan istilah Computational Fluid Dynamic (CFD). Pada penelitian ini dilakukan pengamatan wake effect pada ladang angin menggunakan metode pendekatan simulasi numerik yang dibagi menjadi dua bagian yaitu daerah near wake dan far wake. Diameter rotor sebesar 200 mm, kecepatan angin 6,1 m/s dengan arah tegak lurus terhadap rotor. Jarak baris turbin downstream pada ladang angin far wake adalah sebesar 8.85D, dimana D adalah diameter rotor turbin, dan untuk daerah near wake jarak baris turbin downstream adalah sebesar 3D.Variabel bebas dalam penelitian ini meliputi perbandingan jarak baris turbin downstream. Variabel terikat dalam penelitian ini yaitu karakteristik medan aliran di daerah downstream yang meliputi kecepatan angin dan intensitas turbulen serta performa setiap turbin yang meliputi kecepatan putar rotor, torsi rotor dan daya mekanik yang dihasilkan rotor. Hasil simulasi ladang angin far wake menunjukan terjadinya penurunan kecepatan putar pada barisan turbin downstream sebesar 40,5% untuk setiap posisi dan penurunan kecepatan putar pada ladang angin near wake sebesar 41,7-41,72%. Persentase penurunan torsi terjadi pada barisan turbin downstream sebesar 33,78-35,52% pada ladang angin far wake serta 41,7% untuk ladang angin near wake. Penurunan daya pada ladang angin far wake sebesar 43,32-44,42% dan 64,7-65,9% pada ladang angin near wake. Terjadi penurunan kecepatan aksial angin di daerah downstream z=1D hingga z=8D. Penurunan kecepatan aksial terbesar ladang angin far wake dan near wake terjadi pada jarak downstream=1D di bagian pusat rotor. Terjadi peningkatan intensitas turbulen di daerah downstream dengan persentase peningkatan intensitas turbulen terbesar terjadi pada jarak downstream=1D di bagian pusat rotor.

Wind turbine that build one or more than forming a wind farms generate wake on downstream area. Wake generated by wind turbine has affected to wind farms perfomance called wake effect. One of the research methods of wake effect on wind farms is using numerical simulation approaches with computing devices or commonly known as Computational Fluid Dynamic (CFD). This paper primarily aims to investigate the wake effect on wind turbines perfomance on non-staggered wind farms by using numerical simulation. Wind farm configuration with 200 mm rotor diameter was modeled by 2 rows and 3 coloms by two different distance, far wake and near wake. Far wake wind farms was modeled by 8,85D of axial distance, and 3D for near wake wind farm, where D is rotor diameter. Wind turbine was modeled by small scale with 200 mm of rotor diameter, 6,1 m/s wind speed was set on inlet boundary condition perpendicular to rotor. independent variable on this study was the axial distance of wind turbine, and dependent variable was wind turbine perfomance include angular velocity, torque, and power. Flow characteristic on downstream area was investigate by velocity and turbulence intensity contour and profile. Two different simulation methode was applied, 6DOF dynamic mesh method to find angular velocity of wind turbin rotor, and Multiple Reference Frame (MRF) method to find torque. Structured hexahedral mesh generated to all computational domain to get better result. Result of this study showing the angular velocity of downstream wind turbine row was decreased by 40,5% for far wake wind farm and 41,7% on near wake wind farms. Torque of downstream wind turbine row was decreased by 33,78-35,52% for far wake wind farms and 41,7% for near wake wind farms. Angular velocity and torque decreasing on downstream wind turbine was affected to power generation. The power generation on downstream wind turbine was decreased by 43,32-44,42% for far wake wind farms dan 64,7-65,9% for near wake wind farms. The axial velocity of wind was decreased by wake effect on downstream area z=1D until z=8D. The largest axial velocity reducing detected on z=1D, on center of the rotor for both of wind farms. Tubulence intensity was increased on downstream area. The largest turbulence intensity detected on center of turbine on z=1D.

Kata Kunci : Wind Turbine, wind farms, wake effect, computational fluid dynamic, turbulence intensuty, dynamic mesh, multiple reference frame