Could Vertical Axis Wind Turbines be Used Offshore?
© Sandia/ Josh Paquette and Matt Barone
Vertical Turbines Better at Sea?Wind power researchers & engineers have been looking at vertical axis wind turbines (VAWT) for a long time, but so far these haven't gained too much ground on the more traditional 3-blade horizontal axis wind turbines design that can be found everywhere. This could possibly change with offshore wind farms. Vertical axis wind turbines have some benefits that are magnified in those conditions, and maybe - just maybe - it'll give them the upper hand over traditional turbines over time.
VAWTs offer three main advantages: a lower turbine center of gravity; reduced machine complexity (they don't need a control system to rotate the nacelle and point it in the direction of the wind); and better scalability to very large sizes.
These become very important offshore, where installation and maintenance is more costly and difficult.
A lower center of gravity means improved stability afloat and lower gravitational fatigue loads.
Additionally, the drivetrain on a VAWT is at or near the surface, potentially making maintenance easier and less time-consuming. Fewer parts, lower fatigue loads and simpler maintenance all lead to reduced maintenance costs. (source)
And since costs get so much higher offshore, you need economies of scale, meaning, turbines as big as you can make them. VAWTs can theoretically be scaled up more easily than conventional turbines.
© Sandia/Randy Montoya
Still Work to be DoneBut while this sounds promising, challenges remain:
Curved VAWT blades are complex, making manufacture difficult. Producing very long VAWT blades demands innovative engineering solutions. [...]
VAWT blades must also overcome problems with cyclic loading on the drivetrain. Unlike horizontal axis wind turbines (HAWTs), which maintain a steady torque if the wind remains steady, VAWTs have two “pulses” of torque and power for each blade, based on whether the blade is in the upwind or downwind position. This “torque ripple” results in unsteady loading, which can lead to drivetrain fatigue. The project will evaluate new rotor designs that smooth out the amplitude of these torque oscillations without significantly increasing rotor cost. (source)
But if these problems, and others, can be solved, it's very possible that we'll someday have a lot more vertical axis wind turbines, at least offshore.
Via Sandia Labs