Civil Engineering Reference
In-Depth Information
FIGURE 8-18
Dual-axis suntracker follows the sun like a sunflower around the year. (Source: American Sun
Company, Blue Hill, Maine. With permission.)
• one-axis tracker, which follows the sun from east to west during
the day.
• two-axis tracker tracks the sun from east to west during the day,
and from north to south during the seasons of the year (
Figure 8-18
).
A sun tracking design can increase the energy yield up to 40 percent
over the year compared to the fixed-array design. The dual-axis
tracking is done by two linear actuator motors, which aim the sun
within one degree of accuracy (
Figure 8-19
)
. During the day, it tracks
the sun east to west. At night it turns east to position itself for the
next morning sun. Old trackers did this after the sunset using a
small nickel-cadmium battery. The new designs eliminate the bat-
tery requirement by doing it in the weak light of the dusk and/or
dawn. The Kelley cosine presented in
Table 8-1
is useful to assess,
accurately, the power available from sun at the evening angles.
