INGENIEUR
Figure 2. General arrangement of the CAWT
(arrows indicate the wind directions)
Design concept
The cross axis wind turbine (CAWT) comprises
supportive frame and a turbine rotor assembly
mounted on the supportive frame, rotating on
its vertical axis. For converting kinetic energy
from the movement of the turbine rotor assembly
to electrical energy and mechanical energy, an
electric generator is connected to the turbine
assembly.
The CAWT has three main vertical blades that
are connected to the six horizontal blades via
specially designed connectors. This arrangement
forms the cross axis wind turbine. The significant
advantage of the CAWT is that it can harness
omni-directional air flow from the sides on its
vertical axis with the vertical blades of the wind
turbine, and from the bottom of the turbine with
the horizontal axis blades (see Figure 2). The
horizontal blades also act as the radial arms of the
CAWT, connecting the hub to the vertical blades.
Each horizontal blade is arranged at an upward
angle over the horizontal plane. Connectors are
used to couple the horizontal airfoil blades to the
vertical airfoil blades. The vertical wind flow, either
created by the building or a guide-vane structure,
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interacts with the horizontal aerofoil-shaped
arms (see Figure 3). While on-coming horizontal
wind from any direction can be harvested by the
vertical blades, vertical air streams from the
omni-directional shroud can be harvested by
the horizontal blades, which increases the selfstarting capability of the turbine while producing
an aero-levitation force. This aero-levitation force
reduces the bearing friction in the generator,
helping to extend the lifespan of the wind turbine.
Initial lab test and computational fluid
dynamics (CFD) simulation
Initial testing was performed to demonstrate
the capability of the CAWT compared to a
conventional straight-bladed VAWT. The test was
done on a mock-up roof-top where the CAWT and
the VAWT were mounted at a height of 100 mm
above the roof of a building as shown in Figure 4.
Two sets of tests were carried out for the CAWT
and the conventional VAWT. Figure 4 shows the
comparison of the rotational speed performance