The New Zealand Wind Energy Association newsletter gives some information about the status of the Vortec 7 project, reports Thomas Ackermann.
Note: DAWT = Diffuser Augmented Wind Turbine.
“The prototype Vortec 7 is being used for testing and verifying Computational Fluid Dynamic (CFD) modelling to improve and optimise the diffuser topography and technology. The University of Auckland published in January 1998 interesting results on preliminary CFD studies validated by measured site data, which has shown that the expected wind speed up effects, due to the diffuser, across the blade plane is not uniform as assumed by Grumman Aerospace. The speed up effect decreases towards the hub of the turbine compared with the original assumptions by Grumman Aerospace, hence the power output of the Grumman design would be less than the high values first predicted.
Since the publication of the paper, several retrofits to the DAWT machines have taken place guided by the CFD modelling undertaken by the Auckland University. These include the attachment of an aerodynamically shaped nose cone, the streamlining of the nacelle and fitting of vortex generators to keep flow attached to the diffuser wall.
These improvements bring the measured site power augumentation levels to around 3 times at high wind speed and around 4 times at low wind speeds. Further improvements to the as built Vortec performance are sought though attention to centre body surface low. Ultimately the best diffuser geometry is likely to arise from the CFD modelling underway at the University of Auckland, rather than from further (expensive) retrofits to the site machine. As the CFD work at the University has been paying off, it is expected that further improvements will follow.”
The predicted power argumentation was between 5.5 and 8.
Thomas Ackermann
