Simulating Frontal Low Level Jets and Quantifying their Impact on Wind Energy Production

Abstract

Wind energy is becoming an important source of energy and reliable forecasts for the production of wind energy are needed to improve its integration in the power grid. The increasing height of wind turbines results in higher layers of the atmosphere being reached, where other phenomena than the surface-based ones can be of importance. One of these phenomena that can affect the wind energy production is a ramp up or a ramp down; a sudden increase or decrease in wind speed. One of the causes of a ramp down is a Frontal Low Level Jet (FLLJ), a jet stream which forms just ahead of a cold front. When the front has passed, the wind speed suddenly drops. It is yet unknown how well frontal Low Level Jets (LLJs) are simulated by a numerical weather prediction model. For this research, case studies of occurrences of FLLJs were determined based on Light Detection And Ranging (LiDAR) observations, synopticmaps and coarse-resolutionWeather Research and Forecasting (WRF) simulations. The chosen case studies were simulated with WRF using a finer resolution. These simulations were compared with surface observations from weather stations, wind profiler observations, LiDAR observations and observations from a wind farm. From these comparisons it was concluded that the WRF model performed relatively well in general. The general development and dissolving of the FLLJ were simulated correctly, but the timing and magnitude of these simulations can be improved.