Will the continued scaling of wind turbine height and size lead to higher noise pollution levels and larger setbacks, resulting in fewer turbines deployed for a given land area? The implications of these technology trends for future wind energy system installations were explored by researchers from RSG (Vermont), Vermont Environmental Research Associates Inc. and U.S. Lawrence Berkeley National Laboratory.

The development of 22 unique projects at two different prototypical sites was simulated using 11 different wind turbine models to determine output, nameplate capacity, numbers of turbines and receptor sound level patterns between projects using older, current and future turbine models sited within a fixed land area. Wind turbine heights are expected to increase an average of 60%, from 122 m to 202 m, for systems to be installed by 2025. This increase in turbine total height, coupled with larger rotor diameters and sound power level increases, decreases the average number of turbines by 60% in the fixed land area at prototypical sites.

Despite the projected reduction in turbine installs, total installed nameplate capacity for future projects increases by roughly 11% from 395 MW to 437 MW, and estimated annual energy output increases by almost 60% from 1,146 GWh/yr to 1,825 GWh/yr. Output gains are largely driven by significant increases in rated capacity and efficiency of future turbine models.

To overcome emerging local acceptance and permitting challenges, manufacturers are increasingly supplying turbine blades with serrated trailing edges (STEs) — physical serrations on the trailing edge of airfoil blades to reduce turbulent airflow. STEs effectively reduce sound emissions by 0.5 dBA to 3.2 dBA, on average, with minimal impacts on turbine power output. Sound levels at homes near turbines are estimated to be 18% lower, which can also be attributed to increases in setbacks and fewer wind turbines being constructed in the same land area.

Major advantages of wind turbine scaling cited in Applied Energy include higher installed capacities and annual energy output for a given land area, along with attendant economic benefits.