Page 83 - Alternative Energy Systems in Building Design

CRYSTALLINE, AMORPHOUS, THIN-FILM, AND SUN-TRACKER TECHNOLOGIES 59

Figure 3.22 Amonix MegaConcentrator hydraulic arm assembly. Photo courtesy
of Amonix.

A hydraulic subsystem applies pressure to one side of the actuators to move the
torque tube and MegaModules in elevation and azimuth to keep the system pointing
at the sun. The hydraulic system consists of hydraulic valves, an accumulator, a pump,
a reservoir, and pressure sensors. A tracking-control subsystem monitors sensors on
the system, calculates the required movement for the operation selected, and applies
signals to the hydraulic valves to move the system to the selected position. The selected
position could be to track the sun, move to a night stow position, move to a wind stow
position, or move to a maintenance position.
An ac/dc control subsystem combines the dc power, converts it to ac power, and
interfaces with the ac grid. It consists of dc fuses, circuit breakers, and an inverter.
Control mechanism Sun-tracking platforms (see below) result in additional annual
energy generation per installed kilowatt. The average annual energy test of Mega-
Concentrator installations in California and Arizona has indicated that 50 percent
more power is produced than by comparable fixed flat-plate installations. Figure 3.23
shows a typical MARTIFER sun tracker.

Concentrator optics Refractive optics is used to concentrate the sun’s irradiance
onto a solar cell. A square Fresnel lens incorporating circular facets is used to turn the