In the period from 14 October 2002 to 16 January 2003, an early production version of the AIR-X
was installed at the NWTC test site for acoustic noise testing. In addition to the signals required
for the noise testing, additional instrumentation that allowed power performance testing in
accordance with IEC 61400-12 [1] was added. The results of that test are described in this report.
Please note that this test and the test report are not an accredited power performance test/test
report because parts of the NWTC quality assurance system were not followed.

9. Conclusions
1. NREL power performance test results of an early production version of the AIR-X
correspond with those published by Paul Gipe [3].
2. NREL results support the turbulent SWWP “instantaneous power curve” for two of the
three modes of turbine operation.
3. NREL predictions of AEP agree with predictions based on Paul Gipe’s tests [3].
However, they do not support predictions made by SWWP for non-turbulent sites or for
turbulent wind sites with average wind speeds above 5 m/s.
4. Low 10-minute average power compared to instantaneous power results from the control
strategy of the AIR-X, which employs three modes of operation. Performance
degradation is exacerbated by high turbulence at the NWTC test site. NREL expects that
upgrades to the control software can improve the power curve significantly.