Small Power Systems 74550 Dobie Lane Covelo, CA 95428 Call: 800-972-7179 FAX: 707-983-6525 Email: George@smallpowersystems.com

Linear Trackers

 Linear tracker here means a row of panels supported by at least two supports and rotating around a linear axis usually horizontal running from one support to the other. Such trackers are almost always oriented to run East-West or North-South. North-South linear trackers can be sloped, with a slope of latitude being optimal, but the slope limits the length of the row. North-South tracking is much more effective than East-West. Shading of adjacent rows is a problem with both types on flat roofs but on South facing sloped roofs East-West linear trackers can be spaced reasonably close together. East-West tracking only adds about 10% output and seasonal adjustment to stationary panels can be almost as effective.

North-South linear trackers sloped so they are parallel or close to parallel with the earth’s axis work very well. However long rows are almost impossible at temperate latitudes because the support for the high end soon becomes impractical with increasing length. Such trackers produce well year around with best performance at the equinoxes. Shading from adjacent row requires that rows be spaced some distance apart. When mounted on South facing roofs the roof will shade the panels early and late in the day in the summer even if there are no adjacent panels to cause a problem.

North-South linear trackers parallel with the ground are very easy to install especially on large flat roofs. They do not put undo load on any one point, can be moved if necessary for re-roofing or maintenance, and are visually unobtrusive. Their output is surprisingly good but that is because they capture a very large percentage of sunlight in the summer when insolation is at a maximum. Their effectiveness in the winter especially at greater latitudes is poor. This latter deficit can be overcome if the panels are spaced in the North-South direction and some means is made to adjust their angel with the season either manually or automatically. Shading from adjacent rows is problematic and rows must be 2 or 3 row widths apart for good results. North-South, East-West Tracking , Horizontal, No Shading Theoretical Clear Day Output, Percent of Full Tracking