Flat Plate systems, in their simplest form, are stationary with fixed tilt, the angle of tilt usually being equal to the latitude of the location. They will face south (north) in the northem (southem) hemisphere. With some structures, it is also possible to adjust the tilt periodically depending on the season of the year to gain additional energy. One axis tracking, with the axis of rotation in the north-south direction, increases the energy collected per day. Two-axis tracking results in the highest possible energy collection. The additional cost involved in trackers must be balanced against the value of the extra energy collected. Fig. 4 compares the performance of fixed and single-axis tracking arrays. Both direct and diffuse radiation are collected with flat plate systems.
Concentrating systems utilize only the direct or beam radiation and they must be mounted on one- or two-axis trackers. They are best suited for locations with mostly clear skies throughout the year.