White paper: Possible to dramatically increase power density in wind farms with SeaTwirl's vertical axis turbines

SeaTwirl commissioned the white paper from Dr Pablo Ouro, a researcher at the University of Manchester. It investigated different spacing configurations in windfarms with 25 10 MW turbines placed in five rows. Due to reduced wake interference, VAWT outperformed horizontal axis wind turbines (HAWT) in all scenarios. The paper concluded: "VA[W]T wakes recover faster than HA[W]T wakes due to the different mixing with the atmospheric flows which in turn leads to more efficient arrays."

"It is due to the higher turbulence intensity. A simple way to visualise this is to think of a stream of water. If you put a propeller in the water, it will create a long twirl behind it. But if you stir the water with a spoon, the turbulence it creates will subside much faster", says Jonas Boström, CTO of SeaTwirl.

The most dramatic difference was with slender VAWT, i.e. turbines that are taller but have a smaller diameter, that reached a power density of almost 19 MW/km² compared with 2.65 MW/km² for a typical HAWT configuration. Changing the aspect ratio, the relative width and height, while keeping the area swept by the turbine constant is unique for VAWTs and strengthens SeaTwirl in discussions with developers.

"There are discussions in many countries to increase the power density demands for coming offshore wind farms to avoid building in eco conservation areas. This white paper shows that SeaTwirl can be placed in very dense wind farms without losing much efficiency due to wake effects. It adds to our already strong value proposition for developers", says Peter Laurits, CEO of SeaTwirl.