Trough placement for sun tracking
The advantage of one-axis tracking concentrators is to require tracking the sun only in one direction, because in the other direction these collectors do not perform sunlight concentration. The axis of solar trough can either be placed parallel to the North-South direction of Earth rotation axis, or parallel to the East-West direction of Earth rotation plane.
If the solar trough axis is parallel to the North-South direction, the tracking system must follow the sun in its daily excursion and the sun’s altitude over the horizon depends on Latitude and day of the year. With this layout the solar rays impinge on the collector with an inclination dictated by Latitude and hour of the day.
If the solar trough axis is parallel to the East-West direction, the sun should not be tracked in its daily excursion. However the tracking system must follow the displacements in sun’s altitude occurring every day of the year. In this layout only at noontime the sun’s rays are perpendicular to the entrance aperture of solar trough.
The results of the studies presented in this paper are referred to sun’s altitude over the horizon, so they can be used in both placements of solar trough axis. Considering the North-South positioning, the sun’s altitude represents the daily excursion of the sun, which corresponds to the tracking path that the trough collector must follow. Whilst for the East-West placement, the sun’s altitude indicates the various positions of the sun corresponding to each day of the year, for the chosen Latitude.
