Aircraft technology for turbines

The ‘circulation control’ aerodynamic technology could allow the wind turbines to produce significantly more power than current devices at the same wind speed.

Research aimed at adapting circulation-control technology to wind-turbine blades will be conducted by a California company, Pax Streamline, in collaboration with the Georgia Institute of Technology.

The two-year project, which will lead to construction of a demonstration wind turbine, will be supported by a $3m (£1.8m) grant from the US Advanced Research Projects Agency-Energy (ARPA-E).

‘Our goal will be to make generation of electricity from wind turbines less expensive by eliminating the need for the complex blade shapes and mechanical control systems used in current turbines,’ said Robert J. Englar, principal research engineer at the Georgia Tech Research Institute (GTRI).

‘Because these new blades would operate effectively at lower wind speeds, we could potentially open up new geographic areas to wind-turbine use. Together, these advances could significantly expand the generation of electricity from wind power in the US.’

Circulation-control techniques use compressed air blown from slots on the trailing edges of hollow blades to change the aerodynamic properties of those blades. In aircraft, circulation-control wings improve lift, allowing aircraft to fly at much lower speeds and take off and land in much shorter distances. In helicopter rotor blades, the technique - also known as the ‘circulation-control rotor’ - simplifies the rotor and its control system and produces more lift.

The ARPA-E project will apply the technique to controlling the aerodynamic properties of wind-turbine blades, which now must be made in complicated shapes and controlled by complex control mechanisms to extract optimal power from the wind.

Because they would produce more aerodynamic force, torque and power than comparable blades, the blown structures being developed by Georgia Tech and Pax could also allow a reduction in the size of the wind turbines.

A major question is how much energy will be required to produce the compressed air the blown blades need to operate. Preliminary studies done by Prof Lakshmi Sankar in Georgia Tech’s School of Aerospace Engineering suggest that wind turbines with the blown blades could produce 30 to 40 per cent more power than conventional turbines at the same wind speed, even when the energy required to produce the compressed air is subtracted from the total energy production.

The new turbine blades will be developed at GTRI’s low-speed wind-tunnel research facility located in Cobb County, north of Atlanta.

Officials of Pax Streamline see the circulation-control technology as key to the development of a new generation of turbines that could significantly lower the cost of producing electricity from the wind.

‘With this grant, we can rapidly accelerate our research programme and, within the next two years, deploy a prototype wind turbine that demonstrates our game-changing technology,’ said John Webley, Pax chief executive officer,