1. MULTIPLE FANS TEST - INTRODUCTION
The performance curve of a wind turbine can be measured in a number
of ways. The most accurate but expensive way might be the speed controller
controlled generator/motor option (used in Blackwell & Sheldahl, 1977).
An alternative to this method is the classic method of friction brake.
However, this method does not produce complete result under certain condition
(see result of Grylls, Dale, & Sarre, 1978). A less well-known method
is the angular acceleration of the rotor inertia mentioned in Musgrove
(1978) research paper. Equipment needed is minimum yet the method is capable
of producing much complete result than the band brake method.
The wind turbine model used in this testing is a small 0.5x0.5m straight
bladed Darrieus VAWT. This model was constructed during the author final
year thesis project, which included a brief test. The brief test using
only band brake under single large fan was done hastily due to constraint
of time. To obtain a more accurate estimation of the model performance
and to gain more information on the testing work, a much complete set
of tests was performed after the author graduation under the author own
initiative and with the green light from the previous thesis supervisor.
The first trial test, which was reported here, was under multiple large
fans while the second actual test was in the wind tunnel. This trial test
using large fans served as a good preparation before the actual test in
wind tunnel. In this trial test, both the band brake and inertia method
were used. Instead of using only one fan, the number of fan was varied
until the maximum of 3.
From this simple fan testing, the rough measurements of the model performance
under various conditions were collected. The performance trend with variation
of wind speed was analysed from these results. The effects of different
number of fans to the model performance were also discussed. Finally,
the results from the band brake and the inertia acceleration method were
compared.
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