They’re getting better…WhenI was cutting my teeth in the PV industry, I sold nothing but UniSolarpanels and laminates. UniSolar works well in diffuse light because ofits triple-junction technology which is more responsive to the sun’slight spectrum. Therefore, directly tracking the sun’s path was not as important and, because thin-film PV takes requires more area, tracking becomes cost prohibitive.
Iwas also conditioned to think why anyone would add somethingmechanical–requiring maintenance and susceptible to breakdown–tosomething that works well statically, the solar panel. In fact, whenresearching trackers earlier this decade I read one PV system ownerusing a tracker say "if you have enough time on your hands and like totinker, use a tracker. Otherwise, I don’t advise it." But since thenI’ve become more accepting of tracking.
Single-axis tracking(SAT), which pivot panels along the sun’s path from east to westthroughout the day can increase electricity production over fixed flatpanels by as much as 38%. SAT panels produce 23% more power than arraysfix tilted at 15 degrees south. Obviously, this is significant if one’srebate or feed-in tariff is based on monthly kilowatt-hour output.Power purchase investment groups also came to require single- ordual-axis trackers to make the numbers work for a viable power purchaseagreement.
So in order for trackers to go from novelty tomainstream, they had to become better overall at what they doparticularly for large-scale projects. And they did. The apparent nextphase of large-scale (sometimes called utility scale) PV systems is inconcentrated PV arrays uti
lizingdual-axis tracking. CPV panels use less silicon and maximize thatsilicon’s output with mirrors or Fresnel lenses sometimes requiringless area than flat plate panels, less mounting hardware, less labor toinstall. One company, Opel Inc., in Shelton, Connecticut, says itsMk-Id high concentration photovoltaic module (at right) with itsdual-axis tracker will require 25% less gross DC wattage than aflat-plate array to get the same kWh production. The Mk-Id design hassunlight shining through a 11"x11" fresnel lens which concentrates rayson a tiny 10mm x 10mm silicon chip. The module with dual axis trackingsurpasses output of fixed-flat panels by 40% and 15-degree fixed panelsby 35%.
So who needs PV tracking?Anyone who needs to eke out as much performance from the panels as theycan. Trackers by nature are more appropriate for ground-mounted systemsbut there are exceptions.
It’s suggested readers conduct theirown online research on trackers for residential scale projects. Forlarge-scale projects some other major tracker manufacturers besidesOpel, include the RayTracker (photo at top), Wattsun Tracker, APSTracking (developed by Arizona Public Service) and ET Trackers.