Full wind rose wind farm simulation including wake and terrain effects for energy yield assessment

Highlights: • A novel technique for estimating the capacity factor or the aggregated energy yield of a wind farm is developed. • CFD simulations accounting for wake and terrain effect and full wind roses are employed. • The number of CFD simulations are reduced to only 3 per wind sector, significantly saving computational effort. • The CF of an onshore wind farm is compared against different solutions with increasing level of description. • Results become very close to measurements when both wake and terrain are considered. In this work, CFD simulation along with the site complete wind rose are used for the first time to estimate a key magnitude for the project development of a wind farm, the capacity factor, which is directly related with the energy yield. The large computational cost that restricted CFD simulation for such a task is drastically reduced by means of a novel interpolation-extrapolation methodology, requiring the simulation of only three inlet velocities for each wind rose sector. This methodology is based on the velocity at met mast and results of the reference velocity for each wind turbine from pre-simulated cases, which are then used to compute a wide range of cases not explicitly simulated. A comparative study is carried out, in which the measured capacity factor of an onshore wind farm in the Argentinean Patagonia is compared against different solution approaches. In the particular case of this wind farm, it is found that the separate effects of wakes and terrain produce errors in the opposite sense, and results very close to the measured value are achieved when both are considered. Also, the increase in the number of simulated direction sectors from 16 to 32 does not significantly change the results.