Updated June 2022 Solar tracking is an interesting mechatronics challenge. That’s because it seems a simple design objective: Keep the solar panel oriented perpendicular to the sun in the sky — no big deal. A kid could do it if he could be kept outside on bright sunny days to make adjustments every 15 minutes all day long when there’s daylight. This is probably a bad idea, as surely it would certainly constitute child endangerment … but you get the idea.
The point of solar tracking is to keep the solar panel perpendicular to the sun as the earth and sun both move during a year’s time at a given location … and location matters. Depending on what the latitude is, the geometry of the annual cycle of the sun can dramatically vary.
The type of solar cell is in use also dictates the most suitable solar-tracking routine. Traditional silicon photovoltaics don’t require much accuracy because the cover layer that protects the silicon diffuses incoming light — so ±10% in either direction will work. For concentrating solar technologies (and there are several) accuracy is paramount. Accuracies of 0.1° of angular position are frequently specified due to the fact that alignment is critical to the performance of many of these systems.
What is interesting is the number of different solutions for solar tracking that are currently installed around the world. According to a report done by Photon Magazine, there are more than 150 companies worldwide supplying different tracking solutions. Many claim increases of output electricity up to 50% for two-axis tracking. So why aren’t all solar photovoltaic systems on trackers?
The most widely used systems move as many solar panels at one time as possible using a single motor and gear reducer based on planetary or strain-wave gearing. This makes sense from a cost engineering standpoint, but there is some risk. If the gearmotor fails, the output can drop off to zero multiplied by however many solar panels are on that tracking system. Notwithstanding, reliability has been good and almost every major utility scale solar project has ground mounted system trackers. Generally these are single axis trackers such as the Sunpower T-20 with a fixed elevation.
Of course, every once in a while there’s a novel design that defies description. Check out the Qbotix robot on a guide rail that adjusts solar-panel arrays in large installations:
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