Wind farms and their turbines have been growing over the past decade – both in area and in height.
The larger a turbine, the more complex its interactions with the atmosphere. Small variations in local meteorology can have a big effect on the power generated by a wind farm.
One thing to pay attention to is low level jets, or LLJs – a type of wind that occurs in the lower atmosphere. New research, published in the Journal of Renewable and Sustainable Energy, investigates in detail the way LLJs interact with wind farms.
“A simple way to think about LLJs is to visualise them as high-velocity ‘rivers’ or ‘streams’ of wind within the atmosphere,” says Srinidhi Gadde, one of the authors on the paper.
These jets were known to affect the power production on wind turbines. The research ran simulations to examine the effect of turbine and jet height on power production.
When the LLJs were at the same height as the turbine rotors, the front rows of turbines impeded the wind, meaning turbines further back generated less power. But when the LLJs were slightly below or above the turbines, the simulations found that more wind was pushed into back rows of turbines, thus generating more electricity.
The researchers say this has implications for the placement and predicted energy outputs of taller wind farms.
“These much larger turbines are operating in very different atmospheric layers than smaller turbines used 5–10 years ago,” says Gadde. “At these scales, local meteorology and extreme shear events, which frequently occur, can impact power production.”