Solar Tracking Tips: To Track Or Not To Track?

Passive Solar TrackerThe idea of installing a solar power system that automatically tracks the sun throughout the day, increasing its output by as much as 30% seems like such a great idea, but is it worth the extra expense and maintenance issues? Let’s take a look at the pros and cons of a solar tracking system.

First, some definitions. A Passive Solar Tracker has no electrical motor turning the solar array. It uses the heat of the sun to change the balance of the tracker, making the west side get heavier throughout the day, causing the tracker to turn west. During the night, the system cools down and the array turns back to the east awaiting a new day. This is usually accomplished with canisters of gasses that change weight with heat.

Active Solar TrackerAn Active Solar Tracker has a motor, gears, and controller, that move the array from east to west, and with a dual axis tracker, also changes the tilt of the array slowly throughout the seasons, creating the optimum sun/array angle. Active trackers generally cost several times more than a passive tracker, but also increase the array output more than a passive tracker.

Both trackers will produce more power output than a fixed array. Trackers are often used in off grid solar power systems, where optimizing the output is crucial. Let’s take a look at how much more power they produce, and whether it is worth it.

Solar designers use insolation, or sun hour, charts to calculate how much electricity a solar array can generate in different locations. This chart shows the different sun hours based on the tilt of the panels, for a fixed array, single axis tracker, and dual axis tracker. Let’s take a couple of examples to compare the potential daily output of a 3,000 Watt off grid solar system.

Insolation Chart

Watt Hours generated per day by
2520W Off grid solar system in Worcester, MA

Mount type and cost

System Cost

January

July

Average

Fixed 2,520W
$1,400

$16K

5,739Wh

9,284Wh

7,596Wh

Single Axis tracker
$3,500

$18K

6,583Wh

12,322Wh

9,452Wh

Increase

$2K

15%        
844Wh

33%   3,038Wh

24%     1,856Wh

Dual Axis Tracker
$6,300

$21K

6,921Wh

12,998Wh

9,790Wh

Increase

$5K

20%      1,182Wh

40%       3,714Wh

29%     2,194Wh

Fixed 3,360W
$2,000

$17K – 19K

7,653Wh

12,380Wh

10,130Wh

Increase

$1K – $3K

33%       1,914Wh

33%       3,096Wh

33%     2,534Wh

Wow! A 40% increase in the output from a dual axis tracker over a fixed pole mount in the summer – almost 30% average! And 25% average increase for a single axis tracker. That seems like a no-brainer right there. OK, but let’s compare the added cost of the tracker with what it would cost to do a fixed mount with 33% more panels.

A 2,520W off grid system, with 9 SolarWorld 280W panels, DPW Top of Pole Mount (TPM), Midnite Classic 150, Magnum MS-PAE-4448, and 12 Outback AGM batteries for 534Ah, plus all of the bells and whistles to put it all together costs about $16K. Adding 3 panels to the system and using a bigger top of pole mount, as well as the additional bits and pieces needed to add a fourth string adds about $1,000 to $17K. If adding 33% more panels turns out to be bigger than a single TPM and the charge controller can handle it, plan on the price increasing about $3,000 to add a second TPM and charge controller; totaling $19K.

Now let’s consider the same 2,520W off grid solar system, but with a ZomeWorks UTRF-168. That system would cost about $18K. Going a step further to an Array Technologies dual axis tracker, that system would cost about $21K. In this example, a single axis tracker costs about the same as adding 33% more to the fixed array, and a dual access tracker costs more than a 33% larger fixed system.

So, it’s not so cut and dry. If you can fit the 33% larger fixed mount solar power system onto the existing charge controller and stay with the one TPM, it is less expensive to just increase the size of the array. You wouldn’t have to worry about mechanical issues of the tracker breaking down or facing the west in the morning. Also, as you can see from the comparisons, the increase in production from tracking is greater in the summer, when your system is already performing at its best. Adding 33% more panels to a fixed mount adds 33% output throughout the year, not just summer. You can see you get a better output in the winter and yearly average with the bigger array than even with a dual axis tracker. But if your priority is maximizing your summer performance, using a tracker instead of a bigger fixed rack will provide you with the most power in the summer.

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Amy Beaudet

Solar Queen at altE
Amy Beaudet has been in the solar industry at the altE Store since 2007. She’s been a sales rep, an instructor, and an all around solar evangelist, sharing her passion for solar around the world. When not at work, she’s either sailing or skiing, depending on the season, but odds are good she’s still talking about solar on the boat or on the slopes.

About Author

Amy Beaudet
Amy Beaudet has been in the solar industry at the altE Store since 2007. She’s been a sales rep, an instructor, and an all around solar evangelist, sharing her passion for solar around the world. When not at work, she’s either sailing or skiing, depending on the season, but odds are good she’s still talking about solar on the boat or on the slopes.

2 Comments

  1. Mark Gunderson

    I have just found out that my grid tie system has just been going back to the grid with out any benefit to me. Really all I want too do is make my own power. My meter runs backwards and I was sopost to have used 100 kwh for the month . Instead I was charged for 450 kwh. I have built a great tracker that picks the sun earily in the morning and follows to sunset. I am so discusted by what happen that I was thinking of a robust off grid system. I would like to set up a meeting to talk about my options. I only live a hour away. I need a robust system with battery’s that will last! I have bought panels from you in the past. Thanks Mark Gunderson

    1. admin

      Hi Mark – We have notified your sales representative and he will contact be contacting you. Do you have a net metering agreement with the electric company? Net metering requires the electric company to be signed off.

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